GS850GL Valve clearance questions.

[Smellii]

Before I forget, this is a link to a very good video about replacing shims which is the tricky part most how-to's don't provide much detail on for the absolute noob...like me. http://www.youtube.com/watch?v=elKilUuKM8U

Back story: Just bought my 82 GS850GL (shaftie). First cylinder has no compression at all (used compression tester). Not exactly sure what is causing it but after measuring clearance of cylinder 1 intake valve it's much higher than the others at .229mm (.009in). At this point I'm assuming this is the cause.

Questions:
1) Now that I have my measurements how do I calculate exactly which new shims I need?

2) Some of my valves have no clearance (or less than .0015 which is thinnest feeler I have). Is this ok? Can I simply leave these alone? If compression is bad in this cylinder should I consider replacing with a shorter shim?

3) Is the valve clearance specifications for the GS850GL the same as the GS750 of the same year? If not what are the specs or where can I find them?

 

[Nessism]

Basscliff provided you with his Mega welcome in your first introduction thread. Inside you will find links to a service manual which will teach you how to adjust the valves. Cliff also has a valve adjust tutorial which you should read as well. Most of your questions will be answered if you go though the information he has compiled.

 

[Guest]

Hello, Welcome to the GSR and congrats on the GS850. The one valve with .009" clearance is probably pretty noisy, but it won't effect the compression. Specs are the same as a 750 or any 2 valve engine, .001-.003" or .03-.08mm. The tight valves can be causing a compression loss, if they are so tight that the valve doesn't close. Generally speaking looser is better since the valve clearance becomes less as miles add up and the valve seats wear. To decide what shims you need, measure the shims you have and obtain a replacements by subtracting the needed clearance from the shim you have. Example: clearance is .01mm, shim is 2.75mm. Replace with 2.70mm to get .06mm clearance or 2.68mm to get .08mm clearance. Always measure your shims and don't trust markings. Ray

 

[Smellii]

@Nessism Yeah I went through the site with a fine tooth comb and learned an awful lot and really appreciate resource. I was, however, left with only a few holes in my understanding. Manual for an 850 isn't present and wasn't 100% confident I could use the GS750 service manual as a suitable replacement when dealing with engine internals -cuz of the bigger bore. Read through both 16 valve and 8 valve tutorials but they lacked pictures of the crucial parts I needed. ... really trying to be thorough before asking for additional help.

 

[Nessism]

Here is the 850 manual link from Cliff's site... http://www.mtsac.edu/~cliff/storage/gs/GS850_Manual_HiRes.pdf

The factory manual has a table on how to figure out what shim you need.

No clearance is BAD. Maybe burned valves. Lets hope not.

Too much clearance can mean a bent valve, crud under the valve holding it open, or a hack mechanic was working on the engine and used the wrong shims.

Valve adjustment on all 4 cylinder shim and bucket engines is identical. 550/650/750/850/1000/1100G - all the same.

 

[Smellii]

@Ghostgs1 Thanks for clearing this up for me. Appreciate your time answering my questions.

 

[Smellii]

@Nessism Thanks for the service manual -so surprised I missed the 850 manual that I went back to the site to find it.. and still can't. Must be buried somewhere. (irrelevant now I suppose)

Going to tear it down further to take a look at the actual valves based on your insight of my erratic measurements.

Thanks again.

 

[Nessism]

Cliff has the 850 manual sort of in the header. It's a little hard to see.

Don't go all crazy and pull the cylinder head off or anything until you have tried everything else. Have you ran the bike yet? It's not uncommon for the compression to increase once the bike is on the road and given a good thrashing. Shakes the cobwebs out so to speak. Italian tune up!

 

[Smellii]

@Nessism haha. now I see it. sheesh! (red faced)

It idles fine but spits out the left exhaust every 3-8 seconds or so. Took it out around the block once but can't open it up yet because it doesn't have plates (yet) but it seemed strong and smooth -a strong runner. I'm confident cylinders 2, 3, and 4 are good (minus routine adjusting) but because cylinder 1 has absolutely no compression I'm fairly convinced (which means nothing from a noob) there is a gaping hole somewhere preventing a vacuum/compression/combustion. I'm dying to get in there to look at the cylinder hoping the problem is obvious at that point. Any suggestions on what I might try before I crack open the case?

 

[BassCliff]

Hi,

@Nessism Thanks for the service manual -so surprised I missed the 850 manual that I went back to the site to find it.. and still can't. Must be buried somewhere. (irrelevant now I suppose)

Valve Adjustments (8 Valve) (PDF file)

Thank you for your indulgence,

BassCliff

 

[Steve]

Actually, the tricky part for a "noob" is figuring out what shims you need in there.

There's a guy named "Steve" here that has a spreadsheet that will help you figure that out.

Just take a look down there

.

.

 

[BassCliff]

Hi,

That guy named "Steve" has a pretty handy resource in that spreadsheet. But basically you measure the clearance and if it's too tight just slip in the next smaller shim. Then re-measure to be sure it's in spec. Once you do it you'll find out how simple the procedure is.


Thank you for your indulgence,

BassCliff

 

[Smellii]

Fixed

Fixed

I tried to measuring and adjusting the shims myself and ended up worse than when I started. With my head hanging I admitted my limitations and brought the motor to the shop. They found a bent valve right away by spraying this aerosol in the valve and watched it drip through the closed valve opening. Apparently the bent valve was pounding on the seat so long they had to machine the seat to correct it. They also adjusted my valves so I'm good to go now. Putting the engine back on the frame tonight.