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Saimese carbies

  • Thread starter Thread starter erjeff
  • Start date Start date
siamese carbies

siamese carbies

erjeff,lots of great offerings from the members to dwell upon and check out in your troubleshooting.Hope you can try them out,they may reveal an overlooked cause(s). I will say,having this carb set also to perhaps(up to you):Gently screw down all 4 pilot needle screws(too hard/tight,little o rings can break/split ).I tried best idle senarios etc.Found to my surprise(because it got good results,for bad idle/driveabilty),4.5 to 5 turns up from bottom was the charm to tame unruly dragon.Just another tale in the Siamese Twins story.Work/Ride Safe ,let us know what goes on.
 
erjeff,GSR community,social groups has GS550 group:has probably for certain crossed paths with the legendary Mikuni BSW30SS aka/Siamese/Carbies you have as possible current concern/project.
 
I'm experiencing the same issue on my 83 gs550e. I cleaned the carbs and changed the jetting to correct service manual specs and now sometimes it will start no choke and clean. Then it dies out after going up the street and only starts on choke. Then it dies out for good and I usually kill the battery. I supplemented a gastank for diagnosis with good flow and a paper inline filter. Carb bowls are getting gas when drain plugs are pulled. And slow system on carb has been gone through. How bad is it to be one pilot screw oring short?. And do intake boot orings stick out from bolting surface or do they sit flush in the groove? Mine look to not be sealing.
 
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Hey Guys, here's an update.

I pulled the carbs again and tore them down. Cleaned everything again and made absolutely sure that all passages were clear. I did discover that the main jets were reversed from the normal position. The 95's are supposed to be on the outboard cylinders and 102.5's on the inboard but they had been switched by the PO. I know it wasn't me because the first time I tore them down I made a scribe mark to be sure everything went back to its original spot. Not sure how much of a difference this would make though.

When I got the carbs re-installed she started up and ran great even with no choke. Synched them as best I could and went for a test drive. Ran better than ever but would still immediately stall when I'd let it idle at stops or in turns, although it would idle just fine when started up in neutral.

I then pulled the valve cover and adjusted the valves. Some of the exhaust valves were too tight and the intakes tended to be too loose. I also turned in the pilot screws a full turn (they had been 3 turns out) synched em again. Now it's running perfect!
 
.erjeff,celebrate that,taco dinner maybe?I feel your good feeling.
 
erjeff said:
I then pulled the valve cover and adjusted the valves. Some of the exhaust valves were too tight and the intakes tended to be too loose.
Click to expand...
Hopefully you let the engine cool COMPLETELY before adjusting the valves. :o

The manual calls for a COLD engine (not run for 8 hours) before checking clearances.

.
 
I let it sit overnight before messing with the valves. Set them all so that a 0.10mm feeler would just slide in but a 0.12 wouldn't go.
 
Hi,

Thank you for reminding us that it's always a good idea to do all of the required maintenance in order to have a well-running motorcycle. Congratulations on your success! :)


Thank you for your indulgence,

BassCliff
 
wha..what?! whats all this talk about different size main jets on outer and inner carbs? Am i missing something. Admittedly I didnt read all the posts leading up to this one.
 
snicrep5 said:
wha..what?! whats all this talk about different size main jets on outer and inner carbs? Am i missing something. Admittedly I didnt read all the posts leading up to this one.
Click to expand...

Sounds like you didn't read the manual either.:p
 
Hi,

snicrep5 said:
wha..what?! whats all this talk about different size main jets on outer and inner carbs? Am i missing something. Admittedly I didnt read all the posts leading up to this one.
Click to expand...

Perhaps you should.

For this particular bike, the '83 GS550 with the "Siamese" carbs (BSw30SS), the inner cylinder jetting is different from the outer cylinder jetting. I think this was also the case for the '84-'86 GS1150. The inner cylinders run hotter so they get a little more fuel in the mix to keep them from overheating. It's all documented, if you want to read manuals and such. There's a handy-dandy carb spec sheet on my little website.


Thank you for your indulgence,

BassCliff
 
The 1983 550L only has two duplex carbs instead of four. Each of these serves two cylinders and has two main jets that are different sizes because of the way air flows through them.
 
oh kay, once again im assuming were talking about gs 1100s. (guess im very self centered). and not very observant. btw ive read parts of the manual that pertain to what im working on. I get better info from here than the book.
 
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