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Carb Tuning

  • Thread starter Thread starter ryankal
  • Start date Start date
R

ryankal

Guest
I finally received all my replacement parts for my BSW30SS carbs and began rebuilding last night. I ended up using JB Weld to repair bad threads. It worked perfectly - drilled and tapped like a dream. I got my carbs installed and the bike fired right up. Ran well for 30 sec or so, I ran through to some higher rpms, then it started to idle poorly and then die out. I made some adjustments to the pilot screws, idle adjust, etc and had it running, though very poorly and I had to have the choke on, as well anytime I gave it throttle it would die out. With the choke off it would die. There was also occasionally some light white smoke from one of the exhausts. Today I went back, after reading some more about tuning, and I couldn't even get it to start.

Any thoughts on what might be happening? Did I botch the carb rebuild? I followed the manual and the instructions found through the site and bike cliff. I know very little regarding tuning engines, though I do understand the principles. My thoughts are that since I needed to have the choke on to have it run well (after the initial period where it ran very well), that perhaps I'm not getting enough gas flow?

Any input appreciated.

Ryan
 
Possibly a fuel flow issue. Did you prime the carbs? Is the vacuum line connected to the petcock? Is the fuel or vacuum line pinched?
 
ryankal said:
I finally received all my replacement parts for my BSW30SS carbs and began rebuilding last night. I ended up using JB Weld to repair bad threads. It worked perfectly - drilled and tapped like a dream. I got my carbs installed and the bike fired right up. Ran well for 30 sec or so, I ran through to some higher rpms, then it started to idle poorly and then die out. I made some adjustments to the pilot screws, idle adjust, etc and had it running, though very poorly and I had to have the choke on, as well anytime I gave it throttle it would die out. With the choke off it would die. There was also occasionally some light white smoke from one of the exhausts. Today I went back, after reading some more about tuning, and I couldn't even get it to start.

Any thoughts on what might be happening? Did I botch the carb rebuild? I followed the manual and the instructions found through the site and bike cliff. I know very little regarding tuning engines, though I do understand the principles. My thoughts are that since I needed to have the choke on to have it run well (after the initial period where it ran very well), that perhaps I'm not getting enough gas flow?

Any input appreciated.

Ryan
Click to expand...

Usually when it won't idle without the choke the pilot circuit is plugged up.

Which bike is it and what have you done to the carbs already?
 
Did you have the airbox on while trying to rev the engine? :-k

Without something over the mouth of the carbs that will smooth the air flow, they will fall flat on their proverbial faces when asked to deliver anything more than a fast idle.

If you want to verify, take a shop rag fold it in half, then drape it over the carb intakes. Clamp the rag over the intake of each carb (use the airbox clamps). You can now run the bike somewhat normally. You can even take it for a ride around the block, but this is not proper enough to do any jetting checks.

.
 
I completely disassembled the carbs, cleaned them in a dunk can. Replaced the float needles and seats, replaced the pilot jets, pulled out the pilot screws and replaced the o rings, replaced float bowl gasket, cleaned every passage way I could think of with spray carb cleaner. I believe I set the float level correctly. I reinstalled on the bike. Put in a new air filter and hooked up air box. I had the tank off and ran a long fuel line to the carbs. I didn't have the vacuum line attached, but had the petcock on prime ( new petcock). It fired up and ran well for a few moments then I revved it and it sounded good until idle and it died. After that it was intermittent, I tried some adjustments to no improvement. Then this morning I mounted the tank, attached vacuum and fuel line. I checked that the carbs had fuel by loosening the float drain. The bike wouldn't start.

Ohh, and it is an 85 GS550L.

Thanks,

Ryan
 
So after further inspection, I am thinking that the needle jets aren't moving to allow gas through the main jets. I can move them by hand, but what function of the carb would cause them to move up to allow fuel through?

I have gas feeding to the carb in prime mode (though there are air bubbles in the line at the petcock). I, at least did, have gas in the float bowls. And I have a spark at the plugs. Any thoughts?

Thanks,

Ryan
 
Spark

Spark

Double check that all that tank removal business didn't unplug the ignition
I speak from experience
My ignition relay failed to
Easy to test your way up the line for continuity
I too went from running to nuthin so first step I pulled a plug grounded it and dang no more spark...
 
I pulled my carbs and inspected them and they look to spec. I am thinking it is ignition. I have some new plugs on order.

Ryan
 
I installed new spark plugs today and the bike idles great! I need to adjust the throttle cable, oil change, new tires, then I think its ready for a road test.

Thanks for the help guys.

Ryan
 
I didn't even think to pull them. I will check them in the next couple days. What should I be looking for?

Thanks!

Ryan
 
Thanks guys. I already rode it, hitting a few different rpm ranges. It felt good, but I would like to check the plugs. Can I still perform this test since I have ran through the ranges already? I also fully tightened the plugs already.

Thanks,

Ryan
 
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