Jetting Delima.

[LONG-ROD]

k I have a 250r cylinder with the 310 sleeve, bored for 67.5mm piston 39 pwk pyrmid reeds and a 19cc dome running 927 oil with VP 110 I have 172 main jett but seems a little rich everyone else seems to be running smaller main jetts, but my engin builder says I need to be at 188 on the main it wount run for crap with that jett I am in Kansas City very high hummity low 90's I run a foam filter no lid, anyone have any idea of about whare I should be on the main to keep it on the safe side and not to hot.

[2muchquad]

Try going richer until it wont clean out up top then back off a size or 2.Imo its the needle position thats more important,thats where most people ride at most of the time 3/8 to 3/4 throttle.You dont want to be lean there.Some people like it real crisp up top and want every last bit of performance and some people will be more conservative and would rather save the motor and run a tad rich.;)

[Aceman]

Originally posted by LONG-ROD
k I have a 250r cylinder with the 310 sleeve, bored for 67.5mm piston

:huh Your engine is around 257cc's but you have a 310 sleeve??

If it's running a little fat up top drop the main a size or two. Plug chops! And I think your engine builder might be a little fuzzy with his jet sizes....:ermm:

[86 Quad R]

as stated. do a WOT plug chop and see what color it is. if black then back off a size at a time until ya get a honey color. then adjust the needle. afterwards, plug chop the main jet again.

ace. ya can get the bigbore sleeves installed in the stock cylinder that starts at OEM bore.

[LONG-ROD]

It feels great in the middle just a tad flat on top I think I am going to leeve it I want this motor to last a little while. It just drinks the fuel so even if I lean it a little I don't think it will make much a diffrence in fuel economy.

[Aceman]

Originally posted by 86 Quad R
ace. ya can get the bigbore sleeves installed in the stock cylinder that starts at OEM bore.

That's cool!


Originally posted by LONG-ROD
It feels great in the middle just a tad flat on top I think I am going to leeve it I want this motor to last a little while. It just drinks the fuel so even if I lean it a little I don't think it will make much a diffrence in fuel economy.

You are the only person I know who even considers fuel economy when jetting a quad. Look at the plugs, don't be scared to go down a size or two on the main if you think it needs it. You are not going to lean sieze the engine dropping one size to make a jetting pass. But if you can live with a flat top end.......then so can I.;)

[peeping TOM]

w-o-t = wide open throttle.. just in case u didn,t know .... thats how u find out what main jet u need in,,, its impossible for anyone to really to tell u what jet u want in,,,, u need to do a plug chop....

[LONG-ROD]

I have done many and they are kinda black but loren Duncan is telling me it must be somthing else like electrical and that is why I am have to lean out my main.