Wont start??

[PaRedneckRiders]

Went riding the other day and made it about half way up a hill and it bogged and shut off.
Will crank and try and fire every once in a while but will not run
Only thing i can think of it timing because it rolls over and every once in a while it will pop but it will not start. I pulled it and tried to pop start it and it started but wouldnt run would just fire and if you pulled in the clutch and tried to give it gas it would shut off again. Any ideas??
Prob gonna check timing tomorrow if that isn't it run a comp test and also check valve clearance while im at it.

[400exmxrider15]

I'd say your on the right track. That or your stator coil is going out....check if your getting a strong spark?

[PaRedneckRiders]

Ya its defiantly getting good spark im gonna rip into it today to see what i can find.

[rd2005]

We just had the same problem with my 400ex. I would pull it & attempt to start in 3rd gear. It would try & even start but die just seconds after or when I touched the throttle. We found we had a blown cylinder head gasket. It was blown to where I lost just enough compression to keep it from running. Your situation sounds very much like ours. Keep updating on how its going. Good Luck!

[PaRedneckRiders]

sorta doubt it is a head gasket it is BRAND new and has mayb 30mins of ride time on it.

[CJM]

Remember the timing chain? Wonder if it wasnt tight enough?

Friend of mines tensioner blew up, the engine would fire but make a glug, glug noise when trying to do so.

[rd2005]

Originally posted by PaRedneckRiders
sorta doubt it is a head gasket it is BRAND new and has mayb 30mins of ride time on it.

Our head gasket had very little ride time on it maybe 3 hours but it was put together by an individual who had no clue what he was doing. Also he over torqued the headbolts making it worse. Just sounded very much like my situation.

[PaRedneckRiders]

Alright, i was gonna look at it yesterday but i haven't had time yet, been busy the last couple days trying to get other things done.

[PaRedneckRiders]

Pulled it apart and timing is on, i check the plug again just out of curiosity and its not as blue of a spark as i would like i think that could be it.
Going to get a new one and throw it in to see what it does.

[PaRedneckRiders]

Tried multiple things today
New plug
Timing again
Head gasket
Next thing im thinking is either the coil or mayb just it needs complete top end.

[PaRedneckRiders]

Alright, i still have nothing.
I charged the battery just to make sure but its trying to fire just wont run.
Also what should comp be with 11:1 like what would be a rought estimate of what an 11:1 426 should run comp wise?
Timing is on new plug different head gasket running out of ideas do you think it could be the coil??
It has spark but mayb its just not enough.?

[400exmxrider15]

my idea is that its running really rich and is fouling the plug out as soon as you turn her over. thats what mine did. I took my propane torch and got my plug super hot (red appearance) and put her back in and has never once fouled out on me...check plug gap too, too much and wont spark, too little and it will ground out...

[PaRedneckRiders]

I had a 42 180 in the stock carb and idk what it in this 450 carb i think its a 50 185

[PaRedneckRiders]

Think i May have found the problem.
Its got about 130psi of comp but i pulled the cylinder and the ends of the rings are FRIED and WAY OUT of service limits.

[CJM]

Interesting...never seen that one before.

Improperly matched cyl to piston?

[PaRedneckRiders]

Idk, i was sorta thinking that to. Im gonna check it today to see how much clearance there is between the piston and cylinder wall.