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Bike won't start after carb cleaning

  • Thread starter Thread starter oldgsfan
  • Start date Start date
O

oldgsfan

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Honest, I did search but couldn't find an answer to my problem and it's probably 'cause the answer is too basic.

But I did a carb cleaning, took the carbs apart, cleaned them out, replaced all the O-rings, installed new gaskets in the float bowl, had to replace all the idle mixture screws 'cause I mangled them getting them out.

I gave them all 2 1/2 turns out. I did the bench sync using the tutorial.

Yesterday, finally installed the completed job. I also have new intake boots and new O-rings for those, and new boots on the airbox.

OK, so initially, the bike leaked a lot of gas, from the airbox near #3 carb. I did a search and saw that was a common problem so I gave the carbs a good tap with a chunk of wood and that problem went away.

So there's no leaking gas but the bike won't start. It turns over but nothing doing, not even with full choke.

Before starting, I put the petcock on prime for about a minute, then turned it back to the ON position and gave it a go.

I've checked my connections and the hoses are going where they should.

Is there something obvious I'm overlooking? I'm pretty green with mechanical stuff so I'm thinking there's something I should have done but didn't, or I royally screwed up the bench sync.

Any suggestions would be much appreciated.

- Hector
 
was the bike running before you did the cleaning of the carbs? did you check your valve clearances?
 
If you've followed the rules in the carb tutorial, all should be well. One rule of thumb that I always follow after a carb rebuild is to get things running on fuel that I add (through the plugs or the carbs, take your pick) and then go for the "on it's own" approach.

I would give it some more PRIme and wait until you can smell fuel before hitting the switch. Speaking of switches...where's the kill switch at? :eek:

You never know, it happens (to everyone) at some point in their life...:oops:
 
Sorry, yes, the bike was running actually pretty well before I did the carb cleaning.

I only cleaned them 'cause I don't think they had ever been cleaned and because I was replacing my intake boots, which were really falling apart.

I have not checked my valves. I do plan to do that at some point, but didn't want to tackle that job just yet.

I'll try running PRI a little longer and see if that helps.

I did try to be diligent in following the tutorial, particularly with the bench syncing.. and, yes, I had hoped all would be well.

Sadly, that's not the case.
 
Uh..there isn't a face red enough for me to post.. suffice it to say Dave8338 had the best suggestion.

I found the kill switch.. sheesh. :o
 
idle too high

idle too high

I experienced the same thing, just completed rebuild of carbs for my 80 GS850 45k miles. I put them on and it refused to start. Last night I saw your post and the reply suggesting that I prime the engine until I can smell gas this worked. Started right up tonight and without choke which it never did before. This site is great and the replies are really appreciated.

My question tonight is: now that I got it running, i can't get the idle to come down, in fact after I put the air box covers back she runs at almost 4000 rpm. I'm inclined to think that it is running too rich...not enough air. As part of the rebuild I drilled out the air screw covers and removed all 4 screws, cleaned everything really well, and put screws all the way in and backed out 2.5 turns. Could this be my problem? I also replaced the float needles and seats, they were real bad and all rubber parts including intake manifolds, got o rings from cycleorings.com. Only concern is that float needles don't come with little screens so installed without..I hope this is not problem.

Also, with engine cold I did compresion check and they look good about 120 psi straight across. engine warm about 130 psi. The valves (clearances) were last done at about 40k (at a shop). I want to do this again myself but I don't think this is the current problem since before rebuild it did idle normally.

The other problem I had is the #2 plug thread was not too good, plus was real tight from beginning to end, I didn't like this so I greased up a plug chaser and ran it through...very carefully, the plug goes in real nice now and tightens up just fine. In fact when I removed the gas tank I noticed that the plug wasn't all the way down...not a good thing.

Thanks so much for the help!
 
Did you try to turn the idle speed adjuster (the one under the carbs) does the idle go lower or higher when turned?
is the throttle cable binding,mis-routed,ect. keeping the throttle plates open?
are the choke plungers being held open because of the choke linkage?
 
Well, after getting my bike to start, I also had the high rpms.. I did back off on the idle adjuster, but it didn't bring the idle down that far.

So I pulled my tank off and backed off the idle air mixture screws one more half turn. This means that, in the end, my screws were backed out three full turns, not just 2 and 1/2.

That brought the idle down to a range I was happy with, and I was able to massage it bit more with the idle adjuster itself.
 
idle too high

idle too high

Thanks for the reply, I backed out air screws another 1.25 turns (3.75 total). this lowered the idle to about 3500 from 4k. Something just ain't right. Don't know what I will try next, unles my logic is wrong and I should be turning the screws in...
 
Thanks

Thanks

I'm still working on my fast idle problem after complete carb rebuild. But I just want to say thanks to all on this site who have made this project that much more enjoyable....I was actually a member a few years ago but had to re-register this week. In my previous life the site and so many on it helped me to rebuild my brakes, stator, carbs (1st time), forks, seat, paint my fender (came out real nice) etc....Many, Many Thanks and I hope that I may have accumulated some knowledge that will assist someone else.

Charlie
 
gs850cmc, open a new thread and let's figure it out from there.
 
gs850cmc said:
I'm still working on my fast idle problem after complete carb rebuild. But I just want to say thanks to all on this site who have made this project that much more enjoyable....I was actually a member a few years ago but had to re-register this week. In my previous life the site and so many on it helped me to rebuild my brakes, stator, carbs (1st time), forks, seat, paint my fender (came out real nice) etc....Many, Many Thanks and I hope that I may have accumulated some knowledge that will assist someone else.

Charlie
Click to expand...


Fast idle should not be corrected by turning the mixture screws. If anything, you turn them to get the highest possible idle. All you've done is dump extra gas into the engine that can't burn.

For the high idle you first step is to make sure the throttle cable is routed and adjusted correctly. Then make sure the throttle isn't hitting on something that is holding it open. One common culprit there is the clutch cable or the book clamps. If all is correct there then adjust the idle stop screw. If those three things don't fix it your problem is probably inside the carbs.

But, as you know, 4000 rpm idle isn't right and needs to be corrected. If it's the throttle sticking open you could find yourself in a very dangerous situation if you try to ride like that.

Remember that the throttle cable should have some play in it. When you twist you should see some slack in the cable. If it's too tight you might get in increase in RPM when you turn the handlebars full over to one side.

It's probably something simple. You find it soon. Good luck
 
Listen to Larry above, don't adjust the mixture screws to adjust the idle.

Make sure the throttle linkage is not binding. When you twist and release the throttle you should here the butterflys close with a thunk.

If the throttle is working properly and you still get a high idle, or an idle that hangs and doesn't want to settle down to the proper level, that typically means the mixture is too lean. Intake boot O-ring leakage is very common if your model bike has them, or there could be some other reason for the lean mixture. Fix the problem at the source, don't monkey around with masking the problem.
 
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