bob654 Posted May 10, 2020 Author Posted May 10, 2020 (edited) Just had a looked based on what you said ,the ones with the squashed o rings have a rubber inner the nicer looking ones have a metal inner. Thank you, little by little. Edited May 10, 2020 by bob654 1 Quote
mark35gun Posted May 10, 2020 Posted May 10, 2020 unless the airleak was massive it wouldn't stop it firing on no 3, just weak mixture, the bigger the leak the weaker it becomes (relatively) make sure the float isn't stuck open on no 3 if it is stuck open it will cause that cylinder to flood. change all o rings, there should be 4, 1 on each of the inlet rubbers replace and make sure they are well sealed to the cylinder head. have you checked for a spark on no 3? a good test for airleaks once you have put it back together and running is to spray wd40 or similar all over the inlet rubbers while running, if the revs raise/alter, then there,s a leak, no need to lag it, just a bit will do. if you are careful its possible to pinpoint the leak. sounds like no 3 is flooding though. 1 Quote
Gixer1460 Posted May 10, 2020 Posted May 10, 2020 The numbers on the rubbers should largely be the same with the last few increasing from left to right (usually) like CO10, CO20, CO30 and CO40. Look on the Alphasports website and check what the part numbers should be - https://alpha-sports.com/suzuki_parts.htm 1 Quote
bob654 Posted May 10, 2020 Author Posted May 10, 2020 1 hour ago, mark35gun said: unless the airleak was massive it wouldn't stop it firing on no 3, just weak mixture, the bigger the leak the weaker it becomes (relatively) make sure the float isn't stuck open on no 3 if it is stuck open it will cause that cylinder to flood. change all o rings, there should be 4, 1 on each of the inlet rubbers replace and make sure they are well sealed to the cylinder head. have you checked for a spark on no 3? a good test for airleaks once you have put it back together and running is to spray wd40 or similar all over the inlet rubbers while running, if the revs raise/alter, then there,s a leak, no need to lag it, just a bit will do. if you are careful its possible to pinpoint the leak. sounds like no 3 is flooding though. Thank you. I think your right, it can only be a small air leak, and so not this problem, I have ordered new o rings. I checked the floats and could find nothing unusual. I have checked for spark and have good strong regular spark. I did the wd40 test, before with no result. Again I agree I also think 3 is flooding. Although it does not leak when off or from the bottom of the carb. Strange how it changed cylinders when I swapped the vacuum hose to a different carb last time. Quote
Captain Chaos Posted May 11, 2020 Posted May 11, 2020 (edited) 7 hours ago, bob654 said: Again I agree I also think 3 is flooding. Although it does not leak when off or from the bottom of the carb. Strange how it changed cylinders when I swapped the vacuum hose to a different carb last time. If you take off the vacuum pipe from the intake rubber and suck on it, maybe some fuel comes out of it. That would indicate a f*cked fuel tap. Edited May 11, 2020 by Captain Chaos 1 Quote
bob654 Posted May 11, 2020 Author Posted May 11, 2020 (edited) 10 hours ago, Captain Chaos said: If you take off the vacuum pipe from the intake rubber and suck on it, maybe some fuel comes out of it. That would indicate a f*cked fuel tap. I checked this and it worked as it should. Thanks for posting. Edited May 11, 2020 by bob654 Quote
bob654 Posted May 11, 2020 Author Posted May 11, 2020 What about this? What if it is firing... Only very poorly? How much air leak from intake rubbers would it take to f up the mix enough to only ignite some fuel sometimes? The near one is from 2 the other poorer one is from 3 and was coated with old silicone. Quote
BigT Posted May 11, 2020 Posted May 11, 2020 12 hours ago, Captain Chaos said: If you take off the vacuum pipe from the intake rubber and suck on it, maybe some fuel comes out of it. That would indicate a f*cked fuel tap. A better test would be to cap the vacuum port on carb #3 and run the bike with the petcock on Prime. If the bike runs better, it's the fuel tap. Fuel taps generally only last about 30 years 1 Quote
bob654 Posted May 11, 2020 Author Posted May 11, 2020 On 5/10/2020 at 6:16 PM, Blubber said: I think nr 3 still has its oring only that much compressed it almost bonded in. That seal is important . Hence the halfcocked attempt to seal . Replace the oring... fit a new one and forget. All 4 would be my preverred action NR3 ?? Quote
bob654 Posted May 11, 2020 Author Posted May 11, 2020 I got some new o rings today so will fit tomorrow. I dont think these have removable o rings. I have two like this and two metal and rubber with groove ( the real deal). Uh. I thought about putting a ring on top and screwing it against the head. Or else its new rubbers at 50 quid each. Quote
Gixer1460 Posted May 11, 2020 Posted May 11, 2020 (edited) 22 hours ago, Gixer1460 said: The numbers on the rubbers should largely be the same with the last few increasing from left to right (usually) like CO10, CO20, CO30 and CO40. Look on the Alphasports website and check what the part numbers should be - https://alpha-sports.com/suzuki_parts.htm I did a search on the Alphasports site and i've got a problem! Early GS750's had slide carbs and a monoblock attachment to the head not individual rubbers! Later 750's had individual rubbers and CV carbs but the rubbers were slip joints held with hose clamps! Then I looked at the GS850 fiche - CV carbs and individual bolt on rubbers - two types a LH side pair and a RH side pair - part numbers 13110-45100 for RHS and 13120-45100 for LHS ! ! ! I wonder if someone has put an 850 head on the 750 bottom end? See here . . . . parts #25 & #26 I think the inlets should all have o rings so you may potentially have the wrong rubbers and maybe the wrong carbs ? ? ? Edited May 11, 2020 by Gixer1460 Quote
gs7_11 Posted May 11, 2020 Posted May 11, 2020 17 minutes ago, Gixer1460 said: I did a search on the Alphasports site and i've got a problem! Early GS750's had slide carbs and a monoblock attachment to the head not individual rubbers! Later 750's had individual rubbers and CV carbs but the rubbers were slip joints held with hose clamps! Errr, no. Not correct. 1 Quote
bob654 Posted May 11, 2020 Author Posted May 11, 2020 (edited) I have been searching many sites and seem to find all 750 77/79 are part number 13110-45000 replaced with 13110-49000 unfortunately I cant find out if there is an o ring removable from here. The 850 and 1000 share this part. and this does not have sides, I think. https://www.Eblag.co.uk/itm/Suzuki-77-79-GS750-GS-750-GS850-GS-850-GS1000-Intake-Manifold-Boots-13110-49000/202730479839?hash=item2f33ada0df:g:oIYAAOSwqO5c1zgx Cant seem to find good second hand ones and the new ones are 140 quid without importing from USA. Can I put an o ring on top and bolt to head?? A little basic only may work long enough to test. Sorry if that sounds rough. Edited May 11, 2020 by bob654 Quote
gs7_11 Posted May 11, 2020 Posted May 11, 2020 4 hours ago, bob654 said: I got some new o rings today so will fit tomorrow. I dont think these have removable o rings. I have two like this and two metal and rubber with groove ( the real deal). Uh. I thought about putting a ring on top and screwing it against the head. Or else its new rubbers at 50 quid each. They do have o-rings. They're just deformed. 1 Quote
gs7_11 Posted May 11, 2020 Posted May 11, 2020 https://www.Eblag.co.uk/itm/Suzuki-GS750-GS1000-NEW-Carb-Inlet-Rubbers-O-Rings-Manifolds/111982768450?epid=1789233247&hash=item1a12b17142:g:O1sAAOSwiYFXI4d5 1 Quote
Gixer1460 Posted May 12, 2020 Posted May 12, 2020 11 hours ago, gs7_11 said: Errr, no. Not correct. What wasn't? It was a query / assumption, not a statement of fact based on what I could find! Quote
Blubber Posted May 12, 2020 Posted May 12, 2020 12 hours ago, bob654 said: Can I put an o ring on top and bolt to head?? A little basic only may work long enough to test. You can try en have a friendly machinist cut a new o-ring groove in the old one 1 Quote
bob654 Posted May 12, 2020 Author Posted May 12, 2020 At approx 5 min in you can see this guys hose set up. Quote
bob654 Posted May 12, 2020 Author Posted May 12, 2020 htt 2 mins after putting together no throttle setting yet and still on choke. Quote
BigT Posted May 12, 2020 Posted May 12, 2020 23 hours ago, gs7_11 said: They do have o-rings. They're just deformed. I can see the O ring in there. Just dig it out with that pick. If you need new boots, use CruzinImage.net You probably need new boots. Air box tubes wouldn't , either 1 Quote
BigT Posted May 12, 2020 Posted May 12, 2020 5 hours ago, bob654 said: htt 2 mins after putting together no throttle setting yet and still on choke. Doesn't sound like it's running on all 4 cylinders Quote
BigT Posted May 12, 2020 Posted May 12, 2020 10 hours ago, bob654 said: At approx 5 min in you can see this guys hose set up. I wouldn't be taking advice from this guy, except if you want to fumble thru your issues like him 1 Quote
Hariii Posted May 14, 2020 Posted May 14, 2020 Interesting, i have the same problem that cylinder 3 won't really work like the others. First i thought of the carbs and cleaned them again. Didn't really do the job. Then i sprayed some brake cleaner at the inlet rubbers while the bike was running and the damn 3 exhaust pipe instantly got as hot as the others and the rpm turned up. Checked the rubbers and they look the same like yours. Instead of just replacing the o rings, i decided to order new ones. Afters 40 years, probably not the worst idea. If this doesn't help, i will do that damn vacum test by capping it...God i truly hate vacum petcocks Cheers and good luck with your problem 1 Quote
bob654 Posted May 18, 2020 Author Posted May 18, 2020 I o ringed the inlet rubbers and found the not firing on 3 was the connection at the coil.Thank you all. Running on 4. 1 Quote
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