87 250R gremlin

[Ononewheel]

Whats up guys? Long time no see, it looks like I have not posted in about 4 years!

I am helping a buddy troubleshoot his 250R this week. He fouls plugs pretty often, usually one per ride. Here is what I know.



On the carb: The jetting seems to be close all the way across the throttle range, no surging, sputtering, bogging or anything. It has never missed a beat and runs like a raped ape.

Fresh piston, rings and bore: made no difference.

Electrical: I think the gremlin hides here. He reduced the gap on the plug and it seemed to help it not foul them, but then started again. Thats what makes us think it is here.We have been trouble shooting with the clymer manual and almost everything checks out but...

The secondary coil test, I think it should be 7.4k to 11k ohms, and it is 3k ohms.

The kick test, it seems to spark weak but it is blue. Not fat, just blue.

The stator, pulse generator and everything else is within specifications, but there is no real way to test the cdi box.

Do you all have any ideas?

[Ononewheel]

No one?

[ZSNOW]

try a hotter plug or try a different oil, belive me makes a big difference lol

[wilkin250r]

When you check the secondary of the coil, how are you checking it? Try taking the plug cap off, and check the resistance directly at the wire.

I haven't seen too many CDIs give a "weak spark". I've seen some give intermittent spark, off and on, but not weak.

How do you know the jetting is good? Just because it runs good? My R used to run great, and idled for a total 5 minutes on a new plug, then wouldn't idle at all until I put a new plug in. Turned out to be a jetting issue.

Fouling plugs is most often a jetting issue. What color is the plug after it has been idling for a few minutes?

A hotter plug might help, or an Iridium plug.

[86 Quad R]

has a plug chop been done on the engine? as stated just because it runs ok doesnt mean its jetted right. i'd do a WOT plug chop and get the main dialed in and then focuss on the pilot circuit.

9 x's outta 10 the low speed jet is the culprit of plug fouling.

[Ononewheel]

I just back here to see your replies. We did put a cdi on it and that helped the spark tremendously.


As mentioned this is my buddies quad I am just trying to help him out. It seems it has an idling issue. He has been able to mask it by turning up the idle adjuster, which is part of the choke knob. You have to turn it waaaay up.

So today I put in a smaller pilot or slow jet. It had a 48, I put in a 45. There was a definite improvement. I noticed the filter looked pretty dry so we oiled it, and are now back where we started.

So I need to figure out how to lean out the idle mixture a little more.

Any thoughts or ideas?

[86 Quad R]

run it for a spell after oiling the filter to rid it of accessive oil then start the trouble shooting process again. it is important that the float needle be in working order and that the float is set to spec.

since the 45 pilot seemed to help things out. i'd try and adjust the pilot screw and see what that does.

if the pilot gets too lean it will develope a flat spot upon blipping the throttle.

ideally you want the smoothest/highest possible idle with the pilot between 1/2 to 1 1/2 turns out.