Back Firing but Different?
 

First up...a great site and very helpful.
Second..Thank God I didn't see this site before I bought my second hand 94 XT600E....amazing how many things can go wrong.
Third.....until recently I was really happy with my bike.

It has only done 34000 kilometres and most of the riding I've done is around town..usually with a three quarter full to full tank of Premium Unleaded petrol.
With that sort of riding it hasn't missed a beat BUT...
on the last 3 extended rides I have experienced the 'back firing' and surging symptoms referred to in many of the 114 pages of threads I've just read.
My problem may be different to others in that it tends to happen when I have travelled between 60 and 70 kilometres...and quite unsettling when the last two instances occurred at the exact same place...on a flat piece of road doing around 115-120 kmh.
I've started each ride with a full tank of petrol.
It has been suggested that it could be the 'strainer on the Reserve' and that it is blocking causing fuel blockages. It was suggested that short rides around town with a near full tank would see any sediment 'sloshed around' and not being a problem and that longer flat rides sees the strainer(filter?) blocking.
How would I check this?
Does it require me to remove the fuel tank?
If this isn't the case I'll have to go down the many paths cited in the threads I've referred to: perished inlet rubbers, kickstand safety switch, blocked petrol cap breather, float needle filer(?), etc.
Thanks for your help.
Mick

Also, reset your carb settings to standard!

That can also be a few other things...

bad connections at the "ECU"
cam shaft not correctly aligned



Check'em all! Have fun!

Vando :cool4:

surging
 

hi mate daft question but have you tried a new plug:thumbup1: or checked the gap good luck

Do the basic things:

Fresh plug
Clean/replace airfilter
Clean carb

Also, take the tank off, remove the tap and make sure the filters on the tap are clean. It would also give you the chance to clean any crud out of the tank itself.
By the way, I wish I lived in a place with a name like Wagga Wagga. Dartford just doesn't have quite the same ring to it!

Geoff

Thanks so far...will have a crack at all of the above..although the plug is only recently fitted.
How hard is it to get the tank off?
Can you reach filters, etc without removing the tank?
Thanks
PS Any time you get to Wagga Wagga give me a call...61000 population...great place to live.

Remove the two bolts under the seat, then take the seat of. This reveals a nut on the tank, off with that, take the fuelline of, and you can rock the tank of. Pull up in the bottom part of the tank, and rock it backwards. To ease installation, spray wd40, silicone oil or just abaout anything, on the two (one in each side) rubberpads on the frame, which the tank rests on.

When you have the fueltank of, inspect the backside of it, they are usually not coated aswell there, so they rust a bit easier.

Thanks Jens

Drain the tank, with the tap in the reserve position, into a can. Place tank on a bench/desk/ironing board/whatever, but upside down so you can access the two bolts which hold the tap in. (Use newspaper or something to protect the paintwork.) Ease the tap out of the tank, hopefully preserving the gasket between it and the tank. Clean filters and tank with some petrol and reassemble. Sit back and enjoy a cuppa and a ciggie, job done. Thinking about it, maybe not the ciggie! :rofl:

Geoff

Heading into winter down here..I'll make sure I've got a fire going while I clean the tank!
Thanks for the help.

Even if its a NEW plug - try another NEW one - they are mass produced and not of the best quality now-a-days.

Is your fuel tank filler cap - breather clear. If its blocked it'll effect the running more at higher revs. Also, check carb manifold rubber for cracks/splits & tightness.

Could be one of a number of things.... Good luck!

Another 2 cents of advice
I suggest you give more diagnostic information
You state only that you have 'back firing' and surging. and travel 60-70 km at 110 Kmh.

What throttle position?
Were you accelerating or decelerating or constant speed?
Are there large altitude changes on this ride?
If you change throttle position what happens?

Typically if fuel supply is an issue you can get only so much throttle and any further advancement will cause the power to fall off rapidly with a increase in intake noise.

As checking for plunged filters and such I would simply loosen the screw at the bottom of the float bowel , capturing the fuel into a container and calculate fuel flow. you should be able to flow close to 4 gallons per hour (sorry for the US measure) you can time it and calculate it no need to sit there for a hour.

OK if all is good? I suggest you change the needle position on the primary carburetor. the needle needs to be raised.

There is a possibility of a ignition issue but In my experience it is easier to rule out fuel first (other than changing spark plug first)

I have had more ignition issues than carburetor in my 26 years of ownership of a TT600

I have had a similar incident that you describe and it was the trigger coil on the outside of the flywheel it would go open and closed with temperature causing it to go to the secondary retard pickup, happened near the same location every time (due to heat soak I suspect)

Good luck and let us know what you find

























/

Still checking
 

What throttle position?
80%-90% (Weight on Board 115kg..250lb)
Were you accelerating or decelerating or constant speed?
Gradual acceleration
Are there large altitude changes on this ride?
No..flat all the way 300ft asl
If you change throttle position what happens?
Ease off throttle after backfire/surge and bike regathers momentum

Typically if fuel supply is an issue you can get only so much throttle and any further advancement will cause the power to fall off rapidly (YES) with a increase in intake noise(Can't say).

Thanks...still checking.

Yes definitely sounds like lean to me.
did you say how fuel cap is vented?
if not a direct hose type that is easy to check, i would loosen fuel cap when symptom occurs. there are emission type caps that might fail closed?
carburetor vents might also be a possibility.

My KTM 640 let me down last week. Rolling on the throttle it would sputter and die. some times its would start back up...sometimes it would try then back fire out the exhaust leaving the smell of fuel in the air.

The problem turned out to be the connection between the spark plug cap and the ignition wire. They easily pulled apart. I trimmed about 1/4" off the wire and twisted the spark plug cap back on. The bikes been running great ever since.

Good Luck!

daryl