Stripped cam chain tensioner lock

[akpasta]

Hi folks,

I was adjusting my cam chain tensioner and when I screwed in the lock bolt it stripped.

What do think could happen on a cb77 cam chain tensioner/cam chain if the locking bolt doesn't lock the tensioner mechanism, allowing the spring to just put full tension on the cam chain all the time?

As opposed to honda fours where lock bolt pushes straight on the tension spring, The older tensioning lock-bolt on twins is a bolt that comes in perpendicular to the tensioner shaft and the bolt presses against the shaft to lock it, meaning the pressure is all on the threads in the tensioner cover and they finally stripped. Now the tensioner is free to apply spring pressure to the cam chain. The tensioner moves in and out a matter of mm's when running. Problem??

You guys experience that at all? In my experience honda chain tension "adjusters" never seem to do anything anyway, I always followed the service instructions of turning the engine to "t" or whatever but when I loosen the lock bolt there's never any tension taken up. I dunno.

[LOUD MOUSE]

The fact that the shaft moves when the engine is running should give you a clue to the answer. ................lm

Hi folks,

I was adjusting my cam chain tensioner and when I screwed in the lock bolt it stripped.

What do think could happen on a cb77 cam chain tensioner/cam chain if the locking bolt doesn't lock the tensioner mechanism, allowing the spring to just put full tension on the cam chain all the time?

As opposed to honda fours where lock bolt pushes straight on the tension spring, The older tensioning lock-bolt on twins is a bolt that comes in perpendicular to the tensioner shaft and the bolt presses against the shaft to lock it, meaning the pressure is all on the threads in the tensioner cover and they finally stripped. Now the tensioner is free to apply spring pressure to the cam chain. The tensioner moves in and out a matter of mm's when running. Problem??

You guys experience that at all? In my experience honda chain tension "adjusters" never seem to do anything anyway, I always followed the service instructions of turning the engine to "t" or whatever but when I loosen the lock bolt there's never any tension taken up. I dunno.

[philrock]

I would strongly recommend not running the motor without the tensioner lock bolt working. Helicoil the threads or get a new casting or complete assembly - many assemblies are available on ebay.

This part was made with at least 2 different horizontal spacings on the mounting hole centers. If you get a new casting or assembly, take care to get the right hole pattern.

I have a complete spare assembly with 41.65 mm horizontal hole spacing, but the wheel is shot. Replacing the wheel and / or swing arm would be a bit challenging because these parts are riveted on.

Best bet is the Helicoil solution.

Phil

[akpasta]

Thanks folks,

I will buy a 6mm x1.00 helicoil kit. That is the correct pitch yes? I assume it will pay for itself as that is the most common fastener size on lots of old bikes.

[philrock]

6 x 1.00 is correct. Buying the kit will definitely be cost effective. Use the longest insert you can.

[akpasta]

Heli-coiled the stripped hole. All good now!

Didn't need a longer heli-coil than the one provided in the kit, that was plenty to get enough torque down.

[G-Man]

Phil

I have been refurbishing these tensioners for a while now. This is a summary of some of the posts in my 1961 CB72 project thread....

http://www.honda305.com/forums/cam-chai ... 36264.html

G

I would strongly recommend not running the motor without the tensioner lock bolt working. Helicoil the threads or get a new casting or complete assembly - many assemblies are available on ebay.

This part was made with at least 2 different horizontal spacings on the mounting hole centers. If you get a new casting or assembly, take care to get the right hole pattern.

I have a complete spare assembly with 41.65 mm horizontal hole spacing, but the wheel is shot. Replacing the wheel and / or swing arm would be a bit challenging because these parts are riveted on.

Best bet is the Helicoil solution.

Phil