New owner

[carpetbagger]

Rings and valves may be good, but the compression test doesn't tell you if your valves are properly adjusted. It only tells you that they probably don't leak when closed. As far as I know, the only way to tell if they are adjusted correctly is the hard way.

[Mikey82]

Appreciate your help and advise Thankyou, what plugs do you guys run your bikes on,I have been using NGK 8ES
Looking at all my options to cure the sooty plug syndrome..
I presently have a max speed of 80 mph and after a short run the plugs get rich...causing a judder response when blipping throttle, but once throttle is opened I have good power.
I know I,m getting closer👍👌💪

[erki52]

Afternoon. From experience with my '78 GS750 I have the fuel screws (the ones underneath the carbs closest to the engine when in situ) turned out 1/2 turn and the air mixture screws (those on the sides of my VM slide carbs) out between 2.1/2 and 3 turns. The plugs are a light tan colour, I can hit 85-90'sh without too many issues. I run a Marshall Deeptone exhaust and foam filters and have spent many a wonderful hour fettling the carbs getting them to work right (nearly there !).

The advise to check the shims is very good advice. After re-shimming mine I had to strip it all off as the valve guide on number 1 cylinder (the one that only ever got warm, not hot) was in at a slight angle.

Guide now replaced and she's nearly running properly but it's sometimes like herding cats getting her to run properly but every time I change something, the bike improves...….then I shag it all up by diving in without engaging my brain.

[carpetbagger]

B8ES is the correct plug for a stock or nearly stock setup. The plugs are most likely not the problem.

[Big T]

The plugs are not the problem

[Mikey82]

Thankyou very much for your help.
i will change the settings clean the plugs, go for run (on the bike of course) if sooty the valves will be checked.
Done most things to the bike, but not delved into the valves,yet...so may drop into bike shop and get them checked..
Thanks again will update👍👍

[steveb922]

Checking valve clearances isn't complicated. You need a new valve cover gasket, 10mm (?) spanner, feeler guages, and a manual. The manual can probably be found on Basscliff's site.

If any of the clearances need adjustment, then you need appropriate size shims and a removal tool.

If you apply a thin layer of grease to the gasket, you may well be able to re-use it.

[Mikey82]

To update this thread, this is my first time at checking valve clearances.
i turned the crank until the cams were facing upwards. And did the clearances in pairs
exhaust 1 and Inlet 4
exhaust 4 and inlet 1
exhaust 3 and inlet 2
exhaust 2 and inlet 3

I have the following clearances above the shims.
Exhaust.
1. 0.13. Shim 260
2. 0.3.
3. 0.3
4 0.7

Inlet

1. 0.6
2. 0.8
3. 0.9
4. 0.4



as you can see all within tolerance except no.1 exhaust with the bigger gap, I removed the shim and the shim size is 260.
( no number on shim so had to measure)
to get within tolerance what size shim do I need?

would I be right in saying 3.4 ( to make the tolerance 0.5 ??

Thanks in advance..

[Big T]

Go back and measure following the factory manual
, or the tutorial on the Basscliff site

Also, what standard are you using, mm or inches?

Clearances tighten over time, so I'd be changing the .3 and .4

[steveb922]

As BigT says, you're close but not quite there. Check page 81 here: http://gsarchive.bwringer.com/mtsac/..._77-82_all.pdf

There may be slight differences between the way you measured, and the factory way, due to pressure on the other end of the shaft. The factory way is precise.

If you get similar measurements, basically you need a thicker shim to take up slack, or a thinner to give more room. On that 0.13mm measurement, with a 2.65mm shim, you would go up one size to 2.70mm, giving you a clearance of 0.08mm. Having said that, excessive clearances are unusual, as valve trains tighten over time. Which is why BigT suggests you change your tightest clearances - they're just about on the limit.

But. most importantly, re-measure using the method in the service manual. If it's not clear, don't be afraid to ask.

And while you're measuring clearances, remove (one at a time!) all your shims and record the sizes. If you want a spreadsheet to do this, contact member 'Steve'. And never rotate your engine over an empty bucket - you might chip a cam lobe.

[Mikey82]

Thanks I did the test according to the Haynes manual which said to turn the crank and measure whichever cam was facing upwards, so hopefully it is correct.
i measured in mm

[salty_monk]

It would be very unusual to find a Valve / shim that is so out of wack... They close up not open up. For it to be this far out it would have to be an error (or act of laziness - right shim not available) when they were last done.
It's very unusual (in my experience) to find shims fitted that are bigger than 280

Keep going. Slow & methodical wins the race with these bikes....

[Mikey82]

Thanks for the link, very helpful, makes it a lot easier...

exhaust 1. 0.38 clearance and 260 shim
exhaust 2 0.30 clearance and 2.65 shim
exhaust 3 0.30 clearance and 2.70 shim
exhaust 4. 0.40 clearance and 260 shim

Inlet 1 0.80 clearance and 270 shim
Inlet 2. 0.80 clearance. and 270 shim
Inlet 3. 0.60 clearance and 2.75 shim
Inlet 4. 0.40 clearance and 2.80 shim

checked and checked again.

so replace all exhausts and inlet 4 do you agree..
any chance you could advise the shims I need to purchase and best place to get them?
Thanks in advance..


Having looked at the shims I have and what I need I would suggest I can use the 2.65 and the 2.60
i need to buy 3 shims 2no.@2.55 and a 2.75 not 100% sure I,ve worked it out right?.

[Big T]

Go down to the Consumer Information/GS Parts and Services/GS Valve Shim Club, that's the best place for shims

Your calculations on shims is correct, however, get yourself an additional 2.50 shim for future use and to swap around so you don't have an empty bucket while you do the swapping

[salty_monk]

They generally close up very slowly. Exhausts quicker than inlets. I'd be surprised if those weren't the shims it came from the factory with.

Looks like you need 3-4 shims. There is a shim club here & international postage of small stuff is quite cheap (and takes about 5-6 days to UK on average).