Bad running

[sirloveyou]

Hello
Need some help
My firestorm has been running really crap & lumpy for a little while now, basically at full throttle it is ok but holding a steady throttle it jumps & misses and applying the throttle it's very hesitant !
I took it to a local garage where it was dynoed the carbs were set up, timing checked & valve clearenes checked, it definitely needed the tune up, revs alot cleaner etc but when warm still misses, pops and judders.
The garage thinks its a electrical fault ...
Has anyone else had a fault like this or is there a common issue that would cause the poor running ...
Any help or advice would be greatly appreciated
Thank you
Daniel

[benny hedges]

surely an ignition fault would show up on the dyno?

or has it started doing this after the dyno work?
if it was after the carb work maybe a carb diapgragm was pinched when it went back together?

sounds like its an issue with timing advance though so first thing id suggest is look under the tank on the right hand side, at the rear carb linkage and check the throttle position sensor is plugged in.
to test if the tps is working you will need the tank off (easier with airbox off too) get a multimeter set on ohms and measure the resistance between the top & middle pins on the sensor (not the plug lol)
it should be 500ohms or less

when you open the throttle, the resistance should increase smoothly and snapping it shut, it should return to the original reading.
could wel be its fkt or someone has tried modding it and broke it.

other things responsible for timing advance are the coolant temp sensor - (not the fan switch) so is the temp dial stable or all over the place?

then check the wiring under the seat, near the tail light.
very often it can get wet under there and water can get in the loom and in the connectors.
unplugging and plugging back in works wonders!.

the big 16pin connecter is the icm (ignition control module) which calculates the advance and sends readings back to the clocks and passes current to the cdi, which is the smaller unit on top of the icm.
you need to check these are all plugged in securely with no wet / corroded contacts.

check the earth connections.

in a dark garage, with the bike running, check for the ht leads arcing under the front of the seat on the right, and under the front of the tank on the left.

also bridge out the sidestand switch as this has stumped a few owners in the past, with the same symptoms.
failing that you'd be as well hooking up with another owner and testing parts by substituting with a known good spare, ie coils, icm, cdi.

it might also be worth you draining off ALL the fuel and adding fresh.
its possible you have got a bit of water in the tank or bought fuel contaminated with water - this would also give the same symptoms.

have fun - and report back

[sirloveyou]

Thank you very much for your detailed reply !
Looks like me, the storm & my multi meter will be very busy this weekend !
I'll post my findings and fingers crossed she will be thumping sweet again

[sirloveyou]

got the bike stripped
tested the tps sensor reading 800+ohms, also as u turn the throttle the resistance builds but as u go past 1/4 throttle the resistance disappears !
So I guess this is the issue !
Looking on lings this is a expensive part !!!
Thank you very much for the info !