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Hi. Long time reader, first time writer here. Working on a 300 fourtrax. The cam chain was sooo loose that it would hit the guide and then the guide would hit the tensioner. Making a "tapping" noise. No big deal. So I changed the chain. When I go to time it the marks on the cam sprocket will be straight across the head with the punch mark on the sprocket at the top. But if I check the crank it is off by 1/4" or so. No problem I think, I am one tooth off, move it and I am almost lined up with the " f " mark. What is my problem? I pulled the flywheel cover off to check the key way had not sheared off moving the markings. Everything was good there. Any Ideas would be great.
 

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Thanx for the pm trx2five0. However, I checked all of those items. The decompression lever on the 300 is a manual decompression lever. If I remember right the 250x motors have a cable. I think. I can't remember if the cable was on my 250x's or my old 300ex. Any other suggestions though I will take. I can't remember if the bottom cam chain sprocket is seperate from the crank or is all one piece? If not, possible that key way sheared? I dunno.
 

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Hi. Long time reader, first time writer here. Working on a 300 fourtrax. The cam chain was sooo loose that it would hit the guide and then the guide would hit the tensioner. Making a "tapping" noise. No big deal. So I changed the chain. When I go to time it the marks on the cam sprocket will be straight across the head with the punch mark on the sprocket at the top. But if I check the crank it is off by 1/4" or so. No problem I think, I am one tooth off, move it and I am almost lined up with the " f " mark. What is my problem? I pulled the flywheel cover off to check the key way had not sheared off moving the markings. Everything was good there. Any Ideas would be great.
First of all You alligned the timing on the exhaust stroke.... TDC the flywheel will have a "T" lining up with the notch on the case. That would explain the no compression and the tooth off. look at your flywheel again. Second you are correct sir the 250X had a cable activated Decropression system. I was tossing Ideas as to the no compression now I know why you are 180 out.
 

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Discussion Starter #4 (Edited)
Ahh, maybe I screwed up here writing that. I did line up with the T. But the line on the sprocket close to the back of the machine will be below the head. If I move it one tooth to get the marks parallel I am lined up with the F. there is no in between to get it to come out right. Hold on a minute here. you say notch on the case? I have a notch on the case and also an arrow. Should I be lining up with the notch or the arrow inside the case lined up with T?
 

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Discussion Starter #5
Don't I determine which stroke I am on by cam placement? Lobes down in the oil res, compression stroke right?
 

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Yeah, line the "T" up with the mark on the case and the cam lobes should be down, so the valves will be closed. Sometimes the mark on the magneta wheel can be off just a hair. Just pull your spark plug out and make sure your piston is up on TDC, with the "T" on the magneta wheel as close as possible with the mark on the case. Worry more about where the piston is, itself, than where the mark is. NOTE: They usually have a line above or below the "T". The LINE, not the "T", is what you should line up with the mark on the case. Sometimes it's real hard to see the line, because of the oil on the magneta wheel. Also, there will be a little slack in the timing chain, before you put the tensioner back in. Make sure the side of the timing chain opposite the tensioner is tight, leaving all the slack in the tensioner side. That way the tensioner will take up all the slack of the chain. This is a little hard to explain with words, but I know what you are talking about. I have had the same problem plenty times.
 
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