Tap, Tap, Tap xj700

we have just changed the timing chain, tensioner and guides on my xj700. This machine is new to me and has an indicated 6675 miles on the clock.

We carried out the above without removing the head.....Motor out, split the crankcases etc...bottom end all good. Wear on bores, etc suggested indicated mileage to be about right
The cams were retimed, they were way out, when we stripped the motor we discovered the tensioner was at full extension and there was still 20 ml play in the timing chain.
Tappets checked and then engine screwed back together.
We fitted the individual "pod" type filters and raised the needles to compensate.
Fired it up...caught almost immediately and ran

We have a tap.....it's coming from the left hand side of the engine,(as you sit on the machine), and increases with engine speed.It wasn't there before.

We haven't balanced the carbs yet.....YICS tool in the post from Chacal...

Anyone have any ideas............. before the motor comes out and we strip it again.

Would appreciate any help as we really don't want to motor out and tear it down if it's something as silly as carb imbalance

 

Not something as simple as an exhaust leak or pipes not tightened up enough? 7.2 ft pounds should be the correct torque... That's simple . Hope it's an easy fix.

 

So you did check the valve clearances?

If you have a scope try and id exactly where the tap is loudest. Or use a piece of conduit to find the closest point where the noise is coming from.

Unbalanced carbs could create a 'galloping' idle but wouldn't create a tap. Of course the valves when properly adjusted do make a light tapping noise as the lobes hit the shims-but it isn't discernible as rpms increase.

 

It's a dry tappet.... but why ???? Pulled the cambox cover....chucked oil over the cams.....Left it for a bit.

Started it up ten minutes later .....no tap. Then it gradually re appeared....

Shut it down....removed the cambox cover.Fired it up.....we should have been covered in oil.....nothing

THink we may have lost a seal that sits on top of the oil pump.....if it's been misplaced pump just chucks oil into crankcase instead of up into head....engine out this weekend and check it out

 

There are no Tappets.
The Cam Lobes contact the Valve Stem Shim -- directly.
Solid Lifters.

You may be hearing a Valve needing Adjusting.
You might actually be hearing the Valve closing.
If the Valve Shim -to- Cam Lobe clearances are within specs you should have nothing to worry about.

Some noises are GOOD Noises.
Hearing the Valve Train operating is Normal.

When you DON"T hear the Valves is when its dangerous.

But for Peace of Mind, ... Examine the Cam Lobe and Shim.
Look for any evidence of Oil Starvation.
Scratches, flaking or discoloration due overheating.

 

Apologies....terminology crash

Over here tappets are a global term for any sort of valve operating mechanism be it OHC or pushrod....

What we appear to have is a cambucket that has stuck

We belieive it to be caused by oil starvation to the cylinder head...as I said....it disappeared when we drenched the cams in oil....also we didn't get soaked to the skin when we briefly left the cam box cover off and fired up the motor.....

We will ,as you suggested check the cam lobes etc before we restart

Take issue with you on one point.....don't expect to hear any valve train tic on any OHC motor that I've screwed together.....means I've been sloppy on the shimming.....

Other than that thanks very much for the input....will let you all know what transpires and whether or not we had been naughty little boys and forgot this flaming oil pump o ring when we rebuilt the engine

Brilliant site by the way......just bought a YICS blanking tool from Chacal...even with the postage to the UK it's still damn good value for money

 

Timing chain adjusters shouldnt be wore out with less then 7k miles. Not to say i could not happen. Does it get worse when it gets hot? If it gets worse when hot could be a brg If the valves are set on the loose side noise should quiet down a bit as everything grows. I just hope its not a piston pin rapping when the guides and tensioner wore with miles that low sounds like it was started a lot after long periods of sitting. Use the stick to ear method see if you can pin point it exactly. Also pod filters transfer a lot of valve noise and carb noise. Also reset the tensioner just in case the chain was a little bound up. It does sound like valve train noise. Better safe then sorry if you cant find anything then i wouldn't worry about it to much

 

Hold on now; dangerous conclusions are being jumped to.

If you have a "sticking/stuck" valve bucket, then that VALVE is not closing fully either; the bucket sits on top of the valve. If the bucket stays down then the valve is still open.

Are you using a service manual? Factory, I hope?

Omitting the seal between the oil pump and the block will cause more grief than oil-starving the heads. Take a look at the lubrication schematic in the manual-- the first casualties would be the crank and mains.

There are two other areas of great concern IF indeed you have an oil starvation situation:

Did you use a sealant such as Yamabond #4 (or equivalent) on the mating surfaces of the main bearing "cap" areas of the crankcases, EXACTLY as specified in the manual? This is critical for correct oil pressure.

Did you replace the o-rings (between the head and cylinder) around the two RH head bolts' dowel pins? The two outer RH head bolts' "galleries" are the oil feeds to the head and camshafts.

I'd be very wary of running the motor until you've got this sorted out. Main bearings are not a readily-available part.

MORE LIKELY THAN OIL STARVATION: You said the cams were mis-timed. Now you have what sounds like a sometimes-sticky valve. That would tend to indicate a good possibility of a slightly BENT valve. These are interference motors, maybe it collided with a piston if you turned it over when the cams were out of time.

Have you checked the valve clearances? Since this problem surfaced?