Thrust washers on rocker shaft

Britbike850

Britbike850

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I’m replacing my intake valve seals and I may have lost a thrust somewhere in the head…found 2 using a magnet…I thought there were 3…used a boroscope but don’t see anymore. The manual calls for 1. The undisturbed intake valve has 2..
Don’t want to leave a floating washer in there
Rod
 
Britbike850 said:
I’m replacing my intake valve seals and I may have lost a thrust somewhere in the head…found 2 using a magnet…I thought there were 3…used a boroscope but don’t see anymore. The manual calls for 1. The undisturbed intake valve has 2..
Don’t want to leave a floating washer in there
Rod
Click to expand...
Normally, there is one thin plain steel washer on the outside and one steel spring washer on the inside. People screw that up often. What type of washers did you find and what type washers do you find on the undisturbed side. Look carefully around the valve springs - that's where they usually fall.
 
Hey Greg,
Thanks for the reply…there are 2 on the undisturbed intake valve…very thin thrust washers…I thought I removed 3 on side I’m working on…my memory ain’t what it use to be…found 2 using a magnet…I had placed a dab of grease on them so they would stay in place…the magnet picked them up on the exhaust upper chamber…used a boroscope with no luck…probe around on the exhaust and intake side with a magnet for 3.5 hours with no luck…I’m afraid it may have gone down the pushrod opening (if there was 3 instead of 2)…I have an old 850 head and it has 2 washers…
Don’t want to pull the head but don’t want a floater…may try a shop vacuum reduce down to 1/4 hose
Thanks for any advice,
Rod
 
Britbike850 said:
Hey Greg,
Thanks for the reply…there are 2 on the undisturbed intake valve…very thin thrust washers…I thought I removed 3 on side I’m working on…my memory ain’t what it use to be…found 2 using a magnet…I had placed a dab of grease on them so they would stay in place…the magnet picked them up on the exhaust upper chamber…used a boroscope with no luck…probe around on the exhaust and intake side with a magnet for 3.5 hours with no luck…I’m afraid it may have gone down the pushrod opening (if there was 3 instead of 2)…I have an old 850 head and it has 2 washers…
Don’t want to pull the head but don’t want a floater…may try a shop vacuum reduce down to 1/4 hose
Thanks for any advice,
Rod
Click to expand...
Some here don't like the spring washer, some put one or more flat washers on each side, some think it's best to have the rocker adjuster entered on the valve and do all sorts of things to accomplish that. When I drop them, I use a strong flashlight and look around the springs. I've never had one go down the tunnels - they're on the exhaust side of the head!

BTW, IMHO, centering the rocker is bad - the valve is supposed to turn.
 
milfordite said:
Folks will use differing amounts of the thin washers to try and center the rocker over the valve.
Click to expand...
Yep I've done that myself in the past
But as Greg says the valves are supposed to turn so the rocker should be offset to the valve
 
Isn't there a school of thought that says that when you shim the rockers to get the correct amount of offset (or offcenter) to ensure the valves rotate, the valves don't rotate anyway?
 
Isn't there a school of thought that says that when you shim the rockers to get the correct amount of offset (or offcenter) to ensure the valves rotate, the valves don't rotate anyway?
 
Stephen Hill said:
Isn't there a school of thought that says that when you shim the rockers to get the correct amount of offset (or offcenter) to ensure the valves rotate, the valves don't rotate anyway?
Click to expand...
There are a lot of schools of thought. Setup normally, they work fine - that's my school of thought. AFAIK, if the adjuster hits them dead center they will not turn.
 
The valves cant rotate with the stock spring and retainer setup. Some engines used a special retainer that did allow the valve to rotate. Don't believe me than just try to rotate one with pliers and the valve on the seat and off the seat the rocker arm will never put the force on it needed to rotate it.
 
bill said:
The valves cant rotate with the stock spring and retainer setup. Some engines used a special retainer that did allow the valve to rotate. Don't believe me than just try to rotate one with pliers and the valve on the seat and off the seat the rocker arm will never put the force on it needed to rotate it.
Click to expand...
Well you'd have to try that test at over 6000 rpm to be sure
 
marshg246 said:
BTW, IMHO, centering the rocker is bad - the valve is supposed to turn.
Click to expand...
I have only seen the top of used valve stems with one straight line scratch marks caused by the valve adjuster contact. There is no way for a valve to turn and there is no evidence that I have seen that they do. I like to see nicely centered valve stem to adjuster contact. And use bronze spacers instead of the Spring "washer" as they call it in the parts book. And different thickness "thrust" washers to get minimum end play. They can be had in 15 and 30 thou.
 
Last edited:
baz said:
Well you'd have to try that test at over 6000 rpm to be sure
Click to expand...
No, just look at the wear marks on the valve tip.
I just looked at maybe 20 old valves, and they all have linear wear marks.
They did not rotate.

edit: @CarlH, we posted the same time.
I also use bronze spacers
 
Last edited:
Britbike850 said:
Hey Greg,
Thanks for the reply…there are 2 on the undisturbed intake valve…very thin thrust washers…I thought I removed 3 on side I’m working on…my memory ain’t what it use to be…found 2 using a magnet…I had placed a dab of grease on them so they would stay in place…the magnet picked them up on the exhaust upper chamber…used a boroscope with no luck…probe around on the exhaust and intake side with a magnet for 3.5 hours with no luck…I’m afraid it may have gone down the pushrod opening (if there was 3 instead of 2)…I have an old 850 head and it has 2 washers…
Don’t want to pull the head but don’t want a floater…may try a shop vacuum reduce down to 1/4 hose
Thanks for any advice,
Rod
Click to expand...
Have used the shop vac for the same purpose.
This attachment helps with stepping down to small hose diameter.

Thrust washers on rocker shaft
 
IMHO, you should not be seeing a straight-line scratch, you should be seeing a circle a bit larger than the diameter of the adjuster if you have the standard adjusters.

As I said, many here have lots of ideas on this subject. Generally speaking, they will all work but I don't try to out-think the designers or what has worked for 50 plus years. Since Norton and Triumph at least, have similar systems I don't see them as bad.

I recently had a customer head from a well-known expert with race bikes who machined off one side of the rockers and then used spacers much like you to get the rockers dead center over the valves. Two of those rockers were bent so he machined off a lot from them. Two of the spindles were shot. All four valves passed the standard leak test but not mine, so I lapped them until they did not leak at all. I put in a set of used rockers, two new spindles, the standard thrust and spring washers, and the owner can now be confident that the head is how Norton engineered it but with better sealing.
 
It isn't hard to imagine the valve rotating a tenth or two per minute with the rockers offset.
 
ludwig said:
No, just look at the wear marks on the valve tip.
I just looked at maybe 20 old valves, and they all have linear wear marks.
They did not rotate.

edit: @CarlH, we posted the same time.
I also use bronze spacers
Click to expand...
I edited my post to say " One straight line scratch." or Wear mark. I do my own valve jobs as I want to do as much as I can to get better flow from the seat area and also fit the stem to guide clearance as Precision Machining recommends with their " Black Diamond" product line. For me it is a labor intensive job to do race quality top ends that hold up for years. It is easier if you do the disassemble yourself and make notes on what you need to correct with a few minor adjustments.
BERT said:
It isn't hard to imagine the valve rotating a tenth or two per minute with the rockers offset.
Click to expand...
Think of what the wear mark would look like if a valve tip that rotated with an off-center rocker arm adjuster.
 
Even if the rocker centre was over the circumference of the valve stem it would only be a lever length of around 4mm. The valve springs are about 32mm dia, so a lever length of about 16mm, a ratio of 4-1. If the rocker was 1mm off centre the ratio would be 32-1
It's a big leap of imagination to come to the conclusion that a rocker with virtually point contact on the valve stem could overcome the friction between the valve spring and spring seats.
It is more likely that any rotation that may occur would be imparted by the coil springs
 

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