Valve Height on LM 1000

[OldJock]

Got another question

I was doing the tappets on the LM 1000 and I'm running out of tappet adjustment.

I know that valve recession is a culprit but the heads were rebuilt a few years back and have been like this since, so I'm wondering if they are set to the correct stack height.

There is no mention of height in the supplement for the LM 1000 so I assumed (always dangerous) that it would therefore be the same as the measurements for the G5, 35.7 to 36mm from the head to the underside of the retaining collet.

Checking old photos before the refurb they appear to have quite a bit more free thread on the adjuster, so I was wondering if that figure is correct.

Going off to try to check what the actual height is but unsure if I'll be able to get a decent reading with the heads is situ

John

 

[john zibell]

John,

The pushrod and rocker geometry wasn't changed for the 1000 LeMans, only the valve face diameter. So, your assumption, in my opinion. is correct. It is possible that when the heads were done, the valve seat was ground too deep instead of replacing the seat. At this point, new seats may be required as valve seat recession is a Guzzi is pretty rare. I've not seen anything too bad, unlike 1982 airhead BMWs which are infamous for that problem.

 

[OldJock]

Its a possibility John, the valves were done by a shop that I really trust and therefore I didn't think about it too much.

I checked the stack height on one of them (they are all pretty similar regarding the amount of thread above the lock nut on the rocker) and it came to around 36.5-36.7 on the valve but it was difficult to get a very accurate reading as its a bit tight with all the hardware. However I do believe its good.

Its not desperately bad there is about 1 to 2 threads left, so the nut is fully on and locked with just a little bit left. Looking at the old photos I appear to have maybe 4 or the like. Its not a huge difference but with the nut running up near the top I started to wonder.

Unless you tell me otherwise I'll run it this year and next year whip the heads off to get it all dimensionally checked.

I'll see if I can get a picture of the one of the heads to show you what I mean and post a before and after to give you a better idea.

At least the stack height is Ok and I didn't foul up there, thanks for the reassurance

Sorry for all the bother

John

 

[john zibell]

So long as you have adjustment, run the bike. I wouldn't pull it apart until necessary. It is possible it is the valve face that is eroding, as I've seen that on BMWs, and not the seat in the head.

 

[OldJock]

Gotcha that's good to hear John

Here are some pictures apologies for quality first to Right then Left Pre followed by Right then Left Post
While I was in there I also checked the head bolts again and all appears fine.............Your opinion is valued on what's normal.

]

Oh Goodie more maintenance next year

John

 

[john zibell]

Going by the last photo, if the valves were eroding, you would have to shorten the screw to have clearance and a whole bunch of threads would be visible above the nut. In this case it looks like cam/tappet wear.

 

[OldJock]

Well that's good news if that's the case.

Could maybe go for slightly hotter cam and new tappets.

Any ideas on how I could establish if it was?

At least the heads aren't going to have to go to a shop and all the associated hassle with that

John

 

[john zibell]

First make sure your push rods are straight. If so, then the only wear point can be the cam and tappets. Good opportunity for a B10 or similar cam.

 

[OldJock]

Yeah John a B10 would be nice

I was talking to friend who knows a good deal about the older bikes and he suggested that I had gapped it on the exhaust stroke. I don't buy that, if you gapped any of the valves on the exhaust stroke then the pushrod would be high, inlet opening, exhaust closing. So to get the gap the adjuster would need to be shortened. Therefore if you gapped on the exhaust the adjuster would have more thread showing not less.

That would result in a bigger gap on the compression where the pushrod was lower, so the gap would need to be closed by lengthening the adjuster

I also went to the trouble of checking using a lollipop stick in the spark plug hole, on the exhaust stroke sure enough as the stick moved down, indicating the piston rising, the exhaust valve was closing and the inlet opening and the tappets had no clearance whatsoever.

The other kicker would surely be that the bike would be horrendously noisy valve wise as God knows how big the clearance would be on compression and the valves would be out by miles..........would it run at all?

Anyway I can check the pushrods for straightness that's an easy job and can be done tonight. If all is good there then I'll box it and run this summer.

My problem is how come all was fine before the strip and now they are so high. I still wonder if the stack height has been set a bit lower than before causing me to use a thread or 2 more adjuster. I never had that much in the first place.

The bike is running champion, going like a Swiss watch, well a rather raucous Swiss watch but performing great and total engine mileage is less than 20k.

Next winter I'll take the heads off check the stack height and if that's in spec I'll be looking for a B10 cam new followers and tappets I guess (wife's goanna love me, all that and building a 1100 sporti from the ground up).

Your time and input John has been greatly appreciated as always; Many Many thanks

John

As a PS to this I checked all pushrods this morning and they are all absolutely fine no warping or bending that I could determine by rolling them on a glass table top

 

[Supaflee]

Hello there OJ and JZ .
I see that together , you've kicked this valve stack theory around a fair bit. Knowing the collective knowledge applied , I'd say it'll need to be an unsolvable problem to beat you two.

I see something in the pics that makes me think straight away , the head gasket which was used to assemble the heads when they were refitted after the top end work was done , is of a greater dimension in thickness than it should be ,and or , when the valves were refaced , the seating area has been cut too far into the valve face .

I'm thinking this will will cause your "perceived " problem. ( to me it's not a problem at all )

I'd just remain aware of this situation that there isnt much thread protruding beyond the locking nut on the adjuster ,,,,,,and ride the bike .

In summary , because ALL the valves seem to appear the same in the head , I'd say its a marginal dimensional difference during machining which has resulted in this situation.
Regards Supaflee

 

[john zibell]

Hello there OJ and JZ .
I see that together , you've kicked this valve stack theory around a fair bit. Knowing the collective knowledge applied , I'd say it'll need to be an unsolvable problem to beat you two.

I see something in the pics that makes me think straight away , the head gasket which was used to assemble the heads when they were refitted after the top end work was done , is of a greater dimension in thickness than it should be ,and or , when the valves were refaced , the seating area has been cut too far into the valve face .

I'm thinking this will will cause your "perceived " problem. ( to me it's not a problem at all )

I'd just remain aware of this situation that there isnt much thread protruding beyond the locking nut on the adjuster ,,,,,,and ride the bike .

In summary , because ALL the valves seem to appear the same in the head , I'd say its a marginal dimensional difference during machining which has resulted in this situation.
Regards Supaflee

The extra thick head gasket would have to be very thick to require the adjusters to be screwed in so far. If the valve seat was too deep then the adjusters would have much more thread showing above the lock nut. So his possibilities are the head gasket very thick or cam/cam follower wear. If he has a very thick head gasket, then he could run regular (87 octane) fuel.

 

[OldJock]

Cheers Guys

Thanks Supaflee & John. The gasket as far as I'm aware is the standard part, ordered from a Guzzi dealer. Of course dealers do cock it all up from time to time and send you the wrong part. Memories of when young and inexperienced trying to install piston rings to a Trident and spending weeks trying to figure why they wouldn't fit. Dammed dealer had sent me an oversize set of rings!!!

Anyway as you both suggest I'm just going to run it. Next year I'll whip off the heads and take a close look at everything.

I agree with John that if the valves were recessing then they'd rise (obviously) this would mean the adjusters would have to be shortened which is the opposite of the problem I have.

If the gasket was too thick then both valves and tappets would move and act like the pushrods were too short and indeed the adjusters would require to be screwed down to compensate.

Either way its nothing too serious I reckon after reassurance from you both, I'm feeling a lot happier about the situation. Its more curiosity than anything else and as the photos show I never had a lot of thread even prior to tearing it down.

Oh and the heads are all torqued correctly I checked that prior to starting to set tappet gap.

Cheers

John