A little missfire

MxMartin

MxMartin

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Nov 13, 2017
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Last week I went on a 30 mile run to a local bike meet. Ride there was fine. Parked up for a couple of hours. Bike started ok but on the run home I had a feeling that the bike was misfiring, not constantly, just stuttering now and then, enough to catch my attention.

I had put iridium plugs in about 200 mile earlier and hadn't checked them since so I whipped them out, they barely showed any discoloration from new, just the hint of grey at the top of the thread but crystal clean on the ceramic and the tip.

Tonight I went on another 25mile run to another bike meet, ride out was without incident, parked up for a couple of hours. Bike started first click and idled ok as I donned helmet and gloves. When I navigated out of the parking lot in 1st she coughed and spat, jerkiness was by far the worst I've experienced so far. I got to a clear path where I could pull away in first and she revved past 3k then it was as though she died or hit the rev limiter, no power, very jerky. I came to a t-junction before I could get to 2nd gear. When I pulled away again she went through a flat spot, then power surged. She kept up this behavior for a good 5 minutes, at each junction. She has always been a little jerky around town in 1st but not like this.

I checked plug caps at home in case I hadn't seated them after pulling the plugs but they were fine. Engine was very hot so I checked oil level and that was fine, just above the minimum where it has always been.
 
My bet is on the head temp sensor!
Does it move slightly when you try to turn with your finger?
Be careful to not break it, just apply little force. If it moves you have to replace it, best with Bosch part...
 
It reminded me of times gone by when you reach reserve in the petrol tank at 60mph and while you were leaning down trying to flip the fuel tap over to reserve with your padded winter gloves on (remember those days lol) the bike would fuel starve, die, then get a splash of fuel and surge, then die again until eventually fuel replenished the carbs.

The first half of my trip home was in town and she really didn't like 1st/2nd gear but once I was out of town and able to open her up she happily pulled hard in the 4k to 6k rpm range.

I will check the head sensors tomorrow. She will get a good run down to the factory on Thursday so if still misbehaving at least I will be in the right place for parts :)
 
See what the boys at Norton Donington say . I would think that should have logged a fault code ?
 
MxMartin said:
It reminded me of times gone by when you reach reserve in the petrol tank at 60mph and while you were leaning down trying to flip the fuel tap over to reserve with your padded winter gloves on (remember those days lol) the bike would fuel starve, die, then get a splash of fuel and surge, then die again until eventually fuel replenished the carbs.

The first half of my trip home was in town and she really didn't like 1st/2nd gear but once I was out of town and able to open her up she happily pulled hard in the 4k to 6k rpm range.

I will check the head sensors tomorrow. She will get a good run down to the factory on Thursday so if still misbehaving at least I will be in the right place for parts :)
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Might be worth trying a 'starting procedure'. With ignition on, twist throttle though full range and return to stop before hitting the start button. This should remind the ecu of throttle position. Might be hocum? but worth a try before swapping bits out etc. Good luck
 
StuartSF2015 said:
Might be worth trying a 'starting procedure'. With ignition on, twist throttle though full range and return to stop before hitting the start button. This should remind the ecu of throttle position. Might be hocum? but worth a try before swapping bits out etc. Good luck
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Hocum? Might be, might not be. Your post reminded me that last night I turned ignition on and blipped the throttle before hitting the starter button. Why I did this I don't know, I never usually touch the throttle, maybe just maybe I upset the ecu in the process. On both previous occasions that the bike has been snatchy/misfiring/bad throttle response has been from a cold start, no warming up, then crawling through a very crowded parking lot for a good few minutes in 1st gear before hitting the road. Usual practice for me is cold start, no warm up, straight on to open road and through the gears... no problems. Maybe I have simply found a scenario that my bike is not so happy with, I should really let her warm up a little longer. Anyways should have a good run tomorrow where I can monitor her more closely.
 
Cold start she goes to 2k for 15 to 20 seconds then drops to 1300. Once in a while takes a little longer. Also one in a while she starts and runs a little feebly so I just shut her down, turn of the key and then restart. 85% first start, never more than twice.
 
Hello MX Martin , How does the 961 fuel mileage compare with the Thruxton 1200 R ?
 
Pleased to report that the recent 150 mile run to the factory and back went without a hitch. It was the usual ignition on, hit the button, start 1st crank, don gloves, into 1st gear, then 2nd and away.... no warm up, nothing, ran perfect. I think my little 961 just doesn't like to spend too long stuck in 1st, throttle just off the rest, then closed, then off the rest as you navigate through crowded bike meets, she much prefers to be on the gas from the start.

My run back from the factory was as the sun was setting, it was a most enjoyable ride with very little traffic. The last hour of the ride was on an empty winding rural A-road (A52 for us in the UK) and the sun had set so I had to rely on headlights and keep eyes peeled for deer and potholes. The air temp had dropped rapidly and was probably around 9 or 10 degC and the 961 spent most of it's time humming at 4500rpm to 5500rpm in 4th and that really is the sweet spot..... she felt so smooth with just enough buzz to let you know she was motoring.... but the sound from those shorties, it was like being in a WW2 warbird as it thundered down the airstrip! If only you could bottle those sensations, would make a fortune on ebay :)
 
OK , I have got those battery draw readings finally. with key OFF I am getting (.99 ma) that's right just under 1 ma. With the key ON I am getting about 5.6 A . Headlamp on ECU powered up etc.. Late 2014 Sport with SC ecu .
 
Glad that the 961 vibes are OK for you. The MCN writer Neeves (last name) said that he was getting a headache from the vibration. This is when they tested the Domi SS to the Thruxton R. On that last comment you can guess which bike won the contest. You own them both and you drive them both . Do more back to back comparisons .
From MXmartin :
My run back from the factory was as the sun was setting, it was a most enjoyable ride with very little traffic. The last hour of the ride was on an empty winding rural A-road (A52 for us in the UK) and the sun had set so I had to rely on headlights and keep eyes peeled for deer and potholes. The air temp had dropped rapidly and was probably around 9 or 10 degC and the 961 spent most of it's time humming at 4500rpm to 5500rpm in 4th and that really is the sweet spot..... she felt so smooth with just enough buzz to let you know she was motoring.... but the sound from those shorties, it was like being in a WW2 warbird as it thundered down the airstrip! If only you could bottle those sensations, would make a fortune on ebay :)
 
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TonyA said:
OK , I have got those battery draw readings finally. with key OFF I am getting (.99 ma) that's right just under 1 ma. With the key ON I am getting about 5.6 A . Headlamp on ECU powered up etc.. Late 2014 Sport with SC ecu .
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1ma is pretty good compared to my 19ma. One day I will get around to asking the factory if they have a benchmark figure for key off drain.
 
TonyA said:
Do more back to back comparisons .
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Why Tony? I have already decided to sell the Thrux after I get her annual service done early next month. The Commando is a keeper, been thinking about adding a Dommi but pretty sure the wife would file for divorce lol
 
OH I see. Everybody that has a Thruxton 1200 loves it I thought ?
 
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MxMartin said:
Why Tony? I have already decided to sell the Thrux after I get her annual service done early next month. The Commando is a keeper, been thinking about adding a Dommi but pretty sure the wife would file for divorce lol
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Get a Dommie that’s the same colour as the Thrux and Park it in the same place.

She’ll never notice...
 
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