baffled by motor gremlins

[travmess]

Hey guys hope u can help out this motor has stumped just about everybody. Its on my brothers xb its a 2 bolt 28.5 non ported with a stuffed crank. The issue is it runs waay rich puking out alot of smoke from exhaust and fouling plugs and sputtering on the top end. I have tuned and retuned this thing as well as two or three others have also changed the air filter, carb coil and plug. Wat the hell else could it be? I kno his rear mount pipe from jetpro is tweaked a but that shouldnt make any difference. I squeezed the needles down from 1 1/2 & 1 1/4 to just a hair over 1 on the high side and about 7/8 on low needle with no imporvement only thing that changed was the plug color which went from dark and wet to grey and dry but still sputtered and smoked on top end.

 

[cordy]

Try venting the tank,make shure your clunk is clear. Also make shure your diaphram filter is clear its a little hole on your carb right behind the air filter. Most guys don't even know it exsists. DDM has a filter for it part #av493.Hope this helps.

 

[travmess]

Has a snappy fuel line kit with a kraken check valve so thats not it and has an almost new clunk on it and the second carb i put on it can straight off my xsc race truck that runs well so no dirt in the carb its clean inside and out same with the other carb cuz i thought it had crap in it too but was clean thanks for the ideas tho

 

[BertR]

have you tried different fuel mix? sounds to me like there is too much oil in the fuel

 

[travmess]

Wouod that make it sputter on top end? Thats one thing i hadnt thought of

 

[Deluge]

It would probably sputter on both the low and the high end. The fuel mixture would have to be quite a way off, because there are guys that run 16:1 with no issues.

 

[travmess]

hmm ok well ill try that tomorow if i get time but im 90% sure he mixed his gas right. this thing has really got be rackin my brain. im willin to try just about anything. the motor prolly only has 6 or 7 tanks on it too. pulled the top end piston and cylinder looked alright minor scoring from the cheesy 'high flow' air filter that the redcats come with but the scoring is very minor ive seen alot worse run ten times better than this thing. not a speck of carbon buildup on piston or head. the one thing i did notice was the ring seemed really loose on the piston to me but it squeezed down like it should when i slid the head back on so idk.

 

[andyken]

I got my XB used, the stock carb had to be very lean. I guess the rev owner over tightened the needles?

I was 3/4-7/8 on low and like 1 1/18 high.

But you said you tried a know good carb?

A restriction of air flow would do that...clogged air filter, under size hole in a gasket?

 

[travmess]

Yea i kno the carb i put on was gd cuz it came off my race truck that i ran last weekend its a 668 same as wat he had on it before no junk hy stuff here lol used brand new gaskets when changed carb. Air filter came off the same truxk and is clean as well. I kno it seems like its not gettin enough air but everything ive changed should have taken care of that. Ive racked my brain on this so much i get a headache just lookin at this car

 

[BertR]

I was wondering if a warped intake manifold would cause the problem? The only time Ihad a issue with mine sputering on the top end was the clunk was clogged up and starving it of fuel.I know you said its new clunk but man. Take the clunk off and rase the delivery line off the bottom of the tank and see what it does.you tried 2 carbs and the same thing happens so its got to be before the carb.

 

[travmess]

I will try it but if it was starving for fuel why would it smoke like it does and flood? Just seems very odd to me how this thing is acting

 

[travmess]

Could it mb be a case of the wrong plug? don't zen motors take a different length plug then cys? All i run r cy f270s so all i have r ngk cmr7h but theres also a cmr7a with a lil longer reach i beleive the head does not say chung yang o it so im assuning is a zen?

 

[BertR]

Yeah I hear what your saying..Spray water on it and feed it after midnight and see if them gremlins pop out lol. If it is not the filter I am just as stumped as you.

 

[travmess]

Lol im about ready to man this thing is cursed or somethin. The guy that owns our local large scale hobby shop gave him this motor for free came out of his nutech i beleive but it was just barely broken i when he got it. Never heard it run before my brother got it tho

 

[travmess]

Its a very remote possiblility but could it be his kill switch acting weird? Hes got a v2 killer bee. Idk man just a shot in the dark

 

[Deluge]

Could it mb be a case of the wrong plug? don't zen motors take a different length plug then cys? All i run r cy f270s so all i have r ngk cmr7h but theres also a cmr7a with a lil longer reach i beleive the head does not say chung yang o it so im assuning is a zen?

It would say Zenoah on it if it were a Zen head. The CMR7H is pretty much the standard for CY's and Zen's, so that shouldn't be a problem.

 

[Deluge]

It's possible the kill switch could be causing the issue. I've heard of bad units or loose connections causing misfires. Disconnect it and see what happens.

I'm curious about the damage to the pipe. Any large dents or bends can cause performance issues.

 

[travmess]

Ill try unhooking the kill switch and see he got the killer bee used so theres no tellin. And the pipe damage its major and no big dents i straightened it back out some but still not perfect. He bent it landing tail first straight up and down and plugged the pipe with dirt its all cleared out now tho. I can take a pic or two in a bit if u still think it could be the pipe

 

[andyken]

I suppose a kinked exhaust could do it...

 

[travmess]

Mb if it was severe but u can hardly notice it now.