Gas tank Drained over night. Stuck Float?

So I have had my '81 Xj650 off the road for about a month. I had one cylinder stop firing. After testing compression, etc.. I took apart the carbs and found that I had a broken float post. Bought a set of salvage carbs and replaced the body on the #4 carb, re-installing all my internals from the original.

I then wet-set, bench synched, set fuel mixtures and had it running well but was having some fuel delivery issues with my filter and fuel line. While working on the bike the other day I accidentally left it on prime for a day.

I came back to an almost full tank of gas that had been drained. There was some wet gas areas near the bike and the airbox has a little gas in it. I smelled the crankcase and smelled some light gas smell. Couldn't determine if it was coming from the crankcase or all the gas on the bike and ground.

I have two questions.

#1) When I wet set the floats, they were all within spec. If I had a stuck needle and do the clear tube method, how high above the edge of the bowl will the gas go?

#2) If I had almost a full tank of gas drain into the crankcase because of a stuck needle, would it be visibly obvious when I open the crank case cap? I would assume that much gas would fill that baby up but everything looked pretty normal.

I started it briefly and it acted as if the engine was stuck for a second and then kicked over fine. I immediately shut it off. I think I will change the oil just to be safe but any clarity on this would be a huge help.

 

With a float needle stuck opened, the gas will not stop going up your clear tube except if your tube is long enough to have its free end higher than the level of your fuel source.

 

Oops, bad idea & sounds like you may have hydro locked your motor.

Never a good idea to start the engine when the oil could be full of gas anyway as (aside from the fire risk) you can ruin the plain bearings.

I'd advise you to drain the oil as you said, & first off replace it with a cheap 20/50 before you try the engine again. If it seems OK then replace the oil again with your usual brand (M/C wet-clutch specific, maximum SG grade) after warming it up, the 2 changes is to get rid of the last of the gas residue.

The reason the gas leaked when you left the petrooster on prime is likely down to one or more of your float valves leaking. This can be slow so may not show up while wet-setting, but as a rule if there's any sign of wear or mark on the needle's rubber tips you should replace them & ideally the seats as well before using the bike again (Chacal at XJ4ever has them in stock)

Drain & replace the oil first before it damages anything internally (seals & chain guides can suffer from sitting in gas), ideally leave the gas tank empty or disconnected until you have the carbs sorted

Welcome by the way, sorry the circumstances aren't rosier. We'll get you sorted though :wink:

 

Yeah, if you left it on prime, and you had an empty tank when you went back out, you got a crankcase full of gas. DRAIN it and replace it.

Now, fix the float issue. In the mean time, you can also make it a point to remember to never leave the bike on PRI. You can also put an inline fuel shut off.....like what you'd find on a lawn mower, snowblower, snowmobile, etc.......

Dave F

 

Hi Dave, would you mind chiming in on this thread too please, need a little backup/reassurance lol http://xjbikes.com/Forums/viewtopic/t=42071.html

 

Thanks for the thoughts on this, it sounds like I was on the right track with the problem. I will drain the oil tonight and get it replaced before any further damage happens.

While I was wet setting previously, the needles and valves looked ok. Although I found that to get close to the 3mm spec on two of the carbs, I had to have the floats bent to the point where they might be hitting the top of the carb body before the needle is seating in the valve. If they weren't hitting, it was damn close. Any idea how to remedy this? I could see the floats physically stopping while the needle has not completely sat, causing the leak.

Also if it is a slow leak, any way to test this since it may not be evident with the clear tube test?

 

That's strange that the floats would be that high, are the spring parts on the ends of the needles free to move or jammed in? Also, are all your parts identical & floats fitted the right way up?

Might be worth getting needle/seat kits from Chacal (XJ4Ever) as something's certainly amiss here... I think the only "test" for a slow leak is to just eliminate it as a possibility :? Shouldn't be that huge of an issue as long as you remember to take the tap off PRI in future, but all the same you want them right really to get the best out of the bike

 

Yeah, I thought it was weird as well.

Leaving it on prime was a bonehead move that I am now paying for.

The spring parts on the needles all seemed to move freely. That is actually what made me think that the float was hitting the carb body before the needle sat properly. On #3 and #4 it seemd like the float would hit the body and the tang of the float had not quite pressed in the spring on the needle.

Needles are all the same size but I will pull the carbs off again and check for any damage to the tips and the seat.

 

There's your problem I believe, the needles can't be seating properly (the flow should cut off without needing to depress the spring tips, they're just there to provide damping against the engine/road vibrations)

I'd seriously consider replacing them if there's any doubt, Chacal's parts are tried & tested good quality stuff (the old seats *can* be polished up with 2500grit wet&dry but I think it's a pain to do & is not 100% guaranteed to work, and the needles can't be done a thing with as they're rubber tipped)

 

Your assessment was correct. One of the float tangs got bent too far and was keeping the needle from seating properly. I fix the float and flushed the engine with a cycle of oil.

Seems to be back in working order now. Thanks for everyone's help!