Topic: 1982 Honda CB650SC Cam Guide and Tensioner Help

[papi_sosaa]

Hello,

I'm in the middle of rebuilding my engine and unfortunately my cam tensioner and guide are cracking. I don't feel comfortable putting them back into a fresh engine so I wanted to see if anybody had a set that they would be willing to sell off or if somebody can point me in the right direction to get these parts. Realistically I only need the slipper and the guide.

[papi_sosaa]

Tensioner

[papi_sosaa]

Guide

[fizzlebottom]

Good news and bad news.

The good news is that the same thing is happening to every single slipper and guide in just about every SOHC CB650 in the entire world. and they aren't crumbling (yet). So long as you reinstall it correctly and keep up with chain tension adjustments & oil changes, you're fine.

The bad news is that nether Honda nor any aftermarket companies have made these particular parts since ~1982 and there are literally 0 available worldwide unless someone is hoarding parts. Used ones pop up on eBay, but every single one I've seen is cracked.

CB650 cam chain tensioner parts are some of the few that I think are 100% gone from this world. Use what you've got until it don't work no more and then sit on eBay and hope for the best.

Tensioner assembly: 14500-426-010
Slipper alone: 14520-426-010
Guide: 14611-426-010

[papi_sosaa]

I could gamble it and spend $200-300 for a higher mileage CB650 engine but who's to say what the condition of those tensioners are.

Getting another engine might even be beneficial because my engine was so caked in mud and dirt that it might've overheated at one point. 5 of my 8 valves were leaking past the seals and all of the o-rings were cooked. If I buy another engine and it turns out to be good, I could use my freshly machined top end on the spare bottom end and call it a day.

Not sure yet, going to inspect the piston and rods for play and go from there. Still hoping to find a tensioner and guide.

[fizzlebottom]

I could gamble it and spend $200-300 for a higher mileage CB650 engine but who's to say what the condition of those tensioners are.

Getting another engine might even be beneficial because my engine was so caked in mud and dirt that it might've overheated at one point. 5 of my 8 valves were leaking past the seals and all of the o-rings were cooked. If I buy another engine and it turns out to be good, I could use my freshly machined top end on the spare bottom end and call it a day.

Not sure yet, going to inspect the piston and rods for play and go from there. Still hoping to find a tensioner and guide.

Unless there's something you haven't mentioned, mud and dirt aren't really indicative for any overheating. It probably has some bad oil leaks that are just making it look worse. Valve seals and o-rings are all replaceable. I don't think it'd be a great idea to gamble on an engine of unknown condition just for a tensioner & guide if they're not actively breaking pieces off. Change your oil and adjust your cam chain tension and you'll be fine.

I hope you are able to find a tensioner, but I'm not holding my breath. I called South Sound Honda today and they have none, even though their site isn't showing them as Not Available.

[bryanj]

The 650 out of the mid fours is the only one with primary chain tensioner and a hyvo cam chain so it is nearly as much a red headed child as the 550 k3/4.
Also for info it is not a bored 550 but a stroked 550

[papi_sosaa]

I dropped the top end off at the machinist and he said the guide itself looks okay but the tensioner slipper is no good and wouldn't recommend putting it back in.

The slipper is cracked pretty good towards the ends where there is the least amount of material.

Worse case scenario, I reuse the tensioner and hope it lasts long enough for me to at least enjoy the bike for a while.

[fizzlebottom]

I dropped the top end off at the machinist and he said the guide itself looks okay but the tensioner slipper is no good and wouldn't recommend putting it back in.

The slipper is cracked pretty good towards the ends where there is the least amount of material.

Worse case scenario, I reuse the tensioner and hope it lasts long enough for me to at least enjoy the bike for a while.

I'll stop after this. I appreciate a professional's opinion, but I would take that opinion with a grain of salt. I get that your tensioner is cracked. I can also all but guarantee that they all are. Even "good" ones removed from salvage bikes. The material simply was not meant to stay elastic for this long.

Even the FSM says only one thing about when to replace either the guide or slipper:

Inspect the slipper of the cam chain tensioner for damage or excessive wear. Replace the tensioner and guide if the Teflon coating on the slipper is worn out.

That either tells me that they weren't worried about cracking alone, or that they were unable to test the material long enough for cracks to even form.

Point is, I know mine is cracked like yours. I even have a spare that's cracked like yours. I'll run it without hesitation because there honestly is no other option aside from giving the bike up.

[papi_sosaa]

The Teflon coating is peeling on the backside of the guide but the tensioner is 100% in terms of the coating. The machinist didn’t really look to deeply at both parts, he saw the cracks and just said he wouldn’t recommend using them.

I ended up buying another ‘82 CB650SC today as my parts bike for $200 CAD so I’m going to open up the block and see how that tensioner looks.