My first post seemed to be ignored, but I can be a little terse at times. Comes from being a grumpy old bastard. Hang on! I was like this when I was a grumpy young bastard.

You have not replaced all the seals because it is impossible to buy them. Attached is an image of the location of the 4 mid-body seals and another image showing what they look like when they are beyond serviceable limits. How old are yours exactly? There is a very good chance that yours also look like this, and even if they don't, it is only a matter of time before they do.

The good news is that I am making seals for these in collaboration with Matt Harper from Harper's Ultrasonic in the UK. The bad news is that it won't happen overnight.
cheers
Blair

Blair I think he has standard or maybe SP Mikuni carbs on the bike as he mentions the TPS, I don't think the flatslides have any kind of TPS system.

Dobbs :-D

Ok my bad! I heard SP and thought FCR Ooops! Ignore everything I said and carry on.
Thanks for setting me straight Mr Dobbsic

I think the SP GSXR carbs are something like 1mm larger than the standard ones and have the TPS on them.

Now that I am on the right page.
This "forum troubleshooting' is fraught with difficulty. This case interests me of course so I want to redeem myself.

quote:
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Well I've had another look at these carbs today and replaced every oring again, except the slide holders as I simply forgot about them. Doh!
I decided to go for a 1.5mm thick oring for the pilot screws after trying two sets of 1mm ones with little joy.
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a/ Does this mean that you originally fitted new slide housing o-rings and did not replace them a second time? If not then what does it mean?
b/ Your pilot screw o-rings should be have a cross section of approximately 1.18mm. Are all of your other o-rings just "something close"?
c/ Have you replaced the jet housing seal?

This is how I see your situation from what I can understand.
1/ Assume the motorcycle used to work correctly since we do not know otherwise.
2/ Carbs are cleaned ultrasonically. This will surely turn already rotten seals and o-rings to crumbs.
3/ Some seals are replaced with unknown parts. The op has admitted to using the wrong size pilot screw o-rings, so assume all of them could be wrong.
4/ Jet housing seals are not replaced.
5/ Throttle shaft seals are not replaced nor mentioned as being checked.
6/ Slide housing seal replaced??? Cannot tell.
7/ Motorcycle does not run at low speed, and we do not know if it runs at high speed apart from when stationary.
8/ When idle speed adjuster is wound in there is no response.
9/ When choke is operated (with idle speed already adjusted to a high speed) engine runs at high speed. This indicates quite clearly that there is insufficient fuel passing through the pilot circuit.
10/ Adjusting pilot mixture screw circuit has no effect. See 8.

Assumption:
Pilot circuit is not passing sufficient fuel.
Please test this by using a hand held spray bottle with some fuel in it (set to deliver a mist rather than a stream) and spraying some fuel into the intakes whilst running.

If the assumption is correct then the obvious possibilities are.
1/ The jet housing seals are leaking, which is very likely, and since the pilot circuit is sealed against the air in the top of the float chamber by the jet housing seal then how can the pilot circuit draw anything else but air? The op has not informed us if the jet housing seal has been replaced.
2/ Pilot circuits are blocked.

cheers
Blair

Hi Blair,

Firstly, I think you have already redeemed yourself as I think your explanation of what's happeneing is spot on! I'm as guilty as anyone for not reading things through properly.
Anyway, I haven't thoroughly explained the situation but so you understand a bit more.................the bike was a winter project I picked up as a complete dog that had been sat in a garden for the best part of ten years without turning a wheel. I have never ridden it across my workshop yard let alone in anger! I stripped it to the frame and built it all back up again, giving only minor attention to the engine internals. Valve clearances were done and are spot on, compression is good on all cylinders so I'm happy the internals are fine. Cam timing is ok and the coils and pick up have been swapped out for known working items from my other GSXR so again, I think I can rule that lot out.

As for the orings, I initially bought a set of them that was supplied by a 400 greybike forum member to another GSXR owner who, had decided he'd had enough (more common than not!) so I'm assuming the sizes were correct I then started to doubt the first set of new rings so I sourced another set, the ones that are in the carbs now, according to the famous Tony Sleep guide, to see if there was any improvement. Both new sets also visually matched the original orings that had sat in the carbs for some years and, that were surprisingly in one piece when I initially stripped them, so I'm happy the sizes are correct. Carbs were sent for cleaning. minus all seals and seperated into four. The seals between the carb bodies, as you well know, are almost impossible to source so I just soaked them in 'Gummi' (use it to soften the rubber on the seals around my cars convertible roof) and reused them. They certainly dont leak fuel so I'll assume they are ok for now.
The orings in the slide holders were replaced the first time but not when I replaced the orings the second time so again, I'm pretty happy they are ok.
The only thing I didn't replace was the main jet block seal so your suggestion that it is letting air by seems perfectly logical. The idle circuit is perfectly clean, I have checked and double checked every passage, even after ultrasonic cleaning and blown fluid through to make sure.
With the pilot screw seals, I just wasn't comfortable with a 1mm section oring so in desperation more than anything I used a 1.5mm section ring with the same internal dimensions. It slipped in a little tighter and felt like a better seal but ultimately made no difference.

Thanks for all the input. Think I'll be heading over to your website shortly for some bits!

Cheers
Paul

Avinitboys,
Ok got all that clear now. Don't forget to check the throttle shaft seals. (I have not been able to afford the mould to get these made. Maybe one day. )
They are not expensive and although it seems scary to replace them it is not so bad. Just use new screws and Loctite 242 when reassembling. Do not even think of trying this with a Phillips screwdriver. It will end in tears. JIS crosshead only.

1/ Tighten one screw without Loctite when you have the butterfly in position.
2/ Then apply Loctite (tiny amount on threads only) to the other screw and fit.
3/ Remove first screw, loctite and refit.

Some people insist on staking the screws. I wouldn't bother, but it might give you peace of mind.

Keep us informed.
cheers
Blair

Thanks for that Blair.
I'll check those when I pull everything apart again.
I have been over to your website and, for my own peace of mind, have ordered a full seal kit from you. At least I know that every single replaceable item is bob on and definitely the correct size and profile. If I still have no joy, then it probably points to something else but, I doubt that very much! I'm certain your right about the jet block seal. Why wouldn't it be leaking after years sitting in the fuel bowl?
I'll keep you posted
Thanks again everybody
Paul

Quick update......

I received all my o rings and seals from Thailand (thanks Blair) and set about fitting everything, paying special attention to getting things seated properly etc. it made absolutely no difference!
So..........I pulled a set of carbs off my spare bike, having resisted doing so because of thm not being SP carbs and unbelievably, it started and ran perfectly!
At least I know for sure that its all carb related and can rule out other things, having changed the coils, pick up and plugs twice. Really wished I hadn't been so hell bent on using the SP carbs and tried another set earlier.

So the question is now......what could be wrong with these carbs. Crack in the body possibly.

Ok that is in the hard basket now. The question is
what is different between the carbs that work and the carbs that don't?
Are all the diaphragms in good condition, no holes?