Any Yamaha mechanics on here ?

[diymirage]

My wifes TTR125 had a small oil leak, which I tracked down to a missing bolt on this 'tower'

Best I can tell it's a valve tensioner of sorts

I took the other bolt off to match it up and now..it doesn't want to go back in (feels like there is something in there pushing it out)

Anyone know the trick?

Thanks !

 

[diymirage]

Never mind, I figured it out (chatgpt to the rescue)

Turn out that Lil 10 mm on the back gives access to a cammed plunger in there

With that 10 mm off, I can get a flathead in there and "twist" it back in


It's all back together now

 

[tjpatte]

That’s a cam chain tensioner that is spring loaded. Take the bolt out of the tower to relieve the pressure, install the body and bolt it in, then insert the bolt and spring into the tower. Don’t rotate the engine until it’s all back together.

 

[jos51700]

Ditto. Cam chain tensioner. If there's any rattle noises, shut it off and find out why

 

[tjpatte]

To add, if there are teeth on the protruding shaft then you will probably have to disengage a little paw that locks into those teeth to get the shaft back in.

 

[diymirage]

. Don’t rotate the engine until it’s all back together.

I may have gently rotated the kick-starter to see if it would go in (it didn't) before I figured out how to back it off

I can't imagine that would cause any issues though?

Ditto. Cam chain tensioner. If there's any rattle noises, shut it off and find out why

Ill let you know tomorrow, I'm all washed up and ready for church

 

[tjpatte]

You’ll probably be fine, it’s not a high performance engine so some shifting in timing shouldn’t cause piston to valve interference. There usually tends to be a lot of slop when you completely pull the tensioner so you don’t want to jump any teeth on the crank/cam. Once you get it back together pull the plug and slowly rotate the motor by hand with the kickstarter feeling for any binding.

 

[diymirage]

You’ll probably be fine, it’s not a high performance engine so some shifting in timing shouldn’t cause piston to valve interference. There usually tends to be a lot of slop when you completely pull the tensioner so you don’t want to jump any teeth on the crank/cam. Once you get it back together pull the plug and slowly rotate the motor by hand with the kickstarter feeling for any binding.

Will do, I'll let y'all know how it did

 

[jos51700]

The biggest issue would be if you had a kickback, either from timing or pushing back against compression, while rolling it over. If you're confident that didn't happen, it's probably fine.

If you were slow and gentle on the kicker, you are probably ok, but I'd roll it over by had a couple times and stop if it binds AT ALL. That would be valve to piston contact at that point.

Alternately, you can pull the cam cover and see if the marks on the wheels are still in line when it's at TDC.

I never understood why nobody made automatic chain tensioners like that for sbm and bbm motors. They're simple as can be.

 

[diymirage]

update, did as suggested, pushed it over real slow, listening for clunks and clanks, all sounded well

fired it up and ran fine
took her for a short ride (front tube is trashed) and a good bath
the last stickers on the fender say "2016" so its been a while

im hoping with that chain tensioner properly installed and resealed the engine will not loose any more oil and stay a lil cleaner