Anybody ever heard of this one? (350X)

[SmokinX]

Just started getting a knocking/banging noise from my 350X ONLY at WOT. The first 9/10ths of throttle range is flawless. It only happens during the last 1/10. I was wondering if I could have bad gas and its predetonating. I always run premium pump gas and never had a problem before. When I bought it 3 yrs. ago the previous owner told be that he thought it was rebuilt so I have no idea what compression I'm running and was wondering if I do have a 11 or 12:1 that it would cause it to predetonate. I know anything over 11 your supposed to run race gas. What does predetonation sound like and when does it occur (rpm level)? ------A friend of a friend who knows quite abit about ATV's suggested (without actully hearing problem) that maybe either the rod or wrist pin bearing wore just enough to cause a little play at high rpm's that on the upstroke, the piston might be hitting on the head. Is this possible? Is there that little clearance at TDC that a few thousanths would cause it to hit the head? I know the first thing I have to do is drain/replace gas. Can anybody speak from experience of this problem? Looking for input before I start. The thing runs and starts excellent (hot/cold). Valves are adjusted properly as with the decompression cable. What does a worn cam chain sound like? I'm sure the decompression cable is adjusted and working properly but how much does it open exhaust valve and could piston be hitting valve if cable somehow holding it open at high rpm's? Would think this would happen seeing that decomp cable is only activated by kicker. Could I possible be getting valve float at WOT from weak springs? Sorry for the long post but I guess I'm trying to get to a solution by eliminating as many possible senarios from your guys experiences. Thanks.

[Tyler]

Detonation will cause a loss of power and will knock at levels of rpm. It's harder to hear at WOT. Valve float will cause a loss of power as well. Has this just started? It could be a rod knock, but you would hear it sooner. Does it matter if the engine is hot or cold? I wish I could hear it. It sounds as though it may be time to dig deeper into the motor.

[84honda200s]

ok isnt the 350x a 2 stroke? i had a sled did that. it was a worn rod end and it slaped and that lead to bad rings and it got real sloppy and only knocked at wot. so i rebuilt it and it ran fine after. well till i blew it up again lol

[SmokinX]

It only does it at the last 1/10th or so of throttle range. I don't think I was losing power when I heard the sound but I didn't keep running it at WOT when sound occurs. I never run a cold engine at WOT so I don't know if it would do it cold. But noise does sound like it's coming from the jug area or higher. I made a run down my road and it was doing it so I changed plug and let it sit for 20 minutes and it still did it.

[84honda200s]

from what you r saying knocking/banging it could be " low octane fuel, crapy fuel or the spark plug of the wrong range" know if there is rapping in there its the rod bearing. now if theres slapping or rattling there is piston issues.


all i can tell you is go the cheapway first then move your way up.

i wish i could hear it for my self.

[trikes4life]

ok isnt the 350x a 2 stroke? l

350x four stroke

250r two stroke

[250r'en +TCB]

what are you running for fuel??? It better not be that E-85 crap!!!

[SYKO]

I bet its your cam chain, it may have to much slack and is warping up, My 200sx was like that before I rebuilt the topend, when I put it together I jsut tightend the cam chain tensioner and alot of noise went away, worth a shot

2 cent

[85ytz250nj]

all i can tell you is go the cheapway first then move your way up.

i dissagree, if its your only ride, i would start with the most expensive and go from there. if someone told you its the crank or a piston, just rebuild it. it may be something stupid or it may be something serious. but until you know for sure, theres no point in possibly doing more damage to the motor. if you start fixing small things and cheap things they will build up. start with the bottom, work your way to the top. thats what i would do.

[Erics350x]

try putting it in to high of a gear and getting on it. if you hear the same noise its detonation . both detonation and cam chains mke a light rattle noise. if its a hammering sound then o better tear it apart before a rod goes.

[SmokinX]

Well I finally had time to screw with it this weekend and I fingered it out. I was running a 145 main so I dropped back down to a 142 and problem solved. It must have been dumping too much fuel in and causing it to predetonate. Best I can figure cause it was knocking pretty darn loud at WOT. Anybody else ever heard of this???

[RedRider_AK]

ok isnt the 350x a 2 stroke? lol

Ummm no.:lol: :banned:

[84honda200s]

i dissagree, if its your only ride, i would start with the most expensive and go from there. if someone told you its the crank or a piston, just rebuild it. it may be something stupid or it may be something serious. but until you know for sure, theres no point in possibly doing more damage to the motor. if you start fixing small things and cheap things they will build up. start with the bottom, work your way to the top. thats what i would do.





you could go high to low if you had the cash to do so.











Ummm no.:lol: :banned:


i had one of them moments lol boy i feel like a moron. lol

sorry guys