[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked)

What kind of plug did you find worked best in the RSA? I do not recognize the one in the picture. We typically use NGK Iridium plugs BR10EIX. Did you index the plug and if so in what direction? Did you find that indexing the plug made a difference.

BTW Frits I tested your head design scaled up to match my 65 mm bore and gained 1.5 HP all the way up from 6000 to 10600 rpm. The gain is comparing my 17-1 compresssion ratio head to the new one at 16-1

Howard Gifford a écrit:

What kind of plug did you find worked best in the RSA? I do not recognize the one in the picture. We typically use NGK Iridium plugs BR10EIX. Did you index the plug and if so in what direction? Did you find that indexing the plug made a difference.

Aprilia did not index them , but I do.
If you click 'citer' in my previous post, you can find the plug description in the picture's name.

Citation :

BTW Frits I tested your head design scaled up to match my 65 mm bore and gained 1.5 HP all the way up from 6000 to 10600 rpm. The gain is comparing my 17-1 compresssion ratio head to the new one at 16-1

IW31 I presume?
Have you ever tried Brisk Plugs?

Howard Gifford a écrit:

IW31 I presume?
Have you ever tried Brisk Plugs?

Hi Howard and Jan and Frits

That looks quite a special plug to me (in particular the attachment of the heavy ground/earth strap). The image code dosen't give a clue to it's actual part number, just the manufacturer and heat range i.e. Denso 10.

We have also tried the Iridium NGK Iridium Resistor BR10EIX but found that the ground strap would detach due to vibration and detonation, causing fairly major piston/insert/cylinder damage. They are a very cheap sparkplug and not really a race plug.

We normally use the NGK Iridium Resistor R7372-10, which is a race plug and has a fine wire ground strap and slightly recessed electrode or the R7282A-10 when using a Honda RS Det sensor.

I wonder if either Jan or Frits may have any obsrvations regarding the different plug designs?

Also it was mentioned about better cooling aound the sparkplug decreasing detonation. Would using a cooler plug, say 10.5 of 11 also reduce detonation and again what might be the effect on power and running characteristics?

Frits, in which orientation do you index the sparkplug?

Best Regards

Ian

Hello
I am not sure were to introduce myself. I am a 2 stroke enthusiast also and to see the simple but great responses is awesome. To the point answers from the best people that have worked on these engines.
This thread is great. Thank you.

I have been working on 2 strokes like most on here for a long time. I am right behind you Howard
I just spun one of these heads up about 20 minutes ago. I have tried a shape like this before but with out the radius top. It was a little lower and more squared off on the top with about the same compression ratio. I cant wait to try this one.

I would like to know if Frits or Jan have used negative squish band angles before and if they
offer any benefit and if you ever tried dished pistons?

Thank you again.

Negativ squish band = boom :)

SEB4LO a écrit:

Negativ squish band = boom :)

Yes, I agree!
And dished pistons were never tried, there is no logic in them.
They would detach the all-important cooling flow from the piston.

Ian Harrison a écrit:

That looks quite a special plug to me (in particular the attachment of the heavy ground/earth strap). The image code dosen't give a clue to it's actual part number, just the manufacturer and heat range i.e. Denso 10.

Yes, I'm with Howard, looks like a Denso IW-31

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Howard Gifford a écrit:

Have you ever tried Brisk Plugs?

We have been collecting a lot of experience with them over the last couple of weeks. They perform surprisingly well.
What is your experience with them, Howard?

Ian Harrison a écrit:

The image code dosen't give a clue to it's actual part number, just the manufacturer and heat range i.e. Denso 10.

Sorry about that, Ian. Only now did I notice that the name of the image used in the forum is not the same as the name when I post it. The plug was a Denso IW01-34.

Citation :

Frits, in which orientation do you index the sparkplug?

I mount it so the volume between the points is scavenged as well as possible. With most plugs that means a mass electrode orientated left - right. With plugs where the mass electrode lies beside the centre electrode, I let the mass electrode point towards the rear.
Maybe the surprisingly good results with Brisk plugs are something to do with their mass electrode .

Hi Frits, Howard and GrahamB

Thank you for the information once again.

That gives me some more things to try. From looking at the equivalents table the Denso IW01-34 is equivalent to an 11 grade NGK and the IW01-31 is equivalent to a 10 grade NGK.

Is the Brisk plug you speak of a DOR08IR Iridium Racing Plug? Looks economical at $14.99 USD.

Best Regards

Ian

Our experience is very limited with Brisk plugs. We purchased 6 to test . They have not shown any power difference on the dyno but have performed flawlessly so far. A bit more expensive than the NGK standard iridium but cheaper than the Racing Denso and NGK iridium. The one thing I like about the Brisk plug is that the mass electrode is not a weld on piece but is actually part of the shell body. [Vous devez être inscrit et connecté pour voir ce lien]
Their heat range selection is reverse to NGK with the Brisk 8 = NGK10, Brisk 10 = NGK 9

There are the champions plugs too, G54V , QA55V with different indices 10 to 12 !! without proeminent mass electrode , silver central positive core, also used in marine motors I think.

Have someone tried those?

We have tested the Brisk ZS (after a recommendation from Michael Burghard) and it worked really better.
Just changing the sparkplug (blue=Brisk, red=Isolator)
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But I corrected the ignition point (later), the hp is now nearly the same but the power band got much wider (no diagramm on pc).
Tested it on the track and it worked very well.

It's depending on the ignition if the Brisk does a better job then NGK and co.

Howard Gifford a écrit:

IoTS you seem to be a bit of a sarcastic sob but I will ignore that for now. Obviously you seem to have had success with thin wall pipes so good for you! Your pipes seem to be imune from vibration fatigue but I have been around long enought to see a pipe failure or two as well. Thin pipes (under .035") tend to have shorter life spans. Most of the failures I have seen were due to vibration. Cracks appear within inches of the cylinder or where the tail pipe welds on. Also the weld-on fittings for temperature sensors seem to be a source for cracks to develop on thin wall pipes. Going to .040 or thicker reduces the likelyhood of pipe failures. if you argue that fact then I cant help you..

Thanks for the compliments Howard.My pipes don't crack so I'm not really need of any help at this stage, but thanks for the offer anyway. I actualy can't take any credit for that it's all down to JOHN BRADLEY who showed me all the tips

With Denso 01 means platnium/iridium construction 27/ NGK 9 is as hot as they go. Used a 29 or 9.5NGK for many years Denso seem to last indefinantly, the R series NGK platnium/iridiums make more HP but 'drop off' a bit after a while in use(dunno why though). The platnium ground electrode plugs are most definantly superior to normal iridium, Denso call it 'Flying Fire Voltage' think that means less voltage to fire the plug and less misfires. Excellent resistence to fouling, they don't take a bit to 'clear' out of the gate/ off the line.

hello, Mr Frits, are you still alive? i bought a riwa 50 in your country, made by aalt toersen and i would like to know a way to contact him, because i have a lot of questions to ask about my moto. thank you and have a good day

Hello Ronath,
If someone were to reveal my email address or phone number on an open forum, I would certainly not be very happy. And I assume Aalt will feel the same about this.
But the Riwa Kreidlers were built by Rieks van der Wal; Aalt was only working there. You can reach Rieks here: [Vous devez être inscrit et connecté pour voir ce lien]

Thank you very much for your answer. The riwa i bought has been prepared by aalt. I bought it at brummen's and i go next saturday to pick it up in this town. The moto is selling with a picture of aalt and some words written by him to make sure he has worked on. I can give you my mail but i don't know how to do not to be on the forum for the same reasons you gave me. I must leave my house for 3 or 4 hours so if you answer me, i won't be there until 8. Have a good day

fpayart a écrit:

The sizes are 39.5 width x 27.5 height (without the radius).
Now I can imagine your next request
The opening time is 196 ° measured without taking into account the radius.

Edit by Damien (Francis's son...), Maybe you were talking about this dimensions ? :

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HI, are you able to send me that Cad file? It would also be nice to have some info on the engine it goes on.

Regards //Dennis

This question is for Frits and Jan. The RSA engine looks to have a superior porting design and layout as cast but as with most engines there is the insatiable need to get in with a grinder to clean things up and do any port matching. My question is,,,how many hours were spent "race prepping" a cylinder before it was deemed raceable? Also was there one cylinder that stood out as superior to all the others and was impossible to duplicate the power output on the dyno? Who was the main man with the grinder?

I guess that the quality of the casting reached a level that allowed the barrels to be 'ready to race ' right after nickasyl process ..... And a dyno session


Blommen : Usualy on forums when you enter you do a first post to introduce yourself ......

Blommen a écrit:

HI, are you able to send me that Cad file?

Hey Dennis, I think you just proved that the Swedish have a great sense of humour .

Kom igen Blommen !

"Presentation" topic

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Tak !

This question is for Frits or Jan.

I remember Jan said the lower part of the C port is almost always lower than the B and A
ports in most engines. I always thought this was done to stop ring snag on the way down.
I have a hard time making out Aprillas bottom of C port. Did you v the bottom of C port to
put ring back in groove?

Interesting question.

Jan said "It also proved to be VERY important that the lower side of the transfer ports was not lower than
the piston in BDC. Also the C-port!" some months ago. Seems logical.

But right now I am also wondering why I see the lower side of the C-port clearly under BDC on the rsa-drawings.

Regards