The International CBX Owners Association

Just got home........barely. After reaching running temp the tappets started making noise intermittently on a regular basis. Each noisy spell lasts just a few revolutions and then returns to normal and it does this cycle on a regular basis. When the noise starts the engine RPM increases and then returns to normal when the noise ceases. I noticed the pattern several days ago but it was not as severe. When the engine is cold it doesn't happen.

I pulled the valve cover off and checked to see if maybe a cam was coming loose but every thing is tight. I also checked the pulse generator to make sure it was tight also.

Twin, it's late here (1230) lemme get my head around that tomorrow....Until then, you say the cycle is on a regular basis, at what RPM & what is the time (duration) between the "cycles" ?

The tappets make noise for about 3 seconds followed by 3 seconds of quiet. This doesn't start until I have been riding for a few minutes and the engine is at temperature. Would a loose cam chain do that? I just loosened the chain adjusters front and back and gently pried a little slack in the intake chain and the adjuster did not take the slack back out.

....the RPM goes from 10 to 14 on the dial.

I may have an idea what is going on. I pulled the crank cap and used a wrench to turn the crankshaft backwards and slack appeared in the intake chain. The tensioner is free but is not removing the slack. How do I get the rubber plug out so I can see what the tensioner is doing? How do I free up the tensioner? I hope someone can answer this tonight as I am supposed to go show the bike off tomorrow.

When you turn the engine back and cause slack, the clamp bolt does not hold the tensioner-rod. You do not need to take the rubber plug out to see that. If the rod of the tensioner moves, the clamp bolt does not hold. In that case, most likely, the thread is shot.
You may have to helicoil that.

I checked again and it is working ok. I guess there is supposed to be a little slack when the crank is turned back. I re-set the tensioners and the noise and RPM increase started again once it reached running temp. The weird thing is that it runs perfect when it is cold.

The chain tensioner from the bottom end to the exhaust cam, adjusted from the rear of the cylinders, is set by a large spring. When you loosen the nut the tensioner should move. From age or other factors, the sliding parts will not slide. When doing the valve clearance adjustment, I tapped the tensioner with a small hammer. The adjusting nut was loose and the adjuster snapped into a new position. Others have noted the same situation.

The tensioner is only meant to take up the slack of the chain when it is running in the correct direction.

Also the rubber wheel that rides against the chain will eventually harden with age and heat.

Good morning ...

To add to the excellent advice, I was wondering if the noise was worn oldham couplers/cam joints....Would it give the "clickety click" noise associated with tappet problems ???

Thanks for the advice. The people on this forum have been a real help. I pretty much went over the tensioners and even tapped down on the tensioner that fastens from the back of the engine with the nut loosened and it didn't do anything so I guess it is doing the job. The chain it controls is tight also. The front tensioner is moving freely also.

I slept on this last night and was also wondering about those Oldham couplers. If you heard it you would swear it has to do with the cylinder head. The lifter noise is coming from the left side and since the idle changes when it is happening I am guessing the left intake cam. Since it runs perfect before heating up heat is the key. This gradually became bad. I had noticed the lifters making noise and figured the shims just needed replaced on a cylinder or two. Yesterday was the worst with the lifter noise being louder and the idle seesawing along with it. It also affects excelleration. I quickly got on the highway so I could get home quicker and there wasn't any noise at speed and it ran good. When I pulled off the highway and stopped at a light the seesawing had disappeared probably because the highway ride cooled things down some.

twinegar wrote: . The front tensioner is moving freely also.

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So that we do not misunderstand each other: The tensioner rod must NOT MOVE during operation! Only when you loosen the set bolt it should slide, thus allowing the spring tension to bend the tensioner more and press the slider against the chain.

The locking bolts are working and the tensioners are fixed in place.

Looks like I will have to show off one of my 750's today instead.....
Now I have 2 CBX's dead in the water.

This may be way out in left field but would it be possible that a cylinder liner is loose? They're press fit but if originally marginally press fitted... then with heat, aluminum expanding more...? Liner rotating or some vertical movement? May be part of the reason for the 6 cylinder base o-rings we were wondering about earlier.

It is definitely lifter noise. The oil problem was on the other CBX with 24K miles. The CBX with the lifter noise has 14K. I am getting ready to re-check the rear tensioner to make sure they are working before I move on to something else.