intermittent running issue

[shaneo]

having an issue with the rvf which is doing my head in.

fri night rode the 30km's on the freeway to my partners work, no issue. on the way back, after about 5kms, it started missing, losing power etc, consistant with running out of fuel. tank was full, fuel filter was full, everything seemed ok. Pulled over to let the bike sit, fires up fine after a couple of minutes.

Take the backroads home so im not on the freeway. 20 mins later is does the same thing. excepet this time, it wont sort itself out after sitting for a bit. get home grab trailer and headback to pick it up. try to fire it up, no dice.

Wheel it to the back of the trailer and then try again, just cos. runs 100% perfect. huh??

sat, strip carbies and clean, clean fueltap and new fuel lines and filter. also pulled out sparkplugs and cleaned them as well. they werent coked up or anything. double check tap operates ok, no worries at all.

on the way down to Phillip Island sat arvo, after about 40 mins on the freeway, its starts misfiring and carrying on again. i keep a constant throttle and after about 5 mins, it doesnt do it again. on the way home last night, starts misbehaving again but a minute later its fine and stays fine.

does anyone have any idea what else i could look at?

keep in mind:
- carbs cleaned
- fueltap cleaned and tested
- new lines and filter
- cleaned sparkplugs (<2,000km on them)

[magg]

What's with the "new fuel lines and filter", filter should be part of the tap.

Sounds like an electrical problem. Fuel issues usually give a loss of power not a misfire.

Do the lights etc. function ok when the engine misfires?

Can only suggest you start by checking the condition of all connectors associated with the ignition system, broken wires can be intermittent and not visible under their insulation, and then measure the voltage at the ignition control unit.

Also worth checking the battery voltage with the engine running just to eliminate the charging system.

[shaneo]

What's with the "new fuel lines and filter", filter should be part of the tap.

Sounds like an electrical problem. Fuel issues usually give a loss of power not a misfire.

Do the lights etc. function ok when the engine misfires?

Can only suggest you start by checking the condition of all connectors associated with the ignition system, broken wires can be intermittent and not visible under their insulation, and then measure the voltage at the ignition control unit.

Also worth checking the battery voltage with the engine running just to eliminate the charging system.

theres the intank filters but i run an inline filter as well for piece of mind.

oh there was a loss of power. i had to use full throttle to keep the bike moving.

yup, all lights work with no noticeable dimming,

Battery voltage measures 12.9 at idle and around 14-14.2v at rpm.

[Neosophist]

if the vaccum pipe is collapsing it will shut the fuel off and youll get that missfire / running out of fuel symptom.

I had that many times.

[shaneo]

if the vaccum pipe is collapsing it will shut the fuel off and youll get that missfire / running out of fuel symptom.

I had that many times.

i didnt even think of that! cheers, ill look at modding the tap.

[Ben_OB1]

No need to (HRC) mod the tap dude, just get a new vacuum hose - no big deal really!

Ben.

[Cammo]

Adding an inline fuel filter can cause issues like you describe. The carbs are gravity fed which is only just capable as standard, you don't want any sort of filter slowing the fuel flow.

Each carburettor has a gauze fuel filter, no need for anything more.

[pip]

Filter & vac have been covered, it's also checking the tank vent.

[shaneo]

thanks for the ideas.

OB1: it is a new vac line. mind you its a pretty soft line.

Cammo: there has been a filter inplace since ive had the bike, i might try ad run it without.

pip: thanks, will do.

[Jarlly]

Sounds a bit like mine currently- it'll inconsistently run out of revs anywhere between 10k and 14.5k. I've rebuilt the fuel diaphram and replaced the vac line (with a super-thick one) on mine to no avail. Tank vent is next on my list.