KTy

Temperature is part of the K constante. Thus, higher K means higher temperature (if other variables are stable). RED -> 24°C GREEN -> 80°C KTy -

What is the optimal shape of the crank with the gaz mixture flow coming right in its middle (like my engine or iloeisenberg's one) ? Smooth, round and symetrical ? Sharp and toward between the cheeks ? :plemplem:

Two simple questions * Is it a "time bomb" to rebore a cylinder to its last oversize ? My Polini 133 was rebored a year ago to 57.8mm, I have to rebore it to 58mm to fit a GS piston... Worthless ? * What is a safe clearance (tolerance ?) for a GS piston in a Polini 133 ? 7/100 ? Or a little more ? Thanks KTy -

@Gerhard: Your ETS crank is an original one ? Recut ? Picture ? No problem to put it on primavera (VMA2T) cases ? Does anyone want to comment on Jannek's crank ? Could this be the best option for huge case induction ? Having a look at engine like NSR 125 and TZR 125, the crank is full-circle (with counterweight) not really "flow favorable", maybe the cheeks are quite thin... So is it really worthless to do like Jannek ? Another thought: Due to my engine induction design, I have quite a lot of "dead space/room" in my bottom-end engine, especially just after the reed valve. Besides that, the displacement is only 133cc, so I'm actually thinking that any kind of crank (maybe smoothed a little) will do the trick perfectly (that is, make it easy for the mixture to flow inside the bottom-end of the engine). Thinking too much ? :grins: :puke: KTy - :wasntme:

That's what I am a bit affraid of... balancing... Moreover, on a full circle one that is suppose to be best dynamically balanced, I think it could be easy to do something wrong... Right or not ? :heul: :plemplem: Thanks again

The difference between a 19/20mm and a 20/20mm is only the bearing size of the flywheel side ? I can still use my ET3 ignition on a 20/20mm crank ? :wasntme:

53.5mm crank ?? What is that from ? So according to you, a full circle mazzu crank with a little bit of work to smooth it and make it "flow favorable" could let enough room for the mixture to flow inside the case... That's a major concern... Thus interesting... Btw, if I change for an ETS crank, what are my options for the ignition ? There is HP4 flywheel for small cones crank compatible with an ET3 stator ? Thanks Gerhard, you're so kind to me :love: KTy -

Alloha everybody ;) So, after about 500km and lots of stress, I finally broke a ring on my engine... At the same time, I don't know if it's related, but I can see that my crankshaft flywheel cone doesn't spin perfectly centered. Thus, I have to change crankshaft and piston. As for the piston, I'll probably go for a GS one in 58mm (My Polini cylinder/piston were previously rebored to 57.8mm). As for the crankshaft, I'm not sure what is the best solution... Should I go for: * A standard "racing" mazuchelli ? * A flow favorable one (Worb5 or home-made) ? * The thin cheeks full-circle fabrizi one ? Engine is: Polini 133, ~185°/~130°, zirri silent, vForce3, KOSO 32,... http://ktylife.free.fr/vespa/KTy133/CartersFrais%e9s1.jpg ... Engine already hit 10000+rpm, so balancing is important. I'm concerned that maybe a worb5 or a home-made crankshaft will be more badly dynamicaly balanced compared to a standard mazuchelli... But I may be mistaken Last question: I need a small cone crankshaft because I have an ET3 ignition unit (flywheel was lightened to 1.4kg with HP4 fans)... Is it much better to have a large cone crankshaft in terms of reliability or ... ? Thanks for your advices, KTy -

Question: I have widely and wildly open the 3rd transfer on my engine cases... Do I have to open also a window in the GS piston or it is not necessary ? http://ktylife.free.fr/vespa/KTy133/Segmen...e9/DSCN2166.JPG http://ktylife.free.fr/vespa/KTy133/CartersFrais%e9s1.jpg (work done after this picture was made) I'm asking this because on a NSR 125 piston that I have there is *no* window in the piston... Cheers, KTy -

I'll do that later for you ;) The carb fit inside because it is mounted directly on a RD350/Banshee manifold :D. Without rubber, it's not very "clean" yet (I did it without welding anything), but it makes the scooter ridable in the street at low rpm.

When I want NO sound, I plug this instead of the air filter (it filters the air, not sounds ) KTy -

Get an air filter ! I just bought a Ramair 55mm, fit perfectly my needs ;)

Impressive :) What is the rest of the setup ? (exhaust, carb, work on the engine ...?)

Not so surprisingly, but after 500km and tons of massive accelerations, a ring of my Polini piston also broke yesterday ! What a coincidence ! From what I had recorded (GSF dyno), engine was probably around 20hp @ 8500rpm, peak rpm around 10000rpm... Anyway, the top edge of the piston is in bad shape, the cylinder is fine excepted that the bottom of the exhaust port as been damaged a little bit (1mm). Well, actually, I am intented to think that it was because of my exhaust port transfer too thin... But I may be be wrong, maybe it's the ring that first broke and then damage the port... Or again, probably both Time for a last oversize piston, this will be a 58mm GS ! Oli, here I come ;) Maybe picture later in another thread... KTy

Thanks

By the way, do you use it also for your cylinder gasket ? Because I've been adviced to use Loctite 518 (from a kart engine builder)...

Sorry to invide this thread , but can you tell me if Locite 518 can be put like a sealing gasket between my Polini 133 and my zirri silent exhaust ? Loctite says it can handle 150°C, so maybe it's not enough... :P http://68.72.74.113/PRODUCTS/518.htm

Do you think it can handle the temperature of my Polini with zirri silent ? Loctite 518 is a "red" anaerobic sealer, up to 150°C... Thanks !

I have this little annoying problem... When I drive in 3rd or in 4th gear, if I open full throtle, then it as a tendency to slip repectively in 2nd and 3rd gear... It never happens in 1st and 2nd gear, sometimes in 3rd gear, and quite often in 4th gear. The solution to prevent it is to handle firmly the handle-bar gear selector... All the component have been independently checked (1st, 2nd and gear selector) and have less than 500km (for the 3rd and zirri 4th)... When I rebuilt it, I'm affraid I could have let too much play... Any advice ? CHeers, KTy

I'm running a KOSO 32 on a Polini 133 with vForce reedvalve and zirri silent. I think I have found a "working" setup (132 main, 55 slow, clip to the top), but I am not happy with the air/mixture screw... I'm used to Dellorto and on the KOSO, when I screw the air/mixture screw, it doesn't have a "clear" effect on engine reaction... Is it supposed to work like on a Dellorto carb ?

MiniStrobe is simple, but it does the trick, so I use it from time to time on real engine... Actually, it's quite similar to what it is used on the "equilibreur" (balancing tool), but actually I didn't try ministrobe on equilibreur Yep, my vCDI use a 16F88, *very* nice litle PIC, one of the cheapest, one of the most complete for general purpose ! The vCDI works perfectly on my desk with a frequency generator and a scope When used on my PX125 engine, with the actual board I have made (because it's a mess !) I had some electromagnetic trouble that reset the PIC. So before I can release anything, I have to properly route a new board and put it in a metal box to protect it and see that it *really* works as well as on my desk prototype ! It will be also plug'n play, you don't have to change anything on your engine, you just have to configure some datas (initial fixed timing advance and variable curves) through a terminal on your computer... Well, unfortunatly I always have other stuff that takes my free time, but I should manage to have it done for this september... I hope so :wasntme: For example, I never really finish to improve the balancing tool... That's too bad... :grr: I'll follow you guy's progress, it's very interesting ;)

I used a PIC 16F88, 4MHz, ASM only Some data to share with you Recorded beetween red and white on a standard PX125E "Lusso" engine... http://ktylife.free.fr/vespa/AvanceVariable/ Cheers, KTy

Okay that's interesting... I guess I need a dyno diagram to see if it worth to keep or not the actual 2.34 primary...

I'm asking the question because my idle jet is 55 and it seems it's again too small... The method I use is; The engine is idling around 1500rpm, I open full throttle, and I see if it revs easily. I turn the mixture-screw until the engine has a "fast" reaction. I'm already with a 55 idle jet and the air-screw has less than one turn (and it's not satisfaying)... Should I consider that there is a problem or is it normal given the spec of my engine ? A 60 idle jet could be "normal" ? Specs : http://ktylife.free.fr/vespa/KTy133/CartersFrais%e9s1.jpg and http://ktylife.free.fr/vespa/KTy133/ Thanks !

I take the opportunity of this thread to ask a question I'm still undecided whereas I should open my engine to change the 2.34 primary for a 2.55. The good thing about the 2.34 is that it is less stressfull for the primary elastic thing and for the gearbox, even if the scooter is maybe less agressive... BUT My experience with the 2.34 (while I was jetting doing massive acceleration) is that the scooter start to lift the front wheel "by itself" in 2nd gear :sabber: , so I was thinking that maybe the 2.34 is fun enough... Actually I'm affraid of what could happen with the 2.55 and I'm also concerned about "reliability" (even if of course, this engine will brake one day :D) My question is: According to you, does a 2.55 primary make sense on a ~17+Hp engine smallframe ? P.S: Yes, I have a zirri short 4th