Any ideas welcome

[ianisme]

HI all and thanks in advance for helping.

I have an XJ1100 that is giving me problems. It sometimes starts but runs rough, as if not all 4 cylinders are firing. After running like this for a while I will sometimes get a large backfire, followed by clouds of smoke and an airbox full of oil.

The last time I tried to ride it I made it about 300 yards before the thing just died on me.

The bike sat unused for a while but had been running ok up to that point. I have a feeling it may be carb related but don't let me lead you down the wrong path if you have another idea.

Any thoughts or should I just shoot the poor old thing? Thanks.

[TheDjost]

The first thing I would do with any engine that shows oil in the airbox is check the compression.

Have you changed the oil? Is it running on new gas? How long has it sat? Have you cleaned the carbs?

Try to find the source of the oil in the airbox: remove the crankcase breather hose and check for oil (be prepared to catch it in a jar)

Keep us posted

-Justin

[ianisme]

Thanks Justin.

It has had new oil and gas. I guess I should explain that the oil only appeared after the backfire. My theory, for what it is worth, is that somewhere a large amount of gas accumulated and then suddenly ignited. The resultant big bang may then have blown the oil out of the breather. Don't know if that's logical or not?

It sat for about 6 months and I'm in the process of cleaning the carbs today. I'm just about at the stage of removing the floats so fingers crossed I dont break a post.

I'll let you know if I find anything obvious.

[mitch]

Floats

I think i would clean the carbs sounds like the floats are stuck open check your oil i bet its full of gas. Also check the petcocks to make sure the gas was shut off when it was parked if it was the gas might be leaking past them ..................MITCH

[skids]

Re: Floats

Hello Ianisme. Sometimes fuel in the airbox will get filter oil and dirt in it and it can appear to be oil. How full is your crankcase? Is it above the "looking glass" when the bike is on the centerstand? When you are done cleaning, I recommend that you turn the carb assembly upside down without the bowls on and blow into the fuel tubes, and listen for any leaking passed the fuel valves. I don't remember what model carbs that you have, but if you have carbs later that 79, replace the o-rings around the fuel valves.

Originally posted by mitch
I think i would clean the carbs sounds like the floats are stuck open check your oil i bet its full of gas. Also check the petcocks to make sure the gas was shut off when it was parked if it was the gas might be leaking past them ..................MITCH

[Geezer]

Don't forget to check the timing pick up leads.

Geezer

[sixtysix]

Anywheres near Portland? There is an XS Expert there...how about some of you wonderful PNW ers helping this guy out.

[kf4anm]

fuel

these guys are correct. i just went down the exact same road about 1 month ago with my xj. i had the same backfiring, smoking, oil in the air cleaner problem. my bike was slowly leaking fuel through the carbs into the crank case. it took a couple tries but i drained 7 quarts of gasy oil, changed the filter and plugs, corrected my carb/fuel cock problem and things have been great since.

[ianisme]

I'm just south of Portland (McMinnville) so would appreciate any advice I can get.

Latest update is that I stripped and cleaned the carbs and just put it back together. It ran OK then I got all of the symptoms that Daryl just described. After a couple of minutes it seemed to start misfiring, then clouds of smoke followed by a load of fluid dumped beneath the bike. It looks like dirty fuel so Skids may well be correct.

I guess then that I need to change the oil first? I said it had new oil but that was new before the long lay off. I'll change it tomorrow if I get the chance and let you all know. You guys are awesome; thanks for all your input.

[skids]

I wouldn't change the oil until you get the leaking stopped, or you could contaninate it again. You can change the oil now, but you will probably want to stop the flow from the tank (like remove the tank) just in case the vacuum actuated diaphragm (petcock on the standard or octopus on the special) is leaking with the engine turned off. At least check it to see if it is leaking when off!

Originally posted by ianisme

I guess then that I need to change the oil first? I said it had new oil but that was new before the long lay off. I'll change it tomorrow if I get the chance and let you all know. You guys are awesome; thanks for all your input.

[Geezer]

Originally posted by sixtysix
Anywheres near Portland? There is an XS Expert there...how about some of you wonderful PNW ers helping this guy out.

I'm in Tualatin aout 8 miles south of Portland.

Send me an eMail and we can schedule a time I can look at it.

Geezer

[scalded dog]

The fastest surest way to check oil for gas, use a small stick, dip it in your oil, if you hold a lighter to it and it burns, you have gas in your oil. I learned that right here on this forum. Later 'Dog

[ianisme]

Great tip; I'll try that today.

[TheDjost]

Another tip is to completely remove the airbox and leave it off until you get the bike running like you want it. It will make the task of removing and reinstalling the carbs alot easier, and it will let you see wich carb(s) is leaking gas, so you can go back and re-re-clean the float valves. Another thing that can happen is the float can start leaking. Take it out and inspect it. An easy way is to put it in the freezer (in a plastic bag, so the wife won't freak out) for a couple of minutes. Then dump it in warm water with a weight strapped on. The air will warm up inside an will blow out of any holes.

-Justin

[cbird]

Geezer can diagnose it straight away. That said, probably one of your float valves is totally not working, gas pouring through. I learned my bike had a "repaired" float post when the repair failed and the symptoms were like yours. I fixed it!