81 GS450EX Carb help!!

[Guest]

Ok.. what I have done.

New boots, orings intake
New boots airbox
New plugs
carb clean, new orings, bench sync
valve clearance check - all in tolerance towards the loose side
timing good
new battery, grounds/power, new R/R
new fuel and vacuum line

can't find obvious vacuum leak, no exhaust leak at head.....grrrrrrrrrr

Ok... cleaned carb twice now, didn't need second clean. checked and nothing is clogging up. carbs look great, no tears in gaskets...all looks good, floats are not stuck and bowls are at level.

still takes forever to warm up ( 5 mins plus ) and I live in Flordia.

Since this happens rhythmically, I am thinking I have a vacuum leak or the gas tank isn't venting right...like its sucking out the gas til something finally gives way to let more gas out. Other symptom, when draining gas tank, it cycles the fuel in the line to gas can like a pump, not a steady flow. Flow gets better with cap off, but no significant improvement.

Bogs down at all RPM's... rhythmically, like the bowls are filling up then emptying out depending on speed depends on how fast it happens.

The bike does have moments when it runs fine extended then the bogging happens again...rhythmically.

seems impossible to get a good set on the air pilot as well.

What in hell am I missing.......

Vacuum issue? Tank vent issue? Petcock issue? Coils? It's driving me nuts.

[tom203]

" bike does have moments when it runs fine extended then the bogging happens again...rhythmically. "

Loosen the gas cap on tank - and see if it runs decent . Have you check the petcock for good fuel flow?
The slow to warm up stuff probably means your "choke " circuit (really an enricher) in one or both carbs is plugged up - did you thoroughly dip the carbs? Make sure the choke cable activates fully at carb end.

edit: did you inspect vacuum diaphragms for pinholes /tears?

[Blue Falcon]

" bike does have moments when it runs fine extended then the bogging happens again...rhythmically. "

Loosen the gas cap on tank - and see if it runs decent . Have you check the petcock for good fuel flow?
The slow to warm up stuff probably means your "choke " circuit (really an enricher) in one or both carbs is plugged up - did you thoroughly dip the carbs? Make sure the choke cable activates fully at carb end.

edit: did you inspect vacuum diaphragms for pinholes /tears?

nothing torn, no noticeable pinholes. choke is a lever and works fine...just the engine was taking forever. Cap off made no noticeable difference.

OK, now to what "we",and by "we" I mean me watching a master mechanic, found. Carbs clear, the issue was the APS...aka Air Pilot Screw. I apparently have one carb that is several turns off from the other...and the screw was not fully turned down to stop before backing off. There was a burr in the threads on one side that made it seem like the screw was going all the way down so it could be backed off to set air...fml..... he was irritated he didn't catch it a week ago. The other side was too rich... For now, it is tuned "by ear" but still not "in tune/sync"....desperately need vacuum gauge/carb sync tool, will have to set a time up with Rick.

Tonight, bike ran great...still took 3 minutes of idle and 4 miles down the road before I could take the choke fully off... but she ran purty after that....no hiccups/burps/backfires.

out of all that ..... I learned how much of a pain in the arse the pilot screw can be. The smallest little thing and make the biggest impact.... just ask the dinosaur's

Out of all this...carbs are fine, coils fine, petcock fine, lines fine, spark's fine, gas fine...........Freaking air pilot screws all out of wack....bingo.... mind you he said..."I have never seen pilot screws so sensitive" and why the (insert bad word here) does a master mechanic not have a carb sync tool at his house.. probably the same reason a fence builder has a crappy fence at his house....

Thanks Tom... I was pulling my hair out ( my carbs right now are about a two turn difference from each other on the screws... ) on the physics side of this....I'm trying to figure out how I missed this....should have seen it....even on cheapo vacuum gauges...