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I have a persistent valve tap on this '84 1200 I'm working on.

It seems like just one rocker is tapping, on the left side, which is quiet until the engine is warmed up then the tap is continuous and pretty loud.

Here's what Ive done to this engine:

Machine shop work:

Cleaned and surfaced heads flat.
Replaced all 4 exhaust guides (intakes were ok).
Replaced all valve seals.
Cam lobes and rockers were pitted, they filled and ground.
Not sure what was done with the valves, most likely they only lapped if anything more than cleaning.

I bled the lifters,
Oil distribution plate holes are clear, I replaced the seals,
Checked shim measurement multiple times, one shim on each valve,
I made sure the rocker shafts and rockers are moving freely,
Ran with valve covers off, it appears to be getting PLENTY of oil,
Compression was 155-160 before the head work, it's now 170 all 4.

It's sluggish until warmed up like it's running lean.
Once warmed up it runs great with smooth idle and plenty of power.

The owner says it did tap on this side but went away after a 1/2 minute or so.

Every cold start ( a 1/2 dozen or so) it's quiet then starts tapping once warmed up.
It acts like one lifter is starving for oil but only when warm, or like something is causing the tappet clearance to increase only when hot but what could that be.

I used 10/30 oil for startup as a flush then changed it to 20/50, tap has been about the same with both oils.


I'm at a loss here,
All suggestions appreciated.
 

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All good suggestions so far.

Something not moving freely once hot is a possibility.
The rocker shaft has to rotate freely for the adjuster to work properly.

I've been trying to figure a way to isolate which lifter, running with the valve cover off cant do, all the oil would be emptied from the engine in a few seconds.

This thing doesnt have hydraulic lifters , we call them lifters but they are actually hydraulic adjusters. They push on a notch to rotate an out of round lifter shaft which takes up the lash. Alot of moving parts.

I've been starting to suspect the grind but considering the way these adjust and it's complexity, one of the parts getting sticky is entirely possible.
Something changes once hot, it sounds great when cold.
 

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I talked to the guy that did the cam grind.

He told me he's done many of these 1200 cams successfully and the grind he did on these is very mild, he called a stage one. I didnt get into any specifics but he said this mild grind wouldnt cause any hydraulic adjuster problems or clearance issues.

I'm not very knowledgeable with cams specs and what effects different grinds will have so I have to trust he knows what he's doing having come highly recommended by the head shop in the business for over 35 years.

I described to him how the tap comes on loud once it's warmed up, he said it sounds like the hydraulic adjuster is bleeding off once it's hot.

I'm going to see if I can figure out which cylinder the tap is coming from with a screw driver to my ear and maybe compare compression taken just before the tap comes on against what compression is when it's tapping.
If I can figure out which cylinder is tapping then by swapping around adjusters I should be able to get the tap to move if the problem is indeed a bad adjuster.
 

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Discussion Starter · #13 ·
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Good point Hawker.

I've measured all the shims to be one at each valve.
2 valves had 2 shims before the work, tried putting the 2 back. There was no difference but those may not have been the valve that's tapping.
I may pull all the shims and see what happens.
 

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Discussion Starter · #16 ·
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goldtop wrote:
Just read the quotes above again and I would not be one to blame the cam or the work done.



Stage one is a very mild tuning mod and is done to improve overall performance and is certainly not a race mod. Just out of interest was it done to both cams? This need to happen to both to work effectively
Yes both cams.
 

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Looks like I found the problem!
It took a combination of all the suggestions.

Dennis clued me into maybe the rocker was not centered, that and it acts like the steel rocker or steel rocker shaft was jamming when it gets hot, possibly due to the steel expanding differently, that was my best guess.

Firstly when it was cold I swapped the adjusters with the other side to see if the noise moves, it didnt.
Then with a screw driver to my ear it was fairly easy to hear the #4 exhaust was the culprit.
While hot I pulled the valve covers and alternator cap, turned the engine til #4 exhaust was fully closed and found it very loose. Once I loosened the cam holder bolt the lash was gone. After removing that bolt and getting the end cap to sit as far away from the rocker as the bolt going thru it would allow, I retorqued all the bolts.
Started it up and ran for a good 10 minutes hot with no tap.

I'll post if the tap comes back after a road test, so far it looks promising.
 

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Discussion Starter · #24 ·
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I know just what you mean about missing the simple stuff John, done it many times and made a fool of myself.

Dennis sent me the complete text by PM to accompany the picture above. Thanks again Dennis.
(Pretty easy to miss a step when it's not in any of the manuals your using :X)

I found the exhaust clearance from the collar was less than specified, got that adjusted and havent heard the tap at all on the problem side.
That's what it did yesterday though then came back after a ride so have to see what happens.
The right side has a continuous tap that doesnt seem to change, it's hard to tell but that could be an exhaust leak.
 

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Discussion Starter · #29 ·
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I got a PM request to detail what I did and what Dennis sent me.

Referring to the picture Dennis posted, what I did was to follow the procedure below to center the collar that sits between the exhaust rockers. The center bolt goes thru this collar so that bolt has to be loosened in order to move the collar right or left to get the minimum gap on both sides.

The following is what Dennis sent me:

'84 - '85: Make sure that the camshaft holder center collar is precisely centered; the ends must protrude an equal amount.

Hold feeler gauges between the ends of the collar and the eccentric shoulder of each rocker arm shaft.

After '85: Make sure that the ends of the camshaftholder center collar are flush with the holder.

Hold feeler gauges between both ends of the center collar and each rocker arm shaft.

Tighten the center bolt while using the feeler gauges to maintain the clearances shown below.

Torque: 25 N.m (18 ft-lb)

Clearance:

'84-'85: 0.10 mm (0.004 in) minimum
After '85: 0.30-0.35 mm (0.12-0.14 in)





I found the collar was tight to one side without any gap.
It's interesting to note that if this gap is too small evidently the steel of the rocker and the collar itself will expand with heat then prevent the hydraulic adjusters from working properly. That's what I think happens anyway.

The left side is VERY quiet now. The right side has a tap but could be an exhaust leak, hard to tell for sure.
We'll see after a long test ride if the left side tap comes back.
 
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