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bike not running well...out of ideas! (850gl)

  • Thread starter Thread starter scout127
  • Start date Start date
scout127 said:
I'm also wondering if the bike dies when I open the throttle because it receives a ton of air but no fuel (because the needles are not lifting very well) this would also mimic a lean mixture...right?
Click to expand...
If the bike is on 'choke', opening the throttle will defeat the enrichment process and yes, it will be lean. Basically, when you are on 'choke', you adjust the idle speed with the 'choke' lever, not the throttle.

scout127 said:
Would any of this cause the bike to spit and sputter from the carbs? Just checking because this backfire makes me wonder if I have a timing issue (though I have checked and double checked the timing), or an electrical issue.
Click to expand...
Personally, I think you do have a timing issue, but it's not electrical timing. In the flurry of posts above, you mentioned something about valve adjustment, but I don't really remember if you have done it or not. If you haven't, don't even worry about tuning carbs until you have the valves done. Tight valves (especially intakes) will play havoc with the way the bike runs, especially how well it starts when cold. If you do the carbs first, you will have to re-adjust them after you adjust the valves (unless all the valves are in spec and you don't have to change anything).

.
 
When I talk about opening the throttle, I mean when the bike is idling...after I've released the choke. Still the bike dies...fuel needles do not lift very high (as if there is little or no vacuum.

I think the valve adjustment will be the next thing I check. I put a vacuum gauge on the bike and it read "slow valve timing"...so I think you're right about that being an issue.
 
Do the slides move freely in their bore? Are the diaphrams good? Check them through a bright light for pinholes.
 
scout127 said:
I think you're right, but I haven't gotten the bike to idle well enough to adjust anything yet.

I'm also wondering if the bike dies when I open the throttle because it receives a ton of air but no fuel (because the needles are not lifting very well) this would also mimic a lean mixture...right?

Would any of this cause the bike to spit and sputter from the carbs? Just checking because this backfire makes me wonder if I have a timing issue (though I have checked and double checked the timing), or an electrical issue.
Click to expand...

i would say yes, but most of the time with a spit/sputter or the engine trying to die if you open the throttle would suggest a rich condition. a gross lean condition i guess could act the same way. id lean towards a vac leak and a timing issue. im not versed in how these bikes advance timing, but im assuming its mechanical.

leave the choke on, let it run, and scout for vac leaks.



but first and foremost, a valve adjustment is needed before doing any tuning, period. that alone will make the bike run like poo.
 
scout127 said:
...fuel needles do not lift very high (as if there is little or no vacuum.
Click to expand...
Actually, unless you are riding the bike (or have it on a dyno), you will not create enough vacuum to lift the slides. Simply watching them with the airbox off certainly isn't going to do it. There will not be enough vacuum in there until there is a restriction over the intake (airbox, pod filter, shop rag) and the butterfly is open enough to REALLY get some air moving through there. With no load on the engine, you will not have the throttle open long enough to develop enough vacuum to lift the slides. And, with a filter or other restriction in place, you can't see the slides anyway.

One of the problems with tight intake valves is that they close later, allowing some of the mixture that has been ingested into the cylinder to come back out the intake valve, into the intake tube. In extreme cases, you can actually get a puff of air blowing the wrong way through the carb. The carb does not really care which way the wind is blowing, it will add gas to whatever comes through. The problem is that it is adding gas to what might have been a proper mixture. Next time the valve opens and the cylinder sucks another charge of mixture, some of that air will be going through the carb a third time, making the mixture REALLY RICH. :eek:

I experienced this in a dramatic fashion with my Kawasaki Voyager 1300. It was fuel-injected, but the principle is the same, some of the air that had fuel sprayed into it had already been there before. I fought with this for so long, deposits had formed on the valves and pistons. I bent a couple of the intake valves, requiring some extensive work. I did not do that kind of work on that bike, and the bill was just over $3,000 by the time I got it back with 6 new intake valves, new rings and other assorted new parts, some of which were the last known new parts for that bike. Since then, I have seen what a difference simply adjusting the valves can make when trying to start a cold bike. By the way, "cold" is a relative term. It can apply to a bike that has been sitting in a heated garage overnight or in a parking lot all day while you are at work. It does not necessarily mean 30 degrees.

Please try adjusting the valves and then get back with us and report your findings.

.
 
My slides lift just fine w/out filters.




But they are drilled. :hand:
 
Steve said:
Actually, unless you are riding the bike (or have it on a dyno), you will not create enough vacuum to lift the slides. Simply watching them with the airbox off certainly isn't going to do it. There will not be enough vacuum in there until there is a restriction over the intake (airbox, pod filter, shop rag) and the butterfly is open enough to REALLY get some air moving through there. With no load on the engine, you will not have the throttle open long enough to develop enough vacuum to lift the slides. And, with a filter or other restriction in place, you can't see the slides anyway.

One of the problems with tight intake valves is that they close later, allowing some of the mixture that has been ingested into the cylinder to come back out the intake valve, into the intake tube. In extreme cases, you can actually get a puff of air blowing the wrong way through the carb. The carb does not really care which way the wind is blowing, it will add gas to whatever comes through. The problem is that it is adding gas to what might have been a proper mixture. Next time the valve opens and the cylinder sucks another charge of mixture, some of that air will be going through the carb a third time, making the mixture REALLY RICH. :eek:

I experienced this in a dramatic fashion with my Kawasaki Voyager 1300. It was fuel-injected, but the principle is the same, some of the air that had fuel sprayed into it had already been there before. I fought with this for so long, deposits had formed on the valves and pistons. I bent a couple of the intake valves, requiring some extensive work. I did not do that kind of work on that bike, and the bill was just over $3,000 by the time I got it back with 6 new intake valves, new rings and other assorted new parts, some of which were the last known new parts for that bike. Since then, I have seen what a difference simply adjusting the valves can make when trying to start a cold bike. By the way, "cold" is a relative term. It can apply to a bike that has been sitting in a heated garage overnight or in a parking lot all day while you are at work. It does not necessarily mean 30 degrees.

Please try adjusting the valves and then get back with us and report your findings.

.
Click to expand...


ive seen this happen on cars and 2strokes many-a-time. good info here.
 
Steve said:
Actually, unless you are riding the bike (or have it on a dyno), you will not create enough vacuum to lift the slides. Simply watching them with the airbox off certainly isn't going to do it. There will not be enough vacuum in there until there is a restriction over the intake (airbox, pod filter, shop rag) and the butterfly is open enough to REALLY get some air moving through there. With no load on the engine, you will not have the throttle open long enough to develop enough vacuum to lift the slides. And, with a filter or other restriction in place, you can't see the slides anyway.

One of the problems with tight intake valves is that they close later, allowing some of the mixture that has been ingested into the cylinder to come back out the intake valve, into the intake tube. In extreme cases, you can actually get a puff of air blowing the wrong way through the carb. The carb does not really care which way the wind is blowing, it will add gas to whatever comes through. The problem is that it is adding gas to what might have been a proper mixture. Next time the valve opens and the cylinder sucks another charge of mixture, some of that air will be going through the carb a third time, making the mixture REALLY RICH. :eek:

I experienced this in a dramatic fashion with my Kawasaki Voyager 1300. It was fuel-injected, but the principle is the same, some of the air that had fuel sprayed into it had already been there before. I fought with this for so long, deposits had formed on the valves and pistons. I bent a couple of the intake valves, requiring some extensive work. I did not do that kind of work on that bike, and the bill was just over $3,000 by the time I got it back with 6 new intake valves, new rings and other assorted new parts, some of which were the last known new parts for that bike. Since then, I have seen what a difference simply adjusting the valves can make when trying to start a cold bike. By the way, "cold" is a relative term. It can apply to a bike that has been sitting in a heated garage overnight or in a parking lot all day while you are at work. It does not necessarily mean 30 degrees.

Please try adjusting the valves and then get back with us and report your findings.

.
Click to expand...


Yea. This makes good sense and sounds alot like what I'm experiencing in the "spit and sputter". Thanks to all you guys for the advice.
 
When you say rebuilt carbs, you tore them off of the brackets and replace the o-rings in between them, correct?

I saw that you rebuilt them well, but that definition is a bit nebulous for me.

I also take it that you double checked pet-cock fuel flow and properly set float height along with checking fuel levels in the bowls?


I can vow that I sprayed, resprayed, used 175 psi shop air and until I tore the carbs all the way down, dipped them, and used all new o-rings, the bike ran lean. Now, it can be 30 degrees out, and the bike will be off full choke in no more than 2 mins.

Oh ya, you didn't install any after market needle and seats did you? You can throw those in the garbage if you did. OEM is the only way to go.

And as everyone else has said, valve clearance is a huge factor in performance.
 
I didn't soak them. I sprayed and used high pressure air. I did however replace the o-rings in between the carbs (they were broken).

I believe the petcock is working fine. When on prime I get a solid fuel flow. I've tried running the bike on prime, but there is no change. When the floats are set to the height suggested in the manual, I sometimes get fuel overflow when on prime. Is this normal or should I set the floats to get rid of the overflow regardless of what the manual says?
 
update on '83 GS850GL

update on '83 GS850GL

Okay, I'm back. I checked the valve clearances, and they seem fine. They range from .03 to .08. I can't see replacing the shims. Also, my airboots seem fine. They are soft and pliable. Is it really worth replacing them? If not, what is my next step? another carb teardown?
 
I would tear the carbs apart and soak them overnight in carb cleaning solution. The problem you are describing sounds like a clogged pilot/choke circuit. Once the carbs are cleaned and reassembled, use an inline fuel filter on your gas line to keep the carbs clean. Make sure to check the float height during reassembly . It is also a good idea to check the gas level in the bowls once you get them installed. You will need to vacuum sync the carbs once you get it running. Bike will run like crap until you get this done.
 
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