Loud knock

[dxcody]

Ok, so when i tried to start my 400ex after i installed my hot cam, it turned over a few times and stopped and right before it stopped it made a loud CLANK! But then i did it again and it fired right up and runs fine, but it does that almost every other time i start it, but it makes absolutly no wierd noises when i am riding.. Oh and another thing is, it shuts off when i am coasting, It idles fine but it dies when i am riding and i pull in the clutch without keeping it revved up. ?? Help!

[NMills]

Are you 100% sure your timing is correct? was your piston at TDC?? lines on the cam sprocket and lobes lined up right??

[CJM]

Ya installed something wrong.

Lobes on the cam must be facing down, cam gear must have lines parallel to head and the other line facing upwards, when you adjusted the valves the piston must be at top dead center-the rockers will be loose. You adjusted your valves to .005 and .006 inches as well right?

Honestly just taking a shot int he dark-but that loud clank mighta been your piston hitting the valves and bending them. Or its outta time somehow.

[dxcody]

Originally posted by NMills
Are you 100% sure your timing is correct? was your piston at TDC?? lines on the cam sprocket and lobes lined up right??

When i had the head off i put the piston at TDC and made sure by looking at it that it was, then as i installed each part, i looked on the flywheel to insure that it had not moved, and i guess i will just have to take everything back apart and examine it, like i said it runs fine but sometimes this happens when you try to start it and i really didnt want to break anything so thats why i came here.. thank you for the reply, i will check the timing and all that valves, when i take it apart i would think that i could be able to see some wear on something from whatever is making the noise.

[dxcody]

oh and yes the horizontal lines were even with the head and the vertical mark was at 12 o clock actually about 12:30 since the engine sets leaning.

[CJM]

Kinda hard to say then if timings fine. Probably gotta tear it down to really figure it out.

Personally I think you mighta bent a valve, easy to tell since the top of the piston will be scored.

[dxcody]

Originally posted by CJM
Kinda hard to say then if timings fine. Probably gotta tear it down to really figure it out.

Personally I think you mighta bent a valve, easy to tell since the top of the piston will be scored.

CJM i really want to give you a big thanks here, you are always one of the first ones to reply to my poastings and heck i am pretty sure you are the one that told me to start posting in the 400ex page and not just the Powertrain page. (sorry about that i was a rookie lol) i will go over eveything and let you know how it goes.

[CJM]

NP man. I hate to say tearing it down is the best option-but with timing and cams and if somethings out first thing to go is the valves.

Id do it in this order just to see:
1. Check compression, min need is 100psi, spec is 128psi or close
2. Check valve clearances
3. Turn engine over by hand, see if it makes noises
4. Check the usual, gas, oil, carb, hows the plug, etc
5. If none of that solves it then its time to check the topend. Tear it apart carefully and look for wear. Pay carefull attention to the cam, the dowel pins that hold it in, the bearings, cam chain and tensioner. Nothings there look further, check the play int he piston (should be there but very minimal), then check the head and the valves, so forth and so on.

[dxcody]

turns out it was my starter.. its going out and the gears were getting twisted (as so to speak) and making that slamming noise.

[CJM]

See, I had thought of that originally, but when you stated it wanted to die and not run right I thought topend.

Glad you figured it out.

[dxcody]

well see what made me really start thinking is when i thought it was a bent valve, but then i thought "shouldnt it keep turning over even though the piston was hitting the valve, so it kinda made me think of the starter, so i took it apart and it looked like a metal recycling place in there.. haha thanks buddy

[4WheelinDemon]

I have the same problem on mine. But it never died out before. Oh well good thingnyou found out now.

[dxcody]

THE REASON MINE IS DYING OUT IS I THINK MY FLOAT IS STUCK OPEN MAYBE BECAUSE IF I LEAVE MY GAS ON WHEN I AM NOT RIDING IT, I GET GAS MIXED IN WITH MY OIL.. I THOUGHT I FIXED IT BUT I GUESS NOT