305 Cam Chain Tensioner

[NBD925]

I looked through all the posts and have not seen any complete information on the Cam Chain Tensioner rubber wheel replacement. I know this has been discussed before but none of the posts have been followed up with what was used and how it was done.

I was in need of a good Cam Chain Tensioner for my 1966 Honda Dream. I have two tensioners now but each has its own detrimental problem. The first one has a rubber roller that looks like a sprocket. To far gone to do the Ed Moore resurfacing trick. The second one has a stuck roller. The needle bearing that the roller rides on was rusted and completely stuck. No amount of lube or heat would allow it to move.

I took to disassembling this Cam Chain Tensioner and roller so everyone can see what the internals of the cam chain roller look like.


DSCN0269 by adam.corts, on Flickr


DSCN0268 by adam.corts, on Flickr

Here are the options I have seen offered:

You can make a wheel out of Derlin:
If you choose this option what are the dimentions? Now I know you can just use the old wheel to find the demintions but I cannot use the original needle bearing because it is rusted. Is there a replacement for this bearing or are people using a different bearing? Are people making the Derlin wheel for use with a bearing or without?

You can get a replacement wheel from a Z1 Kawasaki - guide roller (12055-002):
How are people adapting the part? What bearing is being used for the center?

What are people using to clamp the wheel in the tensioner? Are you just tapping the center pin for a threaded bolt?

Hopefully we can get to a conclusion on the Cam Chain Tensioner mystery.

[DCON]

hey nbd. im very interested in this. i had no idea there was a needle bearing in there!
it seems to me that there are several rubber rollers on the market. some for only 20 bucks.
any chance you have a caliper and can measure the parts in the pic? is that an oring on the pin for the roller?
is there any numbers on the bearing cage?
id love to be able to help come up with a solution. i can measure a good wheel on monday and get some measurements for you. i have some great machinist friends, my boss has at least 15 lathes and a new cnc machine so im sure i can get some work done, lack of time is my biggest hurdle. i havent done it yet but i wanted to take apart a primary tensioner and see if it could be modified...

[mike in idaho]

That's what is commonly referred to as a Torrington Bearing, fairly common and not too expensive. It should be available at any bearing supply house, take the numbers (and measurements) along when you order it. If you're adapting a different idler wheel, you may need to order a different o.d. bearing to suit.

[DCON]

good wheel measurements...
o.d. including chain bump= 43mm
o.d. without chain bump=40mm
chain bump width= 5mm
total width=15.50mm. these are approximate given 7000 miles on wheel. now to get interesting... the primary tensioner wheel was from a high mileage core so with that in mind
primary wheel:
o.d. including bump=42.10mm
o.d. without bump=39mm
chain bump width=8mm
total width=15.50. this wheel has no needle bearing, it has a bushing/sleeve that rides on the axle, and another bushing pressed into the wheel itself. the axle looks identical(though i didnt measure it)
the axle o.d.=9.98mm. the bushing i.d.=17mm( the 17mm can be pressed out).
soooo nbd, what are the measurements of your axle,wheel i.d. and bearing sleeve?
if we can source a good wheel maybe i can have some axles made up, they would need a snapring groove and something to prevent it from spinning in the arm. do-able...

[hondauser]

why not adapt this tensioner design , this one is for a cb 750 (four)
and a similar tensioner exists for the CB350 (twin)
it is interesting to know that the cam chain is the same for the 305, the 350 cb & 750 cb and with the same number of links !!!

friendly MK

[hondauser]

found on the net some time ago !!!

[NBD925]

Hey everyone I just got back to my computer today. Glad to see all this progress on this subject.

Hey DCON, there was no o-ring in the setup I took apart.

Here are the numbers on the bearing as they appear around the rim:
* CROYDON * K - 910

Here are the measurements that I came up with for the original bearing mentioned above:
19mm outer 10mm Inner 16mm Width . . . . the inner portion that rides in the needle bearing area is 17mm width and has gnarls on it to grip the arms that hold the wheel in the tensioner (See Picture two and three . . . second item from the left on the bottom of the picture).

Tensioner Axle Measurements:
10mm Diameter 18mm Length there is a smaller diameter on the axle that is about 9.5mm and 8mm long in the center of the axle also one 3mm hole in the middle of that. This hole does not go all the way through the axle. One end of the axle has a head on it that is 16mm dia and 1.5 thick for half of the dia and 4mm thick the other half. On the other side of the axle there were two tabs that hold the wheel in the tensioner arms. They were 5mm wide but I am not sure of the length dimensions of those tabs. A guess would be 5mm. We might be able to find a better way to mount the wheel on this end.

Tensioner wheel measurements:
19mm Inner 39mm outer (possibly 40mm) 15.5mm wide The center ridge that the chain rides on is about 4mm wide 44mm dia This is a guess because mine is bad. The metal bushing that is molded to the rubber wheel is 16.5mm wide so 1mm wider than the wheel. This metal ridge is 23mm dia and 19mm dia inner.

Here are someone else’s measurements that might fill in the gaps or show what I'm talking about just ignore the Cam chain Guide roller in the left of the picture:


Cam Rollers by adam.corts, on Flickr

Here are the pictures I took. They show the measurements I described above:


DSCN0268 by adam.corts, on Flickr


DSCN0269 by adam.corts, on Flickr

Let me know what else you guys need. That would be amazing if we as a group could find a solution to this and figure out the best material or replacement wheel for this tensioner.
DCON if you have access to a CNC, I’m sure if we could figure out the best material and measurements that someone could write a program for the CNC machine to get it done.