Misfiring Monster, was it me?

[Stu2]

I have owned a Monster 750 i.e since 2013, service as been regular oil, filters and belts changes, basically stuff I'm confident with... However, the last service I added a 'Injector cleaner' to the tank, mistakenly adding twice the amount, 30ml instead of 15ml, bugger. I then had a 80 mile ride, next day a 40 mile ride, perfect, the following day after 6 miles (temp reached 160 degrees F) misfiring both cylinders and refusal to tick over, Once the engine had cooled the bike started and ticked over and I could ride home. I drained the tank, fresh petrol, checked the Coils, replaced the plugs and caps, took the bike out and as before, 6 miles same temp the fault appeared, once cooled it was fine to ride again.
Was it me or is this a coincidence and there is a fault? Anyone had a similar experience?

 

[jerry]

Old fuel filter can cause those missfires and poor running on EFI models , when was it last changed , the symptons are it will run at tickover and low speed but once you try to go quick the blocked filter restricts flow and bike bogs down and missfires ,,,

 

[Mr Gazza]

It sounds like a dying crank position sensor (CPS) to me. which is directly temperature related and will start to play up suddenly out of the blue.

I don't think it's anything to do with injector cleaner or fuel filter. Best way to clean injectors it to remove and ultra-sound clean them.

 

[Dukedesmo]

I can't imagine injector cleaner causing any problem, whether it cleans your injectors or not is another matter but I would say it should be harmless.

As above, check sensors or damp in connectors etc.

The only time my fuel-injected bike (916) ever did similar was when one of the retaining screws on the TPS (throttle Position Sensor) broke and the TPS was 'flexing' with the throttle.

 

[jerry]

Yes Could well be the TPS as well they are very sensitive , but usually only at love revs ,,CPS could be iffy as GAZZA says,, but the EFI bikes need clean fuel filters to maintain pressure flow ,,,,I change mine every 10k miles ,But In Thailand i have had contaminated fuel block the fuel filter after filling up a couple of times

 

[Dukedesmo]

I suppose that, fuel injector cleaner might by it's nature dislodge crap from the fuel tank/lines that could contribute to filter blockage?

I removed and cleaned out the tank on my old Guzzi which then, later that year developed a high speed fuel starvation issue that turned out to be sediment of rust/crud in the bottom of the carb floatbowls that would impede fuel flow but only on full throttle when it would be 'sucking' the fuel up with more force. This, despite having filters (of a sort) on the carb inlets.

I keep meaning to fit proper in-line fuel filters but never quite got around to doing so.

 

[Stu2]

Old fuel filter can cause those missfires and poor running on EFI models , when was it last changed , the symptons are it will run at tickover and low speed but once you try to go quick the blocked filter restricts flow and bike bogs down and missfires ,,,

Hi Jerry,

Thank you for the reply, I'm embarrassed to say, the fuel filter hasn't been changed since I purchased the Monster... One of those jobs, I looked at the closed the manual. However, thinking I'll need to eliminate a or future problem.

 

[Stu2]

It sounds like a dying crank position sensor (CPS) to me. which is directly temperature related and will start to play up suddenly out of the blue.

I don't think it's anything to do with injector cleaner or fuel filter. Best way to clean injectors it to remove and ultra-sound clean them.

Hi Mr Gazza,

Thank you for you reply, I have since tried again and it does seem temp related, 6 miles and 168 degrees F? cool down and runs fine until it reaches the same temp? I've now found the resistance value, so that's the next step to check the CPS sensor... when it stops raining!

 

[Stu2]

I can't imagine injector cleaner causing any problem, whether it cleans your injectors or not is another matter but I would say it should be harmless.

As above, check sensors or damp in connectors etc.

The only time my fuel-injected bike (916) ever did similar was when one of the retaining screws on the TPS (throttle Position Sensor) broke and the TPS was 'flexing' with the throttle.

Hi,
Its so easy to change a oil, filter, service throw in a new addition, the 'cleaner' and assume thats caused the fualt. Would have been so bad if I hadnt have overdosed the bike!

But I will now check your suggestions.

 

[Mr Gazza]

I've now found the resistance value, so that's the next step to check the CPS sensor...

Bear in mind it will probably check out fine when it's cold.
Try a 3 mile trip out and then back home to the tester, or take your tester out with you?

 

[Stu2]

Will do!

 

[gallardo]

My bike keeps misfiring too. Y2K M600. About to give up on her. Every year is the same and a pig to start. Changed spark plugs yesterday, starts but seems flooded and slowly shuts down. Help please!

 

[Stu2]

My bike keeps misfiring too. Y2K M600. About to give up on her. Every year is the same and a pig to start. Changed spark plugs yesterday, starts but seems flooded and slowly shuts down. Help please!

Hi,
Never had trouble starting the Monster, just recently have this problem, once warmed up? Could the CPS give yours issues too? Just a thought, I know the bikes are poles apart, my mate had a Suzuki Bandit, bugger to start and tick over, had the Carbs, ultrasonically cleaned and set up, been fine since. Sorry I'm not much help?

 

[Stu2]

Monster misfiring update...

So taking the plunge, back in April I sourced a CPS in Germany for half the price of the Ducati part. It was the correct part number and was dispatched very quickly, once received I checked the dimensions, identical to the original, apart from the maker.
Fitted and started on choke... horrendous, stuttered, revs all over the place, wouldn't tick over. Refitted my 'faulty' original, started ticked over and revved cleanly? I then checked the resistance of the new part, it wasn't 800 ohm it was 1200 ohm?! I contact the supplier, they asked for my Bikes details, suggested the part was faulty and supplied another one free of charge. It came and I checked the resistance... again it was 1200 ohm?
I have now ordered the part from Ducati and await its arrival, I will be checking its resistance before I fit it.

I'll keep you posted!

 

[Mr Gazza]

Are you measuring the resistance with the sensor fitted in the bike or on the bench?
Reason I ask is because the sensor has to be shimmed accurately for the correct airgap.
There are very thin metal shims under the sensor to achieve this, which presumably would have been correct for your original sensor, but maybe not for your new one(s). Don't know if incorrect airgap would alter the resistance, but worth checking.

To be honest I don't know what the air gap should be or how to check it, but another kind soul will be willing to share the info I'm sure..

 

[Stu2]

Are you measuring the resistance with the sensor fitted in the bike or on the bench?
Reason I ask is because the sensor has to be shimmed accurately for the correct airgap.
There are very thin metal shims under the sensor to achieve this, which presumably would have been correct for your original sensor, but maybe not for your new one(s). Don't know if incorrect airgap would alter the resistance, but worth checking.

To be honest I don't know what the air gap should be or how to check it, but another kind soul will be willing to share the info I'm sure..

Hi, thank you for your message, yes the resistance was measured on the bench, the dimensions are identical, so assumed the clearance would be the same? It will be interesting to see what the Ducati part measures as they state it will be the original part?

 

[dacs]

If you have a copy of the Haynes manual on 2 valve twins to 2005, the CPS (Haynes call it a timing sensor) is in chapter 3B page 9, paragraphs 34 to 49, with a rubbish photo 8.37
I've included what I hope is a better photo below. There is a screw-in plug on the front of the left (when seated on the bike) crankcase half directly in line with the sensor (circled on photo) If this is removed there is room to get a feeler gauge thru the hole and measure gap between the timing gear and the inside face of the sensor. Bear in mind that the timing gear has a recessed section which triggers the sensor, and you need to be sure you're not measuring that. The air gap should be 0.6 to 0.8 mm. The gap is changed, if necessary, by adding/subtracting metal shims between the engine case and the sensor housing. Replace access plug sealing washer and CPS sealing ring rather than reusing them.
My understanding is that a CPS problem should result in a stored fault code that a Ducati workshop would be able to recover.

 

[Stu2]

If you have a copy of the Haynes manual on 2 valve twins to 2005, the CPS (Haynes call it a timing sensor) is in chapter 3B page 9, paragraphs 34 to 49, with a rubbish photo 8.37
I've included what I hope is a better photo below. There is a screw-in plug on the front of the left (when seated on the bike) crankcase half directly in line with the sensor (circled on photo) If this is removed there is room to get a feeler gauge thru the hole and measure gap between the timing gear and the inside face of the sensor. Bear in mind that the timing gear has a recessed section which triggers the sensor, and you need to be sure you're not measuring that. The air gap should be 0.6 to 0.8 mm. The gap is changed, if necessary, by adding/subtracting metal shims between the engine case and the sensor housing. Replace access plug sealing washer and CPS sealing ring rather than reusing them.
My understanding is that a CPS problem should result in a stored fault code that a Ducati workshop would be able to recover.
View attachment 852

Thank you, I've now purchased an Haynes manual... very different from the one I had for a Suzuki GS550 in the 70's! Still waiting for the new CPS to come to Ducati Stoke. I'll keep updating on my progression and hopefully misfire cure!