starts but will not stay running

Fellow Riders. I have been working on a problem with my bike for 3 months. I was running fine, and I pulled into my yard on day and left it sitting. Went out the next morning and tried to start the bike. It would turn over and after a very long time, 5 minutes or longer it would start, and run for just a few seconds. Pulled the seat off and found it to be pushing gasoline into the air filter, I mean shooting it through. A guy has been looking at it and says he out new plugs in it, which I had just done a week prior to the problem. Bike started out just being hard to start, so I would have to choke it and then open the throttle. Would start and run. I adjusted the throttle screw and seemed to work for a while until the last day I rode it. First thought is might be the chock cable but shop told me it was the issue. And ideas where to start? I am lost in this one.

Thanks,

Doulgas

 

Sounds like you've got an issue with the carbs.

You will need to:
Test fuel petcock
Clean the carbs
Sync the carbs
Adjust float levels
Replace air filter
Replace plugs
Change oil and filter
Might as well check/adjust the valve shims while you're at it, or you'll never get it tuned

If you ran it with the crankcase flooded with gas you may have done more damage to your motor.

But the above things is where you need to start.

 

What kind of bike? Shooting from where, can you tell? Check your oil and see if there is fuel in the crankcase-put your nose over your fill hole and smell - toasty nutty oil or volatile hydrocarbon smell?

 

1982 Yamaha 750XJ Maxim. If I took the seat of and removed the ail filter and tried to start the bike, once it started you could see black, oil, looking gas coming straight into the air filter chamber. Had a guy change the plugs, which I had just change the week before, changed to oil and filter as well. He told me it will start but will not stay running. Appears he fixed the gas pushing into the air filter. Since bike will start but dies with in seconds of it starting he is thinking electrical problem with rectifier. I was having trouble with it staying at idle when I turned the wheel, so I thought it was the throttle cable. Did some adjustment on it and reajusted the idle. But once it started flooding out I figured it was more serious than a throttle cable or idle screw. May have to just part it out.

 

It is. You have an issue with the carbs. Best guess: stuck float. It is letting gas flow from the tank, through the carbs, and into the crankcase. The "oily gas" you are seeing is just that - oil and gas mixed, being sucked up through the crankcase breather tube, and into the airbox.

The only solution is to pull the carbs and clean them, change all the fluids, and the filters, set float heights, sync the carbs. Adjust the valve shims while you're at it.

Also test the petcock. It should only flow fuel while in the PRI position when the bike is off. ON and RES should only flow when the motor is being cranked over creating a vacuum.

Why part out a bike that you said was "running fine" when all it needs is some routine maintenance?

 

I dont know half as much as most of these guys and I agree.

 

100% agree with tskaz. Do what he said then ride it. WET SET the floats when you put the carbs back together, check the float pins-- are they straight? roll them on a sheet of glass (picture frame or...) polish them--- chuck them in a drill and use 1000 0r 1500 grit wet/dry, wet the paper with wd-40 or pb blaster get clean and polish the float body where the pins GO IN AT. finally, wth the bowls off hold the carbs in the right side up position and work each float a few times wathching its operation and movement of each needle. make sure you are running the spring loaded viton tip needles and GOOD NEW SEATS AND SEALS. K&L has a great kit, I think its 18-5111?
Anybody remember that part#? chheck it out.
but yeah-what tskaz said

 

Wait, whoa slow down.

If it's pumping gas/oil into the airbox, the crankcase IS full of gas.

The first thing you need to do is understand how it's supposed to work:

-the petcock is vacuum operated, and is supposed to be OFF when the motor is off, as long as it's in ON or RES. The PRI position allows fuel to flow regardless of vacuum signal.

-the float valves in the carbs are supposed to stop fuel flow when the float bowls are full to the correct level. FOR SOME REASON YOURS AREN'T.

You have a common issue with the carbs (stuck/sticky/misadjusted float) and possibly a petcock problem as well.

Carbs needing to be cleaned and adjusted is just a part of normal maintenance on an XJ; what you're seeing is not some "terminal problem" just the effects of neglected maintenance.

Parting out a perfectly good XJ because of a stuck float makes no sense; if we all did that there wouldn't be any left to ride. All 3 of my XJs came to me with carb issues, sticking floats and peeing gas everywhere.

IT COMES WITH THE TERRITORY. Fix your bike. Start with an oil/filter change; then don't run it anymore until you get the carbs attended to.

 

Thanks guys. I will get the carbs cleaned. Really makes sense to me now that I see the rest of pointing to the same issue. I poured cleaner in it once and it seems to work for a short time, so I guess it is time to take the carbs off and get at it. The only reason to part it out is due to shortage of funds due to a divorce and a job cut back. Will take it down and put it back together as I can afford to. Again, thanks guys.

 

Right don't give up on it yet. I can totally sympathize with the lack of funds and I have managed to get my XJ back up using this site and some creative efforts for parts.

Follow the advice and you will get it. It's getting cold around here anyway so it's a good time to work on it and get it right before it warms up. Just to diagnose your carbs will only cost you your time. And then you'll know what is wrong and how to fix it. Doing the valves is important as well and it really isn't hard-even though at first it sounds like it is.

Start with the oil/filter change, and then check your valves (all you need to check them is a feeler gauge (metric best), an allen wrench for the cover, and a 19mm wrench to turn the crank). Use this site and read up on how to get it all done. Then pull those carbs and let's figure out what's going on. Since it went from running fine to flooding the crankcase I'm betting your carbs are getting gunky and varnished and a float stuck. But before you ride you will have to make it safe (brakes) etc.

If you get stuck anywhere and need some help, I'm nearby and can come and get you unstuck-especially after this week as my finals are over.

 

you're a good man MM.

 

Don't forget that petcock. If it flows in ON or RES you need to attend to that or you'll just waste your money on the oil and filter change.

If need be you can install a 1/4" on/off valve for a lawn mower. Cost about $4 at the local auto parts and it will keep the gas in the gas tank until you can attend to the system.

 

Also, you don't want to fix the carbs and change the oil and think it's all good. Some of that fuel-diluted oil will stay in the middle gear housing, so you'll want to do another oil change after about 100 miles to get as much fuel out of there as you can. Diluted oil does bad things to your motor.

 

Good points tskaz, don't want anymore fuel overflowing into the crankcase. At this point I would probably just pull the tank off anyway since the carbs, & valves will require that. I would buy the cheapest oil I could for that first change and then turn around and change it after the first time the engine is back running and gets hot.

 

No, it needs to have MOTORCYCLE OIL used at all times rather than soak the (probably original) clutch in "cheap (car) oil."

The common quote from all of our advice has been "start with an oil and filter change."

Do that.

Then ensure that no condition exists that will allow the engine to get filled back up with gas while you solve the issue. (Which includes disconnecting the lines and/or pulling the tank.) But get that gas-diluted oil out of there NOW before it creates a whole new range of problems for you.

 

Sorry bigfitz I should have clarified. I use relatively expensive motorcycle oil ($9 qt) in my XJ, so I meant cheap motorcycle oil. Between the adivce I got on here (mainly from you) and what I read about current car oils with their modern additives, I'm convinced moto oil only. Much like ethanol laced fuel was never meant for CV carbs either.

I would add one other thing-just because I'm a bit OCD when it comes to clean-I would also thoroughly clean out the air-box with a lint-free rag.

 

As always, trust the experts. Correct on the diagnose, floats were sticking and carbs were dirty. Was lucky enough to find a friend of a friend to do the work bartering. Now I have to find a really good price on tires, find replacement for the original headlamp housing and the speed/tach. But tires are first on the list.

 

Good going. Now check your valve clearances before you're back with "now it won't start once warm."

 

Hi Douglas - Can see from your recent gallery pic that there is a lot of staining on the alternator cover from fuel dripping out of the carb...

Just backs up what everyone is saying.

Nige

 

NigeW

Thanks. You and the rest were dead on! The bike had been setting for over a year when I bought her so I just rode her till she died. Wasn't my plans but life sometimes dictates other things.

 

as for your tires-- I got a set of Kenda Challengers from American Motorcycle Tire on line- shipped to my door 120.00 "H" range and all weather, pretty good tire rides well, corners well.. I have about 3500 miles on them and I like them, I plan on getting another set.
just throwing it out there for ya

 

Thanks skw1972. I will take a look at them and start saving up my nickels and dimes.

 

Also consider (Fitz will back me up here) Avon Roadriders - you get what you pay for...

With respect to skw1972, there's probably nothing wrong with the Kendas at all (I had a cheng shing - or whatever- on the front of my bonnie for a few years - never had a problem and other people reckoned they were sh*t).

Just my opinion that you can't go wrong with the Avons on this bike.

Nige

 

True; however, they aren't the longest-lasting tires out there, by a long shot. But they sure do WORK.