XJ650 will only run for a few miles then quit and wont start

I have a few problems..
Well, first off... I cleaned and rebuilt the carbs, Synchronized them, and colortuned, and the bike was running GREAT. After a little while the bike started to throw a thick white smoke out of the right side exhaust. I would take the #4 plug out and it would be covered in a thick slude like oil build up. I would have to clean or replace plugs like once a week. Then the bike started to have a petcock leak. So, I bought a rebuild kit. When i got my rebuild kit i noticed that the diapragm for the petcock was different to the one that was in my current petcock. I bought the kit on eBay, i thought they had sent me the wrong kit. I took my petcock and went to the Yamaha dealership and they pulled out a parts book and told me that the petcock that i had was from a KAWASAKI! I have no clue as to what year or model kawasaki the petcock came from so i had to buy a new petcock. I finally replaced the petcock and it ran better than ever! BUT, it only ran fine for a day or two. Now, when i start it, as soon as i hit the throttle it back fires pretty bad. Or sometimes its really hard to start. And when it does start, it runs real rough and i will only be able to ride for a few miles before the bike stalls out and refuses to start up again. I would let it sit for a couple hours and it would start right up again.. But, again, after a few miles she just quits on me. The bike is not smoking at all now, I pulled the plugs out and they are not covered in oil or sludge, they are just kinda black and have somewhat of a SOOTY build up on them. Also, i can hear a popping noise in my air box. I checked the air filter and it looks like there was a little explosion in there, the foam from the filter is all burnt up and melted from the inside. My throttle response is real sluggish and when i let off the throttle in neutral, the engine deccelarates slowly, sometimes doesnt even idle, i have to keep revving the throttle to keep it running.
Can anybody help me out with what might be causing my problem? I really have no idea and cant think of anything else it might be. Any help would be greatly appreciated. Thanks!

 

Backfiring is generally a lean condition.

At this point, if you still have access to a colourtune it might be good to try it again.

My guess? You've got fuel level issues in the floats. That could be the result of a fuel line not allowing enough fuel, or that in changing parts you've changed the rate of flow to the floats...

Sooty plugs - that could be the result of only idling at the moment. It's hard to tell much at this point...

Also - do you have a fuel filter?

Check none of the lines are pinched.

Drain the float bowls into a cup - let it seperate. Perhaps there is a lot of water in the fuel? That would certainly starve the bike for fuel... if it's got lots of crude in the bowls then perhaps it's time to install a new fuel filter and do a mini carb clean.

 

From your narrative; it seems like you have a couple of things to investigate.

Petcock = Supply. There may be some issue with that Petcock not getting opened as it should which would eventually cause the bike to be starved for fuel and quit ... maybe even run lean and backfire before it does die-out on you.

I once had a seasoned Yamaha Tech try to help me over the hump of a similar problem trying to tune a 750.

Because the bike would run well for a short while; I was convinced that the problem was ignition related in some fashion. His experience with dealing with the problem, over many calendar's, had him sit me down and make me say: "It it runs for a moment; it's the carb's. It's always the carbs."

Since the alternator brushes were great, charging system good, everything ignition working tip-top, ... I reluctantly pulled the carbs and found crap in the bowls ... even though the carbs were cleaned and set-up for less than a week.

We're all at the point where time has taken its toll on our bikes. Since we really cannot know what's happening within the tank and with the fuel we're buying, these days, maybe we all should install a clear, inline fuel filter and give our minds a break on issues like these.

You should also check for the possibility you might have started a crack which led to an air leak when you did those carbs recently.

I'm sure somebody will recommend you try "SeaFoam."

Weather you check for air leaks, reset the mixtures or swap the petcock out to see if its a supply issue ...

Don't do everything all at once. You might have a combination of two things ... or, only one. If you make adjustments to more than one thing at a time ... you really won't be sure what you altered was the problem and not know where to start if it rears its ugly head again.

 

Looks like you have a couple of things going on. I'm with the other gurus and suggest a colotune again. The first could have been somewhat errant due to a leaking petcock. The sludge is most likely from the YICS channel. The wet fuel from the leaking petcock loosened it up and it headed for your cylinder. I would also check the resistance on your sparkplug end caps. They should be 5ohms for #1 & 4 and 10ohms for #2 & 3. Note that this is just the caps. You will have to remove them to check them. Then check your coils while there just to be safe.
The damage to the air filter is most likely a lean carb. Lean carbs backfire through the air filter. Rich carbs dump extra fuel into the exhaust where it backfires through the muffler. This is a general rule but every time I have heard a backfire through the carb I have always enrichened that carb to cure it, then verified my action with the colortune.
I had trouble with an intermitent spark on one bike and opening the mixture screw all the way didn't cure it. So I checked the cap and yep, it was shorted. Replace it and then reset the carb which was of course very rich.

 

Re: XJ650 will only run for a few miles then quit and wont s

Thanks alot guys!!
I dont have an in-line fuel filter. The petcock is brand new, so i guess i'll do another carb clean and check it with the colortune again. Also, how do i check and adjust the float bowl levels in my carbs? Thanks again!!

 

Re: XJ650 will only run for a few miles then quit and wont s

I agree with the other Guys but for the heck of it I’d try running the bike on the PRI setting if it runs better there you greatly reduced what you have to look at. When I was having problems with a suspected fuel delivery problem I bought some clear fuel line. Using that I was able to watch the fuel dry up while in the On Position. It was neat to watch how I was able to idle without too much problem but if I brought the RPM’s up the fuel would begin to dry up cause the valve wouldn’t let ENOUGH fuel through keep up with the need. It tuned out to be a partial vacuum BLOCK for me.

 

Re: XJ650 will only run for a few miles then quit and wont s

Of course as bright as the clear fuel line might seem it was offset when some weeks later when out riding the bike started to run crappy. I flipped over to PRI ran great so I thought my problem had returned. Stopped at a Gas station on my way home. Changed the valve back to ON (so the PRI setting wouldn’t flood out the carbs while filling up) started the bike and drove away 15 min later I realized I hadn’t flipped the valve back. 8O I had just run out of gas! Oh well live and learn. (I hope)

 

Speaking of fuel filters, mine is never full and most of the time it looks like it is empty even though the bike keeps running. I dont think this is normal and as I am planning to pull the tank for some dent repair and painting, I was thinking about a petcock rebuild even though it does not seem be causing any problems.

I was I am getting ready to pack her up for the winter and I am building my list of things to do while the snow flies. Carb clean and rebuild with new socket head screws (Almost everyone has a mangled head), painting and changing my very close to the limit alternator brushes are already on the list. I will probably add the petcock just because it will be out all ready.

 

Re: XJ650 will only run for a few miles then quit and wont s

XJ650, did that new petcock have a screen filter on it?

When you look in your gas tank does the part under the fill cap look like shiny/silver? Or rusty?

Did you pull all 4 plugs and look at the electrode? What did they look like?

My guess is that you may have made a mistake that I made when I 1st used my Color tune. I adjusted till the color turned whiteish, then adjusted untill the color turned blue and left it there. WRONG!
I should have adjusted in the blue zone but more toward the yellow. Seems that I adjusted my carbs too lean.

the other thing I think it could be is the filter not being on the new petcock let trash into your needle and seats, there are screens on your seats and they may be plugging??!!??

Fuel filters are cheap insurance and a sure backup to protect your bike.

Another thing you might try is tapping on your carbs to see if there is a hung up float.

You can also drain your float bowls with a piece of tubing into a jar and see if there is trash in your float bowls.

Good Luck
Mike