81 GS650L, Choke doesn't do much/anything

[DaveP]

Not having too much trouble getting the bike started, but the choke doesn't have any effect. Bike will stumble along below 1,000 rpm on cold start and eventually I will be able to give it some throttle to get it warmed up and idling smoothly at 1,100 rpm. Carbs were dipped, all o-rings replaced, passages picked, and carb cleaner could flow through the enricher passage and pickup tube. Choke cable is also actuating the plungers, but idle is not impacted by the position of the choke. Original air cleaner too.

Operation has been the same independent of weather conditions and time between starts.

From other posts, it seems that the choke should have an impact on the idle rpm at start up to help the bike get warmed. Even mention of half choke so the engine doesn't over rev before oil is circulating.

Any direction on what I should take a look at?

Thanks,
Dave

[2BRacing]

The choke will have a definite effect on RPM at start up, if all passages are properly cleaned. Are the small holes in the bottom of the float bowls that feed the choke pickup tubes properly cleaned and open? Look at pages 50 and 51 of 77 of the CV carb rebuild tutorial. When you spray carb cleaner down the pickup's passage in the float bowl, it must "spray", not "flow", out of the little hole at the bottom of the float bowl (hold it away from your eyes!!).

When you set the choke to start the bike, you must NOT twist the throttle at all during the start-up, or else that enrichening circuit will be inoperative.

[tom203]

It seems unlikely that all four carbs have clogged enricher circuits. Did you leave the choke plungers out of the dip? (Hopefully yes)
my bike ain't interested in cold start unless "choke" is fully up. Then it goes crazy till choke is backed done abit. Drive away and fully off within two minutes- if I don't turn it off it will hesitate on accelerating. So yes, the choke should have a big effect.
Did you bench sync the carbs, so throttle plates appeared just about fully closed on idle stop screw?

[DaveP]

I did follow the carb rebuild tutorial and did make the mistake the first time of almost shooting myself in the eye with carb cleaner when the spray came flying through the passages. They were clogged before I started, but I had fluid spraying through all passages before putting things back together. Wouldn't think that they all clogged up again in a short period of time. Sta-bil is in the fuel that I have been using.

Choke plungers were not dipped due to the rubber end cap.

Bench sync was done and vacuum sync at about 1,500 RPM once the bike was running. Then idle set back to 1,100 RPM.

Throttle is not touched at start-up to stay on the enricher circuit. Once it has stumbled along for 5-10 seconds, then I try to start feeding it some throttle to get the idle up and smoothed out.

I can pretty much move the choke cable back and forth with not much noticeable difference.

[tom203]

What you describe says your enricher circuits aren't working- odd that all 4 appear to be doing nothing. I would think that just having two going would be enough to produce high idle at cold start.

[jbird7262]

Not to hog the thread, but a question about the choke operation, GS750E. It seems that my choke is always held in the down posisition by spring pressure, even if I pull the knob up, it won't stay in the up posisition. What holds the choke up verses chokes mounted on the side of carbs. verses knobs mounted on the triple tree?

[tom203]

?.........What holds the choke up verses chokes mounted on the side of carbs. verses knobs mounted on the triple tree?

On the triple tree mount, you can tighten the nut (black plastic doohickey just below knob)to add more friction to hold knob up

[jbird7262]

Thanks, I'll ck. into that.

[tom203]

Back to DaveP....... What I don't understand is how your bike can still run OK with choke plunger open- this is letting extra air pass behind throttle plates mucking up mixture . See attached pic (sorry about sizing ) for Keihin carb but mikuni uses same idea

http://faq.ninja250.org/images/e/e8/Jim_carb_10.jpg

[DaveP]

Choke is full closed once it is running and idling smoothly.

Starting procedure:
Fuel on prime or run.
Choke fully open.
Start.
Stumbles around below 1,000 rpm.
Play with choke knob, no changes.
Start closing choke.
Add throttle to improve idle (enricher circuit must be working somewhat because opening the throttle too soon will kill the engine)
Choke closed.
Hold throttle at about 1,500 rpm for a bit.
Ride away...

[tom203]

Since it rides/idles OK once warm (when you don't need the enricher circuits), indicates that no/little fuel is climbing up "choke" passages and reaching plunger area.

[DaveP]

Sounds like do over time.

[tom203]

Winter fun! I'd probably pull and separate carb rack, remove fuel bowls and choke plungers, stick gumout tube into each plunger fuel inlet and see if you get good spray flying out those little tubes.then blast thru bowl orifices.

[81GS850]

I just pulled my carbs apart on my bike... You didn't mention the condition of your tank? Rusty? Willing to be you have tiny rust particles getting in the orfices plugging stuff up. I'm about to coat my tank in red-cote tank sealer found at O'reillys. Also what are your float heights set at? How is your gas mileage? I was managing about 32-33mpg when my bike should be getting 40+.

[barnbiketom]

o-rings behind intakes and INTAKES good????? Does the bike run CORRECTLY after warm up? all the time? does the idle hold true ALWAYS after warm up?? I just wonder if the o-rings behind the intakes are allowing air leaks. all 4 on mine were BAD.. including the intakes.. bike would run but not perfect.
If your intakes are bad ( i can't believe they aren't if stock) and/or o-rings, then enriching would merely accommodate the already lean condition at startup.. and maybe NO HIGH IDLE...??