Backfiring and not running well at all

[entoria]

Last week I went for a great ride. Bike was running well (apart from clutch problems... need to look in that still). The when I went to start it the next day it was backfiring loudly and loping really badly as it if it was not running on all 4. I pulled the plugs and gave them a clean. Disconnected plugs and made sure there was arching when I put it near the frame so I know I got spark on all 4. That didn't change anything.

So I pulled the carbs and gave them a good clean with compressed air. Put them back in an still no change. All header pipes get really hot except number 4 which gets hot but I can still touch it with my hand without getting burnt.

I also did a compression test and they seemed to be within spec.

Why would it suddenly not run right and backfire? It is hard to rev it and the throttle response is really weak. Increase the revs and it backfires out of right hand side tail pipe.

Any suggestions?

 

[Jarney]

Sounds like you've covered most everything. Only thing I could suggest would be to swap plug wires/coils/plugs from cylinder to cylinder and see if anything changes or check the fuel flow/tank for dirt/air filter/carbs again for dirt. Good luck. Later.

 

[entoria]

I was thinking of putting the stock coils back on it again as I have been running the stick coil mod with great success. Usually a backfire means that fuel is getting in but not detonating but then suddenly it does and so you get a bigger bank. I was wondering if I had a stuck valve or something in that area but a compression test came out fine. I will also check out valves to see if adjustment is within spec or that pick-up coil is good. Any other suggestions would be most appreciated.

 

[salamander]

Going (at least part way) down the fuel, air, fire path ...

You seem to have the fire since you have spark on all 4 plugs, and Jarney's idea to swap things around will help to confirm that. As you swap around, the backfiring might not change, but the cool cylinder might, so just be sure to check the headers each time, too. If the weak cylinder seems to follow a particular plug cap, check for arcing between the cap and plug well wall when the plugs installed -- I'm wondering if having the plug out of the well for your spark check you might have no arcing and so a strong spark, but in the well the arcing weakens the in-cylinder spark.

+1 on Jarney's suggestion to check the carbs again, especially if the plug swapping doesn't give you anything useful. You might could get an idea of whether you're getting enough gas into the weak cylinder by disconnecting all the plug wires (so the engine won't take off no matter what), removing the plug from the cylinder you want to check, and turning the engine over with the starter -- see if the gas smell is strong from the plug hole. No open flames around for this, though! If it does seem to be a fuel problem, a carb cleaning with more than compressed air might be needed to get at the small passages.

Since there only seems to be one weak cylinder, the only air related thing I can think of would be a vacuum leak on the weak cylinder's carb -- it seems like that would have to be one heck of a leak, though.

Good luck.

 

[SandstoneSmitty]

... when I went to start it the next day it was backfiring loudly and loping really badly as it if it was not running on all 4. ...

Check for exhaust leak.
My backfire problem came from the seals between the header and power chamber. I did this cheap and easy to fix about 2 or 3 years ago. My ‘Lil Girl’ runs solid with nice low harmonics. </SPAN>

 

[entoria]

I will check for exhaust leaks next. That makes sense. Thanks for that suggestion.

 

[entoria]

Still no luck! Cylinder 4 is cold and the bike just won't pull so I figured that number 4 is not firing. Here is what I did today but not change

I took out the stick coils and put the original coils back in - no change but it is not backfiring anymore
I took off radiator and made sure exhaust header bolts were tighter than a nun on a Sunday - no change
Replaced the CDI with another - no change
Replaced the pulse coils with another - no change
Took off the carbs and blasted them with compressed air and then balanced the carbs - no change

I am wondering if it is a stuck valve or something in that region.

As I originally mentioned, it was running great the one day and went on a good ride. The very next morning when I started it, all the problems began.

Anybody got any ideas? Heeeeellllp?

 

[paulfun]

Just blowing compressed air threw the carbs wont always clear a plugged iddle circuit. If you havent removed the pilot jets and adjustment screws and ensured they are clear along with the progression holes your carbs might still be the culprit.

 

[entoria]

Yes I am thinking that may be the case. I was revving it today and then I heard a pop and the little plug that gets put on each carb body when the emission crap is removed got shot up into the air. I will put the carbs off (again) and do a thorough cleaning on it and then report back.

 

[entoria]

OK, still not working. I pulled off the carbs like I have done so many times and stripped them down. Used carb cleaner and compressed air plus the e-string off a guitar to make sure there were no blocked holes. Put put them back on and fired her up. She starts but still not firing right as cylinder 4 is cold and now so is 2.

Here are a few questions:
Could a loose connection in the headlight cause this?
Could incorrect valve clearance cause cylinders to misfire?
Could a fault in the fusebox cause this?
Could a stuck valve cause this?

I am running out of options and fast. Please can someone throw in some more suggestions. I am getting desperate.

Many thanks

John

 

[jrrenfrow]

Just had my carbs done by Rick. Better than new now. His work is awesome. He even added a missing choke mount and no extra charge. Best $180 I ever spent. Go Oldskoolcarbs.com and check his work out.



This link has picks of my zl1k carbs he rebuilt

http://s591.beta.photobucket.com/user/wildmanv65/library/1 2011 xs1100/zl1000 13


Rick West "OWNER" http://oldskoolcarbs.com/
Rock Hill, SC
phone 803 412 1781
WE REBUILD ALMOST ANY TYPE OF VINTAGE OR NEW MOTORCYCLE CARBURETORS

Rick West
1536 Glasscock Rd
Rock Hill, SC 29730

 

[entoria]

It is easy for you guys living in the US to just send your carbs to Rick. However, living here in New Zealand would cost me an absolute fortune to sent them there and back plus the cost of repair would be able $400 NZ and would not be worth the money. I know my carbs inside and out and could even rebuild them with my eyes closed because I have done them so many times. I know every nook and cranny in these and have also had them ultrasonically cleaned with parts replaced. I know when my carbs are acting up and I am pretty sure it is not this time. I have now gone through them 3 times in the last week so I am almost certain it is not them. Carbs are really not that difficult or a big mystery. I can bench synch them and when I put my gauges on them when they are back on the bike, I am usually spot on. This is not anything against Rick as I know he does a superb job. I am just confident enough to redo my own as I have been rebuilding bike carbs for about 15 years now.

 

[Jarney]

If you are sure of your carbs and tank or don't have spares to swap out to eliminate them as the problem, I would check the valves next - even though compression test came out good. I don't see the fuse box causing this problem - not sure what else this could be. Checking the connections throughout the bike and in the headlight would be good and easy to do regardless. Good luck. Later.

 

[entoria]

Thanks Jarney. I will check the valve clearances next.

 

[rkerg]

My 900 was backfiring once and it turned out to be the red connector under the tank on the right. It was half way connected so the bike would run but not very well.

 

[87kawzl]

Try blowing on the carb vent tube to the check valve. My check valve was all plugged up, I cleaned it with carb cleaner, ez enough and worth a shot.

 

[entoria]

Yeeehaaaaah!!!! She lives again. I checked the valve clearance and that was all in spec. Fired her up and cylinder 2 was still not firing. I had done everything I could think of. And then it occurred to me that each time I pulled the spark plugs out, I would put them back in the same cylinders again. So I swapped them around and the cold cylinder moved to another one. Now I knew what the problem was. For 17 years I have been riding and never once did I ever had a spark plug go bad.... until now. Now onto the next problem. The thing with this bike is as soon as I have fixed one problem, then another immediately crops up. Next is to tackle the clutch problem and also kick stand switch is now playing up.

Many thanks to all those who offered advice.

 

[madmanncr500]

Glad to hear it!!! Kick stand switch...took mine off and wired the two wires together...if your that numb minded to forget to put up the kick stand..then ya dont need to be riding at all!!( not you im just saying)...whats up with the clutch!!??

 

[entoria]

The clutch is not properly disengaging when I pull the lever. It creeps forward and if I put the brake on to stop it, the bike stalls. I think I am going to have to pull the clutch cover and check the plates for wear or if they are sticking together. I have another post here with questoins relating to that.

 

[madmanncr500]

Have you tried flushing the clutch system out? Alot of times that gets over looked and never changed...i know when i got my 900 the fluids looked like mud!! try that..