I know there's are a few threads on this problem but I thought I would post my findings. A couple of weeks ago on returning from a run on on the bike I just felt it misfire slightly at low rpm, thought nothing of it as I was nearly home. Last week went on a run to Skipton (about a 80mile round trip) got there fine didn't miss a beat but about 5 miles from home started to misfire at around 3000rpm with throttle only slightly open. Above 4000rpm the bike ran fine. So after trawling through forums etc it seemed that the most common fault is the front coil due to being exposed to water and debris from the front wheel. I took the coil off to find the coil casing slightly corroded, the hole and coil was full of condensation which I was suprised as having owned the bike for 6 months it has never been out in the wet. So I decided to replace the plug and coil to which I'm awaiting delivery. Today as the weather is grim up north again i thought I would just check the top cylinder coil and plug just to be on the safe side and was shocked to find it in worse condition than the other. The plug looks like it's been under the sea...no condensation though. So I think another coil will be being ordered...£££ The coils I've taken off are the original ones from new, I've ordered the updated coils. So just thought it might help those who think that it's just the horizontal cylinder that gets corroded. Have a look at the picture the plug and coil on the left are from the vertical cylinder. I just hope it cures the misfire, I'll keep you posted.......
I had to modify a 16mm socket to remove the plugs.. I've ordered a sealey thin wall socket to fit the new ones.
@RearGunner I presume you know that coils can be taken apart. The nose section pulls off, be careful you don't loose the spring that makes connection with spark plug tip though! I found a bit of Scotchbrite very effective for cleaning rust from stick coil body and spark plug.
Thanks John, yes I've removed the rubber from the coil and have cleaned up the contacts to be honest the contacts looked in good condition it's just the outside of the coils that look grubby and corroded. I have only ordered one coil to which I will fit to the horizontal cylinder and hope it cures the misfire.
Excellent. Just wondering if you managed to get the plugs torqued up properly and if that might relate to the problem somehow.
It's the first time I've looked at the plugs since having the bike, the top one wasn't in all the way I suspect whoever put them in didn't have the correct socket, there's a fair chance that could be the cause of the misfire...
Exactly what I suspected. The Sealey socket will allow you to install the plug properly. Let's hope you're luckier than me, I have an idea that having one plug not properly in place may have caused the problem with my ecu, although Derek thinks that's unlikely. Fingers crossed that your new coil and socket do the trick.
Exactly what I suspected. The Sealey socket will allow you to install the plug properly. Let's hope you're luckier than me, I have an idea that having one plug not properly in place may have caused the problem with my ecu, although Derek thinks that's unlikely. Fingers crossed that your new coil and socket do the trick.
Ok time for an update, I'm still waiting for my spark plugs to arrive so the progress on the misfire has ground to a halt for the time being so as a new relay arrived today I decided to move the fuel pump relay. I removed the battery box and took off the old relay which was in ok condition but not great. I've put the relay up near the rubber square on the left of the battery box but there doesn't seem enough spare loom to put the loom in the rubber square (which would be ideal). I cleaned the heatsheild a squirt of acf50 then secured the battery box back on the bike. It seems very tight on the loom at the top right hand side???? Is this normal??? The cut out in the box doesn't seem big enough to accommodate the loom???? Any advice would be welcomed See pics Thank you.....
I'd be interested to hear you're findings. I have a post about my 749s not revving past 8,500rpm. Ended up being the timing out by 180 degrees from dealer not knowing what they were doing when changing belts. It's not solved completely though as it keeps misfiring but happens randomly across the rev range, sometimes I can hit the limiter then rev again an won't go past 6k. Seems to change every time I let the revs settle to idle and rev again. Going back to dealer for them to find the issue as I don't know where to start, fuelling? electrical?
Spark plugs arrived this morning so on with the show. Fitted the new plugs and one new to me coil (38010143a) to the front cylinder with silicon grease on the rubbers. Started up very easily so went on a run. All ok, no misfire until about 6 miles into the ride where the bike just seemed to hesitate for a split second in third gear about 3000rpm but then accelerated smoothly with no sign of a misfire for another 30 odd miles. Heading back home about 5 miles from home on a slight incline slight open throttle third gear at about 40mph misfires again, not as bad as original misfire but still there. As soon as I open the taps it accelerates fine, in general it does feel better/smoother at low rpm. So not fully cured but definitely better, I'm going to drain the fuel tank and get another coil for the vertical cylinder as I think it will help, other than that I'm confident to use the bike as it certainly feels smoother than before and i just can't get enough of the sound it makes..
Went out again on Wednesday evening for another ride on the 999. Run consisted of 7 miles twisty road then 5 miles motorway 80mph ish... Came off the motorway and started to misfire at 4-5k higher than before.....once past 5k ran fine. Stopped for 30 mins then rode another 6 miles ish, started to badly misfire at 5k, felt like it was going to cut out on me but when brought back to a lower rpm ran ok. After that went to a pals for a brew for about 20 mins went to start it, hardly turned over..... turned ignition on and off then started ok...????...... So there are a few things I can look at, it has a power commander fitted maybe I could disconnect it ?? My gut feeling is that its an electrical fault because whilst out on it I turned the headlamp off and in doing that the misfire seemed to improve but not disappear, this could point to a bad earth, a common fault.. its charging at 14.4v with the headlamp on which I assume is good. Is there a fuel filter on the 999? If there is, where is it? Your help is appreciated.
