Can't idle anymore

Hi everyone,

Last year I rebuilt my carbs and all was great. I've been using a good working machine ever since then. Except until now.

I did an oil change after a ride, set the oil the about 3/4 of the sight glass, perhaps a little more, but not over the top.

Did another small ride a few days later just to warm it up for color tuning and carb sync (valve clearance check was already done in between). Cylinder number 4 was running a little rich, but nothing crazy, same for carb sync, nothing way out of line.

Once everything was set I turned it off.

Now it won't idle at less than 3-4000 rpm and if I attempt to do it, it'll slowly die off. Also it doesn't run smooth like it did before when the throttle is open.

I was a little puzzled and about to do another check of everything, until I realized that my oil level was waaayyyyy above what I'd set it at!?

So I'm kind of confused as to what may have happened, could the gas be leaking into the oil pan or something like that??? Should I do another oil change and see what happens before I try to color tune and sync it again?

My spark plugs are all black and oily, which is a sign that the engine is running rich from what I understand, but how could that be when they were fine BEFORE I tuned the mixture to be leaner!??!?!

 

Sniff the oil. Does it smell like gas? It shouldn't. If it does, you got gas leaking into the crankcase. That can be a stuck/leaky needle combined with a petcock that doesn't shut off when it should.

If your oil smells like gas change it ASAP and check needles and petcock.

 

Thank you so much for the quick response.

I have metal tipped needles, shouldn't that prevent this sort of thing? (They're also brand new)

I forgot to turn the petcock back to normal the other day and left it on prime, could THAT cause my petcock issue? I thought the carbs would just fill up and stop the fuel from flowing... If so, if I do an oil change and try it again could that work or should I open up my carbs asap?

 

Sounds like what mine was doing when I had two stuck floats after cleaning my carbs. Kept overrunning into oil but I was also getting it overflowing into airbox.

 

The oil does smell like gas by the way.

 

That probably excludes the needles being leaky, but it does not exclude them being stuck. Even needles that operate properly 99% of the time can stick occasionally. This is why you keep a vacuum petcock ON and turn off a manual one. A piece of dirt, a tiny metal burr, it really doesn't take much to impede the free movement of the needle.

The thing that stops the fuel is the needles. Prime keeps gas flowing whether the engine is running or not, so having a needle stuck open is your problem.

One thing I've heard people try (I haven't done this myself) is drain the carb bowls completely. That ought to cause the floats to drop and get moving again when the bowls refill.

Also, was setting the float height part of your carb rebuild?

 

Change it ASAP.

 

Ok, I'll warm the bike up, change the oil, drain the carbs and if it's still doing it, we'll move into surgery.

Thanks!

 

Do not warm the bike up. Don't start it. Just drain the oil and leave it sit with the oil filler cap off for a few hours so what gas that remains in the case can evaporate. Then refill with a cheap oil, warm the bike, and change the oil again using your preferred brand.

Running an engine with gas-contaminated oil makes for a fast trip to Rebuild Town.

Gas-contaminated oil cannot maintain the film thickness that is required to keep the bearings and bearing journals separated. When they make contact the surfaces become scored, and once scored it becomes increasingly difficult for un-contaminated oil to maintain the required film thickness. The bearings and journals continue to wear at an increasing rate, and you get to see what the inside of your engine looks like (one way or another).

Gas-contaminted oil is a great deal more combustable than un-contaminated oil. There is a very real possibility (I say this having gone down that particular road personally ) for combustion to occur in the crankcase, at which time some very bad things occur (once again, you get to see what the inside of your engine looks like, though a great deal more dramatically this time). The risk increases with an older engine that may have less than ideal sealing of the piston rings.

 

Oh gosh, now I'm scared :S.

I'm not sure at which point the oil got so mixed up with fuel. Hopefully after I'd done all the maintenance on it... It would have been running for the color tune and syncing .

Thanks a lot for the heads up! I didn't start it when I did this oil change because the mechanic at the shop told me not to, but I'll also follow your advise and do another oil change right after I had the oil run through the engine.

 

If it did run for a while with gas in the crankcase all is not lost. Bearing and journal wear can go on for quite a while before absolutely needing a rebuild; just run it until you start noticing a bottom end knock. It might happen in a few months, or it might happen long after you've sold the bike.

 

I wouldn't lose any sleep.

The consensus of the Motorcycle Press when they reviewed these Bikes, back when, was that these Engines were: "Bullet-proof" "Hard to Kill"!

 

Yep.
https://www.youtube.com/watch?v=Hzh0rtyCfFU

 

That doesn't mean you can't blow one up running it with diluted oil or one super-lean cylinder.

We've seen thrown rods, holed crankcases, and multiple holed or seized pistons on this forum over the last few years. It can be done.

Back to the original problem: if you left it on PRI, then all that did was enable your STUCK FLOAT to fill the motor with gas.

Pull the rack and wet-set the float levels. In the process you'll quickly discover which one isn't shutting off.

A sudden rise in oil level is our best "early warning" sign of float issues. That's why it's a good idea to make it a habit to check the level before every ride to ensure it hasn't suddenly risen.

 

I opened them up and carb number 4 had it's float set so that it wouldn't push the needle in until much later then all the others (I'm guessing that's what allowed it to overflow). I bent it gently so that it would be the same as everything else (its what they tell you to do in Hayne's manual anyways), but I wondered what made it bend?

Could it be just from being push to its maximum level over and over the metal is getting tired and bends more easily?

I haven't put the carbs back on the bike just in case someone has had this happen before and knows what causes it. Otherwise I'll just put them back in tomorrow when there's light outside and check the fuel levels to see if that fixed it.

Thanks everyone, you all continue to amaze me with your magic knowledge .

I'll also make it a habit of checking the oil level systematically every time I start the bike now instead of every other time...

 

You check and adjust the float levels (fuel levels) with the carbs OFF the bike.

See: http://www.xj4ever.com/setting%20fuel%20levels.pdf

 

Eh yeah, I basically do that but instead of using some sort of tube arrangement I use the bike to hold the carbs in place and the fuel tank to drop the fuel in them. I use the center stand on my garage floor to keep it straight. Is that bad?