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Does your oil smell like gas? Open up the filler and smell it

Just to to update this thread.
I have now got a brilliant running Gs750 I have had very sooty plugs in the past and changed the slide level to 2 from the top.
checked plugs after each good run and turned the air mixture 1/2 turn out each time on the carbs which we’re really sooted and now after a good run I have black plugs but not really sooty just black.

Do I leave as is, and clean after each run? I,m nearly fully out on the air screws..
maybe these bikes run slightly rich?

[Big T]

Does your oil smell like gas? Open up the filler and smell it

[Big T]

Well, follow the advice of opening the fuel 5/8 to 3/4 and start with airs double that.

Can't narrow down your issue if you just make wild changes.

Getting there I have now got the valve clearances well within spec, between 05 and 09, took bike for a run, alls well for approx 1 mile then the low throttle opening judder starts, opening her up the response is good, just the slight throttle opening at the lower speed.
i,ve changed the fuels screws at different settings from 1 full turn from closed down to 1/2 turn from closed.
i have changed the air screw from 1 to 2 1/2 turns but still getting very black sooty plugs.
ngk8es plugs new ones, also refitted the old plugs to see if any difference but there’s not.
pilot jets are 0.15 from memory...
All ideas welcome.

[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).

[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

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?.

[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....

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

[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.

[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

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..

[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.

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👍👍

[Big T]

The plugs are not the problem