Cylinders end up dry...

[Staninator]

Hey guys,

Here's another issue I'm facing right now. It seems like my cylinders are dry if I let the bike sit for over a day. It won't start unless I fill up each cylinder with a little bit of fuel... Petcock won't do anything in any position until vacuum happens from the motor. What could be causing such an issue?

 

[Guest]

Umm... you more or less what your cylinders dry. You don't want fuel sitting on top of your pistons. There should be plenty of fuel in your bowls to start and run for a bit. Where is that gas going too? Check your oil and make sure it doesn't have a gas smell. If you do detect a gas smell DO NOT run your bike, drain the oil and take out the filter. Check your float settings. Gas just doesn't disappear like that. Find out what is going on.

 

[tom203]

Hey guys,

....... Petcock won't do anything in any position until vacuum happens from the motor. What could be causing such an issue?

Your petcock should have a "pri" spot in which gas will flow regardless if engine is running. BUT, gas should not evaporate from fuel bowls in one day so you should not have to use "pri" very often, so as Mrbill5491 said find out where gas is hiding.

 

[BassCliff]

Hi,

How much of these maintenance lists have you completed?

**********Quoted from Mr. bwringer************
Every GS850 [and most other models] has (or had) a set of well-known issues that MUST be addressed before you have a solid baseline for further troubleshooting. It's a vintage bike, and it's quite common (as in, every single GS850 I have had contact with) that there are multiple problems that have crept up and slowly gotten worse over the years. It's not like a newer vehicle, where there's generally one problem at a time.

These common issues are:

1. Intake O-rings (install NEW OEM or Viton only - common nitrile O-rings will quickly deteriorate from heat)
2. Intake Boots (install NEW -- these cannot be repaired)
3. Valve clearances (more important than most people think)
4. Carb/airbox boots
5. Airbox sealing
6. Air filter sealing
7. Petcock (install a NEW one)
8. On '79 models, install new points or Dyna electronic ignition (or at least verify that the old points are working correctly)
9. On all models, it's fairly common to have problems with the spark plug caps. These are $3 or $4 each, and often worth replacing if you're keeping the stock coils/wires.
10. Stock exhaust with NO leaks or holes -- good seals at the head and at the junctions underneath.

What I have noticed at the rallies is that very, very few 850Gs are actually running right. Make VERY sure it's actually running the way it's supposed to before busting out the modifications.

Brian's E-Z and fun plan for GS850 happiness:

1) Seal the airbox and air filter with weatherstripping.

2) Ensure no intake leaks. Spraying WD-40 or water doesn't tell you much, since very small air leaks can cause problems even though they won't suck in enough WD-40 to make a difference. Replace your intake boot o-rings and boots if needed, and seriously consider spending the lousy $28 for new airbox/carb boots.

3) Ensure clean carbs with correct settings, new o-rings, and original OEM jets. No, not just squirted with something. I mean completely disassembled.

4) Check/adjust valve clearances (Manual calls for every 4,000 miles. This is not optional.)

5) Ensure healthy electrical system.

6) Seriously consider upgrading coils and plug wires.

7) Install new, stock NGK B8-ES plugs gapped to .031".

8 ) Fine-tune float height and idle mixture screw to ensure best off-idle transition.

9) Clean air filter and reinstall with only the lightest oil mist -- over-oiling and/or letting the filter get dirty is a common and critical mistake, and will make the bike run funny at low speeds and run rich. This may take a few tries.

10) Make sure the exhaust seals are sealing.

11) Ooh, much better now, huh? You're gonna need upgraded suspension - Progressive or better fork springs and shocks. Set suspension sag appropriately.

12) Upgrade brakes with new pads and stainless lines to deal with all that extra speed.

13) Install new petcock, since I'm going to head to the roof with a rifle if I have to read about yet another #2 plug fouling and failed hillbilly attempts to rebuild the petcock and/or deny there's a problem.

14) Oh yeah -- check compression somewhere in there to ensure the valves and rings are reasonably healthy.

15) You'll probably need new OEM clutch springs -- the clutches last forever, but the springs get tired after 20 years or so under pressure. E-Z and cheap.
**********************************************


Thank you for your indulgence,

BassCliff

 

[Guest]

Wow, the post before this one scared the hell out of me. We forget how much we do before we try and ride... Great reminder.
Curt

 

[Staninator]

Umm... you more or less what your cylinders dry. You don't want fuel sitting on top of your pistons. There should be plenty of fuel in your bowls to start and run for a bit. Where is that gas going too? Check your oil and make sure it doesn't have a gas smell. If you do detect a gas smell DO NOT run your bike, drain the oil and take out the filter. Check your float settings. Gas just doesn't disappear like that. Find out what is going on.

I checked my oil today and it did actually smell like gas a bit. I will definitely drain it and change the filter this week. Could this be caused from valve clearances alone?

 

[loud et]

Honestly I am not getting what you are saying by "cylinders are dry"?
What I do know is that if you have a very strong smell of gasoline in your oil, your petcock is malfunctioning or more importantly your float needles are worn and not stopping the flow of fuel.
A carb teardown, dip , inspection and rebuild with new o rings is a very important part of GS maintenance. Especially for one that has been sitting or has not been run regularly.
You can remove and disassemble and clean/rebuild your petcock also. The screen may be clogged and the sediment that has gotten into the petcock over time may be causing it to leak, stick or just not perform properly.
These two issues...carbs/petcock are absolute musts to have operating 100%.
Basscliff has all the info on all this maintenance as he has made it available to you in a previous post.
Your oil change may possibly be a waste of money if you are still leaking fuel so check everything over. If your valve clearences are out, well, thats on the list too ob mandatory maintenance, so I do not know how much effect the clearences being out would have on the fuel/oil smell but the valve adjustment must be done.
Cliffs site walks us throgh this stuff. Good luck I am at the same point with my 550....have to dip and rebuild the carbs and do a valve adjustment. It sucks to have to park the bike and do it all but its better than banging my head against a wall wondering why it wont run right.
Just talkin it out here. lol get into that petcock and carbs. Something is out of wack.

 

[Guest]

I checked my oil today and it did actually smell like gas a bit. I will definitely drain it and change the filter this week. Could this be caused from valve clearances alone?

No, valve clearances won't have anything to do with gas in the oil, you have a bad petcock and or something amiss in the carbs, bad floats, miss adjusted floats, bad needle and seats. Start with the petcock first then work to the carbs. Gas is flowing from the tank to the carbs overflowing the fuel bowls and running into the intakes and down on top of the pistons, the gas then works its way past the rings into the oil, hence the gas smell in the oil. Gotta fix what ever is wrong and DO NOT ride the bike till it is fixed. Don't bother adding new oil and a filter until it is, or you'll just be repeating yourself till you do.

Like Loud_ET said, go to Basscliff's website all the info in the world you need to work on your bike with is there. We will still help you along as you need us.

 

[Staninator]

Thanks a bunch guys! I now have a list of what all needs to be done! I just need a little bit of money and everything should be good I was really thinking about stripping this beast down for the winter and sending out the frame for powdercoat and maybe redo the exhaust. I'll keep everyone posted on things that come up!

 

[kawfeedave]

I checked my oil today and it did actually smell like gas a bit. I will definitely drain it and change the filter this week. Could this be caused from valve clearances alone?

If your float bowls are empty, I don't think you have gas in your oil. The way that would happen is that your petcock is leaking fuel into your carbs, and then you have a needle valve stick open. This will allow the carb to overflow and drain fuel into the crankcase. However, if your float bowls are dry, then you're not having a problem with a leaky petcock.

Are you sure your float bowls are empty? Try pulling the drain screws after letting the bit sit for a day or two and see if anything comes out. There might be another cause of your hard starting that's not related to the fuel levels in the float bowls. Maybe you have a choke problem?

 

[Staninator]

If your float bowls are empty, I don't think you have gas in your oil. The way that would happen is that your petcock is leaking fuel into your carbs, and then you have a needle valve stick open. This will allow the carb to overflow and drain fuel into the crankcase. However, if your float bowls are dry, then you're not having a problem with a leaky petcock.

Are you sure your float bowls are empty? Try pulling the drain screws after letting the bit sit for a day or two and see if anything comes out. There might be another cause of your hard starting that's not related to the fuel levels in the float bowls. Maybe you have a choke problem?

Well my float bowls hold fuel no problem... I have taken them apart before and have drained the fuel. My petcock doesn't leak any gas unless I have it on prime. There is no vacuum to suck the gas out. It's just when it sits cold for over a day it won't start unless I throw some fuel into each cylinder. If say it's warmed up from riding, it'll fire right up! If I start it up the day after I rode it'll also start up with a little hesitation...

 

[kawfeedave]

What do you mean you put fuel in each cylinder? Do you pull the plugs and pour it in, or spray something down the carb throats?

Either way, it sounds like a choke problem. The bike needs more fuel to start when it's cold, and for some reason your choke circuit isn't providing it.

Does it run right otherwise? Any chance you have an air leak somewhere in the intake system? Too much air might overwhelm a good choke system and prevent a cold start. What about airbox/filter, what are you running? Stock airbox? Pods? Something else?

 

[Staninator]

I'm taking out the plugs and pouring gas into each cylinder individually. I'm currently running pods and I'm going to be rebuilding the carbs this winter along with rejetting. The choke works fine but there may be an air leak somewhere.

 

[Homie]

I had an '82 GS750E that had a very similar problem. Wouldn't cold start for nothing unless, like you, a little gas was dribbled into the plug holes with an eyedropper. Once it started, it would restart as long as it wasn't left to sit for more than about 12-18 hours or so.

You know what the problem turned out to be? The engine had low compression across all four cylinders. Apparently the compression was low enough that it couldn't create enough vacuum to draw the fuel out of the carbs on it's own. However, it was just enough to compression to support combustion and allow the engine to run after the fuel dribble. With a bit of cranking it would restart after it first started. I theorized that just enough oil would get up on the cylinders to help the rings seal better and bump up the compression enough so that it could draw fuel out of the carbs on it's own.

You could have low compression. If you do, it could be because of any number of problems, or it could be a symptom of the aforementioned carb float problem. If enough gas is flowing into your cylinders while it's parked, the gas will "wash" the oil from the pistons and cylinder walls and you will lose the sealing effect that the oil film provides. So I would give that compression a look too in your troubleshooting sequence.

 

[Staninator]

I had an '82 GS750E that had a very similar problem. Wouldn't cold start for nothing unless, like you, a little gas was dribbled into the plug holes with an eyedropper. Once it started, it would restart as long as it wasn't left to sit for more than about 12-18 hours or so.

You know what the problem turned out to be? The engine had low compression across all four cylinders. Apparently the compression was low enough that it couldn't create enough vacuum to draw the fuel out of the carbs on it's own. However, it was just enough to compression to support combustion and allow the engine to run after the fuel dribble. With a bit of cranking it would restart after it first started. I theorized that just enough oil would get up on the cylinders to help the rings seal better and bump up the compression enough so that it could draw fuel out of the carbs on it's own.

You could have low compression. If you do, it could be because of any number of problems, or it could be a symptom of the aforementioned carb float problem. If enough gas is flowing into your cylinders while it's parked, the gas will "wash" the oil from the pistons and cylinder walls and you will lose the sealing effect that the oil film provides. So I would give that compression a look too in your troubleshooting sequence.

That makes so much sense! How did you fix your issue?

 

[Guest]

I'm taking out the plugs and pouring gas into each cylinder individually. I'm currently running pods and I'm going to be rebuilding the carbs this winter along with rejetting. The choke works fine but there may be an air leak somewhere.

AAAAAAh no, don't do that, get too much fuel in there and you can hydraulic your motor and could crack a piston. Get a backfire and your bike is toast. If anything use a little spray starting fluid to fire your bike up. If your petcock is set to "prime" you have fuel running into the carbs all the time. Hence the smell of gas in your oil. Shut down and pull the petcock now. As for the compression test go ahead and do that, do a dry and a wet test. If that is inconclusive, you might want to do a leak down test as well. A wet test is a couple drops of oil in the cylinder to help seal the rings. Other then that, I wouldn't ride the bike until you got the carbs rebuilt and the petcock fixed.

 

[Homie]

That makes so much sense! How did you fix your issue?

Aaaaaah, actually I didn't. Here's why. To figure out where the compression problem was I did a Leakdown test on the cylinders. I was hoping that maybe it was the valves and that a valve job would cure the problem. It wasn't. The Leakdown test indicated that it was the rings. So as a minimum, the top-end would have to be disassembled, cylinders checked and honed, pistons checked, and new rings installed. After checking the cost to have that done, I decided that if I was going to tear the top-end apart I might as well put a Wiseco piston kit in it.

But then something happened that I wasn't expecting...

On my way to work I saw a red '83 GS1100E for sale. It had some kind of ugly aftermarket fairing on it, but the lines were unmistakeable and the price was irresistible. So I bought the 1100 and sold the 750 "as is" without fixing the problem. No help with your issue I know. But the symptoms are similar so I would check your compression and if the compression indicates a problem, have a Leakdown test done.

 

[tom203]

.......The choke works fine but there may be an air leak somewhere.

How do you know? at a cold start with "choke" fully applied, after some cranking, pull two spark plugs- any sign of fuel? I doubt your rings are bad ,but tight valve clearances can cause hard cold starting- have you checked valve clearances?