Help required

[seth]

Not my bike but trying to help a mate who's having problems
The bike is tuned yoshi cams ,pod filters ,power commander.
It has run very well untill recently but had developed a slight miss fire when it gets warm at about 2000rpm or when given a handful mid range butbonky when it gets warmed up .
The bike runs prefect when cold ,
Seams a heat related fault but can't pinpoint it

So the guy has changed
Complete fuelpump assy (new)
Tps (new)and set up
Stps (not changed but set up and was Mile's out before)
Starter relay (new)
Starter motor (new)

Doesn't make sense so looking for any suggestions
Thanks

[KiwiCol]

Would sticking it on a dyno show what's happening perhaps?

[gsxbarmy]

Plugs? Coils? HT Leads/caps?

One other thing to check - coil brackets. I seem to recall someone having a similar problem years ago on the old org and it was a fractured coil bracket. Don't the coils earth out through the frame?

[Eric GSX1400K3]

My thoughts would be:
1) stps, the tracking on the sensor sweep could be worn, but usually not heat related.
2) stva system, i.e. the magnet inside the actuator if still fitted?
3) oil temp sensor, I recall Hooli had an issue with his causing it to use a lot of fuel.

[seth]

Thanks for the info so far all good stuff to check
Just to confirm the bike runs perfect when cold and at higher revs when warm only has this missfire 2k-4k revs as the throttle is opened when it's warmed up soon as its past those revs its clean and smooth untill it drops the revs again 🤔

[Hooli]

I'd vote oil temp sensor too, it's the main control for the fuelling changes as the bike warms up. There's approx test values for it in the manual, so dead easy to check as the connector is under the RH side panel (two wires, Bl & Bw I think).

[dave55]

Clean and gap the plugs, better still try another set in, then HT leads and caps. I have had similar fault and was plug breaking down when hot and under load.

[Mick_J]

I had something similar happen to my bike, I changed the plugs, coils, air pressure monitor and I checked the air temp, oil temp and all hoses but it turned out to be the TPS.  I know he has changed it but that's no guarantee.  Bike started perfectly when cold and ran smooth, once hot it would run fine at higher revs but like a pig at tick over (If it ran at all at tick over). I used to turn up the tick over to ensure it didn't stall so I could get home.

[seth]

I had something similar happen to my bike, I changed the plugs, coils, air pressure monitor and I checked the air temp, oil temp and all hoses but it turned out to be the TPS.  I know he has changed it but that's no guarantee.  Bike started perfectly when cold and ran smooth, once hot it would run fine at higher revs but like a pig at tick over (If it ran at all at tick over). I used to turn up the tick over to ensure it didn't stall so I could get home.

Hiya buddy
The bike runs perfectly when it's cold
The current thinking is plugcaps and or coils as a next step (hopefully this weekend)
The biggest problem is he's near London and I'm in Scotland so can't just swap bits from my bike to his untill the fault goes then just replace the faulty part or fix the problem

[Mick_J]

I had something similar happen to my bike, I changed the plugs, coils, air pressure monitor and I checked the air temp, oil temp and all hoses but it turned out to be the TPS.  I know he has changed it but that's no guarantee.  Bike started perfectly when cold and ran smooth, once hot it would run fine at higher revs but like a pig at tick over (If it ran at all at tick over). I used to turn up the tick over to ensure it didn't stall so I could get home.

Hiya buddy
The bike runs perfectly when it's cold
The current thinking is plugcaps and or coils as a next step (hopefully this weekend)
The biggest problem is he's near London and I'm in Scotland so can't just swap bits from my bike to his untill the fault goes then just replace the faulty part or fix the problem

London is bit too far for me to travel to help, hope he gets it sorted soon, you never know we might still get some dry days this year.

[Hooli]

Another thought - SPS.

When the bike is cold it'll be sitting in a different position as the secondary throttles turn backwards to do the fast idle. I believe the secondaries fully open at 3.5k, not sure when they start to open, but 2k seems reasonable?

[seth]

Thanks for all the info and ideas of what could be wrong with my friend's bike.
We finally got to the bottom of it all.

Firstly we think he had a dirty fuel filter/teabag problem so that was all replaced but at the same time he replaced the clutch switch for a brand new one remember this .

The bike still had a very bad missfire as it warmed up (ran perfect when cold and at above 5k rpm)
So he chased the problem changing and setting tps,stps and replaced cam position sensor also replace (2nd hand a set of indicators and coils)
After all this the bike was no better and he rechecked the new clutch switch it was sticking in all the time.
Replaced it again and noticed his leaver was pressing way to much on the clutch switch.
Modded the leaver to give e the switch more room and hayho fault is

So we think the original problem was sorted quiet quickly but the clutch switch caused all the rest of the problems.
The original clutch switch was a bit worn so probably just about coping with the leaver travel as he has h/d clutch plates fitted .
So to finally sort everything he's going to refit a standard set of clutch plates to reduce the leaver stretch and make things more standard to give the clutch switch an easier life too.
The bike I'd tuned and has yoshi cams ect.

We were so stumped as I'd never seen any like this problem before and it was all down to the clutch switch.
I'd be very confident the same would happen if anyone "bypassed" the clutch switch 🤔

[Hooli]

When I bypassed the clutch switch on mine years ago it'd double backfire & cough every time I wound the power on. Used to drink like a fish too. So I can well believe it's the source of all the problems.

Are they original levers? I've got cheaper lookilikey ones on mine & I had to grind the clutch one down a touch as it was always too far out, oddly enough the brake lever needed a small plate epoxying on to stop it being too close to the bar all the time.

[grog]

Well done Seth. Something that should be one of first checks for bad running, always overlooked, wont be now. Simple check for its operation, sitting on bike,motor running, in gear with clutch in. Feathering clutch lever in/ out can hear the motor change from one map to the other. One to remember for people having problems

[Hooli]

Or start the bike, unplug it & go for a ride.

I say that as I've seen the spring in them fail so it randomly goes on & off as the bike vibrates.