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New cam chain tensioner broke 360

MervMaster

MervMaster

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Joined
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Location
NJ
Good evening friends.


When I first refreshed the top end on this bike, the the cam chain sider was cracked in half. I replaced both slider and the flexible tensioner with a new set from cmc. It’s all roses for a while.

Rode about 1000 odd miles over several months here and there with no trouble. With the vintage 1000 coming up next month(my first time), I decide to go for 100 mile loop. Less than 3 miles from home, top end seized. Camshaft fused to valve cover journal. My oil wasn’t making it to the top end.

So, ok, no problem. Better here than in Chattanooga. Rebuild the top end with good used spares. 200 miles later I hear a fun sound like a loose cam chain (very close to home).

Pull the rocker cover, chain moves nice, plenty of top end oil. cam smooth. The cam tensioner looks like it’s too low in the case.

The bottom part with the steel loop snapped off and is now lost somewhere in the bottom end.

Probably did some unknown damage. Any tips for fishing out a little piece from the depths of the case?? I tried with a little extendable magnet but gave up before I pulled the jugs.


If anyone has the time or inclination I’d appreciate opinions on next steps, knowing this bike needs to be ridden hard in 2 weeks.


Yours in rust,

Merv.
 
Did you figure out why the top end wasn't getting oil prior to the rebuild of paragraph 3?

Have you already drained the oil? No sign of the broken-off piece(s)?
 
stl360+450 said:
Did you figure out why the top end wasn't getting oil prior to the rebuild of paragraph 3?

Have you already drained the oil? No sign of the broken-off piece(s)?
Click to expand...

The previous owner must have used some rtv silicone in there at some point. The oil filter screen was pretty well clogged along with the oil passages. It was splashing oil all over the place at idle this morning- so that at least is solved for now.



Haven’t drained the oil on this go round. But the chunk of tensioner is almost definitely too big to come out the hole unless it’s been mulched by the motor.
 
I'm assuming you have a new tensioner ordered - and not an aftermarket one this time hopefully, though I don't know about the availability of a Honda tensioner - and that you're going to pull the top end again to replace it. Hopefully when you get in there you can do more fishing around with a magnet and find the broken piece.
 
ancientdad said:
I'm assuming you have a new tensioner ordered - and not an aftermarket one this time hopefully, though I don't know about the availability of a Honda tensioner - and that you're going to pull the top end again to replace it. Hopefully when you get in there you can do more fishing around with a magnet and find the broken piece.
Click to expand...

Honda NOS are still out there. But I spent a little over $100 for the arm, wheel, and guide.
 
See I’m always on the fence about buying 50 year old parts even NOS and not used. Even if it was made better in the first place, doesn’t the age of the pieces make it just as chancy?

I found the broken piece. it had wrapped around a little ridge, I’d never have gotten it with a magnet from the top end.

so I split the case. No damage of any, kind it just kinda clicked around in the crankcase and got lodged on a ridge.

I’m glad I split the case, there’s a ton of junk in there from the first cam slider that was cracked in half, and aluminum flakes from the last top end. It’ll be ok!


the little brownish thing left of center is the culprit after I dislodged it.






 

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Well this is disappointing news. I just installed a CMC tensioner in a coworkers bike.
I thought the old Honda 360 tensioners were not to be trusted?
 
MrPepper said:
Well this is disappointing news. I just installed a CMC tensioner in a coworkers bike.
I thought the old Honda 360 tensioners were not to be trusted?
Click to expand...


that’s why I went with cmc in the first place, the tensioner recall.

it’s totally possible that it isn’t cmcs fault. I did cook a top end just recently it could have been a side effect.
 
MrPepper said:
I thought the old Honda 360 tensioners were not to be trusted?
Click to expand...

There were two recalls (tensioner and rocker shafts) and a punch mark was added in the middle of the VIN on the upper crankcase for each. So, completion of both recalls would mean something like a colon appears in the middle of the VIN. If the motor has the punch marks, then the tensioner should be a good part.

Note that the tensioner recall was only for certain VIN numbers, so if the bike was not affected by the recall, then it should have a good tensioner even without punch marks.

Screenshot_20220713-214207.png
 
stl360+450 said:
There were two recalls (tensioner and rocker shafts) and a punch mark was added in the middle of the VIN on the upper crankcase for each. So, completion of both recalls would mean something like a colon appears in the middle of the VIN. If the motor has the punch marks, then the tensioner should be a good part.

Note that the tensioner recall was only for certain VIN numbers, so if the bike was not affected by the recall, then it should have a good tensioner even without punch marks.

View attachment 15703
Click to expand...



Thanks for the clarity there. It’s got to be nearly impossible to know if you’re getting a NOS tensioner from the pre recall or post recall time though. They must have had some production of replacement “wear parts” even in the first production run.
 
I'm not sure if the recall document is in the VHT library or not, but you might check (PM ancientdad or LongDistanceRider for access if you need it). I found it with a Google search and it includes a side by side comparison that should help tell if you have the correct Honda part.

Screenshot_20220714-060810.jpg
 
Update: after a nice conversation with Caleb at cmc, they are replacing my parts for free. He also walked me through the components surrounding the tensioner and made sure that everything was in place. AND he brought up the idea that the cam chain itself may be stretched beyond its tolerance and causing the tensioner to bend too far and could have (during the excessive heat of my recent seizure) helped cause the break.

new parts coming tomorrow, will update my results once I’m reassembled.
 
Well, at least they are going to help you out with the parts, considering how short a life they had it would be the right thing to do. I suppose the cam chain could have been affected by the cam seizure, but since it's an endless chain it would require a full teardown to replace it. They're typically pretty durable, and we suggest replacing cam chains maybe more often than necessary but usually because we'd like someone to only have to go in there once.
 
ancientdad said:
Well, at least they are going to help you out with the parts, considering how short a life they had it would be the right thing to do. I suppose the cam chain could have been affected by the cam seizure, but since it's an endless chain it would require a full teardown to replace it. They're typically pretty durable, and we suggest replacing cam chains maybe more often than necessary but usually because we'd like someone to only have to go in there once.
Click to expand...



I’m back from the vintage 1000- I made it maybe 550.

I have cooked another top end for the same reason. Flakes of aluminum blocking the oil filter causing top end oil starvation. So I tore it down today, since that aluminum must be coming from somewhere. (Aside from the chewed up top end bits.)

So I found this. It looks like the cam chain has been slapping at the channel that it runs through. When I pulled the tensioner spring bolt out I heard kind of a “double click” which makes me think I may have never had the chain to the right tension


Is it possible that the chain could have stretched past the point of the tensioner being able to tension it?

The chain is getting replaced regardless. It’s got some hard spots in it. I’d love to hear opinions on master linked cam chains vs rivetedF01EC937-6F4C-4868-9E5D-FDAEFDA2C563.jpg
 
Oh man, that's a bummer.

I would do endless chain as a replacement, if possible
 
Obviously it's hard to say exactly when all that wear happened, and the 360 tensioner system doesn't inspire as much confidence as the older 350 version but it does work when all the parts are functioning properly. That kind of wear happens when the chain is run with some looseness and I suppose it's conceivable that it could have worn that much aluminum away in 500 or so miles. It may well have been that the tensioner lock bolt didn't release the tensioner fully or the push bar/shaft was sticky in the lower case. The best way would be to replace the cam chain with an endless but that requires a bottom end disassembly. I suppose you could use a 219T stake type master link with a DID 219T 92 link replacement. I wouldn't use any cam chain that came with a conventional master link, only a staked (riveted) version if you're going that route. Here's one

https://www.davidsilverspares.com/parts/by-part-number/partnumber_3414/

and the 219T stake-type master link

https://4into1.com/genuine-honda-d-...l72-77-cb-cl-350k-450k-sl350k-cb500k-550-750/
 
ancientdad said:
Obviously it's hard to say exactly when all that wear happened, and the 360 tensioner system doesn't inspire as much confidence as the older 350 version but it does work when all the parts are functioning properly. That kind of wear happens when the chain is run with some looseness and I suppose it's conceivable that it could have worn that much aluminum away in 500 or so miles. It may well have been that the tensioner lock bolt didn't release the tensioner fully or the push bar/shaft was sticky in the lower case. The best way would be to replace the cam chain with an endless but that requires a bottom end disassembly. I suppose you could use a 219T stake type master link with a DID 219T 92 link replacement. I wouldn't use any cam chain that came with a conventional master link, only a staked (riveted) version if you're going that route. Here's one

https://www.davidsilverspares.com/parts/by-part-number/partnumber_3414/

and the 219T stake-type master link

https://4into1.com/genuine-honda-d-...l72-77-cb-cl-350k-450k-sl350k-cb500k-550-750/
Click to expand...


i am 100% disassembled, so im going with a new continuous chain from cms.

i think im missing the little bushing/isolators that are supposed to be top and bottom on the slipper/tensioner- so thats getting jacked around a bit also. hopefully the spare engine i bought has a nice top end.
 
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