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Idlesl fine for 45 minutes of riding then starts to die at stops.

  • Thread starter Thread starter spyug
  • Start date Start date
S

spyug

Guest
1983 550 E. Just out tonight after sealing tank and then recleaning carbs for the 3 rd time in 4 months. Carbs were synched. I also run an inline fuel filter because of all the cleaning. Starts and runs fine. Idles around 1400 rpm. Pulls like a freight train in all gears and is going to get me in trouble:o.

The first 45 minutes are great but then at a light with throttle closed, idle slowly drops and she dies when it gets to 1000 rpm. I could keep it running by blipping the throttle but to take the hand off it dies.

When the carbs were cleaned and rebuilt the first time (in March when I got it) I did put in new o-rings but I didn't change the intake boot o-rings or the boots themselves as they looked ok. It has a stock airbox and the rubbers are soft and seal ok I believe. The pipes and mufflers are stock and in good shape with no holes or leaks.

I'm not sure what to look at, at this point. I tried upping the idle a tad but then it started rising when I came to a stop. Setting it at 15/1600 and it would rise to maybe 2500 or so.

One thing about this bike, it does have some interesting challenges :).

Any ideas folks. My check of the archives didn't really show anything.

As always, all comments are appreciated.

Cheers,
spyug
 
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Not sure why it would take 45 minutes to occure however, from the symptoms that you are describing, it would seem to be running lean. Hence the climbing idle. Two things come to mind. The intake boot o-rings, even though they may "look OK" need to be nice and round (if you cut one in half, the profile will likely not be round...usually oval with two flat sides. They flatten over time, harden, and tend to start leaking.

You may be getting a bit fuel starved as a result of the inline filter.

Other than the two things I mentioned, not really sure what is going on. Have you checked battery voltage with the bike running at +- 3500-4000 rpms?
 
I would think it should have a smooth idle lower than 1400 - My GS1100 calls for 1000 - 1100. It sounds like a vacuum leak that gets worse as it heats up and things expand a bit.
 
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When you sealed the tank, did you also happen to seal the vent? :-k

I would think that venting symptoms would show up sooner than 45 minutes, but it's a possibility. :o

.
 
BSW30SS carbs? All 4 pilot screw covers removed,set highest idle method,cold start enrichment plungers aka/'choke' functioning for proper close and open on/at both carbs,vacuum plugs installed w/good washers after manometer guage sync.job ????.What does battery charging numbers look like before and now after your test ride? Throttle cable tension/slack set properly,vacuum/fuel lines in good shape routed ok not pinched cracked????
 
Hi babes. What liner did you use on the tank? This happened to me when the liner i used, was disolving back into the fuel due to the ethanol here in the uk... (Do'h!)
 
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I recommend a hard stop and replace those intake boot O-rings. Not sure if it's the problem for sure, but those O-rings are sure to leak at some time in the near future anyway so I'd change them now and move on.
 
Agree- re:you didn't replace the 4 large intake O rings and should(must) do so .(Maybe..or not.. for experiment before carbs come off:start up engine,let it warm up in nuetral gear/pos(fan blowing on engine) when engine seems settled/warm idleing nicely,spray wd40,silicone,or other slightlty flamable product around engine intake stub connections to carbs,look to notice any rpm change/increase maybe reveal a vacuum leak area.Keep face/body back from hot engine,safety goggles on.Or don't do this at all,change out all 4 O rings set carbs up and retune them.
 
elrico said:
Agree- re:you didn't replace the 4 large intake O rings and should(must) do so .(Maybe..or not.. for experiment before carbs come off:start up engine,let it warm up in nuetral gear/pos(fan blowing on engine) when engine seems settled/warm idleing nicely,spray wd40,silicone,or other slightlty flamable product around engine intake stub connections to carbs,look to notice any rpm change/increase maybe reveal a vacuum leak area.Keep face/body back from hot engine,safety goggles on.Or don't do this at all,change out all 4 O rings set carbs up and retune them.
Click to expand...


Spraying flamable stuff is not a good check for air leaks on GS bikes in my experience. Best to just do the maintenance (change the O-rings) and stop farting around.

Do the job right the first time...or in this case, the second time. I'm surprised how few people pick up on this simple tidbit.
 
Thanks folks. we have a long weekend coming up and the weather is supposed to be good for most of it so I think there will be a bit of fiddling, rechecking and test riding going on.

would think it should have a smooth idle lower than 1400 - My GS1100 calls for 1000 - 1100.
Click to expand...
I did actually have it at around 1200 but it did seem to dance a bit between there and 1400. At 1400, it stays rock steady.

When you sealed the tank, did you also happen to seal the vent? :-k
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Pardon my ignorance, Steve, but I am not aware of a vent other than through the gas cap which was not on at the time. Is there another one I should be aware of?

Thanks for the input friends.
Spyug
 
That's why I'm leaning towards vacuum leak - maybe Im wrong in comparing an 1100 to a 550; but it should be able to idle lower than that. I could get a smooth idle down to 900 if I wanted to - but I'd rather keep the oil moving around at 1100 rpm's.
 
Freshening up the intake o-rings is always worthwhile, so do that no matter what.

That said, I don't see an air-leak in the symptoms set out in the OP. The idle doesn't climb, but struggles and whimpers out after 45 minutes. A creeping airleak would send the idle up before killing the bike with a bad mixture, wouldn't it?

I think that bad fuel venting is a good suspect here, or that tank seal is clogging the petcock and/or inline filter over time. Might help narrow down the issue by recreating the problem like so.

Take it out for a ride, but aim for home at the 30-40 minute mark. When the bog/stumble starts up, you could try a couple things: (a) do a plug chop to see if its lean or rich; (b) give it some choke to see if that buys more time; (c) loosen the fuel cap to see if there is any vacuum lock hissing; or (d) switch to PRI to see if the petcock is gagging.

Might not be possible to do all of these things in one test, but they might confirm or eliminate potential causes.

Definitely change those intake o-rings though.
 
Things have gone from bad to worse. I decided to put the bike on the I/V bottle so that I could work with the carbs. I also changed the gas hose to a slightly larger diameter and put on a higher capacity M/C specific in line fuel filter.

At first the bike started and idled high around 2000 rpm. After 1 or 2 minutes it came down but getting to the 1000 level, once again died out. I dialled in some extra turns on the idle knob but even after a good 8 or 10 turns there was no improvement to the idle. The bike would then not start without choke. It did fire right up on choke but revved to over 5000. Turning the idle know down brought it back down but once again it dipped to 1000 and died.

It sounds to me now that I have somehow, yet again, got junk in the carbs rather than an airleak or lack of venting problem. This becoming tiring and frustrating that it doesn't look like I'll be riding again this long weekend. Major bummer.

Spyug
 
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Try (maybe) back off large throttle stop screw all the way... so it does not contact the steel v shaped looking plate/stop,the thing where the throttle end cable is attached to.Turn the large black throttle stop screw (aka/ idle adj. knob) now clockwise(Up) so it just touches "v" plate.Hold that setting.now turn/twist throttle/grip on handlebar and watch down below at 'v'plate,do you feel/sense the spring return resistance and see the cable end lifting(where attached) moving upward,it is opening all 4 butterflies off your initial"bench position' and hence throttle grip twisting(more..will correspond to the butterflies movements opening more/larger. now.. After doing above fully open "choke' 100%...attempt start up of engine.Do Not Touch/Twist the twist grip,if starts up,modulate/control/adjust engine exclusively with "choke' control on left side handlebar..let it rev a bit high (don't worry),bring idle down very slowly w/handlebar lever to say 1500rpm,take it slow on decreasing rpm,achieving steady rpm then procede at carb large throttle stop screw..don't burn/cut your hand here..slowly turn up/clockwse screw to just slightly increase engine rpm.Do not close fully yet "choke" via its operating lever..increase rpm with screw knob and back (towards close) with 'choke' lever..ex; increase rpm w/screw knob,lower rpm w/lever.If you didn't change intake orings,try this procedure anyhow.If nogo,get o rings installedetc. and above may/will/possibly help out after install.those 4 pilot adj. screws open them up 3-4 fullturns..maybe more initially,can fine/tune them later.my GS 550ES likes her's open more than EPA would allow Suzuki.More to talk,not whole story..hope this helps you and GS my 550 friend.
 
Thanks. I tried to get her running again just 15 minutes ago and while it will start on choke it will not come down to a proper idle or even run at revs under 2000. I am once again thinking that there is crap in the carbs as this is the symptom I've seen most often with dirty carbs. It is extremely annoying as I've taken pains to try and keep dirt out. I did have dirt in my "jerry can' and while I have been un able to clean it all out, it has been substantially reduced. When pouring gas into the tank or the auxiliary tank I use a funnel with built in screen to which I add 2 layers of coffee filter. In addition on my I/V bottle there is an inline filter and ther is another filter on the gas line itself.

I will pull the carbs again tonight and give them a flush. I need to pull them anyway as I notice one of my float bowls is leaking through the gasket.

Man I am getting tired of this but on the upside, I'm fast at getting carbs in and out :).

thanks for the help and encouragement.

Spyug
 
Before you remove carbs,back the big/black/screw/knurled/knob clockwise/down,way down off that spring loaded stop plate,do the choke thing start up..does the choke lever change engine rpm down/lower? If not maybe when/if you synched carbs on bench they are(butterflies)open way too much or if/when you synched while running that set screw moved when using that little tiny PIA lock nut causing butterflies to move off desired positions.real lousy/tight,hot area to have hands in with very sharp steel edges to cut skin open.an errant move of mere millimeter(s) + or - is so likely to mess tuning up,yeah Siamese Twins sometimes do not have like behavior,they bear close supervison.I would come over border if I could for look see,am not setup w/proper credentials at moment.You will prevail though:)
 
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Read/look analyze all 4 sparkpugs during process to help figure out what's happening;of course remove when engine has cooled close to hand touch temperature.Ensure 'choke' plungers absolutely close and open completly,smooth easy operational movement,operate the/it's lever with carbs off for visual ok,'choke"cable(s) to be adjusted w/fitting on cable sheath near lever.getting cable adjusted is important(hey it all is:)).The 4 nice new intake o rings are.. golden.
 
Hi babes.
I think, now youve put a small inline fuel filter in, it's restricting the fuel flow too much. Ive had all sorts ov probs with inline filters...
Take it off and try again.

Xxx
 
I think, now youve put a small inline fuel filter in, it's restricting the fuel flow too much. Ive had all sorts ov probs with inline filters
Click to expand...

The filter I changed to yesterday is for a large Yamaha cruiser with much higher flow capacity than the one i had on there before. The hose is larger too. It has a much finer filter in it designed to catch all this sediment I seem to be filling it with. I don't normally like filters either but I don't think this one will cause an issue.

At this point and from the symptoms I'm now seeing, I'm fairly convinced its junk in the fuel. I had a close look at my new I/V bottle and I do still see traces of micro sediment and I know that the jerry can I used to fill it from still has some particulates in it despite repeated cleanings. Time for a new can I guess.

I didn't get to cleaning the carbs last night but I'll be taking the afternoon off today and will hose em down. They've been dipped three times now since March so I'll try a shot of spray cleaner and compressed air.

I think I have o-rings that will fit the intakes so I'll change those too.

Thanks for all the help folks,
Spyug
 
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