Bike runs bad at low rpms popping and backfiring

[Speedy7722]

Ok I will buy some carb dip tonight. Will the petcock not running off vacuum have any effect on things? it seems like it doesn't effect the amount of fuel getting to the carbs.

[tkent02]

Alright, thats what I was afraid of. By taking off the valve/cam covers will there be any gaskets that need replaced?

Probably the valve cover will need to be replaced, if it hasn't been removed lately it's likely to be stuck.

[chuck hahn]

The only effect the petcock will have is that there needs to be a way to shut it off when the bike is not running..Ever so slowly, gravity will draw fuel downward and if it gets past the carb bowls it has to go somewhere. That somewhere is that it seeps down into the crankcase and fills the oil with gas. Then what you have is watery oil that will not lubricate and protect the engines internal parts and youll fry that engine as fast as eggs in the skillet. Like i said, pinch it off with some hemos or some small needle nose vice grips till you cann get a working setup.

[chuck hahn]

If it were me...since it has obviously already been sitting like this..I would drain the oil, get the fuel line pinched off and put new oil in before i even think of restarting the bike..better spend 25 bucks on new oil than gamble on frying the engine.

[Speedy7722]

Ok I went out and pulled the carbs and attempted to remove the valve cover put it is stuck pretty good. Any tricks for removing it like heating or beating? haha, and to use carb dip do I need to totally dissasemble everything in the carbs that i can and should I remove each one from the rack or can I leave them attached?

I just changed the oil the other day and even the old oil looked pretty good and was not "watery". So do you think after I install an on/off fuel valve I should change the oil again?

Thanks for your help everybody.

[hjfisk]

Ok I went out and pulled the carbs and attempted to remove the valve cover put it is stuck pretty good. Any tricks for removing it like heating or beating? haha, and to use carb dip do I need to totally dissasemble everything in the carbs that i can and should I remove each one from the rack or can I leave them attached?

I just changed the oil the other day and even the old oil looked pretty good and was not "watery". So do you think after I install an on/off fuel valve I should change the oil again?

Thanks for your help everybody.

Smell the oil if you smell gas change it

[mrbill5491]

Use a rubber mallet on the valve cover and don't get wild with it. It will break loose. Once it is off, make sure the contact surfaces are clean, be careful and don't gouge the surfaces. Break up the carbs from the gang rack. Check the fuel needle and seat while the carbs are apart. Down load the carb rebuild instructions, lay out your parts and orings and make sure you have everything you need. 24 hrs in the carb dip is usually enough time. Looks at your intake boots, those probably need changing as well now. Follow the advice the guys have gave you here and you should be fine.

[chuck hahn]

I usually stick a hammer handle in under the cover and pry up against the engine fins..pops loose real easy. And I was thinking tonight at work..youm said the cans are rusted thru in places? get what they call muffler tape and patch them. Cols air getting sucked into the hot exhaust will / can cause popping to some extent as well.

[Speedy7722]

Valve cover finally came off with a little effort. Now I just got to get ahold of some more feeler gauges and carb dip!

Thanks for the advice everyone.

And I will also see what I can do about patching the exhaust. The owner before us attempted a patch job but it was pretty much useless when we bought it so we just tore it off. Hopefully, when I get everything adjusted and put back together she runs like a new machine!

[850 Combat]

There are a number of tiny air passages between the carb bell mouths and the progression holes at the butterflies. These get clogged and the pilot jet can't flow even if they are clean. There is a very good section on how those carbs work in the GS850 manual on Cliff's site. Those symptoms are classic for pilot circuit problems. The emulsion tubes over the jets can get munged up too. I have gotten numerous carb sets, but not all, cleaned and working fine without dipping them. One thing is to spray carb cleaner into the three holes in the pilot circuit that you can access, and make certain that it sprays out of all the other holes. You can spray into the air jet in the belmouth, the air screw hole where the needles are, and the pilot jet holder. You can't spray into those tiny holes inside the body above the butterfly. I'll bet there are clogged passages in the bodies.

[chuck hahn]

850 combat..take a lighter and ever so easily heat the red plastic tube that comes with most spray cans about 1/2 inch up from the end and gently and slowly bend the straw to get it as close to a 90 as you can. Sticking a somewhat thick soft wire ( think breadtie but a bit thicker here ) into the red straw will help keep the hole open as you bend it. Let it cool in place and then remove the wire. Now you CAN get a great angle to spray from the throat side of the holes.

[BigD_83]

Nice tip, Chuck!

[chuck hahn]

AND....You can do basically the same thing with some vinyl hose that will fit on the tip of your air gun so you can stick it tight to the mholes and reverse some air thru them also.

[Speedy7722]

Well I got a break from school earlier to check the valves and they came out in spec, now just have to order a new petcock rebuild kit, valve cover gasket, and a couple other things.

Smelled the oil and sure enough, smells of gas, so I will change that again.

Now moving on to the carbs and see what happens.