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Discussion Starter · #1 ·
Howdy,
First post, new to motorcycles, amateur machinist, yadayada.
I bought a '72 CL350 off a guy on craigslist about a month ago. The kickstarter was jammed and he was trying to sell it anyways, so he didn't bother diagnosing it. When I took apart the engine, nothing seemed out of whack. The pistons aren't seized, (nearly) everything is well maintained, measured everything and it's within the factory margins- the PO before him seemed to take care of the bike. The most obvious issue I found was that the cam chain tensioner roller and sprocket had rotted and almost completely fell apart- found bits in the engine. I'm not jumping to conclusions, but some of the rubber might've jammed the starter gear. The kickstarter released when I pulled the clutch plates out of the basket. I've read that improperly installed clutch stuff can jam the starter. Either way, I'll readdress that once I put it back together.

Issue at hand: I need to replace the cam chain tensioner roller and sprocket. I know there's newer ones made of steel, nylon, and urethane. I saw a post about alternatives from a few years ago, but noone went into why they thought one material worked better over the other. Haven't found many product reviews either.
Does anyone know the advantages of each material?
Also, could I use a steel sprocket with a rubber roller?
I'm considering machining the roller. Does anyone have the specs for it? I can't even vaguely base a measurement by mine cos it's so decayed.

The cam chain also snapped, but I think that's because I lifted the engine by the head like a dumbass. Apparently it's a new chain, but I guess I should replace it.
 

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https://www.siriusconinc.com/search...&make=1&model=cb350g&part=8&partno=&x=30&y=14

I've been able to purchase all the OE parts from Honda Canada. The big roller isn't listed in the above search but 4 into 1 had them. I also use the EK chain. If the two piece part that the arm pivots on is worn it should be replaced as well. It's in the above search.

Others have used parts from bore tech ...... not my preference though.

I'd advise putting in a one size over set of piston rings with the 3 piece oil control ring. You have to file the end gap to spec but that is easy ..... I put a diamond disc for a dremel into a vice and file both ends at the same time. It goes quickly so measure often if you do this.

I think the timing chain was worn out .... no way it couldn't have taken that load in my opinion.
 

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I was going to do some rollers in nylon because it seems tough enough. I wonder if it'd work for a sprocket.... Side loads would wear it pretty fast I bet. What material would compare to the rubber that you could machine? Pretty sure the Honda parts were molded. That'd be another avenue to look down. Seems there's a buck to be made and a lot of Honda parts are being reproduced. There was a interesting link to a build on adventure rider forum where the builder redesigned the tensioner because he felt the KA offering was crap.
 

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Discussion Starter · #4 ·
Lefty,
What stopped you from doing it?
I think a soft urethane might work for the roller- like street/vert hybrid skateboard wheel material. I'm not sure how well that turns but I have after hour access to the lathe at work so I might give it a shot. Just for the roller though, I don't want to make an indexing jig to mill the sprocket. There's a steel set on ebay by someone in Philly, sells them for $120ish- but if I can figure out how to turn the roller in urethane, I could save $50.
 

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Discussion Starter · #5 ·
Boomer,
Is there an advantage to the OE products?
The pistons seem fine- very clean and measured at factory size. Is there a reason to replace them still?
Could that happen with a new chain if the points weren't timed properly? It doesn't look like the chain has much wear. Maybe it was installed incorrectly? One of the plate chains bent off.
 

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Boomer is suggesting one oversize in rings, not pistons. The reason being is that way you can get the ring end gap set to the minimum clearance instead of what ever they turn out to be. He's not kidding about them grinding down quickly, I use a file because it's slower and less chance of going too far.

Moved to the 350 Engine section
 

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I haven't had the immediate need to try it yet. Skateboard urethane wheels sounds interesting. I've ridden skateboards and have seen some bad wheels crumble. I think one reason the rollers are made of a rubber is to damp the noise. You'd think a tough nylon might get some tiny dents that the chain would naturally ride in, but maybe not always under all circumstances which might not be good. I think I read once on a new part the middle ridge is high enough that the chain rides on its pins, but I'd have to see it to believe it.
 
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