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Author Topic: fitting new cam chain tensioners gt125r  (Read 391 times)

dave2110

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fitting new cam chain tensioners gt125r
« on: March 14, 2017, 09:08:34 PM »

hi all i need to know the procedure for changing the the cam chain tensioners on a gt125r as the service manual isn't that clear.also is there a certain time or mileage when to change them.
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Cloud

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Re: fitting new cam chain tensioners gt125r
« Reply #1 on: March 15, 2017, 11:39:14 AM »


Change them whenever. They're time-bombs and can go at any time.

My personal procedure is to take the engine out, and put it on a bench, so I can easily get the cam covers off, and wind the engine over manually with a socket bar, until it's off-cam on all the valves.

If you pull the tensioner when the engine is on-cam (pushing valves open) you might, and probably will, cause the chain to come off the cam sprockets, messing up your timing. One tooth incorrect will cause the piston to contact and bend the valve.

You can do it with the engine still in. I think. I take the engine out because I check valve clearances at the same time. Not that I ever actually change the valve clearances. But if one was seriously off I might look into it.
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serp

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Re: fitting new cam chain tensioners gt125r
« Reply #2 on: March 15, 2017, 01:56:53 PM »

I don't know how different the GT125 is from the GT250 but for me it was a simple process.
I pulled the 2 bolts and removed the old tensioner.
I cleaned the gasket surface.
Installed the new tensioner with a new gasket**
Done.

** the tensioner is spring loaded so I removed the rubber plug and used a jeweler's screw driver to pull the plunger back then locked it in place with a flat T-shaped piece of metal fabricated from a hose clamp, once in place I pulled the T and the tensioner snapped in place.

Note. The position of the valves have no bearing on chain tension but be cautious NOT to rotate the engine while the tensioner is out to keep the chain slack on the tensioner side. 
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Cloud

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Re: fitting new cam chain tensioners gt125r
« Reply #3 on: March 15, 2017, 06:48:15 PM »


The GT125 and GT250 have different cam chains, sprockets, and tensioners. The basic mechanism for the chain/tooth mechanism is similar, but I have pulled a tensioner before, and had the chain go "chank!" to a new position, meaning I had to re-do the timing. Nae fun.

I have upgraded my cam chain and sprockets to run the GT250 setup, because I'm using titanium valve springs and custom high-lift cams and stuff. But this is not really an affordable option for most 125ers, because to get the 250 setup you need the teethwheel cut off from a GV250 crankshaft.
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dave2110

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Re: fitting new cam chain tensioners gt125r
« Reply #4 on: March 15, 2017, 08:12:18 PM »

can i use the tdc marks . turn to F  then take out tensioner and replace. then turn to R and replace.
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Cloud

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Re: fitting new cam chain tensioners gt125r
« Reply #5 on: March 15, 2017, 09:12:09 PM »


That's probably how you're supposed to do it. Should be fine.
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