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K2 On the road - then not... Cam chain failed...

Jeff K2

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The Bike is scary fast!!! Pretty close to a stock Z1, as I recall.

Dirtdigger told me to put in a new heavy duty cam chain, but I didn't. It broke after about 50 miles of hard flogging. No damage to valves or pistons, strangely enough. The bad part is that I now need to break the cases to find the pieces of the links that failed. Unless someone knows the right magic to get them out.

What chain(s) is/are reliable? Are there any good vendors out there?

Happy riding!
Jeff
 
That sucks man. Get a heavy duty chain from APE or Cycle X. They used to use the same vendor but I have used APE lately for the chains. Did the camshaft seize in the head? The stock chain should have lived longer unless it had a lot of miles on it or something else seized causing it to break. Take a look at the chain tensioner parts, I use an aftermarket slipper type tensioner from CycleS instead of the tensioner wheels. You need to split the case anyway to put the new chain in so no magic needed to get the pieces out as it will all be apart anyway.
 
The chain was heavier than others I have on hand. There are teeth marks on some of the rollers, so I think the chain went slack, bound up and broke.

I will look at the cam bearings for any sign of bad news. I have looked over the chain slider and tensioner wheels - nothing bad in either.

I was running at about 2000-3000 RPM when it died. I had been working it earlier in the ride. There was no indication of bad things happening before it went...

Thanks for the tip on APE.

Cheers,
Jeff
 
Slack on the camchain is a major killer of the chains. Seems odd that it broke at such a low rpm. Do you know how many miles was on the chain? Interested in hearing what you find out once you did further into this.
 
Hi DD,

The chain was in the inventory, so I have no history on the miles... I also found another outer link that had failed in the chain, so I need to find 3 pieces of outer links.
The cam bearings showed no signs of bad behavior. no evidence of any valves hitting the pistons, which I find hard to believe. I will pull all the valves and check for bends.

I have couple of each type of cam chain tensioners, roller vs. sprocket on the upper end. Which type is better? The one I was running had significant wear on the center (raised) area, that I do not recall seeing during installation. The other all rubber ones in my stock are near perfect or perfect.

I did figure out the oil leak problem. Since I only had Clymer manual that spanned '69 - '74, there were no provisions for describing the F1 design of cyl. to head sealing features. Usually I am better at noticing details, but I failed miserably in noting the increased oil return galleys through the head/cyl. I did not install any seals nor dowel pins on all 8 of needed locations. Messy at best... I did notice that I have F1 & F2 heads as well as K heads. Life is learning or dying...

I am now rebuilding the bike. I will polish what will take a polish, leave the pitted chrome/rusted spokes, paint what needs paint for a mongrel/resto bike.

Thanks for tip on the chain. CycleX sent me one that is much stronger than the POS that broke.

I rev'd the motor pretty high. What is a real limit for these?

I got a '79+ exhaust and put early clamp type ends on each pipe. I think it sounds perfect. My wife, not so crazy about the noise. I am now willing to put some bucks into the exhaust, so I would like to have good performance without being deafening. Is that possible? If so, who from?

Thanks again,

Jeff
 
Show me a picture of the sprocket roller. Back in the day they would use a cam tensioner roller out of a cb350(which had teeth) as a "high performance" upgrade to try to fix the cam chain breakage problem but eventually they came out with a heavy duty chain and the problems went away. If the roller was really chewed up then it was probably really hard from age and use and it started to break apart. They should not be hard, they be a little soft, if they are very hard they are junk.

The bottom ends are indestructible in stock displacement. Rods are the weak factor in bigger bore motors and valve springs and cylinder head breathing are factors in the top end. Trips to 9000 are fine but not sustained with stock rods. I have taken mine to 10,000 with my 836 and cycle x rods but only once or twice. The motors pretty much stop making power above 8500 with stock cylinder heads because they really dont flow that well.

Check out the cycle x exhaust if you haven't looked already. They have a 4 into 1 with a muffler, not sure how it sounds though I build my own exhaust and I dont care how loud it is:D
 
DD - I cannot get the pictures to upload... I'll send them to you via e-mail. The upper rollers on all I have are somewhat harder than the lowers. The pics show the lowers I have are all in great shape, except the one out of the K2.

Cyclebuster - The sound is perfect for me, but my son lives in the high rent district of SLC, the bike is for him...

Cheers - Jeff
 
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