GS850 idling issue

[Guest]

Have spent the winter fixing up a '79 GS850. It seems to start, run nicely and idles at a steady 1000 RPM. No rattles, knocks or clattering. But when it gets completely warmed up, like after a half hour ride, the idle drops off so that it will stall unless I keep it alive with the throttle. If it stalls it will start right back up again. Other than that it accelerates smoothly.

Has VM carbs, points ignition, OE air box and exhaust. I have synchronized the carbs.

Any ideas what could cause this?

Thanks in advance.

IMG_3369.jpg

[Big T]

Tight valves

[Nessism]

Pilot screws may be set too rich.

[Brendan W]

.... or the choke system is not closing off completely.

[canuckxxx]

Tight valves

I checked and adjusted the shims in January after I had assembled the engine but have not checked them since getting the engine running. After swapping some shims and buying a 2 new ones I was able to slide my .0015" feeler gauge in at each bucket. I've only been out for a couple of short rides since then.

[canuckxxx]

Pilot screws may be set too rich.

Do you mean the pilot fuel screws that are on the bottom of the carbs?

[Big T]

Pilot fuel screws should be 5/8 - 3/4 turn out from bottom
Where are yours set?

[canuckxxx]

Pilot fuel screws should be 5/8 - 3/4 turn out from bottom
Where are yours set?

1 turn out from bottom. Do you think being out a bit too far would cause my idling problem?

Also, I checked my valve clearances yesterday and found 2 that were tight. Need to buy a shim today then will reassemble and test.

Thanks for help.

[fastbysuzuki]

Running a tad too rich as for the valve clearances i and others on here run them at .004"
At .0015 you can easily pocket a valve and are left with no clearance. ( just my opinion)

[Big T]

1 turn out from bottom. Do you think being out a bit too far would cause my idling problem?

Also, I checked my valve clearances yesterday and found 2 that were tight. Need to buy a shim today then will reassemble and test.

Thanks for help.

Difficult to know without knowing your pilot air screw settings

[canuckxxx]

Running a tad too rich as for the valve clearances i and others on here run them at .004"
At .0015 you can easily pocket a valve and are left with no clearance. ( just my opinion)

That's interesting. Are the valves noisy with so much clearance?

[Steve]

The valves are no noisier at .004" clearance than the are at .0015". If you are thinking in inches, the clearance is basically .001 - .003", so .004 is not that much more. Not that it means anything in this case, but the specified clearance for some Kawasakis is .006 - .010" on the intakes and .010 - .014" for exhausts. Those engines are no noisier.

Valve clearance on our bikes always decreases with miles, so it is in your best interest (and that of your engine) to start on the high side so it can wear toward the minimum. There is no sense in starting at the minimum and going to nothing. Literally. NOTHING. When clearance gets to just below the minimum, they will not close completely, which leads to burning the valves or the head, which gets real expen$ive, real quick.

Could not read your attachment, just too small to read. Please feel free to take advantage of the offer in my signature.

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[canuckxxx]

Well I'm going to have to rethink my valve clearances.

This is quite timely too because my #4 intake has a 2.60 shim and too tight for .0015" so I phoned around looking for a 2.55. Nobody locally had one but one shop had a 2.50. I bought it. Now I can get .005" in (but not .006").

Maybe this is OK...what you think?

[Brendan W]

Is that 2.60 a measured thickness or a stamp?

[Steve]

...what you think?

I think you need to expand your shopping radius.

Z1 Enterprises has all the sizes available, but shipping to Canada might be a bit much. I am sure there are other places that will be willing to order one for you. Yeah, you might have to wait a week or so, but it will be worth it in the end.

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