K75 Valve Shims

My name is Frank Tarpley and I live in Decatur, AL. I bought a 1992 K75s about a year ago. It has 125k miles. I am getting ready to take a 600 mile weekend trip and decided to service the bike. During the valve check/adjustment number 2 exhaust valve measured .007 clearance. I removed the shim and it measured 2.00mm. Am I correct, this is the thinnest shim supplied by BMW? If yes, what are my options at this point? Is it cost effect to remove the head and do a valve job, if that is my only option? Will a gentle 600 mile trip cause any damage?
Thanks in advance for thoughts.

i have an early 85 k100rs and just went through a valve check where i thought i would need smaller than a 2.00mm shim . my math was wrong so i didnt but was told a specialty machine shop could put on a magnetic table and grind to desired thickness.as to what it means being so far out i can not say. also kawasaki has 29mm dia. shims might be handy.good luck

I have no idea what the previous post said.

Acejones said:

I have no idea what the previous post said.

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he made it easy for you to insert periods wherever you feel like.

So my english isn't perfect.
I didn't realise this was grammer class. You could have chosen to try to help original post but you felt you had to make fun of me. interesting.
Yes BMW only sells down to a 2.00mm thickness shim.
A machine shop can grind a shim to any thickness you desire.
My personal opinion your planned trip would probably not do any damage.
Good luck!

don't get your panties in a bunch, its really no big whoop- but adding punctuation really does help a reader's understanding.



btw- grammar.

tarpleyfe said:

My name is Frank Tarpley and I live in Decatur, AL. I bought a 1992 K75s about a year ago. It has 125k miles. I am getting ready to take a 600 mile weekend trip and decided to service the bike. During the valve check/adjustment number 2 exhaust valve measured .007 clearance. I removed the shim and it measured 2.00mm. Am I correct, this is the thinnest shim supplied by BMW? If yes, what are my options at this point? Is it cost effect to remove the head and do a valve job, if that is my only option? Will a gentle 600 mile trip cause any damage?
Thanks in advance for thoughts.

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First, VERY IMPORTANT question: You checked these clearances with the engine COLD (not running AT LEAST 4 hours prior to checking and below 92 degrees F.) Right??


2.00 mm is the thinnest shim supplied by BMW. As whhoon correctly stated, Kawasaki also makes 29 mm shims, but the thinnest that I've been able to find is also 2.00 mm.

Whhoon is also correct that you can take the shim to a machine shop and have it ground to 1.90 mm or about .004" thinner. The cost will vary greatly as setup time is the majority of the cost. If you happen to find a machine shop with a surface grinder that already has the magnetic table installed on it, it would only take a few minutes to do.

600 miles as it is would probably not do any more "damage" than has already been done, but it would probably run better with the clearance closer to spec.

I have had no experience with bikes that the valve has recessed so far as to not have shims available to make it right. Since the valve is "only" .010 mm out of spec., it sounds like the previous owner ran it until it ran like crap and THEN adjusted the valves and then ran it until it ran like crap before he adjusted them again and repeated this about 4 times. He probably NEVER adjusted the valves if it was running ok. Exhaust valves receed quicker the less clearance they have. If they are kept within spec., they last WAY longer.

Tight exhaust valves will run "ok" until they get to about .005-.006", BUT they will start to accelerate wear and recession at about .009".

To fix this, unfortunately you're looking at a valve job AND at least one (probably three) new seats. Cost wise, it MIGHT be better to consider a used engine. There are pros and cons for going either way.

Personally, I would call around and see if I could get the shim ground for around $30 before the trip and then plan on fixing it ASAP after. But I wouldn't worry TOO much about it if I couldn't get the correct shim before the trip.



NOTE TO EVERYONE:

If you've never checked your valve clearance DO IT!!!! You need to know where they are at. Write the clearances down with the date and the mileage. If the exhausts are on the loose side of spec. (.012") recheck in about 15,000 mi. If they are on the tight side (.010") recheck WITHIN 10,000 mi. If you notice a change between checks, you might want to check them more frequently. If you need to adjust shoot for the TIGHT side (.006") on the intakes and the LOOSE side (.012") on the exhausts.




VERY SIMPLE way to check valves:

Pull valve cover. Do NOT pull plugs or wires. One intake and one exhaust (not same cylinder) will be in position to check (check and write them down). Hit starter and within a split second hit kill switch (don't want it to run and fling oil everywhere). Should end up with a different intake and exhaust in position (check and write down). Hit starter and then kill switch to get the third pair (check and write down). Install valve cover.
DONE

Never checked valves before (and I had an airhead in the 80"s). Just thought it was above my skill set.

Using 98Lee's guide, I have been keeping close track on my 88 K100's valves. Easy as pie.

Some here have a wealth of knowledge. Hopefull they can keep even a clutz like me on the road.

Listen, obey and don't be thin skinned if they chastise the unaware. These guys deserve a little respect.

Thanks to all for your response, especially 98lee.

Yes the engine was cold, had not been run for a couple days. Actually number 3 cylinder exhaust valve also measured .007" but a 2.40mm shim corrected the adjustment to .010". The third exhaust valve was .010" (did not check the shim). The intakes were all .006".
I will go on the trip next weekend then decide what to do.

Thanks again.

I was surprised when you said that #2 was the problem because almost always #3 exhaust is the worst (it runs a bit hotter). But in your case BOTH #3 AND #2 were a problem.


You might consider setting the other two (#1 and #3) to .012" and having the shim for #2 ground to yield .012" clearance. Then run it until #2 gets below .009" again (Check often. Like every 3-5K).

I wouldn't grind the shim more than what you need this one time because the lip on the bucket that the shim goes into is 2.00mm. You DO NOT want the lip of the bucket to hit the cam (I don't think it will with the shim at 1.85-1.90 mm).

THEN, once this ground shim is no longer in spec., do something serious like valve job or different motor. With more clearance now you will get a little more milage out of what you've got. Might last a while with a small investment.

+1!

bikerfish1100 said:

don't get your panties in a bunch, its really no big whoop- but adding punctuation really does help a reader's understanding.



btw- grammar.

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I agree with bikerfish!

What is wrong with taking the time and care to use proper English, spelling and punctuation---instead of posting carelessly typed (seemingly random) thoughts off the top of one's head?

Hasn't anyone grasped the idea of proofreading in this day and age? What's the big rush?

It really does help communicating a point or procedure when it is clear what the poster is saying the first time around.

Frank,

One other important comment; If you are going to have a shim ground down, MAKE SURE they only grind ONE side and put that side down (in the bucket). DO NOT put that side up against the cam!!!

Since you can't guarantee the surface finish or the possible change in surface hardness of something done by a local machine shop, it's better to go with the factory finish against the cam to prevent any cam wear issues.



P.S. Let's drop the punctuation discussion and get back to why we are here. I'm sure, somewhere else on the web, there is a proper punctuation forum that would delight someone. This is a MOTORCYCLE TECH forum.

Now, back to the regularly scheduled programing!!!

withoutpuctuationitwouldbeimpossible toknowwhatwehavetypedyouhopefullyhavespentmanyyearsinschoolwhatdidyoulearninenglishclassdoyourselfafavorlearnhowtostructureasentenceandusepunctuationthankyouverymuch

Or as long as a compression & leakdown test check out ok you can remove the head & have the valve stem tip ground down. There is usually no need to replace the seats as long as they are still sealing reasonably well (they all leak a little).

Enough already.

I think it might be time to suggest that all children and their childish games remove themselves from the Garage. There are more appropriate places to play.

The Garage is for bikes, working on bikes and learning about bikes. Horseplay should be left for other places. It is NOT appreciated here!

Enough already! Moderators should not need to monitor tech discussions for manners.

saddleman said:

Or as long as a compression & leakdown test check out ok you can remove the head & have the valve stem tip ground down. There is usually no need to replace the seats as long as they are still sealing reasonably well (they all leak a little).

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I would suggest not going this route.

Once a valve has receded as much as Frank's, the seat will be pretty bad. If you have the head off, you should fix it right. Remember. as the valve recedes, the installed height on the spring gets longer. This lowers the spring pressure. His valve is already over .020" further in the head from where it started thereby lowering the spring pressure and it's a 20 year old spring.

Remember, these motors are supposed to run to 8750 rpm. It would be nice if everything is working as intended.

98lee said:

Frank,

One other important comment; If you are going to have a shim ground down, MAKE SURE they only grind ONE side and put that side down (in the bucket). DO NOT put that side up against the cam!!!

Since you can't guarantee the surface finish or the possible change in surface hardness of something done by a local machine shop, it's better to go with the factory finish against the cam to prevent any cam wear issues.



P.S. Let's drop the punctuation discussion and get back to why we are here. I'm sure, somewhere else on the web, there is a proper punctuation forum that would delight someone. This is a MOTORCYCLE TECH forum.

Now, back to the regularly scheduled programing!!!

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The idea of one side only makes a lot of sense. I don't think I would have considered this.

98lee said:

I would suggest not going this route.

Once a valve has receded as much as Frank's, the seat will be pretty bad. If you have the head off, you should fix it right. Remember. as the valve recedes, the installed height on the spring gets longer. This lowers the spring pressure. His valve is already over .020" further in the head from where it started thereby lowering the spring pressure and it's a 20 year old spring.

Remember, these motors are supposed to run to 8750 rpm. It would be nice if everything is working as intended.

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I'm not sure where you get the .020 wear factor. I know of two K engines that each had one valve shimmed with the thinest shim from the factory. I'm well aware of what a recessed valve can do to installed valve spring height & pressure. As long as the valve & seat look ok I still would grind the tip down. Even if it was moved up .020 I would check spring pressure and probably not even use a shim.

I work full time machining & building $100,000 + race engines and have been doing so since 1970. Grinding the shim down should work as well. But if it tightens up again the head will need to be pulled & inspected.

saddleman said:

I'm not sure where you get the .020 wear factor. I know of two K engines that each had one valve shimmed with the thinest shim from the factory. I'm well aware of what a recessed valve can do to installed valve spring height & pressure. As long as the valve & seat look ok I still would grind the tip down. Even if it was moved up .020 I would check spring pressure and probably not even use a shim.

I work full time machining & building $100,000 + race engines and have been doing so since 1970. Grinding the shim down should work as well. But if it tightens up again the head will need to be pulled & inspected.

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I find it VERY hard to believe that BMW would EVER send out a brand new motor that could not be serviced in the field (no adjustment left). Could you imagine a dealer (who rarely REPAIRS parts (almost ALWAYS replaces with NEW) having to replace the head at the 40,000 mile check up! Could get REAL expensive for BMW.

Every K75 that I have ever adjusted had between a 2.45mm and a 2.60mm shim in it from the factory. I would assume (could be wrong) that even back in the mid '80s BMW was using CNC machines to rough cut the seats, so the dimensions should be pretty consistent. He needs a 1.85-1.90mm shim to make it right. So we're talking .60-.75mm change. That's a .030-.040" change. It has been my experience that once recession starts on these heads, the RATE of recession tends to increase. I don't know whether it has to do with the surface hardness of the seat or what.

There is only a limited amount that the valve stem sticks up above the retainer. Grinding too much off the stem (enough to get it back in the adjustable range) could possibly (?) make it so the bucket contacts the retainer which would be disastrous.



So let's see, your basically saying that when a customer for a $100,000 race engine comes in to have it rebuilt, that you just LOOK at the seats? Quote"as long as a compression & leakdown test check out ok you can remove the head & have the valve stem tip ground down. There is usually no need to replace the seats as long as they are still sealing reasonably well (they all leak a little)." I'm sure you REALLY regrind the seats.

But at some point the added depth of the newly ground seat in the head will cause shrouding of the valve thereby causing your $100,000 motor to perform like an $80,000 motor and your customer finishing in the back half of the field before he decides to move on to a different builder.

Also I doubt you would EVER send out a motor that was machined with no adjustment left in the valves as you stated you have seen on 2 other K bikes and sounds like could be the case with the valve tip grinding if there is not enough bucket to retainer clearance to cut .030" of safely.

All that being said neither of us know what the seat looks like. Unless he decides to pull it apart for a valve job (minimum) we'll never know. In the mean time, a ground shim for maybe $30 will put him on the road for several thousand more miles.