Vacuum problem or something else?

edthebad · L Plate Warrior Joined: 02 Apr 2012 Karma :

I think I have a vacuum problem on my 1995 Suzuki GSX 750F. After having no joy starting it I finally got it to run but only after spraying Easy Start into the air inlets. It would then run all the time I was controlling the throttle but wouldn't idle and didn't want to restart without the Easy Start. I have new inlet rubbers and I've had a sonic clean on the carbs but I'm wondering if there's a way to test to the vacuum of the carbs (I've been lent a tester and wondered if it's just a case of attaching it to the vacuum pipe). Am I right in thinking if I've got new inlet rubbers that the only other seal will be the diaphragm or are there any other parts I should look at replacing. I'd be really grateful for any suggestions as I'm getting more and more frustrated. The plugs are not getting wet when I try to start it which seems to imply that the problem is fuel / vacuum related but I'm afraid I'm well out of my comfort zone here.

Thanks
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Ed

stickybackbob · Trackday Trickster Joined: 23 Mar 2013 Karma :

Get it running and spray wd40 around the inlet rubbers whilst the engine is running. If there is no vacuum leak, then the engine will continue running as before. If the revs change when you spray, then you have a leak.

If no leak is found, then I would start with the pilot jets

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

If it has a fuel filter, remove it. I have experienced lots of trouble with a GT650 that wouldn't start, the problem was down a filter not playing ball with the vacuum fuel tap and failing to flow fuel.

edthebad · L Plate Warrior Joined: 02 Apr 2012 Karma :

No Fuel Filter but I'll try the WD40 trick. The rubbers have only just been replaced but I'm wondering about the rubber actually in the carbs.
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Ed

mentalboy · World Chat Champion Joined: 05 May 2012 Karma :

And leave the Easystart for your tractor.
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Make mine a Corona.

stickybackbob · Trackday Trickster Joined: 23 Mar 2013 Karma :

If I remember correctly, the carb diaphrams don't have a great effect on tickover but could be wrong on that.

You say that the carbs have been cleaned but have they been rebuilt correctly?
Are the float heights correct?
Have the carbs been balanced?
Have the mixture screws been adjusted at all?
Is the airbox properly sealed?

All the above can have an effect on how the bike idles. As before, do the wd40 trick and see what happens....and I agree on the previous post - don't use easy start if you can help it, they get an addiction Wink