Is the cam chain tensioner toast?

kbray0009 · Nov 24, 2021

Hey I'm trying to bring this 75 xs650 back to life and I did git it running, but very badly. I starting tuning by going to adjust the cam chain tensioner. When I take off the cap the piston is sticking out like more than 1/2 inch. I can turn the adjustment out to meet the piston, but now the adjuster is so far out that the cap can't seat. So I take the tensioner adjustment off and take some pictures.

Any idea what's going on? Is the piston supposed to be pushing on rubber?

https://imgur.com/a/UTWtLDI

Thanks!

xjwmx · Nov 25, 2021

I can't tell anything from the pictures. Maybe screw the adjuster out and photo it separately in good light.

gggGary · Nov 25, 2021

I looked also, was baffled.

gggGary · Nov 25, 2021

Do some reading, looking, comparing here;
https://www.xs650.com/threads/cam-chain-tensioners.1056/page-2#post-465622
See if there's something missing or assembled wrong?
Note the "type C" adjuster, originally fitted to 75s, uses much deeper cap than the later types.

kbray0009 · Nov 26, 2021

The above pictures are of inside the engine where the piston rubs against the tensioner.

Looking at the adjuster types, my adjuster looks more like an E type than the C type that I should have on a '75.

I have included some pictures of the adjuster and also what it looks like when I turn the engine over, the piston seems to have too much travel.

https://imgur.com/a/NgC3b1Q

xjwmx · Nov 26, 2021

kbray0009 said:
https://imgur.com/a/NgC3b1Q

Somebody with more knowledge of all adjuster years might spot something now. The video of the plunger coming out half an inch... wow. For my year at least the plunger movement is entirely inside the threaded barrel and as you tighten it movement eventually disappears but it stays flush with the end of the barrel from that point. 5twins has all the various adjuster parts and years knowledge. I could only do guesses on this.

5twins · Nov 26, 2021

Yes, it looks like you have the later type E tensioner assembly but it's been paired with the wrong plunger. The plunger you have may be from the original type C assembly and is obviously too long. You need a type E plunger to match up with your type E assembly. It should measure about 100mm long with a 14mm head .....

The rod portion of the plunger can't be any longer than the screw or it will come out past the end of it, like in your case .....

So, measure your plunger length. I bet you find it's way too long. You should probably also check your adjuster screw length. Two sizes were used in the type E assemblies .....

The length of the screw determines the thickness of the damper washer needed to make the rod be flush with the end of the screw .....

Use the wrong thickness washer and you'll get one of these conditions .....

kbray0009 · Nov 26, 2021

Thanks that's super helpful.

I found a type C assembly on eBay, so maybe I can revert to that.

5twins · Nov 26, 2021

Personally, I'd keep the later type E assembly, just "fix" it by getting the right plunger, maybe the right screw too if it's also wrong. Search eBay for the later type assembly. You can usually find them for around $20 or less. You don't often run across the individual parts, like the plunger, but maybe you'll get lucky.

The later assembly has a smaller cap nut which is needed to clear the cross bar on a linked carb set. The adjuster screw angles down slightly too. That also helps with the carb clearance.

kbray0009 · Nov 26, 2021

Would the E assembly this work with the existing 75 tensioner if I get the right plunger? I'm not keen to take apart the engine if I don't have to.

xjwmx · Nov 26, 2021

kbray0009 said:
I'm not keen to take apart the engine if I don't have to.

It's fun though! Seriously, I think the internally mounted part is all the same, at least except for the first year or two. You can check various years in a parts lookup like in this link and see if the part number is the same for the years (which means it's the same part). BTW, I notice from this the front guide is available. I thought it was unavailable from Yamaha for awhile.
https://www.lexingtonmotorsports.co...34d4fa/00c77619-e519-4a8a-acaf-2a77b9099721/y

5twins · Nov 26, 2021

Yes, the tensioner "blade" inside the engine was the same from 1974 on up to the end of production .....

Type C, D, and E tensioners will work with it.

kbray0009 · Nov 28, 2021

Great thanks all, eBay parts incoming.

Is the cam chain tensioner toast?

kbray0009

XS650 Member

xjwmx

XS650 Guru

gggGary

If not now, When?

gggGary

If not now, When?

kbray0009

XS650 Member

xjwmx

XS650 Guru

5twins

XS650 Guru

kbray0009

XS650 Member

5twins

XS650 Guru

kbray0009

XS650 Member

xjwmx

XS650 Guru

5twins

XS650 Guru

kbray0009

XS650 Member

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