93 GSX-R750 - Cylinder 3 Not Firing - Page 2 - Suzuki GSX-R Motorcycle Forums Gixxer.com
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post #21 of 28 (permalink) Old 08-09-2019, 11:44 AM Thread Starter
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Re: 93 GSX-R750 - Cylinder 3 Not Firing

Sorry, found it in the manual. It connects to a small nipple on the back side of the petcock which I never noticed before. I hooked it up but didn't expect any change which I confirmed. I think I'm going to break the rack of carbs down and go through them all. When I put them back together, I will swap #3 with another and see what comes of it. Thanks
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post #22 of 28 (permalink) Old 08-09-2019, 02:55 PM
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Re: 93 GSX-R750 - Cylinder 3 Not Firing

Was that hose not connected before? If not you should have no fuel flow unless setting your petcock to prime. The vacuum from that hose opens the petcock to allow fuel flow. If it is open to atmosphere you would have a serious vacuum leak on #3.
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post #23 of 28 (permalink) Old 08-09-2019, 04:36 PM Thread Starter
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Re: 93 GSX-R750 - Cylinder 3 Not Firing

It was not hooked up, but since I kept removing/replacing the carbs, I was just using PRI on the petcock to fill them and quickly run the bike.

You're question made me think of something. I just went out to the garage and switched the petcock selector to ON. The bike started right up on choke and ran for a few minutes, but then started running rough and stalled. It would start up again, but rolling the throttle on would stall it. So, it looks like there is not enough vacuum being pulled on #3? Would this change the diagnosis of carb at all?

Last edited by nicksorg; 08-09-2019 at 05:08 PM.
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post #24 of 28 (permalink) Old 08-09-2019, 06:31 PM Thread Starter
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Re: 93 GSX-R750 - Cylinder 3 Not Firing

Split the rack and broke all the carbs down. Next step - order rebuild kits and bath in the sonic cleaner.
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post #25 of 28 (permalink) Old 08-09-2019, 07:29 PM
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Re: 93 GSX-R750 - Cylinder 3 Not Firing

Interesting. It would have been interesting also to see if you moved the petcock tube to one of the other carbs if you had the same result. That would definitely have pointed to a carb/vacuum issue. While the carbs are off maybe a check on the valves to verify clearances/health there as well.

Check the carb sticky in this forum for a good source for all the seals/bushings/o-rings for the carbs.
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post #26 of 28 (permalink) Old 08-09-2019, 07:50 PM Thread Starter
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Re: 93 GSX-R750 - Cylinder 3 Not Firing

On my bike, only #3 carb intake holder has a nipple, so not sure I could have done that extra test.

While I wait for the carb parts to arrive, I might as well check the valve clearances. Thanks, that's a good suggestion.
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post #27 of 28 (permalink) Old 08-10-2019, 08:37 AM
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Re: 93 GSX-R750 - Cylinder 3 Not Firing

Quote:
Originally Posted by nicksorg View Post
Split the rack and broke all the carbs down. Next step - order rebuild kits and bath in the sonic cleaner.
That picture brings back memories... I only have one carbed bike ATM, which hasn't run in at least two years; but I'm extra careful to drain everything when I park it to avoid that. I know where you're coming from, its very time consuming and frustrating to go through all of that just to reinstall them and have the same issue.
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post #28 of 28 (permalink) Old 08-10-2019, 11:03 AM Thread Starter
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Re: 93 GSX-R750 - Cylinder 3 Not Firing

I measured tappet clearance. They were all over the place. Looks like I have to pull the cams which I never like doing. Shim under bucket style sucks.
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