Topic: Primary Chainwheel Damage

[slikwilli420]

not easy for a 50hp design to handle 100 hp !
More so it is not a steady state strain either when circuit racing, it can be from abusive riding styles, I remember on this forum Mark McGraw saying he had a rider that regularly popped the chains out the top of the cases on a certain corner at Daytona and it started to happen when he was getting over 90hp. Chains are tricky to control , resonance, change of load direction, inertia all combine. Certainly good quality chains, tensioner and components help but rarely are they all engineered together in most classic racers, as the old saying goes, anything is only as good as the weakest link.
I have enjoyed this thread , Keith modestly comes up with a fix that has been plaguing the ol SOHC Honda since 1969. Speaking of chains Ive been waiting for Matt to thrash the guts out of his bikes and let me know how the new CX cam chain tensioner holds up.

A season on the cam tensioner and two on the primary and there are no signs of wear at all. I have the cases split now to address a few things so I can get a real good look at the bottom of the cam tensioner. Pulling the head today after the bottom end is buttoned up and will get a look at the top portion as well.

[PeWe]

OK, the primary hub has a harder life without a cush  drive on the wheel.

Bingo!

Gearbox must suffer too. I've seen upgraded parts with stronger dogs on this forum somewhere. Yamiya had newer versions before.

[slikwilli420]

OK, the primary hub has a harder life without a cush  drive on the wheel.

Bingo!

Gearbox must suffer too. I've seen upgraded parts with stronger dogs on this forum somewhere. Yamiya had newer versions before.

Never had any transmission problems though I tend to be pretty hard on 4th gear though that's more me than the bike.

[kmb69]

... Speaking of chains Ive been waiting for Matt to thrash the guts out of his bikes and let me know how the new CX cam chain tensioner holds up.

Me too if we are talking about the PA46 orange ones. ? ? ?

A season on the cam tensioner and two on the primary and there are no signs of wear at all. I have the cases split now to address a few things so I can get a real good look at the bottom of the cam tensioner. Pulling the head today after the bottom end is buttoned up and will get a look at the top portion as well.

Matt, Please post pictures of the tensioners since you will be the first one I know of to give them a real test.
I either read somewhere or was told that you had rivet heads popping off the primary tensioner - is this true?

[slikwilli420]

... Speaking of chains Ive been waiting for Matt to thrash the guts out of his bikes and let me know how the new CX cam chain tensioner holds up.

Me too if we are talking about the PA46 orange ones. ? ? ?

A season on the cam tensioner and two on the primary and there are no signs of wear at all. I have the cases split now to address a few things so I can get a real good look at the bottom of the cam tensioner. Pulling the head today after the bottom end is buttoned up and will get a look at the top portion as well.

Matt, Please post pictures of the tensioners since you will be the first one I know of to give them a real test.
I either read somewhere or was told that you had rivet heads popping off the primary tensioner - is this true?

I still have mirko's stuff on the s750 bike. Three rivet heads popped off sometime this season. I didn't have time to fix it between rounds of racing so I safety wired them so they wouldn't come out fully. I did fix both the upper and lower by drilling out the rivets and replacing with steel ones. I don't forsee any more issues there. I just finished putting the cases back together but the wear on the surfaces was nonexistent.

[kmb69]

I still have mirko's stuff on the s750 bike. ...

Are these Mirko's black, PA6 with moly versions on the cam chain tensioner?
Pretty sure Brent is using the PA6 on his DOHC cam chain stuff also since it is softer and much less susceptible to shock damage.

[slikwilli420]

I still have mirko's stuff on the s750 bike. ...

Are these Mirko's black, PA6 with moly versions on the cam chain tensioner?
Pretty sure Brent is using the PA6 on his DOHC cam chain stuff also since it is softer and much less susceptible to shock damage.

That's right Keith, black material for cam chain and brown for the primary.

[scottly]

I had one that I rebuilt a few years ago with the "heavy duty" rubbers from Europe that turned out to be really nothing more than pieces cut from rubber cord. It had a ton of play in it and and I swapped it for a rebuilt one from Cycle X for the start of the 2020 season. I pulled it apart yesterday to use for my new build and noticed a significant amount of slop between the inner steel portion (holds the needle bearings for the main trans shaft and has splines for the clutch basket) and the outer aluminum piece that is the inner half holding the damping rubbers.

I'm confused: is the bad part the rebuilt one with only one season of use?? And once again, has anyone else experienced this? Bear subjected his sidecar to much worse abuse; maybe he would care to chime in...

[slikwilli420]

I had one that I rebuilt a few years ago with the "heavy duty" rubbers from Europe that turned out to be really nothing more than pieces cut from rubber cord. It had a ton of play in it and and I swapped it for a rebuilt one from Cycle X for the start of the 2020 season. I pulled it apart yesterday to use for my new build and noticed a significant amount of slop between the inner steel portion (holds the needle bearings for the main trans shaft and has splines for the clutch basket) and the outer aluminum piece that is the inner half holding the damping rubbers.

I'm confused: is the bad part the rebuilt one with only one season of use?? And once again, has anyone else experienced this? Bear subjected his sidecar to much worse abuse; maybe he would care to chime in...

That's right. Rebuilt with only a season or two on it. I was going to use it for a new engine with the gl1000 gear when I noticed the issue. Seems no one has seen this which makes me think it's a fluke.

[scottly]

IIRC, Kenny did have a primary related failure where the teeth were ripped off the crank or something? Perhaps the core for the rebuild came from that experiment?

[slikwilli420]

IIRC, Kenny did have a primary related failure where the teeth were ripped off the crank or something? Perhaps the core for the rebuild came from that experiment?

Nah, this piece came from a stock engine I pulled down for parts.