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Unread 03-21-2013, 10:01 PM
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Smithers Smithers is offline
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So to continue with the troubleshooting I put the carb back on the bike and made sure there weren't any fuel leaks. The silicone grease on the dried up bowl gasket and fuel elbow o-rings really did the trick. And when I tried to start the bike I would get nothing for about 5 kicks and then maybe a pop or a backfire. This totally is a sign of a tooth off with the timing chain. BUT I had checked and double checked the timing marks over and over. I even brought in an experienced friend to talk about the possibilities of what could be going on.

#1 I had put my hand over the carb while turning engine over to check for fuel. We have fuel.

I checked the timing a couple times. It's as close as possible. It's not totally exact like I want it but the timing marks that line up on the valve cover head surface are maybe 2mm high on the left when the right is exactly in line. So with the crank at TDC the marks are just right while not to the exact thousandth of an inch in line. Just damn close and so close that moving the cam sprocket or the crank sprocket one tooth would throw it out of whack and not help at all.

This reminds me of a lot of Honda /Acura 4 cylinder engines with their timing belts. When you line the crank shaft timing mark to TDC you want the crank mark just to one side of the timing mark on the block. I forget which side it is but you can line up all the marks perfectly but you have to choose exactly which side of the mark you want the crank pulley line to go on... even with the tensioner installed. One side of the mark will fire the engine and the other side won't. It's a toss up.

On this Suzuki / Kawi 250cc engine I have heard of stories of the cam sprockets actually getting hot and spinning on the camshaft. I couldn't help but think about this causing the timing mark on the exhaust camshaft to be indexed out of alignment that 2mm. This is a rare occurance so I put it out of my head but it did come up in the possibilities when my friend was even questioning the cam sprocket timing mark being off by such a small amount. The only other possibility of throwing off the timing mark is the cam chain stretching. But the engine doesn't have nearly enough time on it to cause this. Stretched timing chains might come up in high hp sportbike engines that hit 50K but not in a dirtbike engine that probably hasn't even had a top end rebuild.

To rule out the timing just follow the service manual procedure. Line up the crank TDC markings. Remove the cam cover and check the timing marks and how they line up with the top of the head surface. Then the manual says to count 28 chain link pins between the exhaust timing mark and the intake timing mark. That's it! As long as you have the timing marks lined up "close" and 28 pins between the cam sprocket timing marks you are golden.

#2 The engine timing marks are lined up as close as possible.

Now to test the spark.

Last edited by Smithers; 03-21-2013 at 10:03 PM.
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