Holding high idle, then settles down - 2 Stroke

[TeamNeilson]

Hey All.

I've been trying to tune my 5 year old son's Eton 70 and i'm not sure what to look at.

I have the stock CDI limiter on it (because i only want him to go as fast as I feel comfortable), but an aftermarket carb (21mm oko) and a Hetrick Pipe (he wants to sound like his brother).

I've got what i feel is a nice tune, it revs up nice but when you let off the throttle it seems to idle high for about 20 seconds, then settles right down to a low idle and almost stalls.

I've tried the pilot screw (2 turns) and have moved the pilot jet to a .42 to get it within the 2 turn limit. I've checked for air leaks with my propane bottle as well as with a can of non-explosive spray (air leaks cause the engine to stall with this stuff) and the engine doesn't change at all during the tests. Compression is good (~130psi) and it always starts first kick and runs great up to the rev limiter.


I'm looking for some things to check, there is a wealth of knowledge here and rather than bang my head against a wall all night, i'd hoped to hear from some of the experts.. I'm lost :)


I also have a clutching question, which i'll post separately.

[TeamNeilson]

Update:

I still don't know the cause, but now with a new plug and a clean carb the symptoms are still the same, except when it got really warm out the bike won't idle and it gets really, really boggy (and smoky) until the bike can get past a quarter throttle.

If there is a hill or sand, the engine can't get up to clear itself out and spin out the clutch (i'm fairly certain I have clutching wrong too now) thus bogs out and gets stuck.

How would I check to see if the pilot is too big or small? I've all but eliminated air leaks as nothing changes when I spray down the motor as it runs.

any help would be appreciated

[hotquads1]

The OKO 21mm was a tuning nightmare , may want to try a little stock 16mm , makes alot better runner for you little driver .

[bulldogfallon]

OKO= Oh No!!


Get rid of that thing--Marc is right....I won't work on a quad with one...some others have had luck, but not worth time IMO

PWK 21 will work with the same cable and intake boot and be a lot more stable.

[TeamNeilson]

Ya. I've noticed the OKO being such an incredible pain and when this motor is in a 'real' race bike its going to get a full work over including carb.


I do think I've discovered the issue.. and none of you mechanics are going to be happy with me about it haha...

(remember the motor is an old air cooled one, so it has the black shroud over the head making some things obscured)

My wife and I were working on it 2 nights back when I noticed the head and base gasket were soaking wet all the way around. I attributed this previously to the air leak test spray but wasn't drying... I took off the shroud and went to take all the head bolts off and they were all finger tight!!! *sigh... I pulled off the head, sent it out to ensure its was level, thank god it was, reassembled it last night. low and behold, it actually idles smooth now. Revs up and settles down and actually responds to air screw changes.

I haven't gotten it right hot yet where it was acting badly before, but I think this could be the 'air leak' I was chasing.. I was focusing too hard on the cases and the intake and totally ignored the possibility of it being a head/base leak..


My youngest has been threatening to 'fire his mechanic'.. Maybe he's right. haha.


Thank you guys so VERY much