Question about 1977 Suzuki GS 750
When i first start this 1978 gs750 the rpm hang at around 3,000, with the choke off. after 30 seconds or so the rpms slowly come down to 1200. the bike seems to be running really rich at idle (smells bad and burns your eyes to be around), but if i try lean out the air screws the idle will just hang. head is rebuilt, second set of carbs rebuilt, new rings, petcock rebuilt, new points and condensors, nothing has helped this problem. past idle the bike runs strong, doesn'tsmoke and doesn't seem to be running rich higher in the rpms. please help me i'm starting to loose my hair!
This sounds like an air leak is making the fuel/air mixture too lean. Any air leaks between the carb and the head will lean the mixture. Old, hard and cracked rubber manifold parts are the usual culprits. Old gaskets and "O" ring seals can leak air also. A bad head gasket seal happens at times also, as does an exhaust valve not fully seating. Air leaks are the idle speed problem.
A different problem is likely present in the carbs and that is what is causing the rich fuel smell. The carbs must be balanced. Example > If three of four carbs are perfectly balanced and one carb is not, then the 3 are "driving" the 4th carb. This will cause gas to spit into the air cleaner from the "bad" carb and can cause a backfire or two. Special vacuum gauges are needed to balance the carbs. Also be aware the carbs must be scycronizsed as well. The slides on all four carbs must lift at exactly the same time when the throttle is cracked.
Go to the site below where you can see a parts diagram for your specific bike. You will select the actual brand, year, model, etc., once you go to the site. Part numbers and prices are also shown. You can order parts from this site. In the event no price is shown on a particular part, the part is not in stock. www.babbittsonline.com/pages/parts/viewbybrandand/parts.aspx
I don't get paid for my answers but I do take pride in them, and I am only trying to help. So if you will, > > A “very helpful” rating for these answers? Thanks!
Posted on Jun 14, 2009
There are 3 things you can do, the 1st is to get some 29mm smoothbore micuni's, or ajust tour idle screw thats located in between the 2nd and 3rd carb. idle rmp's down thur left, idle rpm up turn right.
and i had the same problem i solved it by re-jetting the main jets
Posted on Aug 14, 2009
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Posted on Jan 02, 2017
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