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How to put crank at TDC with top end off?

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I am in the middle of a top end job on my '09 KTM 250SXF. When I pulled the top end off, the bike was not at TDC. My bike has a screw on the bottom end that you can remove a copper washer to find a notch in the crank to find TDC. However, the engine does not turn very easy with the kickstarter. I was imagining it would require little effort but I cannot get it to turn at all to find the TDC.

What am I missing? I can't get the piston on because the connecting rod is below the engine case.

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I did my friend. Something is wrong because if there is no piston then there is no compression to fight. Something is perhaps jamming things up? How about pulling the cover and spinning the flywheel? Keep us posted on how you make out!

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It should turn freely. Not that I would know, but is it in neutral?

If you have another pair of hands to help, you could CAREFULLY use the e-starter to get the crank turning. Very small pulses!!!

Good Luck,

MrHix

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You mentioned the bolt with copper washer. Did you take the washer off and put the bolt back in? if you did that could be the problem, the bolt is against the counter weight. Let us know what it is.

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I actually removed the bolt all together.

I don't want to try the estarter as I can't even move the kickstarter with my foot. I assume something is jammed. The timing chain doesn't appear jammed but something isn't right. I guess my only option is to pull the right outter engine case?

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cam chain?

Ding Ding! We have a winner!!!

tchain.jpg

Back to this TDC bolt. I have the connecting rod at its highest point and I'm looking down the hole on the bottom end and I do not see a slot in the flywheel like I was imagining. Does this bolt just press up against it or is it suppossed to slide in a slot? If I continue rotating the engine I do see a hole on the flywheel but the connecting rod is beneath the engine case.

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Also, will I need a new cam chain? I was able to pull the kinks out by hand and the chain rolls fine without kinking again.

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That will do it.

Glad there was not real problem and have to pull the case apart.

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I am really close to finishing top end rebuild on 450 SX-F. Cam went out of time and my best guess is the POS OEM KTM tensioner is the cause. it happened at a low speed/coasting.

A new OEM cam chain cost me $60. A Dirt Tricks tensioner was $60 off ebay. For all the other time, money and work you've invested, DO IT!! And this is coming from a guy that doesn't like to spend what doesn't need to be spent. And my old chain looked okay, but you need to measure it to see if it's stretched out of spec.

On TDC; I used a socket (14, 15 or 17mm ...can't remember which) to turn the flywheel bolt. There is a detent mark on the gear UNDER the flywheel and starter gear, and a detent mark on the 4 or 5 tooth crank gear (it's an odd looking gear that only has a few teeth on the bottom half of it). those 2 marks need to be lined up. The 2 flat spots on the top of the crank were also facing up and horizontal.

have fun with circlips, head & piston. I had the piston in cylinder, finally got the wrist pin to line up, and then piston pops out of cylinder. I was able to compress rings enuf to get it back in.

you probably know this, but I set each of the 4 rings 90 degrees from one another. I learned that on this site and it makes perfect sense as the rings can't be in line.

back to TDC..... since you're mounting the cylinder and piston, you'll see TDC when the piston is as high as it can go on re-assembly. double check the other 2 gears I mentioned, and also your cams facing outward. did you have to replace cams? there is a special tool to hold down cams so you can also align the cam gears with the double cam chain sprocket, to keep everything properly timed.

I haven't done a lot of these types of motors and there was a lot of things i could have done wrong, so take your time and ask questions, and research. mistakes are expensive on these.

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what year is your motor? How do you know the cam went out at low speed? How did you know it went bad, mic it? Scuffed up?

I am really close to finishing top end rebuild on 450 SX-F. Cam went out of time and my best guess is the POS OEM KTM tensioner is the cause. it happened at a low speed/coasting.

A new OEM cam chain cost me $60. A Dirt Tricks tensioner was $60 off ebay. For all the other time, money and work you've invested, DO IT!! And this is coming from a guy that doesn't like to spend what doesn't need to be spent. And my old chain looked okay, but you need to measure it to see if it's stretched out of spec.

On TDC; I used a socket (14, 15 or 17mm ...can't remember which) to turn the flywheel bolt. There is a detent mark on the gear UNDER the flywheel and starter gear, and a detent mark on the 4 or 5 tooth crank gear (it's an odd looking gear that only has a few teeth on the bottom half of it). those 2 marks need to be lined up. The 2 flat spots on the top of the crank were also facing up and horizontal.

have fun with circlips, head & piston. I had the piston in cylinder, finally got the wrist pin to line up, and then piston pops out of cylinder. I was able to compress rings enuf to get it back in.

you probably know this, but I set each of the 4 rings 90 degrees from one another. I learned that on this site and it makes perfect sense as the rings can't be in line.

back to TDC..... since you're mounting the cylinder and piston, you'll see TDC when the piston is as high as it can go on re-assembly. double check the other 2 gears I mentioned, and also your cams facing outward. did you have to replace cams? there is a special tool to hold down cams so you can also align the cam gears with the double cam chain sprocket, to keep everything properly timed.

I haven't done a lot of these types of motors and there was a lot of things i could have done wrong, so take your time and ask questions, and research. mistakes are expensive on these.

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I am really close to finishing top end rebuild on 450 SX-F. Cam went out of time and my best guess is the POS OEM KTM tensioner is the cause. it happened at a low speed/coasting.

A new OEM cam chain cost me $60. A Dirt Tricks tensioner was $60 off ebay. For all the other time, money and work you've invested, DO IT!! And this is coming from a guy that doesn't like to spend what doesn't need to be spent. And my old chain looked okay, but you need to measure it to see if it's stretched out of spec.

On TDC; I used a socket (14, 15 or 17mm ...can't remember which) to turn the flywheel bolt. There is a detent mark on the gear UNDER the flywheel and starter gear, and a detent mark on the 4 or 5 tooth crank gear (it's an odd looking gear that only has a few teeth on the bottom half of it). those 2 marks need to be lined up. The 2 flat spots on the top of the crank were also facing up and horizontal.

have fun with circlips, head & piston. I had the piston in cylinder, finally got the wrist pin to line up, and then piston pops out of cylinder. I was able to compress rings enuf to get it back in.

you probably know this, but I set each of the 4 rings 90 degrees from one another. I learned that on this site and it makes perfect sense as the rings can't be in line.

back to TDC..... since you're mounting the cylinder and piston, you'll see TDC when the piston is as high as it can go on re-assembly. double check the other 2 gears I mentioned, and also your cams facing outward. did you have to replace cams? there is a special tool to hold down cams so you can also align the cam gears with the double cam chain sprocket, to keep everything properly timed.

I haven't done a lot of these types of motors and there was a lot of things i could have done wrong, so take your time and ask questions, and research. mistakes are expensive on these.

I bought the dirttricks tensioner when I first bought the bike. My bike only has 44 hours on it so everything else should be fine. Only doing the top end (cylinder did nee a replate).

I found that detent mark to lock the crank at TDC.

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you had to replate at 44 hrs?

I bought the dirttricks tensioner when I first bought the bike. My bike only has 44 hours on it so everything else should be fine. Only doing the top end (cylinder did nee a replate).

I found that detent mark to lock the crank at TDC.

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my son was going downhill on a trail, so no gas, just idling basically. he suddenly heard an awful "bucket of bolts in a blender" sound.

upon disassembly, the exhaust cam (closer to where the cam chain tension should be too) had a nasty groove worn on a lobe, and the cam follower had an even nastier deep gouge worn in it. the valve spring retainer split in half, one exhaust valve bent (that was tested by the machinist cuz it was hard to see from looking at it). crappy...KTM only sells complete valve spring assembly instead of the $5 retainer.

the collets were crunched up and the valve guide broke apart. i found a chunk of valve guide in exhaust pipe. what really had me concerned was not finding the valve shim, which eventually turned up on the floor of my shop!! (must have dropped it without knowing).

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