GS500F K7 Running Like a Dog

[kevinator9]

Hi Guys,

Newbie here trying to sort out issues with my GS500F.
Idle is rough and it always backfires (in the carb) when cold and trying to accelerate from low RPM. This is with the choke on.
With the choke off it would not idle until warm (but I took this as normal). Once warm it ran nicely.
I have attempted some trouble shooting today.

I pulled out the air filter box and ran the bike to see where the backfire was occuring. Out the right cylinder manifold gasket where there was a missing bolt.
Replaced the bolt and ran the bike again, noticed it was backfiring out the left little hole of the inlet in the carb of the right cylinder.
On this picture it is where it was 'fuel comes out here' on the right cylinder only.
http://img97.imageshack.us/img97/6642/updatedleak.jpg
Then I proceeded to clean the float bowl, removed the jets and cleaned them. Sprayed carb clean down the two holes in the inlet. Re-assembled. I cleaned both carbs.
The carb cleaner than said to spray some down the carb vent (the one that says 'this one' in yellow on the above picture) so I did while running the bike.
I ran the bike and it was still pretty much the same.
I then decided to run each cylinder separately.
Right hand cylinder will only run with half to full choke and needs throttle to get going. Will not continue with no choke.
Left hand cylinder will run very high RPM with full choke and idles ok with no choke. However when warm the RPM creeps up and sits at 3000RPM.
I have adjusted the idle stop screw to not touch the throttle and the throttle cables are slack to let the throttle sit at closed.

Any idea for what could be the issue? Might be 2 seperate issues?
I have tried the WD40 on both sides boots (airbox to carb and carb to intake) but it doesn't seem to make the RPM rise on either side.
I was trying to avoid doing a valve adjustment but this might be screaming out for one?

[bmf]

Always make sure valves are in spec before taking other steps, it can (and will) drive you crazy if you don't!!


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[gsJack]

If you have good compression cold valves are not your problem, if you have good compression hot and very low compression cold then valves are too tight.  Only takes a few minutes to check compression and then you can get on to finding the real problem.

Not saying valve clearances are not important, it's important to have ample clearance on the exhaust valves for long valve life.  Suzuki spec is too tight for exhaust valves.

[kevinator9]

Darn I have a set of imperial feeler gauges and they are all too large.

The only thing I could determine is that my left exhaust valve is between 0.10 and 0.12mm. All the other valves are below 0.10mm (my smallest feeler gauge).

Went around shops today to try get my hands on a smaller set of metric ones but no luck.

I might have to book it in to the workshop to see if they can get it sorted :/

[kevinator9]

Having a last ditch play around before sending it in after labour weekend.
Drilled out the caps over the idle mixture screws. Lo and behold they were screwed in to the stops. Have set them at 2.5 turns out will see how it goes now.

[Majes]

So how did it go? Had luck?

[The Buddha]

Having a last ditch play around before sending it in after labour weekend.
Drilled out the caps over the idle mixture screws. Lo and behold they were screwed in to the stops. Have set them at 2.5 turns out will see how it goes now.

Probably not before you drilled out the caps. Do you see drill contact marks on the tops of the air screws ?? If so you probably screwed them in via drill bit.
Cool.
Buddha.

[kevinator9]

Well pointed out Budda 

I ended up popping the idle mixture screws out and cleaning them and the hole they go into, had a little bit of black gunk on the end of the screws.
Read the Haynes manual and it said 3 turns out on the screws for K1 models and onwards so I set to that and it is running very well now.
I still think the right exhaust valve might be set a little tight but I am in the process of selling to bike so might hold off on that.