Heads Up On Auto Cam Chain Tensioner Damage

My 73 850 motor has been out of the frame for the past month and in the hands of a very capable and well known Commando engine rebuilder. In short, my motor is very worn out, and needs a lot of parts and labor. More on the cam and valve problems to follow in a later post.

12 years ago I installed the spring loaded automatic cam chain tensioner.
No known problems during that time period, until now.
My guy called me to tell me he wanted me to bring him the stock cam chain slider, and that there was no way he would install the auto unit on my bike, or any other bike. The damage it caused was significant.
It is just too damn tight. Period.
That tightness caused the shaft for the intermediate gear to wear, or increase the size of the hole the shaft goes into,
in the forward facing side of the hole, in both the inner and outer covers. In addition, the shaft movement increased the depth of the hole in the outer timing cover, so much so that my mechanic had to machine a 175thou spacer to take up the slack in the outer cover. In addition, he had to fill in the forward wear part of the inner cover hole the shaft goes in to. He feels the auto tensioner kept the cam chain way too tight. I have seen, and are paying for the damage caused.

I advise everyone to be made aware of this, and seriously consider taking their auto unit out immediately, and go back to the stock set up.. So what if you have to check the tension every 5000 or so miles.

I have warned people of this pile of junk engineering before after the results I have had with them along with NO customer support or warranty after having one fail.other people have reported the NON support also. the trouble is in the design as it WILL NOT float at a preset tension but instead will tighten to the most slack part in rotation and will not release as the engine is rotated and the chain gets tighter with non concentric sprockets. I think that if you want a low maintenance cam drive than Jim Comstock's gear drive will be the ONLY way to go

Just out of curiosity, how many miles did you put on with that tensioner installed?

11,000 on mine and the catastrophic failure was possibly due to something else. Whatever, I won't replace it. Didn't notice any issues with added wear on the spindle fixing or timing cover hole but then maybe 11k isn't enough to show that.

bill said:

I have warned people of this pile of junk engineering before after the results I have had with them along with NO customer support or warranty after having one fail.other people have reported the NON support also. the trouble is in the design as it WILL NOT float at a preset tension but instead will tighten to the most slack part in rotation and will not release as the engine is rotated and the chain gets tighter with non concentric sprockets. I think that if you want a low maintenance cam drive than Jim Comstock's gear drive will be the ONLY way to go

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Maybe a lawsuit would change their customer support? 8)

pelican said:

bill said:

I have warned people of this pile of junk engineering before after the results I have had with them along with NO customer support or warranty after having one fail.other people have reported the NON support also. the trouble is in the design as it WILL NOT float at a preset tension but instead will tighten to the most slack part in rotation and will not release as the engine is rotated and the chain gets tighter with non concentric sprockets. I think that if you want a low maintenance cam drive than Jim Comstock's gear drive will be the ONLY way to go

Click to expand...

Maybe a lawsuit would change their customer support? 8)

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naw I will just bad mouth him EVERY time I get the chance and cost him a possible sale so maybe he will get the hint that way :mrgreen: . I know of severel failures and every one that contacted him it is the same answer YOUR ARE THE FIRST ONE THAT I HAVE SEEN FAIL.

bill said:

I think that if you want a low maintenance cam drive than Jim Comstock's gear drive will be the ONLY way to go

Click to expand...

What's the latest on that? Are they on the market and whats the cost?

I put about 9000 miles on spring cam chain tensioner prior to now seeing the damage done.

zotz said:

bill said:

I think that if you want a low maintenance cam drive than Jim Comstock's gear drive will be the ONLY way to go

Click to expand...

What's the latest on that? Are they on the market and whats the cost?

Click to expand...

They are still in the testing stage, I just didn't want to release them until they were proven to last. Failure could be catastrophic. Jim

And that exact attitude is what we have come to expect.

Thank you!

And that exact attitude is what we have come to expect.

Thank you!