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New Cam Chain - Now it won't start

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I recently rebuilt an 06 CRF450R after the previous owner allowed the exhaust valves to meet the piston - the piston met the cylinder wall - etc. . ..

About the only thing I didn't replace was the cam chain. When putting it all back together the cam chain gear would not match up perfectly to the marks. It was slightly rotated to the left (counter clockwise) of the marks. That's the closest match I can get with that chain. With the setup below and this slightly stretched chain installed it starts first kick every time (cold/hot - it doesn't matter), BUT. . . I swear I can hear the valves just barely tapping the piston, and that scares me.

No it's not the dumb chain slapping my swingarm - I've even wrapped my chain in tons of shop rags to eliminate that possibility (while at idle of course). That nasty sound is definitely coming from the motor.

I've ridden the bike like this for 6.5 hours now and have been nice trying to break the motor in. I'm afraid that with that cam chain when I really do decide to get on it, it'll trash the piston once again. . .and my new kibble white valves $$$$$

Well last weekend I couldn't handle the sound anymore so I bought a new cam chain and installed it. It fits perfectly and the marks all line up just like they're suppose to. BUT... now it won't start to save my life. I bet it took 30 kicks to get it going when cold and about 5-10 when hot. No engine noise though!!

So I reinstalled old cam chain and it started first kick but the engine noise came back. :censored:

So the questions are:

How does rotating the cam chain gear clockwise (to fit perfectly) affect my jetting?

Why did my previous setup work so well with the cam chain gear rotated slightly counter clockwise? We're talking an 1/8th inch off center max, not much at all.

What do I need to do to my jetting so it'll start perfectly with the new cam chain?

Which way is safer to have the cam chain gear rotated? - as far as hitting valves goes

Jetting Setup:

1 3/4 turns out air screw (slightly lean of stock)

#40 pilot (slightly lean of stock)

stock main

stock needle clip position

Elevation:

4500 ft

Temperature:

40-60F

Valves:

Exhaust: both dead on @ .011 in

Intakes: Left .006, Right a loose .006, not quite a .007 though - yet still should be no problem here

Decompression: Perfect as well @ .014 in

Any help would be appreciated folks. Hopefully I'll have the time in the next week or so to try any suggestions you may have.

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Your jetting should not change. As for the hard starting check your valves again. If it was jetted correct befor it should be good now. Clean the carb. Good luck.:censored:

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Thankyou for your reply.

I forgot to mention that I did check the valves at the same time I did all of this and they haven't changed since I first rebuilt the motor.

Exhaust: Dead on .011 in

Intakes: Left .006, Right a loose .006, not quite a .007 though.

Decompression: Perfect as well @ .014 in

Don't forget that I did put the old one back in and it started right up. It's got to be jetting, I just don't know which way. I did try richening up the pilot with the new cam chain installed - no difference, still hard to start.

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I think its your timing. Even though your marks look right doesn't mean its right. Check your timing mark on the flywheel side it should be on the second mark. It will run even if its off one tooth, I would try moving it one way or the other then roll it over slowly if nothing hits try to start it.

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You may already know this, but, you need to be down on your knees and be eyeball level with the marks on your cam sprocket to properly determine if they are lined up. You will arrive at a different conclusion sometimes if you look down from a higher elevation. Same process on the right side of the engine.

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I'm going to say timing as well. You missed it with the new chain, but just happened to hit it with the old one. Just funky luck...

The cam timing wont affect the jetting. Heck, a new cam doesnt even effect the jetting that much if at all. A port job and cam will, but the timing chain has no effect.

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Your cam chain has nothing to do with the jetting or the carb. I would say that you had your timing off. The noise you heard with the old cam chain was just the chain slaping.

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Your cam chain has nothing to do with the jetting or the carb. I would say that you had your timing off. The noise you heard with the old cam chain was just the chain slaping.

But retarding or advancing the timing affects the gas/flow into the cylinder, hence my questions about jetting it differently to accomodate that.

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I think its your timing. Even though your marks look right doesn't mean its right. Check your timing mark on the flywheel side it should be on the second mark. It will run even if its off one tooth, I would try moving it one way or the other then roll it over slowly if nothing hits try to start it.

This may be a dumb question but what "second mark" There's only one dot to line up. I hope you're right though cause I really want the new chain to work as nicely as the old does - but w/o the slappage.

There is some text 180 degrees away from that dot (right side). Am I suppose to be timing it to that text? If so I've got it timed 180 degrees off and it runs like a champ by some miracle.

By the way: THANKYOU ALL FOR YOUR QUICK REPLIES SO FAR. I hope to get this figured out soon.

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I think its your timing. Even though your marks look right doesn't mean its right. Check your timing mark on the flywheel side it should be on the second mark. It will run even if its off one tooth, I would try moving it one way or the other then roll it over slowly if nothing hits try to start it.

A light bulb just came on! I haven't ever checked the timing marks on the flywheel side at all. I've always checked the right side and the upper marks on the cam chain. I probably am 1 tooth off.

Question then:

What is the right side mark even used for? Just to get it close so you know where TDC is, then check the flywheel side to get it perfect???

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But retarding or advancing the timing affects the gas/flow into the cylinder, hence my questions about jetting it differently to accomodate that.

If you advanced or retarted you timing that much to affect your gas/flow you would have bent a valve.

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I think the mark on the right is for lining up the counter balancer shaft and weight. Don't know why there are two marks on the left. (Spark advance?) If after you line it up correctly and it still doesn't work, could the sprocket have slipped on the cam when the motor was damaged? I don't know how you would check that, just some thoughts.

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PROBLEM SOVLED FOLKS!!

Please note that the owners manual, as well as "How-to" articles like this one

ARE NOT THE WAY TO CORRECTLY TIME YOUR CRF450R!!

The correct way is to only use the right side to get the piston to somewhat close TDC. Then use the 2nd mark on the flywheel to fine tune that TDC. Now go ahead and line up your cam gear to the punch marks.

I only used the right side dot before - just like the owners manual tells you to. I went back and aligned the flywheel's 2nd mark (the one most clockwise), then looked back at the right side - sure enough the little dot was a good 1/4" away from it's alignment and sure enough - I was about exactly one tooth out of alignment. I shifted it all to match up according to the flywheel and wulla! Fire in the hole!! No more scary noises coming from my engine anymore too.

Good call jcsjr

My bike now starts like a champ w/ the new chain installed and sounds as good as new. The only reason it ran great w/ the old stretched chain is because I think there was enough slack in the chain that the timing just worked out.

Thanks for your help everyone

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I'v got alot of dumb possiblities only because I'v done alota dumb things.

The motor could be outta time completely....Is the spark plug good? How long has the gas sat in the tank......Wire not hooked up somewhere......Also I was a little confused as its really early for me, but when you spoke of the cam sprocket and moving it forward? are you trying to retard the timing for more power? I know its possible with some cam set ups, but I didnt really read it enough to know what you ment. I dont think your jetting could have that big of an effect on starting, unless you had it just completely wacked.

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I'v got alot of dumb possiblities only because I'v done alota dumb things.

The motor could be outta time completely....Is the spark plug good? How long has the gas sat in the tank......Wire not hooked up somewhere......Also I was a little confused as its really early for me, but when you spoke of the cam sprocket and moving it forward? are you trying to retard the timing for more power? I know its possible with some cam set ups, but I didnt really read it enough to know what you ment. I dont think your jetting could have that big of an effect on starting, unless you had it just completely wacked.

It was just one tooth off the correct mark. Correct mark being the flywheel's 2nd mark.

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Wow, that crank gear mark is way off. All 3 of my CRFs the dot is right on the money. If i were you, instead of using any of your marks i would stick a straw down the sparkplug hole to find TDC, if the crank grear is 1/4" off, the flywheel might be a little off too.

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Wow, that crank gear mark is way off. All 3 of my CRFs the dot is right on the money. If i were you, instead of using any of your marks i would stick a straw down the sparkplug hole to find TDC, if the crank grear is 1/4" off, the flywheel might be a little off too.

That's actually exactly how I did it. The 2nd mark on the flywheel was dead on with TDC when done this way. The dot was about a 1/4" off as said earlier. It starts, runs, and sounds great now.

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