3TJ cam timing ..

petrolhead · Post by **petrolhead** » Mon Nov 21, 2011 10:57 am

Right have decided to set the cam timing on the bike before I go ripping the head off to see if the valves are damaged .
I cant get a good diagram for the timing as the manual I downloaded had crap picture .
So maybe someone can tell me if this is right ,,,

Mark on the generator. T lined up with the crankcase end.
Dot on the end of cam shaft lined up with the dot on the cam journal (think thats the right name for it ).
Intake cam lobe is sitting at 90 degrees pointing towards the back of the engine
Exhaust cam is sitting 90 degrees pointing towards the front of the engine ..

does that all sound right for the cam timing to be set properly ..
And is there a way to check possible valve damage without taking of the head and doing a visual inspection.
Any help would be great ,,

Post by **CMSMJ1** » Mon Nov 21, 2011 11:05 am

how do you set the timing without removing the cam chain?

petrolhead · Post by **petrolhead** » Mon Nov 21, 2011 11:24 am

CMSMJ1 wrote:how do you set the timing without removing the cam chain?

Honestly not sure of the correct method but this is how I done it..
I Removed the cam chain tenisoner and the cam chain guide (upper one )
This gave me enough slack in the cam chain to be fit to turn the cam one tooth at a time and feed the chain back through again..
I know its not the right way to do it but it did work to line up all marks ..Slow bloody job though,,,And frustrating ..

Post by **CMSMJ1** » Mon Nov 21, 2011 11:34 am

The easiest way to check for valve damage is to take the plugs out, get a torch and see what you can see..

or compression test it - you'll know asap whether you've got some damage then

petrolhead · Post by **petrolhead** » Mon Nov 21, 2011 12:29 pm

CMSMJ1 wrote:The easiest way to check for valve damage is to take the plugs out, get a torch and see what you can see..

or compression test it - you'll know asap whether you've got some damage then

Cheers for that..
Will do the compression and hopefully that will have good news,,

Post by **Evilchicken0** » Mon Nov 21, 2011 1:28 pm

If the valves have touched the pistons then they've probably bent, (stem runout is 0.02mm). It will probably run if the run out is more but it will wear out the guides fast.

If the compression is atall suspect then take the head off and check the valves.

petrolhead · Post by **petrolhead** » Mon Nov 21, 2011 2:03 pm

Evilchicken0 wrote:If the valves have touched the pistons then they've probably bent, (stem runout is 0.02mm). It will probably run if the run out is more but it will wear out the guides fast.

If the compression is atall suspect then take the head off and check the valves.

Thanks Evilchicken...
I thought the valves hit the piston first day cause of the noise coming from the engine .
I looked in the spark plug hole and seen what looked like valve marks and assumed the worst from the start,,
But after a bit of thinking the noise might have been the cam chain slapping ..
And the marks I thought were valve marks might have just been the wee circles on the pistons .(dont know what ya call them...LOL..)
I just think the engine might not be as bad as I first thought ,,, Its always normal to think the worst...
But will do the compression and see what it say's but if in any doth at all will just have to rip of the head and do the valves as you say ..

KIYOSHI · Post by **KIYOSHI** » Wed Nov 23, 2011 7:52 am

A comp test will only show pressure loss and not indicate the source of the problem. What you need to do is a cylinder leakage test. This will pinpoint any wear or damage. Air passing through the exhaust is a fault on the inlet valves, air passing the carbs is down to a fault on the inlets valves, air passing through the crank case is down to worn bores ect and any loss not highlighted by the above symptoms will be a blown gasket or fracture which may show itself as pressurising the coolant system.

What made you think the valves had touched the pistons?

Before stripping the engine I would firstly inspect the piston crowns as best possible, look for any clean spots which would indicate a big end bearing failure allowing the piston to touch the cylinder head. This is a common fault on the 3tj and often occurs on 1 and 4.

What was the original fault?

petrolhead · Post by **petrolhead** » Wed Nov 23, 2011 9:57 am

Thanks for the reply KIYOSHI..
What makes me think the valves have hit the piston was the timing was way out ,and when I turned the engine by hand it would lock solid as if seized , After I reset the timing that problem was gone ,There was a botch job done on the Cam Chain tensioner which I would say was a big part of the trouble ..
But I did fire her up yesterday and there is a low down noise in her too so think it could be big end .
I looked at the piston crowns and they seem to be OK from what I can see ,,
I would imagine if they hit it would leave a shiney circle on the piston..??

Must try and get a connection to do the cylinder leak test ..And see what it turns up..
Is the big end bearing failure on 1+ 4 a oil problem I got a crank along with the bike that has been drilled out think it was by BDK for better flow ,

KIYOSHI · Post by **KIYOSHI** » Wed Nov 23, 2011 12:11 pm

It's not the crank they modify, it is the oil feed in the crank cases to 1 and 4 main bearings.

Is it a race engine?

3TJ cam timing ..

3TJ cam timing ..

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