Is backfiring a bad thing? and a couple smaller questions.

[MrGiggles]

As I'm sure a lot of you guys have seen, I'm constantly fixing and tweaking my '99 Bayou 220. For the most part I am just about done, the only thing engine wise that needs to be fixed is the muffler. It runs like a top, and drives great.
Things on my agenda:
1. Get new collar and seal for exhaust
2. Weld rear section of the exhaust pipe
3. Check valve clearance
4. Check rear-end gear oil
5. New tires and wheels (later)
6. New paint (possibly)


Now, my question is, is backfiring necessarily a bad thing? It does it all the time, when you rev it up real fast it backfires on the way back down to idle. It also does it when you are driving and drop the throttle it pops several times until you get back on it. I don't think this is a problem, but I would like to make sure.

My second question is how do you check the gear oil and what kind of oil does it take?

Thanks.

[RCW]

Backfiring being good or bad is something for which there is a straightforward answer.

If your muffler is open to the world and not providing adequate backpressure to the engine, then backfiring can be an indication of a seriously lean condition - if it backfires as you are pulling hard.

If it only backfires when you let off the throttle, and never under load, then it is simply excessive combustible gases building up when the air supply to the engine is shut off. That is not a problem for the engine.

Random backfiring with the throttle at a fixed position would also be a problem, and is generally too tight or burned valves.

I would normally expect a well tuned Kawasaki 220 to backfire just after I let off the throttle on a hard run, especially if the engine had quite a bit of use, and there was no muffler.

[MrGiggles]

It backfires right after you let off the throttle, never while you are on it.

The muffler is on there, but it leaks a lot in the front and where the pipe and muffler join.

And also, I thought that back pressure was only important on 2-strokes? I wasn't aware that it affect 4-strokes. I did notice, however that when there is no pipe at all on the engine I had less torque, but I never ran it long like that.

[86klf300guy]

back pressure is a must on 4 stroke unles you have a race engine above 12.1 comp even still it needs a little bit 2 stroke uses less it uses a freqency that is y the racein bikes have a camber .when you repair that exhaust system the backfireing will subside greatly youll get one or 2 little ones after a hard ride ....say if you have a stock motor in your car and you take the converter off and straight pipe it you will notice more backfire and lack of power and fuel drop same for the quads you have to have a certain amount to help the pressure in the cylinder balance out sumthing like that ...its hard to explain i went to school for engines etc and it been a while...and the size pipe that is used from head to muffler on a 4 stoke can give or take tourqe ..i just put a ewhite muffler on my 300 but i made a hole new header pipe due to the ewhite is 1-7/8 in dia and my old one was 1-1/4 and now i notice it runs cooler and more peep at bottom and top end i also had to rejet it becuase it leaned it out a bit ....keep us posted on the repairs sounds like you about got it beat ;-corey/

[RCW]

A four stroke is just as dependent on balancing air flow as is a two stroke. They do have a wider range of tolerance, but still require a balance to keep them running with the proper air to fuel ratio. From what you describe I suspect it is OK.

On your differential, there should be an aluminum alloy inspection plug with a hex right up on the back of the differential. It is a large round filler plug with an O-ring seal. That is the filler and the inspection plug. Fill with GL-5 90 wt so the oil just begins to be level with the low side of that hole.

It is important to use GL-5 or better rated gear oil to keep from blowing all the oil out the vent hose.