Topic: CB750K2 Primary Chain Length

[MCRider]

For my project bike, I have chaiins out what I think is a low mileage parts bike. Does anyone have a new chain to which I could compare lengths?

I would like to avoid $200 for new chains if possible.

[scunny]

don't know about length but to test which chain is in the best condition hang them both on a nail and the best one will not droop as much, it's easy to see when you compare them.

[bwaller]

Well, I've got new chains in stock, but I'm not sure how you want to measure them. I quess if you had a new chain to compare side by side it might be evident if the used one was r-e-a-l-l-y stretched otherwise how I transfer the info to you is the question.

I'm all ears though.

[MCRider]

Well, I've got new chains in stock, but I'm not sure how you want to measure them. I quess if you had a new chain to compare side by side it might be evident if the used one was r-e-a-l-l-y stretched otherwise how I transfer the info to you is the question.

I'm all ears though.

Thanks to both for responding. Scunny, couldn't tell any difference by hanging them or bending sideways. But setting them side by side (doubled over of course), I align the far left pin of each chain, then travel to the far right and the chain I know is old is about 1/2 the diameter of a pin longer than the other chain from the parts bike. Assuming that same rate of wear on the return course that's a whole pin diameter longer.

And the tensioner is hard as a brick bat and starting to chunk very teeny bits, so its definitely out.

Now I just don't know how the parts bike stacks up to a new one. I assume pretty good, but I'd like to know.

bwaller: maybe you could lay one out on the bench doubled over and measure just half the chain from pin to pin. That might be the easiest way to get a measurement as measuring the whole chain is hard to imagine.

Thanks!

PS: By "in stock" is that personal stash or are you in business?

[Jerry Rxman Griffin aka MuthaF'er]

FYI,  do NOT order 2 primary chains as you will get 2 SETS. Order only 1 and you will get 1 set of 2. You should be able to find 1 set for about $75. You may already know but the shop manual only refers to measuring the primaries in the engine without it disassembled. I can scan and email or post the info if you need it. It also says to replace the roller if damaged or deteriorating.

I do not think you could get an accurate measurement without it being stretched around sprockets simply due to the nature of chains and their many links.

Jerry

[bwaller]

I agree Jerry.  MC if you're spending big money building this engine anyway, change the chains.

Unless you have a new one in hand to check against an old one, it's damn tough.

[Clyde]

There is a method to check the chain as described in the manual.
You will need to assemble the crank, chain and clutch shaft with the tensioner in the crancases.
Tighten the crankcase with 4 bolts and measure the height from the sump plate surface to the top of the tensioner.
A new chain will typically give a reading of 65mm. Honda recommend  to replace the chain if the reading above 70mm(from memory?).
I always check this and if the reading is above 67.5mm I replace the chains.
Check the tensioner to make sure it is not breaking up and is still at least slightly soft (fingernail test). Any evidence of it breaking up and it should be replaced.

[MCRider]

There is a method to check the chain as described in the manual.
You will need to assemble the crank, chain and clutch shaft with the tensioner in the crancases.
Tighten the crankcase with 4 bolts and measure the height from the sump plate surface to the top of the tensioner.
A new chain will typically give a reading of 65mm. Honda recommend  to replace the chain if the reading above 70mm(from memory?).
I always check this and if the reading is above 67.5mm I replace the chains.
Check the tensioner to make sure it is not breaking up and is still at least slightly soft (fingernail test). Any evidence of it breaking up and it should be replaced.

Really? Refer to the manual? What a novel idea!     So I looked in my Clymer and there it is, not much but that's all it takes, complete with a diagram on how to do it. I'll definitley get a new primary tensioner. Then I'll check both the old chains and the new.

bwaler and Jerry make good points about just replacing them. But my mid-western frugality is kicking in and if the parts bike chains are barely used I'd like to recycle them.

If I can use the parts bike chains in Phaedrus II, then I'll have to buy new chains for the cafe racer Free Bird.

Thanks everyone, I have my answer.

[754]

Hey, I just happened on a set of NOS 2 weeks ago.. got a super deal, they had 105.00 marked on them, yes there are 2... at first the guy thought it was a camchain and I bought it, was holding in my hand and thought.. Wayyyy too thick to be camchain.. lol


I will figure a way to measure, I am thinking stretch it out with a bungie and measure across a number of pins or plates to give a number to check against..

[MCRider]

Hey, I just happened on a set of NOS 2 weeks ago.. got a super deal, they had 105.00 marked on them, yes there are 2... at first the guy thought it was a camchain and I bought it, was holding in my hand and thought.. Wayyyy too thick to be camchain.. lol


I will figure a way to measure, I am thinking stretch it out with a bungie and measure across a number of pins or plates to give a number to check against..

Lucky score. Yes my thought was to measure a representative length pin to pin, that should be enough.

I'll use the manual procedure on my old chains, and the olderchains,  just to document some reference numbers.