[2 stroke] Twin 350cc development ?

A little introduction first - we use a TZ 350 engine in a racing sidecar class in the UK - for many years the TZ350 was the main engine used in the F2 sidecar class - but in the early 1990's - 4 cyl 600cc "diesel" engines were allowed into the class - & when they became too fast - we retired - I had no wish to ride one of the "heavy" machines - I enjoy riding a 2 stroke - and also enjoy working on the engine - not so with a diesel...

The 350cc 2 strokes are now only used in a small series of races in the UK - we started racing again - about 5 years ago - and we enjoy riding the TZ - but always looking to improve performance - and maybe try some of the more modern ideas - after all - the TZ 350 is a very old design....

The class we race in allows up to 350 twin cylinder - the only other restriction is maximum carb size of 39mm.

Most people are using the TZ350 - there are a couple of people using the YPVS based engines - one using Banshee cylinders - and one using the CPI cylinders - the Banshee cylinder bike has been very fast - although a little unreliable - so I am looking at whether I should think about building a Banshee based engine - or whether the TZ is / has more potential for development.

During the 2011 season - we ran an engine with a 90 deg firing order - (not quite 90 deg - as the TZ centre splines will not allow it) - we were quite quick enough - but it did have a horrible vibration - it was easy to ride - and did not actually feel very fast - but the lap times were as good as a normal engine - I did worry though - that the engine was more stressed than normal - due to the vibration.

We have a few options to explore:

1. Carry on with the TZ "normal" engine - with possible improvements of Ignition / pipes / carburation

2. Spend time in developing the 90 deg engine. (with possible improvements of Ignition / pipes / carburation)

3. Build a Banshee / YPVS based engine - with better porting & the possibility of using the CPI cylinder.

4. Look into the possibility of building a "long stroke" engine - using a +7mm crank - and finding a smaller piston / cylinder.

5. We have an Aprilia v twin engine with 66mm cylinders - which was reputed to be very fast but fragile (in the previous owners hands) - but I'm thinking the fact that it is so over square will present some problems...

Sorry for the lengthy post - we would appreciate some comments - hopefully none telling us to get a "diesel" - that is not an option - there's no pleasure going down that road...

Thanks for reading this far

Une petite introduction abord très heureux - nous utilisons une TZ 350 moteur dans une classe side-car de course au Royaume-Uni - depuis de nombreuses années l'TZ350 été le principal moteur utilisé dans la classe F2 side-car - mais dans le début des années 1990 - 4 600cc cyl "diesel" moteurs ont été autorisés à entrer dans la classe - et quand ils sont devenus trop vite - nous nous sommes retirés - Je n'avais pas envie de monter un des machines "lourdes" - je faire de l'équitation un accident vasculaire cérébral 2 - et aussi du plaisir à travailler sur le moteur - pas de même avec un diesel ... Rolling Eyes

Les 2 courses 350cc sont maintenant utilisé dans une petite série de courses au Royaume-Uni - nous avons commencé à courir à nouveau - il ya 5 ans - et nous aimons la circonscription du TZ - mais toujours à la recherche pour améliorer les performances - et peut-être essayer quelques-uns des plus modernes idées - après tout - le TZ 350 est une conception très ancienne .... Very Happy

La classe nous courrons en permet jusqu'à 350 bicylindre - la seule autre restriction en glucides est de taille maximale de 39mm.

La plupart des gens utilisent l'TZ350 - il ya un couple de personnes qui utilisent les moteurs YPVS base - l'une utilisant des cylindres de Banshee - et une aide de l'IPC cylindres - le vélo Banshee cylindre a été très rapide - bien qu'un peu fiable - donc je suis à la recherche si je devais penser à la construction d'un moteur de base de Banshee - ou si le TZ est / a plus de potentiel pour le développement.

Au cours de la saison 2011 - nous avons couru un moteur avec un ordre de tir 90 ° - (pas tout à fait 90 degrés - comme les cannelures du centre TZ ne le permettra) - nous étions assez rapide - mais il a eu une vibration yeux horribles roulants - il était facile à monter - et n'a pas réellement sentir très vite - mais les temps au tour étaient aussi bon qu'un moteur normal - je ne vous inquiétez pas - que le moteur a été plus stressé que d'habitude - en raison de la vibration.

Nous avons quelques options à explorer:

1. Continuez avec le TZ "normal" du moteur - avec des améliorations possibles d'inflammation / tubes / carburation

[quote="Emmanuel Laurentz"]


La plupart des gens utilisent l'TZ350 - il ya un couple de personnes qui utilisent les moteurs YPVS base - l'une utilisant des cylindres de Banshee -

Il n'y a pas de valves YPVS sur les moteurs de Banshee, quelque soit l'année. Nous pouvons monter des cylindres de RDLC (31 K par ex) sur le bas moteur d'un Banshee, mais pas sur un bas de TZ, ou alors il faut modifier le gougeonage des cylindres.

CPI based cylinders have a huge potential

I've build a few of them , but the engine you will be allowed to build depends on the rules of the class

At the moment , i have a 543cc CPI cheetah twin , i've set the rev limiter at 9500 rpm for starting devellopement , the torque is just HUGE , Pv are crap and need to be driven by an YPVS engine but i d'ont think you need them , at least on the wet , i do beleive that this engine with pneumatic PV would spin the tires on each gear without driven Pv

Just clear your rules and we will see ...

Emmanuel Laurentz a écrit:

La plupart des gens utilisent l'TZ350 - il ya un couple de personnes qui utilisent les moteurs YPVS base - l'une utilisant des cylindres de Banshee -

Il n'y a pas de valves YPVS sur les moteurs de Banshee, quelque soit l'année.

Thanks - yes - I know the Banshee has no YPVS system - the engine "bottom end" was the basis - the Banshee cylinder machine also had a Nova close ratio gearbox - and used very large pipes - but was supposed to be at the capacity limit of 350cc.

SEB4LO a écrit:

CPI based cylinders have a huge potential

I've build a few of them , but the engine you will be allowed to build depends on the rules of the class

At the moment , i have a 543cc CPI cheetah twin , i've set the rev limiter at 9500 rpm for starting devellopement , the torque is just HUGE , Pv are crap and need to be driven by an YPVS engine but i d'ont think you need them , at least on the wet , i do beleive that this engine with pneumatic PV would spin the tires on each gear without driven Pv

Just clear your rules and we will see ...

Yes - the CPI based cylinders should be the way to go - although we are still limited to 350cc (although there may be some rule adjustments to allow a rebore for steel liner cylinders - of up to 1.5mm oversize - approx 364cc)

If we could go to a lot larger capacity - it should be a lot easier to gain extra power - but we are stuck with the 350 / 364cc limit - that's why I was looking at trying to improve within that capacity - as there are easily available +7mm cranks - if we could get the CPI based cylinder at 61.5mm - and a piston to suit - it would give us a capacity of approx 362.41cc - and a less oversquare engine (61.5 x 61)

From reading a lot of information on here - I am starting to think that the time area improvements - and the aux exhaust ports with that layout - might show reasonable gains - whether it's worth the bother is another matter - but then half the fun of racing is the possibility to make some improvements no one else has tried...?

Gordon Jones a écrit:

... if we could get the CPI based cylinder at 61.5mm - and a piston to suit - it would give us a capacity of approx 362.41cc - and a less oversquare engine (61.5 x 61)

I don't know if CPI can supply undersize cylinders, Gordon. But you can ask Calvin Pollet: [Vous devez être inscrit et connecté pour voir ce lien]

Frits Overmars a écrit:

I don't know if CPI can supply undersize cylinders, Gordon. But you can ask Calvin Pollet: [Vous devez être inscrit et connecté pour voir ce lien]

Hello Frits - I was hoping you would see this post
Should I take it from your reply - that you are thinking the longer stroke option might yield some good results ?
To expand on my thinking....

The TZ350 cylinder cannot easily be sleeved down to suit a smaller piston (I think) - although I know a man that may be able to cast a new TZ cylinder - which could be left with the correct bore size before plating.

The CPI cylinder - if Calvin is able to cast a smaller bore cylinder - we then have the (advantage ?) of the extra ports - but we would then have to use the YPVS engine bottom end - which would really need a close ratio gearbox - and we would also have the wet clutch - I quite like having the dry clutch on the TZ - much easier to work on / repair...


The +7mm Banshee / YPVS cranks are available in lots of places - but - the thoughts I have are whether any of the aftermarket cranks are up to the job....although - at the price they are selling - they could almost be considered a throw away part - especially when compared to servicing a TZ crank - those are becoming very rare (at least the female inner flywheel is) - unless you buy one of the Hoeckle copies that are available (lucky enough to have a proper Hoeckle in my best engine)

Finding a Piston that's up to the job could also be a problem - the only piston I can find listed anywhere near the size I want - is for a Kawasaki - at 61.5mm - but that has a 14mm Piston Pin...(Yamaha is 16mm)

All of this is what could be termed "research" - as funds are very limited - I would want to have a reasonable hope of this being worth the effort before I do too much more - although I do have 3 x YPVS engines under the bench in preparation...(as well as a couple of Aprilia engines & a box of 66mm Hummel cylinders )

I did send several emails to Calvin a couple of years ago - but had no response - maybe the emails just got lost in space - we'll never know...

I have no first hand experience of the CP cylinders - but have seen some reports on other forums regarding seizures - and the guy running one in our series has been prone to seizures - in fact - he has now had the cylinder lined - a mistake I think - but then I'm not running that engine - I can't help but think that some people like to run their engines a lot weaker than I do....

Gordon Jones a écrit:

Should I take it from your reply - that you are thinking the longer stroke option might yield some good results ?

I wonder how you could read that out of my reply - but yes, a longer stroke will do the angle.areas a lot of good.

Citation :

The TZ350 cylinder cannot easily be sleeved down to suit a smaller piston (I think) - although I know a man that may be able to cast a new TZ cylinder - which could be left with the correct bore size before plating.

Yes, it would have to be a very thin sleeve. Or you could bore a couple of millimeters out of the TZ350 cylinder, but that would hurt its structural strength. Casting a smaller bore cylinder is much to be preferred.

Calvin makes a 65/54 cheetah a lot more repliable and potential than tz barrels

Get pv one and drive them with cables

I m pretty convinced that he can provide a 61 stroke unit that you can sleeve to 61 ....

SEB4LO a écrit:

Calvin makes a 65/54 cheetah a lot more repliable and potential than tz barrels
Get pv one and drive them with cables
I m pretty convinced that he can provide a 61 stroke unit that you can sleeve to 61 ....

A lot to think about

To Frits - I'm not sure whether you are suggesting a piston port engine based on the TZ porting would be preferable ? - we did try a TZ700 64mm reed valve cylinder years ago - and while it made the engine very tractable & easy to drive - it lacked top end speed - although - at the time we did not try any changes to anything else - carbs / pipes - everything the same as normal 350G barrel - if we had the time we may have been able to improve it....

I have no first hand experience of sleeving cylinders - I have always thought that plated cylinders are preferable due to the better heat transfer - but I am willing to listen to the arguments for sleeving (they will need to be convincing though )

I guess it depends on whether the CP cylinders have enough material after casting to allow the smaller bore - I have no idea how the casting process works - or whether it is relatively simple to "adjust" the casting to allow more "meat" to work with.

The PV might be desirable - but based on the experience with the TZ reed valve cylinder - I'm thinking that the reed valve would give a bit more flexibility - without the added problems of the PV - we would need a better (bigger) battery to run that - at the moment we run a total loss Ignition off a (very) small nimh battery - although - I'm looking at the Ignitech - mainly because it has better software than our current Ignition - and the ability to save & load curves...

Just for interest - I took a base profile for the TZ350 in Mota - and changed the bore x stroke to 61.5 x 61 - and without any other changes - it shows about 10hp extra (for 2 cylinders) - whether that would happen in a real engine is anyone's guess - but it makes me feel good

Gordie Gordie Gordie, well you won't be needing them 66mm RGV cylinders after all Does the engine have to be from a particular period/era? I think I said before that the latest inline kart engines like Francis Payart's beautiful FPE's would trounce old TZ's (think you said there was a issue with the RH chain drive).
If you are married to the TZ parralel twin configuration, why not shift to the 115mm rod with the Banshee high pin piston for a start?
Use a Zeeltronic with a 120Amp 600grm LiPo battery At the very least you have a quickshift which decreases lap times.
The G cylinder is about as good as it can get "tuning" usualy results in only going backwards.
Do you need more top end , mid range or both?

Gordon Jones a écrit:

We have an Aprilia v twin engine with 66mm cylinders - which was reputed to be very fast but fragile (in the previous owners hands) - but I'm thinking the fact that it is so over square will present some problems...

Hi Gordon,

Are those 66mm cylinders simply bored out from the standard 54mm Aprilia cylinders? or were they originally produced that way?. I'm thinking about the effect on port heights/shapes and the available casting thickness. Seems a strange way to go?

I assume the cranks are 54.5mm stroke, which I calculate would give you 373cc, so if you were going to use it in your class, I guess that you would have to reduce the bore size, anyway

Just interested . . . . . . and is it for sale!!

Oh . . . . and agreed on the 4-stroke

Best Regards

Ian

Gordon Jones a écrit:

To Frits - I'm not sure whether you are suggesting a piston port engine based on the TZ porting would be preferable ?

Not at all; I was merely thinking aloud about how you could reduce the bore.

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we did try a TZ700 64mm reed valve cylinder years ago - and while it made the engine very tractable & easy to drive - it lacked top end speed.

No surprise; by today's standards the TZ700 reeds are too small even for a 50 cc. And the TZ700's port shapes and timings were very mild too.
We once went the other way. Ferry Brouwer, then in control of Racing Shop Katayama, put 350G cylinders, carbs and pipes on Takazumi's TZ750. The beast had at least 20 hp more than anything else in its class and was totally unrideable.

Citation :

I have no first hand experience of sleeving cylinders - I have always thought that plated cylinders are preferable due to the better heat transfer - but I am willing to listen to the arguments for sleeving.

There aren't any.

Citation :

The PV might be desirable.

On a sidecar you won't benefit as much as on a solo; you can get away with a much more temperamental engine.

Citation :

I'm looking at the Ignitech - mainly because it has better software than our current Ignition - and the ability to save & load curves...

Ignitech and Zeeltronic ignitions will do fine on TZs although Ignitech could do with a bit more spark energy; they're working at it. I can't comment on the Zeeltronic's spark energy; I have no first-hand experience with it.

Citation :

Just for interest - I took a base profile for the TZ350 in Mota - and changed the bore x stroke to 61.5 x 61 - and without any other changes - it shows about 10hp extra (for 2 cylinders) - whether that would happen in a real engine is anyone's guess.

I can't be bothered to do the math (it's sunday) but that mod would certainly improve the engine.

I see Frits has posted again while I've been writing this - I'll answer that later

Institute of TwoStrokes a écrit:

Gordie Gordie Gordie, well you won't be needing them 66mm RGV cylinders after all Does the engine have to be from a particular period/era? I Do you need more top end , mid range or both?

Hi Lozza - you've not forgotten about those cylinders have you ?
I've not had a lot of time during the race season - but I am now thinking the V twin will not be something I want to spend a lot of time on - one reason - I have very little experience with those engines - so probably better spending what little time / money I have with the Yam engines - and no - limit on period / era - 2 stroke twin - the fact it's a 2 stroke probably puts the "era" into it...
"Do you need more top end , mid range or both?" - we'll have both please

Up until this season - we've not needed a quicker engine - however - this season - we had a guy join us - running a set of Banshee cylinders - and it has been very quick - always first off the line - and no way I could catch it - and my engine is not slow - there were a lot of whisperings as to the actual capacity - but we have not had engine capacity checks in place - that will change for next year - so I may not actually need any more power for next season...

The 115 rod idea is one that has been tried by others - I believe they were using a barrel spacer with standard pistons many years ago - not got around to it myself yet - even though I have a pair of new RD400 rods sat in a box - I believe it was reasonably successful....

The inline engine idea has been tried years ago with an Armstrong engine - but as you say - chain line is a problem with a sidecar...

The ignition we use now has the Quick shifter (or was it Flat shifter you called it ? ) - the Ignition is good - just the software is ancient - can't save / load a curve - you have to enter all the points in the software & save to the unit - so only 2 curves in the box...

I would agree "The G cylinder is about as good as it can get" - that's why I was so surprised to have the Banshee bike getting away from us - I can hardly believe a 350 quad engine can produce enough power - unless there's something else going on.... - even though I know that engine was running 1.5mm oversize pistons - I still find it hard to believe at 358cc - it could produce what must have been close to 80hp - looking at the Banshee porting - nothing special ? - and running the same stroke as the TZ ??

For next year - the rules are in the process of being adjusted to allow up to 365cc - mainly to allow the Banshee to be rebored when it wrecks a barrel - and we're hoping to introduce capacity checks at every meeting - so there'll be no doubt what we're racing against in future.

The increase in capacity allowed - to 365 - would also allow - within the rules - my idea of bringing the engine closer to "square" than it is at the moment - whether it would be successful is another matter - hence the fishing trip here - always better to get as many heads together as possible - not too many people left these days who know what a 2 stroke is - let alone how they work. (wish I could include myself in that group )

To Ian - I'm sure I've read some posts (a lot actually) you made in a Kart forum - forget which one....but all very interesting....
In answer to the questions - the Aprilia barrels are Hummel - no idea how they started their life....I posted some pictures for Lozza some time ago - they are still there...(some Armstong barrel castings on there somewhere too)

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I bought a complete sidecar chassis & a couple of Aprilia engines / + various other parts - I sold the chassis fairly soon after - (i'm in the process of building a new one now) - the Aprilia stuff - yes - if it will raise sensible cash - it's for sale - there's a couple of complete bottom ends - a box full of barrels (some broken / damaged) - various new / old pistons - + one set of newly plated cylinders....
Nearly forgot - the engine cases have (I think) 50.6mm bore marked on them - so just within the 350 limit...

Gordon Jones a écrit:

To Ian - I'm sure I've read some posts (a lot actually) you made in a Kart forum - forget which one....but all very interesting....
In answer to the questions - the Aprilia barrels are Hummel - no idea how they started their life....I posted some pictures for Lozza some time ago - they are still there...(some Armstong barrel castings on there somewhere too)

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I bought a complete sidecar chassis & a couple of Aprilia engines / + various other parts - I sold the chassis fairly soon after - (i'm in the process of building a new one now) - the Aprilia stuff - yes - if it will raise sensible cash - it's for sale - there's a couple of complete bottom ends - a box full of barrels (some broken / damaged) - various new / old pistons - + one set of newly plated cylinders....
Nearly forgot - the engine cases have (I think) 50.6mm bore marked on them - so just within the 350 limit...

Hi Gordon

Yes, I am usually to be found on the various Superkarting Forums and try and pass on a bit of what I've learned over the years. British, US, Australian, etc.

To be honest after some thought the Aprilia might not be up my street . . . . too many distractions already. But many thanks for the info and I know where to contact you . . . . . . if.

I calculate that you would need a bore of 63.9mm with the 54.5mm stroke to get you just under the 350cc limit.

We used 115mm Rods (20mm pins), with Vertex Aprilia GP pistons in our Canadian BRC tandem twins, which are heavily modelled on Aprilia designs and use the Aprilia gearbox and clutch components.

We just sold our last motor to Australia (this won 2 European Championship rounds whilst we had it).
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This engine has become quite famous in it's own right and was given the name "Scar" due to previous surgery to it's bottom!!
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Best Regards

Ian

hiya Gorden, would it be mechanically feasable to take 64mm CPI barrel & bore it out until the cylinder skirt thickness disapeared & then shrink in an alloy liner for nikasil ?

perhaps use an even bigger bore than 64mm cpi cylinder to get more meat around the bore for stability,

a lot of port cutting but at least you could have your 61mm (or what ever you need) bore in nikasil,

would the better quality alloy used for the "liner" than the cast alloy produce a better nikasil adhesion & finish?

The alloy of the cheetah engines is just great .... But for the other points i do agree with you David

The only problem is that it would be really difficult to re machine pv but if frits says it's useless , i'd sleeve a 72mm +7 stroke cheetah to 61 mm bore

To Frits - thanks for your reply - good to hear stories from the "old days" (proper bikes / engines ) - I hope no one told Takazumi before he rode it...
I remember watching him in a 350 race at Silverstone many years ago - he was a very good rider...
Some of the sidecar guys have done the same with the 350G 4 cyl engine - probaly a bit more manageable with a sidecar - but still a handful...

You confirmed my thinking regarding plated cylinders versus sleeved - and on the power valve issue - we can & do tend to be able to spin the back wheel to get the motor back in the power...different thing when you only have 2 wheels under you...

That's very interesting regarding the Ignitech - is the spark energy something that they would admit to ? - and is there any way of overcoming it ?
We use a Pro-digital now - which has given us no issues other than the lack of better software - it seems able to fire pretty much anything you care to throw at it - the only time it has failed us - is when we have forgotten to change the battery - (it only happened once )

Frits Overmars a écrit:

Not at all; I was merely thinking aloud about how you could reduce the bore.

The bore size reduction - something I will have to make some more enquiries on - there are 2 possible avenues to explore.

1. TZ barrel cast at 61mm - depends on whether that will go ahead fairly soon - I do know he is very busy with other projects - we would then need a +7mm crank for the TZ - possibly modify one from a YPVS based engine - (bearings are correct diameter - flywheel spacing is slightly different) - and source pistons at the correct size.

2. Find out if a smaller bore is possible with the CPI cylinder - sourcing pistons would still be necessary - and a usable gearbox / clutch / primary gears - unless the TZ cluster can be made to work in the YPVS cases - not had time to check all the options - although at first sight - not an option due to the selectors (4 in TZ - 3 in Banshee)

The comment about Mota - I'm curious to know whether it is at all useful for comparison purposes - I don't expect too much accuracy - just to know it "could" be pointing in the general right direction would give a base to work from - I've had Mota for a couple of years now - just not used it to do any actual work yet - it seems there are more accurate software programs available these days....

Ian Harrison a écrit:

I calculate that you would need a bore of 63.9mm with the 54.5mm stroke to get you just under the 350cc limit.
Best Regards
Ian

Not too far away from what we have with the TZ now
The inline twins would be great - other than having the chain on the wrong side

rgdavid a écrit:

hiya Gorden, would it be mechanically feasable to take 64mm CPI barrel & bore it out until the cylinder skirt thickness disapeared & then shrink in an alloy liner for nikasil ?

I had thought about that - although I'm not at all sure if it is feasible with alloy to alloy - & the porting would be a nightmare - unless someone knows better...
Seb - you just posted that before me - I'll have to think about it a bit - I think what Frits was saying about the PV - is that it's not quite as essential with 3 wheels - would be useful - but 3 wheeler's don't tend to "fall over" like 2 wheeler's - I'll take a look at the CPI site porting pictures / dimensions when I get a minute...

Gordon Jones a écrit:

That's very interesting regarding the Ignitech - is the spark energy something that they would admit to ? - and is there any way of overcoming it ?

Like I wrote, Ignitech is aware of it and working at it. The current solution for a single cylinder engine is to put two coil feeds into a single coil.

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...we would then need a +7mm crank for the TZ - possibly modify one from a YPVS based engine - (bearings are correct diameter - flywheel spacing is slightly different) - and source pistons at the correct size.

Doesn't the RD400 have a 62 mm stroke? And I suppose a complete TZ transmission will fit the RD400 cases no problem.

Zeeltronic has constant 35mJ spark energy, don't know if that's good or bad. CPI cylinders will always be better than the old TZ another option is the Athena Banshee kit. Between the 2 is almost everything you would ever want to do to a cylinder. Both those will have to go RZ/Banshee cases. The banshee option is a good one as the components can still be purchased new in the US. They are quite cheap so having engines in a high state of tune and rotated regularly becomes an option rather than rely on one "good" engine.

Now about those RGV cylinders .......................................

Salut Lozza :)
Now i have a desktop computer and not the iphone , i can develop a bit :)


First , and in the order , to get the maximum power , i would run a square stroke/bore then , you have 400Rd low end or a banshee stroker crank

I have studied the problem during hours and hours :)
The 61 stroke +7 banshee crank with 15 rods machined billet are VERY VERY relaible , my +10mm ( 64 stroke ) has about 8 hours and is still 0.00 wear ( 12 k rpm with 73mm pistons ! )

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then a 7mm stroked cheetah , 72 bore and a liner pressed in at 61 bore ( 356 cc )
Cheeaths use Cr250 reed cages that allow big carbs etc etc ( Cr250 are not that big in fact but compared to stock banshee ones , they look huge :) )


About the gearbox , you can acheive a nice racing gearbox using mixes between banshee and street Rz/rdlc bikes

Main problem is to get the rod / piston combo to get easily both to rebuild .....

Hi Gordon

I know it's a bit off your topic, but I thought you might be interested to see a direct back-to-back dyno comparrison between an HPI and Ignitech ignition installed on one our Honda CR250 Superkart engines. The HPI is a 2-curve digital programmable CDI unit, just replacing the stock Honda unit and plugging into the Honda generator and taking the trigger off a raised segment on the rotor periphery. We powered the Ignitech with Lipo battery, rectified and regulated 13V supply off the Honda generator and both (which is actually illegal for us. The regs only allow 1 power source). We also triggerd this in the same manner. As well as the lack opf power with the Ignitech you also see a big rise in the EGT's, which under normal circumstances I would say was due to a retarded ignition. The only other thing I could think was that a low spark energy was taking longer to actually fire the plug.

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The curves programmed in are identical and were verified on our ignition rig prior to installation on the motor. After the big difference we also verified the curves on the motor (by strobe).

I did speak with Ignitech and they couldn't shed any light on the difference and we did check everything at least 3 or 4 times. We did also try both coil outputs feeding into the single coil as suggested in Frits' comments, but it made no difference. Shame as it's a well priced and featured box. Perhaps they have sorted it now. Our boxes are about 18 months old.

We have had exceptional results with the RTD (Racetech Developments) EMX-04 (for singles and tandem twins) and the EMX-05 for a 2 trigger system.

Best Regards

Ian

Ian was the Ignitech timing strobed against a flat line advance curve on the running engine? The rotor need not move far to get +/- 2deg. Were you using the Honda coil? Ignitechs like RGV coils best.
Where are a few PVP,BRC,FPE and DEA dyno graphs?

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Thanks for all the feedback guys
I had just spent the last hour answering some of the points - went away to do something else - and lost the lot - so here's the second attempt.
To Frits - I'd forgotten the RD400 - might be worth looking at - although they are tending to be a bit rare these days - I seem to remember the width dimensions are same as 250/350 - but I think the flywheels diameter was bigger....long time since I worked with them...

Lozza - your comment

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"The banshee option is a good one as the components can still be purchased new in the US"

is probably the most important consideration - I know about the CPI cylinders - and have heard of seen pictures etc of the Athena Banshee kit - what are the differences - & who makes the Athena stuff ?

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Now about those RGV cylinders ..........

If you are serious - send me an email - we can start talking - although my preference would be to sell a complete engine rather than just the cylinders...

Seb - thanks for the link - nice looking crank - is it rebuildable ? - and is the centre "keyed" - I would prefer any crank to be rebuildable at that price...there are so many cranks on the market - difficult to know which are any good - the cheap ones would be worth using if we could get a season out of them - it costs probably more to rebuild the TZ crank...
AS for the cylinder - so many options - need to find out if Calvin can cast a small enough bore - and work out the porting to suit - getting suitable pistons might be a problem too - not too many listed anywhere at 61 / 61.5
I still have to study the gearbox ratios - I have probably all the options listed - when I have time to look at them - the easy (and costly) way out is a Nova close ratio box.

Ian - thanks for the information - I am in no hurry with the Ignition - so hopefully they solve any issues by the time I need it - I wasn't aware of the RTD - although - it looks expensive - did I mention we are a "low to no budget" operation ?
The dyno must be an essential part of your operation - we have no easy access to one in our area - other than rolling road about 50 miles away.
I would be interested to hear if the Mota simulations are of any value in pointing in the right direction - or a waste of time ? - the simulation of TZ350 with bore / stroke changed to 61 x 61.5 was quite surprising - extra 10hp - just from that....

Just another thought on the Ignitech - I know a guy that has been running one for a few years now (probably 2 - 3 years) - he's had no problems - that is on a classic 2 stroke 250 kawasaki - so just wondering if the problem could be showing only on a later design / more advanced type of engine ??

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Were you using the Honda coil?

No swearing here please...

Hi Guys

Lozza,

I can post a BRC dynograph tomorrow from work, but I am conscious of pulling Gordon's thread "off beam".

Of course dyno's work differently upside-down!! but we would never see anything close to 100 on a 250 twin on our Dyna-Pro T62LCC.
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I believe our UK Horses are much stronger than Aussie (or Canadian) ones, but it's only a comparisson. As long as you always use the same ruler your OK.

The strongest 250 tandem twin motor I ever had on the dyno was Aussy, Scott Ellis' SAFE motor that I built/tuned/prepped the last couple of years.

We were using the standard Honda CR250 coils with all ignitions. To be honest they never missed a beat. Is there any year of RGV coil to get and/or do you have a part No.
We are pretty solid on the HPI box. I would like to try an MSD 4217 at some stage which I also believe is also good.

Gordon,

From memory the RTD box is about £350.00, but I'll check that out.

Heres an image of some of the ignitions we run or have tried on the Honda.
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From the left: PVL, HPI, RTD, Ignitech

Yes, the dyno is the most used tool in our toolbox, but it does eat time like you wouldn't believe.

Our current single exhaust was basically developed by copying what has gone before and then by very tedious trial-and-error on the dyno. If I input our engine data into the MOTA exhaust design programme, I get something quite different. We have a "thinny" and a "fatty". Here is the "fatty":
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I'm guessing that you (and others) had problems with the Honda coil?

Best Regards

Ian