Bike problem can you shed some light

LB’ers outside of what happened to me can some one shed any light on this one.

Was going along on the bike, and at about 5k revs it starts julting (as if choking) I found if I cruised at 4k revs was fine but over 5k julted again… managed to get home slowly but any ideas why this might be happening?

Thanks in advance.

…not a mechanic or anything, by any stretch of the imagination… but mine did this on the motorway - in the heavy fog… eventually it stalled… and i coasted to the hard shoulder… and it started up fine, it was crappy untill the fog lifted - stupid 'ehh ?

I’d guess at dirty fuel lines, dirty fuel (happened to be before) or airfilters need changing… something like that ?

if it was affected by fog, why would the fuel lines spring to mind?

Maybe the airfilter is taking in too much moisture into the mix.

I’d go along with Oli’s advise. Basically your air filter sifts all the small bits of dust out of the air and stops them going into the engine, when it gets wet then theres less space for the air to get through the filter, so the engine chokes.

Could be an air filter problem, the harder an engine works the more air it would need, this means at higher revs the air fuel filter would be worng and may splutter or backfire. Try cleaning or changing filter.

is it an older bike? maybe carb icing?

yes it is anolder bike, someone mention a spark plug to me could this cause the problem?

that wouldn’t affect it at differing revs, that would be a constant cough/splutter/cough/splutter/stop.

it may have conked out I just dont know it started spluttering so I pulled over straight away…

it may have conked out I just dont know it started spluttering so I pulled over straight away…

now that does sound like the biggest load of bollox ive ever heard…

Symptoms sound like Carb icing, used to have it on the ZX7 but only in October and March. Wind chill brought temp down too much, the thermostat on the carb heaters was in a warmer place and didn’t open. Carb Icing is a massive problem if you get it.

This sounds like a mixture problem. You should have an idle jet and a main jet at least in the carbs. The main jet will probably not really kick in until about 4000 revs. I would hazard a guess that you have an issue with fuelling through the main jet if its not the air filter. This could be caused by a blockage or even by a fuel filter problem. Not sure if you have a tap on the tank, they can cause problems as well.

thanks, wanting to sae some money if I can where is the air filter on a Honda NSR, I have not raken the fairings off as yet so maybe a case I will see it once taken them off but any ideas?

Under the tank, in a big black plastic housing.


carbs Icing ( warm up)

Water in fuel (refill)

Water in carbs ( sucked in from carbies) check pipe

Cracked/eroded HT leads ( check at night for sparking in dark environment & replace if required)

naturally check fuel lines are not restricted in any way- have you had the tank off??

At your earlies convienience, put in an INLINE fuel filter- simple to fit and will help reduce some future fuel problems

Kind Regards