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no fuel getting to cylinder

  • Thread starter Thread starter signguy35
  • Start date Start date
S

signguy35

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i posted this on my project thread but i didnt get any responses so i thought i would try here. 1981 GS550T

I have done a deep clean on my carbs and reinstalled them. i got a new petcock and that is installed as well. also new intake boots. i hook all the hoses up and turn the petcock to prime. wait for a bit and then put it back to on. Try to start and it will turn over but no vroom. it also has started to sound like a leaking air after the first second of hitting the start button. i took the plugs out to check them and they are bone try. i have fuel in the bowls, i checked the drain plugs. i sprayed some starting fluid with the air cleaner off and it will start that way. if it will start with the fluid does that mean that my carbs are ok? i have the top air screw out 3.5 turns.

only thing i am nervous about my carbs is that my slides didnt really want to easily go up and down when i was putting them back together. does the air sound that i am hearing maybe the slides trying overly hard to move up? i do not want to take this to a shop i would like to take care of this myself and prove to my doubting dad that i can do it all.
 
Did you follow the carb rebuild tutorial as linked on Basscliff's website and my signature? Is the airbox and air filter installed? Is the bike stock or modified?

I'd start by measuring fuel level, not just checking for fuel in the bowls. Sounds like fuel is not filling the bowls like you suspect.
 
stock, airbox and air filter is installed, only took off when i shot starting fluid in there.
 
If you didn't clean carbs like in that tutorial , they aren't clean enough! The idle circuit passages are tiny and once clogged only a full strip and dip will likely work. The fact that it came to life with starting fluid reinforces this view.
The slides don't move up during start up, so they could be frozen and bike would still start if it had enough fuel and air.
when you dismantle carbs again, figure out why slides are sticking.
Make sure you understand correct "choke" usage -applying throttle during cold start defeats it.
 
it was a complete strip and dip. new orings too. i had every tiny piece off and cleaned. even after the complete dip once i put the slides back in they still didnt slide with ease.

does the sound of air after i hit the starter button make any sense?
 
You dont know for sure if your float bowls are filling correctly unless you measure the heights correctly using the correct methods. Are you sure your petcock is working? have you had the hose off and tried all three settings? On and reserve= no fuel when bike not running, prime= fuel running freely when bike not running. If you have free running fuel on prime, onto the fuel bowl level check. Are you giving it enough time to fill? Not sure what carbs are on yours but ive had the vm carbs apart and cleaned on my 79 GS1000S. I think each slide is connected to a bell crank which is connected to a single throttle rod which runs through all the carbs. This is connected to a linkage and then throttle cable. If you have CV carbs I believe the throttle operates a butter fly valve which creates vacuum above the diaphragm causing the slide to rise and fall. AFAIK this would mean that if you have CV carbs you should be able to lift the slides with a finger, if you have VM carbs they will be fixed. Anyone feel free to correct me on this though. Are all vaccum pipes and inlet tubes sealing ok?
 
I have CV carbs, and yes the Petcock is working as it should. is there a way of checking the levels of fuel bowls with carbs attached?
 
Ok, full strip and dip, new o-rings, etc.Is "choke" being used correctly ? Apply fully, no throttle at all and crank it. If still no go, pull spark plugs and look for signs of fuel.The sound of air stuff is unlikely the carbs' vacuum pistons - can you isolate the noise? Did you or PO have cams off? Checked valve clearances?
 
signguy35 said:
is there a way of checking the levels of fuel bowls with carbs attached?
Click to expand...

Yes there is. Look in your service manual for the technique, or check the carb rebuild tutorial from Basscliff's website (or my signature).
 
Devon bloke said:
If you have CV carbs I believe the throttle operates a butter fly valve which creates vacuum above the diaphragm causing the slide to rise and fall. ... Anyone feel free to correct me on this though.
Click to expand...
The vacuum above the diaphragm has NOTHING to do with the butterflies.

The vacuum above the diaphragm that lifts the slide comes from the lower pressure in the venturi (the area directly under the slide), which is caused by increased air velocity. OK, that "increased air velocity" is caused by open butterflies, but the only vacuum the butterflies cause directly actually results in the slides going DOWN.

.
 
When i got to clean my slides during the strip and dip i didnt want to ruin the diaphragm so i just blew carb cleaner all around it and wiped it off. the color of the old varnished gas came off. i never dipped the slides i guess. is that wrong?
 
Dip will destroy diaphragms. They should be spotless and slide freely.
 
signguy35 said:
When i got to clean my slides during the strip and dip i didnt want to ruin the diaphragm so i just blew carb cleaner all around it and wiped it off. the color of the old varnished gas came off. i never dipped the slides i guess. is that wrong?
Click to expand...

I usually soak a rag in carb cleaner and wipe off the slides by hand, taking care to not get any on the diaphragms. When going back together, I usually wipe down the carb body or slide areas as well.
 
Steve said:
The vacuum above the diaphragm has NOTHING to do with the butterflies.

The vacuum above the diaphragm that lifts the slide comes from the lower pressure in the venturi (the area directly under the slide), which is caused by increased air velocity. OK, that "increased air velocity" is caused by open butterflies, but the only vacuum the butterflies cause directly actually results in the slides going DOWN.

.
Click to expand...

thats kinda what i meant but you put it better ;)
 
ill pull the carbs off tonight or Sunday. once i take the slides out again how do i clean it better than rubbing it with rag full of carb cleaner? should i also have some sort of lube to make it slide easier? Thanks.
 
I pulled the carbs last night and only one of the slides was stuck still. other three were free. so i took that slide out and cleaned it again. I put the carbs back on but took the air box off just to see if it would start. i didnt want to mess with getting the carbs back in between the intake and air box. took me long enough last time and i just wanted to see if it would start and if it did i would put the air box in. still no start though. it should start though even with the airbox off right? i guess i will do another strip and dip. i didnt have a air compressor last time to blow it out so i will do it this time with one.
 
Yes, it should have started, even with the airbox off. Be sure and have your fire extinguisher close at hand, though, in case it backfires through the carbs.
 
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