Running hot, maybe too hot? Jetting suggestions welcome

[Chicago Ben]

Hey guys - if you have followed my other threads you know whats going on but if not I finally got my moped running with a new Keihin Carb (PWK 28mm)

My setup is - 52mm Ruima BBK, PG Typhoon (V8) pipe, Pop Pully, Keli Clutch, 28mm Keihin PWK, port matched by Traffic, 1000 rpm center, polini triple springs and 8.4:1 gear set. I have an uni foam air filter.

I'm currently running a 55 pilot jet with a 125 main jet.

I took it out last night and it really hesitates to get going - I spiked at 370 F last night and I had to ease it home... I'm scared it might have been too hot - I will be doing a compression test later.

Does anybody think these jets are THAT far off from where I need to be? My A/F screw is about 1 full 360 out.

[Chicago Ben]

oh and when Traffic built my engine it was right at 130 PSI on the bench - with the help of a few base gaskets

[Mystic]

Definately up the main since you have more air being pulled through the larger carb you have to equalize with more fuel. I would venture to say 140ish then drop down if it is rich and then play with the needle position to get the midrange temps close to where you wont it. it is rather difficult to get it perfect

[Chicago Ben]

Thanks - that's what Traffic was saying on the main jet - I'm getting mixed advice on safe temp ranges on this board - some say " I run mine at 425 all day" others say 350 is literally the danger zone. I know these cast Ruima bores aren't bullet proof - is there a temp I should be really shooting for here?

[evilone]

I'm with mystic. I was thinking 138 main. As long as you're under 400 degrees you should be good

[Chicago Ben]

I'm with mystic. I was thinking 138 main. As long as you're under 400 degrees you should be good

evil, wanna take a trip to chicago and buy this thing off me? haha - I'll cut ya a sick deal

[Mystic]

Heck you just got you problem smoothed out now you gotta go back and change all the stuff back that you fooled with trying to get the bump problem solved. Try the larger main like 145 and see what it does 3/4th to full its always a good idea to start rich then go down once you get the main sorted then you can fine tune the midrange

[Trafficjamz]

your main needs to in the 140 range

your temps need to stay under 400 at WOT

Spikes of over 400 after letting off WOT are normal

Heat spikes of over 425 After letting off WOT need a bigger pilot jet

[Bear45-70]

He has no clue what he is doing and has learned nothing thru this whole process. He is better off selling it.

[evilone]

evil, wanna take a trip to chicago and buy this thing off me? haha - I'll cut ya a sick deal

I'd like too but i'm already too busy to tune mine.

[Chicago Ben]

Pulled the engine tonight after getting a 90 psi compression reading. The studs were loose...

The cylinder walls look fine, head appears ok, piston had just a bunch of carbon buildup

I have cleaned everything up and reinstalled the top end, going to do a bench compression test next. (Anybody care to share their method for cranking over on a bench?) If compression is good will reinstall, if bad going to try to cut new base gaskets.

If all goes well, going with suggested jetting. looking for 135-140 main, most likely 60 pilot.

If I cannot get the compression right , may be looking for a new bore...

[Chicago Ben]

Spikes of over 400 after letting off WOT are normal

Heat spikes of over 425 After letting off WOT need a bigger pilot jet

Are you running ruima bores that hot?

[Chicago Ben]

Carbon buildup or destroyed, you tell me?

[Mystic]

looks good to me

[swimmingfree]

i see red gooo on the intake manifold ..if you have to gooo you may not have a good seal ..
swimmingfree