South West Bikers | Motorcycle Forum

Took my L1 ZXR400 on a 50 mile run yesterday hit some traffic getting out of Bristol and was running a bit hot but got out into the countryside towards cheddar after doing decent speeds and stayed at a mates.... The next day it was cool but clear and pretty warm I let the bike warm up using the choke like usual for about 2-3 mins and set of easily sticking to 30 ish at high gears for the first 10 mins and as I got up to some national speed parts I stayed in 6th and as I gradually accelerated to about 50 and it back fired loudly with a sudden loss of power but then straight back on and fine again then it happened about 5 mins later
After this the bike seemed to be running fine and didn't do anything wrong
Any ideas?!? I know it's an old bike and it was still cold I'm also running quite a loud and large MICRON exhaust however although I haven't had it long it's never done it before?

Cheers

two things

why do you ride with gears like that ? on a 400 you want to be using the rev range, plus sitting at 30 in 6th is going to bog it down completely.

A back-fire or backfire is an explosion produced by a running internal combustion engine that occurs in the induction system rather than inside the combustion chamber. Unburned fuel or hydrocarbons ignited from a slower burning, lean fuel air mixture that is still burning inside the cylinder when the intake valve opens. Not to be confused with afterfire which is caused by an excessively rich fuel air mixture that is not completely burned during combustion. It is then ignited in the exhaust. A visible flame may momentarily shoot out of the exhaust pipe. Either condition causes a popping noise, together with possible loss of power and forward motion.(wiki)

it may need the carbs balancing but if you are going to continue to work the engine that way then is will give you crap acceleration and require you to de-coke it soon.
failing that, buy a twin, you can ride them like that.

Ah I only ride it like that because the engine was still pretty cold

I'll go back to giving it the beans a bit more then if I experience it again I'll give the carbs a go

still take it easy when cold, low gears, just be gentle, you don't want to nail it from cold as you will kill it

Generally, the advice from most manufacturers nowadays is start and go, just take it easy until the temp starts to rise. A bike sat still running on choke can be just as bad - the rich mixture in a cold engine wash's any residual lubricants out of the bore's, wearing the piston rings .....

As Simon says, run the bike under light load, using the gears to keep it happy - just don't thrap it to the red line or make it slog in a high gear until the temp is up.

From what you say, the backfire was probably due to slogging in a high gear requiring a larger throttle position and ending up with a rich mixture in the exhaust ..... the engine then "coughed" to clear itself.

Oh, and in my (limited?) experience, twins don't really like being slogged either (except mebbe Hardley's), it's just that people seem to think thats what they should do ....

Never having had the chance to 'slog' any twins I'm rather jealous Moose , crazy nights in Newton Abbott eh ;) ..............