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Gs850Gl bogging at speed.

  • Thread starter Thread starter stoy75
  • Start date Start date
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stoy75

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Hey guys and gals. New here and need some help. I just purchased a gs850 a month ago. It is a 1982 with 40000 miles on it. Seemed to run fine the whole way home which was about 70 miles. My boat habits kicked in and I changed the gear oil both primary and final, changed the oil, and put in 4 new plugs. Shortly thereafter I noticed that when cruising at a consistent speed both highway, 55, and local, 35, the bike want to bog in and out sometimes and when the throttle is either rolled on and cracked it bogs and then goes. A few more observations is it has started to backfire on decel a lot more sometimes. Seems to "throttle down backfire" less when it is not bogging. It starts on minimal choke. Had to get a new battery as the last three year old one died. Any ideas?
 
Ok. Carbs stripped and dipped. Manifold boots and rings replaced. Problem seems to have worsened a little. Out of curiosity I put the petcock on prime and went for a ride. Problem was still there but bike had substantially more power and the problem did lessen a lot. Rode around on prime a little longer and problem almost disappeared and bike ran much much stronger.
 
Sounds like you may have a vacuum issue??? Did you check to ensure your hose is not kinked in any way?
 
Which vaccum line and what size is it. I'll just replace it. Should I rebuild the petcock too.
 
Instead of replacing parts right away just look at it. It will be the smaller of the two hoses coming off the petcock to the carbs. I think someone said it was 6mm but I'm not positive.

If you KNOW your petcock is bad, then replace don't rebuild it. Most people here have a really hard time getting rebuilt ones to work properly. It's a lot easier and cheaper in the long run to purchase a new one from someone like Z1 Enterprises than it is to fight with that kit.
 
I know the line is connected on both sides. Just figured a vaccum line would only be a dollar or two. How would I test it.
 
A good test to do would be to take your tank off (with the fuel lever on "ON") and set it in your garage overnight to see if the petcock leaks.

Then, you can hook up your vacuum line to the petcock (with the tank still off) and apply a vacuum to it (suck on the end of the line) to make sure that fuel flows out of the petcock when a vacuum is applied.

New rubber parts (vacuum hoses, fuel hoses) isn't a bad idea for a 30 year old bike in general, especially when fuel/vacuum hose would only be a few bucks.
 
Tank was off all day yesterday when replacing the carb boots and not a drop on the floor when in the on position.
 
stoy75 said:
Tank was off all day yesterday when replacing the carb boots and not a drop on the floor when in the on position.
Click to expand...

the leaking bit without vacuum tests to see that your petcock shuts off when the bike isn't running. More of an issue if you have gas-oil or flooding.

Do check that fuel flows with a vacuum applied though; that test is more to see if your petcock is starving your carbs for fuel when your bike is running.

If that passes, then you have a blockage somewhere else limiting fuel flow. Possible culprits would be kinked fuel line, stuck float valves, dirty carbs, dirty petcock filter.
 
Do you also have an external fuel filter on your bike? If so, yank it off. There's no reason for it and most that people use are too restrictive for our gravity fed systems
 
I do not have an inline filter. What sizes are the fuel and vacuum. I am going to just replace em. I don't get the issue. Uggh.
 
Go to your local shop and ask for fuel and vacuum line. Fuel is 7mm and vacuum is 6mm I believe. Don't get the SAE size as it will not fit correctly.
 
Is there a chance this is the problem? I'm starting to feel like I'm chasing a ghost.
 
Have you done tested your petcock for vacuum issues yet? Is the airbox properly sealed? What other stuff have you done besides the FULL strip and dip?
 
Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. stoy75,

Sorry I'm late to your party. Let's get started... New Members, CLICK HERE!!

That link takes you to the "mega-welcome" information. Click on the "mega-welcome" and you will find a couple of maintenance lists. Every item on that list must be properly attended to in order to have a safe and reliable motorcycle. You see, the thing about buying a 30 year old motorcycle is that it usually needs about 20 years worth of maintenance. Everything starts with properly cleaned/rebuilt carbs (do not use "carb kits", get an O-ring kit from http://cycleorings.com), adjusted valves, air-tight intake system, clean charging system, etc. Avoid the "Top 10 Newbie Mistakes" and you'll be fine.

See my little website for "how to" guides to all the normal maintenance tasks.

Welcome to the forum. Keep us informed.



Thank you for your indulgence,

BassCliff
 
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