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Old 05-11-2013, 04:22 PM   #1
b1pig OP
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GZ250 oil sight glass replacement... tips?

long story short. petcock left in "prime".
float hung open.
flooded intake and cylinder. fuel was in oil.

cleared cylinder and intake.
drained oil. refilled. started it and ran it for a couple of minutes. drained it and refilled it. ran it till warm... and aparently there was still some fuel in the case. shoulda left the fill cap a little loose... but the oil sight glass popped out while i was it was sitting and idling.

so.
got new clutch plates (most likely contaminated) and oil filter. since i have to pull the side cover off anyway to put the sight glass back in, its no big deal. the metal/plastic is surrounded by a rubber seal, and it just looks like a resistance fit. i figure a c-clamp with appropriate size socket(s) will work fine to reinstall it.

the only thing that has me wondering a little is that there seemed like there was a small bead of RTV that ran around the junction of the metal/plastic and the rubber seal on the inside. It was blown loose with the sight glass assembly.

Seems to be a straight forward thing to do, but sometimes the simplest things can have a complicated step in there somewhere. Factory service manual has no reference to the sight glass.
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Old 05-11-2013, 06:14 PM   #2
NJ-Brett
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Fix the carb float problem.

If it had sealant, use sealant.
If not, don't.
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Old 05-12-2013, 12:37 AM   #3
b1pig OP
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it was.
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Old 05-12-2013, 08:39 AM   #4
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Never installed a sight glass before, but maybe use a light smear of high temp RTV as a "lubricant" in the cover hole before pressing the glass in? When pressed in from the outside this should push a small amount of sealant inward to form a "bead" around the inside edge.
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Old 05-12-2013, 09:33 PM   #5
b1pig OP
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well. adventure riding meets adventure repairing, i guess.

i got it taken care of today. turns out, the sight glass is just a slip-fit. the rubber seal around it is all that holds it in. you could install it from the outside or the inside. theres no taper to it. since i pulled the cover to replace the clutch plates anyway, i smeared a semihealthy bead of black RTV around the perimeter of the seal. should hold up fine.

fresh oil and a new K&N filter and I've got it running.... just not running well. leans out over 1/3 throttle. guess i'll try and run some seafoam through it next. i thought i had everything cleaned out pretty well with the carb cleaner. had it apart twice. got the pilot screw out 2.75 turns. idles like a champ, though.
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Old 05-12-2013, 10:01 PM   #6
JerryH
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Still trying to figure out how gas in the oil could make the sight glass pop out. Couldn't be pressure, the crankcase is vented. As for the clutch plates, gas should not hurt them. If you had to remove the clutch cover anyway, I would ave probably removed them and soaked them in engine oil, and put them back. Gas is pretty much the same thing as oil, same ingredients anyway. Shouldn't be anything in an engine that gas would hurt. You are lucky you didn't hydrolock the piston and break it and/or bend the rod when you tried to start it.
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Old 05-12-2013, 10:15 PM   #7
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Quote:
Originally Posted by JerryH View Post
Still trying to figure out how gas in the oil could make the sight glass pop out. Couldn't be pressure, the crankcase is vented. As for the clutch plates, gas should not hurt them. If you had to remove the clutch cover anyway, I would ave probably removed them and soaked them in engine oil, and put them back. Gas is pretty much the same thing as oil, same ingredients anyway. Shouldn't be anything in an engine that gas would hurt. You are lucky you didn't hydrolock the piston and break it and/or bend the rod when you tried to start it.
This ^^

Still a little unclear on what caused the sight glass to pop out. Oil with friction modifiers can contaminate clutch plates but gas shouldn't have hurt them. The real danger of flooding the engine in this way is, as JerryH says, that the cylinders are usually flooded first and then leaks past the rings into the crankcase. Then if you try to start the engine you can bend a rod because gas isn't compressible the way normal combustion gases are.

If the bike won't run up past 1/3 throttle that would indicate that either your main circuit is clogged, or maybe there's an issue with the float height/needle and seat causing the engine to starve for fuel at higher revs. Have you taken the carb completely apart and checked all internal passages?
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Old 05-13-2013, 12:13 AM   #8
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well. gas expands when heated... and at a lower temp than oil would.. that was my theory. and when i say gas got into the oil... a LOT of gas got into the oil. it was pathetic... i wont even suggest how much it could have been.

i know where you're coming from about the gas being a petroleum product... but the way i saw it was that the bike spent 800 miles at under 35 mph on a motorcycle safety course before we bought it. with only 1600 miles on it now, you wont believe what the front brake pads looked like... just made sense to swap em out anyway and not risk a later failure. cheap insurance i suppose.

i removed ALL of the jets. if it could be unscrewed from the carb, i removed it and sprayed Gunk carb cleaner through it. everything seemed to be flowing good. after the fuel leaked into the engine, i thought the float hung up, so i pulled it off a second time, recleaned the whole thing again and then took a little time to try and readjust the float height.

if the float was the issue, it would be because the float bowl didn't have enough fuel in it, right? to be flattly honest, I'm not sure which jet in the bowl is for what circuit... other than the needle jet, which is obvious.

tuning tips appreciated.
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Old 05-13-2013, 06:37 AM   #9
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Quote:
Originally Posted by b1pig View Post
well. gas expands when heated... and at a lower temp than oil would.. that was my theory. and when i say gas got into the oil... a LOT of gas got into the oil. it was pathetic... i wont even suggest how much it could have been.

i know where you're coming from about the gas being a petroleum product... but the way i saw it was that the bike spent 800 miles at under 35 mph on a motorcycle safety course before we bought it. with only 1600 miles on it now, you wont believe what the front brake pads looked like... just made sense to swap em out anyway and not risk a later failure. cheap insurance i suppose.

i removed ALL of the jets. if it could be unscrewed from the carb, i removed it and sprayed Gunk carb cleaner through it. everything seemed to be flowing good. after the fuel leaked into the engine, i thought the float hung up, so i pulled it off a second time, recleaned the whole thing again and then took a little time to try and readjust the float height.

if the float was the issue, it would be because the float bowl didn't have enough fuel in it, right? to be flattly honest, I'm not sure which jet in the bowl is for what circuit... other than the needle jet, which is obvious.

tuning tips appreciated.
In that case it's probably a good call to go ahead and replace the clutch. If used as a trainer by newbies it's probably seen its fair share of abuse.

Was the bike running ok when you bought it?

I'm not familiar with the carb on that bike. But basically there is the pilot jet (the smallest one) and the main jet. Pilot controls idle. Main controls WOT. The needle basically covers everything in between with some overlap between the circuits at various throttle positions as it transitions between. The main should be screwed into an emulsion tube. The emulsion tube is a longer cylindrical brass tube with very small holes in the sides down it's length. Just squirting carb cleaner through often is not enough. If the bike sat for a long time and really gunked up the carb you have to make sure that EVERY orifice is completely open and free from crap.

I've successfully cleaned clogged jets by soaking in heavy duty paint strippers, soaking overnight in carb cleaner, carefully using very fine cutting torch tip cleaners (welding shop or even the welding section of Lowes), but most people will say to just buy new jets. They're cheap and you can waste a lot of time dicking with them. Float height is pretty critical, as is the condition of the float needle and seat. Generally speaking, most carb's float height can be set by taking the carb float bowl off, turning the carb upside down and lifting the float. Now, while watching the float needle very carefully lower the float until you see the little spring loaded plunger just begin to depress. This tells you when the float is seating the float needle. There may be a casting line on the float itself. if so, this line should generally be parallel with the bottom face of the carb when the needle seats. If severely out of whack, carefully bend the little arm that pushes on the needle and check again. A little goes a long way. You may want to do a little research and reading up on carb function for more details about exactly how carbs work and why they don't.
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Old 05-13-2013, 06:00 PM   #10
b1pig OP
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in the "general" idea... i have an idea, but lack the experience, which is what i aim to change.

this one has 3 jets in the bowl. the needle jet, and then two more. there is what "looks" similar to an accelerator pump on the side of the carb... its apparently vacuum actuated. i pulled the cover and diaphram and cleaned that out too.

all of the jets were removed and cleaned individually... but it may not have been enough i guess. the wife hasn't been in a position to ride. It has sat dormant for almost 2 years. last summer, i pulled the carb and cleaned it out because i forgot to drain the carb. it ran great after that... i then drained the tank and carb and stored it. wouldn't start unless i palmed the intake. smelled like varnish. i pulled the carb again, and it had a bunch of residue in it and the jets were plugged.

heres a vid of it running last night. you can hear the hesitation on one of the earlier revs.

https://www.facebook.com/photo.php?v...3316232&type=3
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Old 05-13-2013, 06:30 PM   #11
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I still can't picture the "needle jet" thing. Most carbs that I've dealt with have two jets in the bowl, a pilot jet, and the main jet extending down into the fuel in the float bowl. The main is usually screwed into the bottom of the emulsion tube and the needle comes down from the top of the emulsion tube. With this set-up the needle meters the amount of gas coming up into the airstream in the venturi and the main jet limits that amount at max throttle. Can't say that I've every seen a carb with three jets in the float bowl although some do use an air jet in the incoming side of the venturi, but that a whole other animal...

The pilot controls idle up through around 1/4 throttle, the needle regulates fuel from just off idle on up and the main regulates total amount of fuel allowed at WOT. There is of course some overlap and interaction between the circuits. For example, the pilot is always feeding it's fuel into the system adding to the overall fuel flow. It doesn't just stop off idle. And then there is the airscrew which allows some fine tuning of the pilot curcuit. And then there are pumper carbs, which I don't have any real experience with.

Other than making sure that the jets are spic & span, make sure any and all internal passages will pass carb cleaner and aren't clogged. Double check the float height. One way to inspect this with the carb on the bike, is to attach a clear tube to the bowl drain, run it up alongside the bowl and open the drain screw. The gas will come up in the tube to the level that it is inside the bowl. It should be pretty close to but not over the gasket area.

Also make sure you inspect the slide diaphragm for any small tears or pinholes. Any damage here will cause the slide to not raise in response to throttle inputs since it can't respond properly to increased vacuum. This will also lean it out under throttle and not allow it to rev.

These are all just general ideas since I'm not really familiar with the carb design used on that bike. I've worked on a few different types over the years and some of them have had me scratching my head for a while trying to figure out exactly how they function. But usually with enough time and looking at it, squirting carb cleaner in every orifice I can find and seeing where it shoots out, I usually get it sorted.

Sorry I can't give you more direct advice, but good luck. I'm sure with enough time and experience tinkering with it you'll get it running like a champ.
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Old 05-13-2013, 06:56 PM   #12
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thanks, randy.
every little bit helps.
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Old 05-13-2013, 07:01 PM   #13
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I have heard both the main jet, which the needle goes through, and the pilot screw, which has a sharp point, referred to as "needle jets" but that is not the proper name for either of them.

In order for what sounds like the entire contents of the gas tank to wind up in the crankcase, one of 2 things would have to happen. Either the float needle valve (the one thing in a carb that correctly has the word "needle" in it) did not seal properly, either because something was blocking it open, or because it was worn out. A piece of trash blocking it open is far more likely where something like this happens suddenly. Or, the float would have to be stuck at the bottom, leaving the needle valve open, and not raising to shut it off when the float bowl was full. That is not likely in your situation either. That usually happens when the float bowl has been empty for a while, the float sticks on the bottom, then someone opens the petcock, and drains whatever gas is in the tank through the carb, and into the cylinder.

In any case I would remove the carb, take it apart, and check everything out. I'm betting on a piece of dirt holding the needle valve open. I didn't realize it had been used as a training mule, and probably dropped a hundred times. That is unlikely to damage the carb, but may be why the sight glass fell out, or if there was sealer on it, maybe the gas melted it. But I would think that if that were the case, hot oil would have also eventually melted it. Probably just got banged around to much.

One thing I would do, to help prevent something like that in the future, is to install an inline fuel filter between the petcock and the carb, to keep dirt out of the carb.
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Old 05-13-2013, 08:04 PM   #14
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I

One thing I would do, to help prevent something like that in the future, is to install an inline fuel filter between the petcock and the carb, to keep dirt out of the carb.
Good advice there... On an old bike that's been sitting it's very common to have rust in the tank. It can get scaley and start dropping the occasional rust flake into the fuel to make it's way down into the carb. You've seen how small the orifices in a carb are, so just think what sort of havoc a few of these small rust flakes can cause on fuel metering, not to mention blocking the float needle valve and flooding the engine. Sometimes this can cause an intermittent problem that can be a nightmare to figure out. A cheap inline filter can save a ton of headaches.


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Old 05-15-2013, 09:53 PM   #15
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ran a seafoam/gas mix through it and let is stand for a while. fresh gas in the tank. still some hesitation around 1/3 throttle, but its not holding the bike up. it pulls through the lean spot pretty well. Told the wife she has to take it out twice a week minumum. we've got a couple of 10-25 miles loops of county roads that we like to ride.

she took a short 10 minute ride this evening before i came to work. first time she's gotten to ride it in a year. let our 17yo sit with the babies while we both took the ride. she definitely noticed the lag on the throttle, but she has vowed to put some miles on it this summer.

i also turned the pilot out a little more. its at 3 turns out now. that did seem to help the throttle transition. no smoke or strong (rich) exhaust odor at idle... so i'm wondering if i should go another 1/4 turn. pretty sure it was originally (stock) at 2 turns. i probably rode the thing close to a mile in the yard running mostly 2nd gear, but lugging it in 3rd through that flat spot seemed to help clear it up some. this afternoon when i started working with it, it would not pull through second gear unless you cycled the throttle from WOT to 1/4 back and forth several times. by the end of the day... you can creep the throttle past 1/2 throttle with only a little stutter.... but it pulls on through. had to chase the ole lady down. she ran it up to 65 and gave the thumbs up....


thanks for the tips. i think i'll have to reroute the fuel line for a filter. the petcock and the carb are only about 3" apart. the tank is pretty clean and really is "rust free"... but that doesnt count for general trash. still, with a +1 front sprocket, the windscreen and the saddle bags, the little 250 still holds its own.
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