Can Chain Tensioner fell out, what could be damaged?

Hello,

Last night I went for a ride and on my way home the cam chain tensioner fell out (didn’t realize until this morning when I found a pool of oil under the bike and the tensioner siting under the carb. I believe it happened in the last 30 min of my ride since I didn’t see any oil or anything when I stopped for gas. Most of that riding was highway/city riding (since it got dark and I was b lining home).

it’s a 1977 XS650D that I replaced the pistons, cam chain, can chain guide, etc. about 500 miles ago.

When riding I didn’t notice much of a change in how it was running which I am guessing is because the cam chain is new and was tight as heck when I installed it.
With the amount of oil I am just amazed I didn’t lose traction on the rear tire or at least notice a loss of traction, I am wondering if this amount of oil could be from the last mile or so of riding? Prior to that I took a number of turns where I leaned the bike.

After work today I am planning on:
-confirming cam chain didn’t skip a tooth.
-change oil/clean filters
-check compression
-clean up this oil mess

but is there anything else I should check?
Could something else be damaged? (I am hoping compression test will tell me if there is valve or piston damage)

Also Has this happened to anyone else? I followed the directions in the manual when reassembling the tensioner. Is there a trick to making it not back out?

Thank you in advance for all your help.

Your plan sounds good to me. See how much oil you had left when you pull the drain plugs. But my first guess is you dodged a bullet and it's going to be fine. A tensioner loosening is rare, but the cover needs to be snug. IIRC it was the next year yama added a lock nut. @5twins has diagrams and descriptions of the variations.

Well, it appears this is yet another strike against the notorious type D tensioner your '77 model came equipped with. If you look at all the different tensioner versions used over the years, you'll see the type D was the only one that didn't have a lock nut to lock in your adjustment setting. The acorn cover nut served this purpose. My main issue with that was installing the cover nut could make your adjustment tighter as you tightened it down. It seems you've stumbled upon another equally bad issue - if the cover nut comes loose, the whole tensioner assembly can fall out, lol .....



I highly recommend you start watching eBay for a type E tensioner assembly. You can usually score one for around $20 or less. More details on the reason for upgrading are here in posts 22 and 23 .....

http://www.xs650.com/threads/cam-chain-tensioners.1056/page-2

Thanks for the replies!

Update on the bike:
- Cam chain is still set correctly (used the pin hole on the camshaft under timing advance unit to confirm it is at 12 o clock and 6 o clock at TDC for each cylinder.
-Changed the oil, there was less than a half quart in there but it was pretty clean, there was some small specks of metal in the side oil filter, but considering it had new pistons 500 miles ago a small amount of metal debris is expected (right?). The lower filter/oil pickup filter did not have any debris or anything.
- Compression is at 150 psi on left and 145 on right. Compression test done by kicking 3 times with throttle open, repeated 4 times each cylinder to make sure consistent reading. (note: i checked compression on left first, then right so i may have kicked a little stronger on the left lol)
-took off exhaust valve covers and inspected camshaft and i did not see any excessive wear or damage.

Based on this I think the Bike is still in good shape, just needs a good bath to get the oil residue off of everything.

In regards to the Cam Chain Tensioner I am missing both the spring and the damper so will have to replace those, but the damper is not available on Partzilla. Do you know what this piece actually looks like? is it just a rubber washer? I have attached a screenshot of the parts I am missing.

Since I need to buy parts anyway I am going to look for a XS650E cam chain tensioner assembly, but if I cant find one in time I may just buy the spring and try and figure something out for that dampener.

Thanks again!

In particular, look at post 23 I linked to above. That one explains about the damper washer. You most likely had the copper washer type.

Yes, by all means get a type E assembly for a replacement. Don't even bother with the type D like you have now. The type E assembly came along by possibly late '79 but for sure by 1980. All the parts are the same between the type D and E except the plunger, plus the addition of the lock nut on the type E. You can leave your original housing in place on the motor and just swap the new parts into it.

Here's a type E plunger and spring, and it's marked way down .....

https://www.ebay.com/itm/382194154065?epid=1822941924&hash=item58fc8bfa51:g:W5kAAOSw9hdazVLw

You can buy the lock nut, copper damper washer, and the copper sealing washer for the lock nut here .....

https://yamahaxs650.com/product-category/engine/cam-chains-chain-guides-tensioners/