Can't get it to idle....

[two85atc250r's]

Well my new engine runs great I just can't get it to idle. I am running a 36mm PJ with a 160/48 jets and the idle adjustment seems to do nothing at all. Is the slow jet maybe too rich? Will that affect idling? I have a twist throttle so to tell the truth it doesn't really bother me that it won't idle because I just keep the throttle cracked back just a little and I don't notice. The air screw doesn't seem to do anything either. Any suggestions on what I might can do or am I just gonna have to live with it? Other than this one little thing I have no complaints at all. No dead spots in the power band, the thing seems to pull like crazy all the way to the top of 6th gear. Are the PJ's just notorious for not idling well? Appreciate any input, thanks guys.

[wilkin250r]

There isn't much happening at idle. I've never taken voltage measurements, but I think your spark is rather weak, your dynamic compression isn't very high, heat isn't high. Let's face it, at idle, you're barely running at all. It doesn't take much to push it over the edge and kill it.

A lot of times if you're too rich, the quad will idle for a minute with a fresh, new plug, but then fouls just enough to kill the idle (but it still runs at higher RPMs). Try a new plug, see it if idles for a little while.

Otherwise, we'll do a plug reading just like other jetting issues. With the quad warmed up, put a new plug in (don't burn yourself) and fire it up. You won't need to be moving for this one, you don't need to be under load. Using your throttle, get as low RPM as you can, basically as close to idle as you can get and still stay running for 10 seconds. Then, slowly let the RPMs drop untill it dies, and pull the plug, and see what the plug tells you.

Since you're not generating enough heat to really burn off deposits, it should be pretty dark, but it shouldn't be jet black, and it should never be wet. It should be a dark gray. If it's black or wet, you're too rich, drop your pilot jet size.

[TheNewn]

Not to 'steal' the topic, but is a 48 pilot'smaller' than a 45 pilot?

Is it the same as the main jet, bigger number, bigger jet? Or is it like leak jets in 4 strokes, small number, bigger jet?

Or am i way off?

[two85atc250r's]

No its the same as the main jet, bigger number, bigger jet.
I'll do some plug chops at idle and see what the plug tells me.
thanks Wilkin.

[Aceman]

Here's a good tuning guide that may help you:

http://www.duncanracing.com/techfaq/Tech_keihin-carburetion-jetting.phtml

[86 Quad R]

a 48 does seem a bit rich to me. are you for certain that the float level is set right and that the float needle is completely shutting off fuel? i've seen a seeping float needle and/or improper setting of the float cause similar issues. especially on the pj carb.

[wilkin250r]

Originally posted by 86 Quad R
a 48 does seem a bit rich to me. are you for certain that the float level is set right and that the float needle is completely shutting off fuel? i've seen a seeping float needle and/or improper setting of the float cause similar issues. especially on the pj carb.

True, but if his float valve wasn't seating properly, he would also see evidence of this by way of fuel flowing from the overflow tube.

[my88r]

i run a duncan with flow work 36 pj

my jetting is

DGK needle 3rd clip
main is a 160
pilot is a 55

this is what duncan told me to run.

[two85atc250r's]

Well I went and rode it some more today and noticed that I do have fuel coming out of the overflow tube. Does this mean that my float valve isn't seating? What can I do about this? I didn't think to look until now, it's probably been doing it the whole time. Any suggestions? Thanks.

[86 Quad R]

its normal for some fuel to come from the overflow while riding. is it coming from there while sitting and engine off?

fyi: a little trick i use to address a seeping float needle is to make a tight lil ball with either scotch brite or fine steel wool and stuff it into the needles place followed by a long screw bit and polish up the seat.then blow out the passages with compressed air.

[wilkin250r]

Hmm. I don't know about polishing up the seat. I've never seen any get damaged, and I've never seen any get corroded unless the carb has been sitting for several years. But you get one goofy slip and nick or damage that seat, and you need a whole new carb.

New float valves aren't that expensive. I'd fix this issue before I went on a wild goose chase for idle problems.

[86 Quad R]

have ya seen what today's gas can do when allowed to set for more than a week inside of a carb? especially with pre-mix added. :eek2: