Cam chain tensioner interchangeability help

[C-Los SD]

Got a possible issue with my cam chain tensioner install. I started with 73 TX650 256 motor. I had installed a 447 rephased crank and cam and new cam chain. I reused the original lower chain guide and tensioner (pic below) and buttoned everything up. In the process of reading about valve adjustment, I came access a post about when swapping 256 to 447 cranks to change the cam tensioner, but nothing really definitive. My problem is, I already sealed up the motor and have everything perfect and don't want to wait for new gaskets and clean off the three bond and start all over in order to replace the lower guide.
So, can I reuse my old style guide and tensioner with a 447 crank and cam, or do I have to change it all over.

Thanks

 

[ANLAF]

Is the engine now up and running?

If it is, have you been able to make the correct adjustments - cam tensioner, then valves, then timing, then carbs?

The function of the cam chain tensioner is to maintain optimum performance on valve clearances and, therefore, timing. Unless you have read something pretty startling (in which case it would be common knowledge) then there is no real concern.

People have their preferences, but if there was a major Change-the Tensioner issue on re-phasing you would have come across that in your preparation.

I have looked at the variations of tensioners and there is no great departure in function - mine is the model after the one you show with the locknut. There is one thing you can do, and that is to check to see if there are any posts which might point to tensioner failure and re-phasing. I can't find anything.

If there is an issue, someone will jump straight in and help you out.

Anlaf.

 

[C-Los SD]

It's not running yet, but it is put together and really trying to avoid taking it apart. My concern is not the rephase, but using early style tensioner and lower guide with a later model crank and cam that have more teeth on the crank and cam sprockets.

 

[TwoManyXS1Bs]

The camchain on `70-`73 was the early 256 style, different pitch from the later `74-on 447 camchains. The sproket on your tensioner needs to match the camchain pitch. Don't think there was a later-pitch sproket, research time. Since the engagement occurs over only 3 teeth, or so, may not be a severe issue, especially if the sprocket teeth are worn a little. Your call....

 

[650 bobber boy]

Yeah as twomany said the pitch is not right... I have done the same thing !! 256 cases with rephased 447 internals.. I also had the same tensioner as you.. My tensioner was as new so teeth are perfect and as I knew the pitch was different on the crank and cam I laid my new 447 cam chain out flat on a clean table and ran the tensioner sprocket up and down the chain and you could feel the sprocket skip/jump every few teeth so yes if I was you I would pull it down and swap it all out for 447 parts... Even if your sprocket is warn down and feels smooth, do you really want to use warn parts in your freshly built rephased motor ?? I certainly wouldn't...

Also once the older style guides ware and need replacing, have fun finding good ones !! Just easier to put brand new 447 parts in now and be done with it I reckon..

Also number 2, lol. The cog setup with two cogs that go's in between the crank and the cross over shaft for the electric start setup needs to be replaced also well the rear cog does anyway... I can't off the top of my head remember which way around it was but one mix does fit and work but with a bit to much play and the other doesnt mesh at all !! So you have to make sure you use a 447 rear cog with the 447 crank...

 

[C-Los SD]

Thanks for the confirmation with the tensioner.
Are you referring to gears 4 and 5? In comparing the 256 and 477 starter gear cogs, the 447 has 23T for both and the 256 has 24T and 25T. I didn't even think about changing those gears. Thanks for the tip! XS650.com is awesome.