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Uh-oh, think the motor went....

  • Thread starter Thread starter riskadh
  • Start date Start date
R

riskadh

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Hey guys, just had an 'incident' with my gs1100gk and thought I'd post a thread just for some constructive feedback. My bike had been running sluggish as of late, so upon checking the plugs, they were pretty charred. Purchased new plugs, put them in and fired the bike up. So far so good. Hopped on to go for a quick ride around the block, and to my amazement, the backfire it had been doing went away :-D. However, during the ride, whenever I would attempt to shift, the bike would die and would need to be restarted. It was at this point that I wanted to just get home to look at this problem. But on the way, it really began to sputter and and it accelerated in a wavy rhythm (would go, then bog, then go, then bog...). Went to turn the corner to my apt complex and it died in the middle of the turn so moved to the sidewalk. Looked down to check the carbs, wires, and choke when I noticed oil just flowing on the ground coming out of the air filter box. Now, I am no genius, but to me it sounds like I may have had a piston or two go out :cry:. So obviously my guess is the motor is now blown. So just looking for some other "alternative suggestions" [-o<. Also, if anyone has rebuilt a motor before, how difficult is it, what is the best source to get a listing of parts, or is it time to scrap her? Thank you!
 
My guess would be you filled your crankcase full of fuel and it hydraulically locked up the engine. Pull the oil filler plug and do a sniff test...if it smells like gas and the crankcase is overfilled then fuel leaked into the crankcase. You may be able to just drain the oil and refill, but if it is full of fuel you need to find out what is leaking(ie. petcock, needle and seat, etc.). Good luck.
 
And this would cause oil to come out of the air filter box? Interesting theory, I will have to check it out....
 
riskadh said:
And this would cause oil to come out of the air filter box? Interesting theory, I will have to check it out....
Click to expand...

You have a breather hose running from your valve cover back to your air box which is designed to recirculate blow-by from the engine and reburning it to reduce emmissions. If the oil is contaminated with fuel and the crankcase is overfilled, blow-by would increase to the point you are describing. Or you could have a blown engine, but without severe abuse these engines are virtually indestructable.
 
moto_dan said:
You have a breather hose running from your valve cover back to your air box which is designed to recirculate blow-by from the engine and reburning it to reduce emmissions. If the oil is contaminated with fuel and the crankcase is overfilled, blow-by would increase to the point you are describing. Or you could have a blown engine, but without severe abuse these engines are virtually indestructable.
Click to expand...

Moto Dan is right on, in fact I'd say he's got the most likely cause. To elaborate on his post, the motor has a huge tunnel for the cam chain between the two middle cyls. The tunnel is a big cavity that goes from the bottom of the crank all the way to the top of the head and the breather tube he talked about, so oil can and does leave the motor this way.
 
Well, doesn't look like a blown motor after all. Went out this morning to try to get it in the garage, it fired right up and ran fine into the garage. However, I decided to not go around the block in case this happens again. I haven't drained the oil yet, but upon pulling the cap off the crankcase, it did smell like some gas had gotten in there. Now, doing some research on the petcock, it appears that it is the valve under the gas tank with the on/off/reserve markings correct? If so, I haven't been switching it to off when not riding, could this be the demon that has been haunting my bike???
 
The petcock has 3 settings, 'Prime', 'On', and 'Res'. make sure your not set to 'prime' at any time unless you ran out of gas and just refilled it, or the bike has been sitting for quite some time. If you seet and leave it on prime, it can let fuel by the floats and flood the engine with gas.
 
and obviously, by having it on prim (which is what the guy who sold me the bike told me to leave it on) would cause the crank case to fill up with gasoline as well as oil right? As well as cause the problem which I am working with as described above?
 
Last edited:
AAAAAGGGGGGHHHHHHHHHHH!

Sorry, I just promised a little while ago that I'd scream if one more person wasted any more time trying to nurse along an obviously worn out petcock for far too long.

1) You need a new petcock. They don't last forever. Buy a new one and forget about it for another 20 years. Don't screw around with a rebuild kit or eBay. Call up Cycle Recycle II or Z1 Enterprises and get the correct part.
http://www.crc2onlinecatalog.com/
http://www.z1enterprises.com/

2) Do NOT start or ride the bike until you replace the petcock and the contaminated oil. Oil mixed with gas is a very poor lubricant.

3) You need a new petcock. No, you can't replace it with a fuel valve from a lawn mower. You don't need to replace it with a Pingle, but it is possible if you insist. The original petcock lasted 20+ years, and the new one will, too.
 
riskadh said:
and obviously, by having it on prim (which is what the guy who sold me the bike told me to leave it on) would cause the crank case to fill up with gasoline as well as oil right? As well as cause the problem which I am working with as described above?
Click to expand...


Absolutely correct. This is a well-known problem in the GS world.

And chances are excellent that your bike will be perfectly fine once you replace the petcock and the contaminated oil.
 
Sorry to make ya scream BW, but thanks for the tip. That will put my mind at rest knowing it isn't a blown moter \\:D/.
 
Well, drained the oil on the bike today and came away with 2 gallons of fluid, yep TWO GALLONS!!! :shock: So looks like the petcock was the main culprit. But does anyone know of a way to test the petcock besides waiting for it to go out?
 
I just rebuilt everything on my 81GS850 from gas tank through carbs. I took my petcock apart and cleaned it up, and learned a little about it.

Your petcock has three settings, prime, run or on, and res (obviously). On prime, gas should flow freely out the opening without leaking anywhere else. On run and res, no gas should flow or drip at all unless the motor is on.

A small vacuum hose runs off your petcock. When the motor is running, carb #2 provides suction to this tube which opens the petcock in run and res position. To test the petcock, you dont even need to take it off the tank. Simply detach this hose from the carb, and give it a little suck. Gas should flow as freely down the gas line (not the vacuum line you are sucking on) as if the petcock was on prime. Check for drips underneath the petcock, dripping down hoses, etc. If your petcock works like this then it is fine. If the gas flow is restricted, if there are any leaks, previous replies to your thread were right, toss it and get another.

I took mine apart just to see how it worked, turned out my problem as a small black gasket had been installed improperly. Petcocks are actually beautifully simple little valves, but there is no need to keep a defective one around.


Good luck!
 
OK, now this problem just got a little tricky. With the petcock in the 'ON' position, the bike won't start. Switch it to 'PRI' and it starts, so back to 'ON' once it's running. The bike runs for a bit before it stalls. Adjust the idle speed until the only option is an RPM of about 8000 or stall. Figure I'd pull off the tank and take a look at the petcock. Much to my suprise, the vacuum line off the petcock goes absolutely nowhere. Of course, this could be the reason the bike would only run on 'PRI' which is what the previous owner had told me. :? The vacuum hose is only about 6" long and points in the direction of the battery. So this becomes a two part question. 1) I believe this hose is to short to do it's job correct? and 2) The hose is to fit someplace near/on carb #2 correct?
Once again, thanks for the help :oops:
 
The vacuum hose for the petcock should be attached to a fitting on the #2 carb.

If you look in the carb cleanup series, you'll see it:
http://thegsresources.com/images/carbs/002_View Engine side.jpg

Here it is with a big red arrow pointing to the fitting:
carb2.jpg


The engine will run like crap with the big vacuum leak if this fitting is open, too.

Hope this helps!
 
so if it really is just the vacuum line disconnected, and you've been leaving it on prime, there is also likely a leak in one of your float valves. means you probably need to clean the carbs, but who doesn't but earl? do you leave the bike on sidestand often, or center? the float valves will be more likely to let fuel past on sidestand if the petcock isn't stopping it for any reason.

be sure you haven't got a vent line instead of the vacuum...:wink:

a new diaphram for the petcock can work, but it also does just lead to more hassle. I think some of us are just suckers for hassle...!!

you can also likely just clean the float bowls if you don't feel like a full carb cleaning, check out the carb cleaning series either way, it has all the photos and descriptions. in the links on the left on the homepage!

g'luck!! I thought I'd blown a piston when it leaked into my #2 thru the vacuum line once too, man was I happy to find out it was only that stinkin petcock!!!
 
I think the issue will just turn out to be the vacuum issue. With the tank off the bike, it does not leak any gas unless the petcock is in the 'PRI' position. Or at least I hope it is. Painting the tank as long as I have it off the bike now, so once I get it painted and glossed, we'll find out. [-o<
 
SUCCESS! The bike is up and running, sounding, and feeling better than the day I bought it. That vacuum line was the reason the previous owner could never keep it running. It also fixed the major backfire that I had going on. Thanks to all that gave advice! \\:D/
 
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