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View Full Version : Big problem? I need help!!! 300 fourtrax



2Red and 1Blue
01-16-2010, 10:58 PM
I have run into a problem here. I replaced the timing chain. The old one was sooo loose it was hittting the guide then the guide was hitting the tensioner. Made a loud almost knocking noise. Anyway, I put a new chain on. I go and rotate the crank to TDC. Align the cam sprocket marks. However, this is not coming out right. If I line the marks up it is not totally TDC. If I move it either way it is off. Linig the marks up I would estimate being off on the crank 1/4". I tried it this way and nothing. My compression is down and no fire. I haven't tried to move it back and start it. Could the lines be off on the sprocket?

Here is a summary.
1. Moved crank to TDC
2. Align the marks on the cam sprocket
3. If I line them up it throws me off TDC.
4. If I try to move it back a tooth it won't line up.
5. Cam lobes facing down at TDC
6. Punch mark at the top of cam sprockt at TDC
7. Adjust valves at TDC at .006
What I am doing wrong here? Or what could be my problem here?

TrailerHauler
01-18-2010, 12:10 PM
I just had to pull the head off my trx 300 fourtrax to redrill and tap for one of the studs on the exhaust header. Since I did that and threw it all back together, I realized it was time for a new head gasket (thought I could get away without one) as there was pressure in the crank case. And since then the timming chain was clicking. So its torn down for the second time ever in the last 14 years for a new timing chain and head gasket right now.
Back on topic, I noticed last time I disassembled, and reassembled the top end that the hash marks on the cam were a little off when the engine was at tdc whether I moved it forward or backward a link. I think that might have been due to a streched timing chain.

Make sure its at TDC according to the flywheel, no matter what. Then line up the cam hash marks flush with the head as close as you can. If anything line it up so that when your looking at the hash marks the cams tilted a little bit towards the back of the quad. Then put in the cam chain tentioner which should take up the slack in the chain and in result line it up for you.

number52
06-26-2011, 11:38 AM
remove the spark plug and make sure the piston is at TDC when the T mark is aligned. If it's not you could have a slightly stripped flywheel key. I've seen it a few times on other bikes