full throttle misfire

[holla]

Hi all, after putting the new airbox rubber on the RD03 and making sure there were no air leaks i went out on it last weekend i noticed a small misfire once but thought nothing else of it........................

however i went out on it today and on 3/4 to full throttle it holds back and misfires. i was about to fit a new fuel filter and whilst the tank was off i decided to put the old plugs back in in case it was a plug problem................ it wasn't !!!

any ideas ????

do you think that the mixture is wrong now there is no air leaks ???
i checked the plugs on a plug chop and all 4 were nice and clean, by making the air box air tight it would make the mixture slightly richer if anything but the plugs didnt show this.

could it be a coil, i hope not as this could prove difficult to diagnose,

my next thing to look at will be to remove the carbs and remove the float bowls to see if theres any crap in there, i'm hoping that something has partially blocked one of the main jets. i've never had the carbs off before and wasnt going to touch them until i strip the bike down in the winter but now i have no choice.

is there anything i should know regarding removing the carbs/disconnecting cables etc etc.

thanks

[AlanH]

is there anything i should know regarding removing the carbs/disconnecting cables etc etc.

Make sure you are in a good mood when you start. It's one of those jobs...

Actually it's not too bad really but some bits are a bit fiddly. Take a photo of where all the cables go first. It may save you a headache later.

[YEN_POWELL]

You haven't trapped a fuel pipe have you. A small pinch will let enough fuel through for lower revs but not enough for higher.

[tedmagnum]

Could be the fuel cut off off valve in the carb... Lets enough drain through for lower TP but not enough for full throttle action..

Misfires are usually a dirty carbs, incorrect jetting, bad coil, blocked air filter or fuel starvation...

Have you got a friend who will let you try their coil ??? There are ways to check your coil if you have a multimeter ???

probably not the coil though if its only occasional misfire.


Pain I know, but its just a case of trial and error im afraid...

[holla]

Thanks guys,its not the air filter as its new, The fuel pies are reasonable but i might order the one from the left side fuel tap (as your sat on the bike) to the t piece, It bends at 90 degrees at the end and isnt too good.

Do you think the choke will be ok as they arent seized up and are clean inside when you remove the plungers, The choke lever flicks back about 1/3 then you have to push it back for the remainder ( is this working normally ??)

If theres any doubt with the choke, i'll order 2 blanking plugs off wemoto and the fuel pipe/pipes and see how it goes.If that doesnt work i'll strip the carbs and have a look inside, I think i'll order new float valves before i strip them down if thats the case.

Thanks for all your help and i'll keep you informed

Ian

[holla]

One more thing i just remembered,when i removed the air box (the bit that sits below the tank) The rubber that connects to the right carb that pushes into the plastic airbox was all siliconed in. I removed all this and cleaned it up expecting it to be split somewhere due to all the silicone, but there was no splits and it fitted perfectly without the need for more sealer to be used when refitting.

It doesnt need siliconing in does it??

What i think i'll do is set up a remote fuel tank and start it up and spray wd40 around all the connections to see if its an induction problem.

If you can let me know if the rubber needs to be siliconed in i'd be very grateful

Thanks

Ian

[GSPD750]

One more thing i just remembered,when i removed the air box (the bit that sits below the tank) The rubber that connects to the right carb that pushes into the plastic airbox was all siliconed in. I removed all this and cleaned it up expecting it to be split somewhere due to all the silicone, but there was no splits and it fitted perfectly without the need for more sealer to be used when refitting.

It doesnt need siliconing in does it??

What i think i'll do is set up a remote fuel tank and start it up and spray wd40 around all the connections to see if its an induction problem.

If you can let me know if the rubber needs to be siliconed in i'd be very grateful

Thanks

Ian

NO silicone. The clamps require light torque so that you do not pop
the rubbers off. That is the key...not too tight. Just snug so that it almost feels loose. Silicone is not a good idea as pieces could get sucked through the carbs later on. Maybe a very thin layer of silicone lube (non-curing) or petroleum jelly (Vaseline) applied to the inside lips of the rubbers to ease install and help seal. Not too much so that it will attract dirt.

[holla]

is it possible that the fuel pump could be faulty at higher revs or would it either work or not work ??

my thinking was if theres a diaphram in there it might have a hole/split in it and under light use its not noticable until it pumps at a higher rate then it doesnt pump as much as it should ??

could this be true or am i talking complete bollo*cs ????

let me know

thanks

Ian

[holla]

Today i changed the choke cable and new exhaust gaskets and it still misses at higher revs. I came back and isolated the fuel pump.............. still the same I think i might replace the float valves next.

tedmagnum said there was a way of checking the coils with a multimeter.............. how do i do that ?

there are no air leaks as i've rigged up a remote tank and whilstr running it sprayed carb cleaner around all joints and revs dont change.

so far i've:


- Replaced all exhaust gaskets

- Isolated fuel pump

- Fitted new choke cables

- checked for air leaks

- Fitted new plugs, air filter

- cleaned carbs

whats next ???


Thanks

[YEN_POWELL]

How about the fuel tap, maybe it's clogged. I'd try riding with the tap set to reserve first in case the fuel gets round a possible blockage that way, if it was still the same I'd check the tap by removing it and looking at the internal filter. Have you replaced the inline fuel filter?