High idle at times.

[KB87]

Hi there, im new to this forum and new to biking i guess, well big bikes anyway! I've not long passed my test on a 125 and bumped up to a zxr400 about a week ago. Love the bike to bits and havent had any problems at all. My issue is that as i come to a stop say at traffic lights my engine will be idling at around 2k revs, smells really rich too. If i let the clutch out slightly just before stalling it the revs drop back to about 1400ish and is fine and doesnt smell anymore either, It is restricted to 33bhp maybe this could be casuing it? i cant say i know a whole lot about the mechanical side of bikes and would like to get an opinion before maybe taking it to a garage and if its even worth taking it to garage for something so small?

Thanks in advance.

[RedexRobB]

Hello and welcome to the forum

The idle should be about 1200rpm. But the problem you describe is a problem alot of people here have, and its usually caused by the inlet rubbers that connect the carbs to the engine.

What you can do is get the tank and airbox off and spray carb cleaner round the inlets. If the revs change in any way, its more than likely the inlets. What happens is they suck in air and leans the mixture out causing the engine to rev slightly. You can try taking them off and using sealant on the flat edge and round the outside of the inlet itself. Otherwise you may need another set.

Hope that helps

[cargo]

Something has just occured to me

This rev hanging thing seems very common...................I wonder is it possible that because of the restricter washers fitted between the rubbers and the cylinder head that it is the fault of the washers being there that causes the air leak and therefore the rev hanging.

The rubbers have an "o" ring to make the seal with the head but the washers don't (or do they ?)

Also for bikes that don't have restrictor washers could it be that the "o" rings are just old and dozed ? once again causing the air leak. Those "O" rings are in a fairly unpleasant envoirment with heat and petrol fumes ?

Just thinking out loud

Have to say if my bikes do it I've never noticed but then I keep the tick over a little higher than would be normal on a road bike

[RedexRobB]

your absolutley right cargo, those washers dont have an o-ring between the head and the washer. So that is more than likely the cause if someone hasnt had the idea to seal them already

Replacing those o-rings first would be cheaper than the inlets to start with aswell.

[KB87]

Thanks for the replys guys i will definitely give this a try soon.

[TOMY]

Mines restricted via washers and has exactly the same problem. so yeh could be a intrinsic flaw with the washers sealing