my bike did the same yesterday.....out a run and I thought right ok time to open it up a bit.....the first ive had it over the ton mark then a felt it slow then catch again
then when a slowed down to bout 30 40 then open the throttle again it would shudder kinda like going onto 3 cylnders
was down at it earlier and started it up seems fine but theres deffo a flat spot low down any ideas.....sorry to hijack the thread
When I had my gen1 I had similiar cutting out and misfiring at speed and cut the ht leads back, cleaned all the connectors up, even drained the float bowls to see if there was any muck inside and changed the fuel filter.
I then found the cause by pure luck, I was mounting my camera and the engine was running and I just nudged the ignition key with my hand and the engine cut out. The ignition barrel was that badly worn the key was loose.
I temporarily solved it by by slightly bending the key until I got a second hand ignition unit, which I found a right twat to fit!
It might be worth just checking yours out.
A really don't think that's the problem with mine I'm going to get plugs first an try that
Cdi unit maybe if coils and leads fail? Isn't there anyone close by you could borrow?
It crossed my mind that it might be the cdi unit, but I'll wait till coil comes before I do anymore. A local dealer has a thou so he might be minded to traspose bits over . i've no illusions that a main yamaha dealer would cost me a packet ,
Ignition barrel is ok I think . the key fit is good anyhow.
29-09-14, 10:15 PM
(This post was last modified: 29-09-14, 10:28 PM by unfazed.)
A faulty Ignitor would effect 2 or 4 cylinders.
An issue with the coil would effect 2 cylinders,
An arcing plug cap or problems with a carburettor could effect just one cylinder.
Corrosion withing the Plug cap can cause misfiring which can come and go.
Bypass the Ignition Key circuit to rule out the Ignition switch if necessary.
New coil came today , after fitting ,misfire fault has gone ! Can't be sure on the "Sudden death issue" ,Time will tell ! But i'm quite happy at £20 delivered for a new coil. I'll update after a good long ride
Sudden death issue could be corrosion in the connector to the pickup coil, located under the tank.
I rode 30 miles with engine running well, last night , left the bike for a couple of hours and then back to the sudden death syndrome. Finally started after a lot of cranking. I wagged the side stand ,ignition key and kill switch neither of which seemed to make any difference. I only remember seenig two terminal blocks under the tank , both of which I separated and WD 'd. This is weird having two electrical issues at the same time.
I think the coils are a red herring.
Ignition switch and/or the big white connector under the tank. WD40 isn't much of a contact cleaner, either. I really recommend replacing this connector with better quality individual connectors. It's a known issue and even if it isn't the cause of your present misfire, time spent doing this will pay in the future. 
I would think there is defo 2 issues , as I have had this, " not starting issue," months before the misfire came on.
what does the black wiring plug "under the tank" link up , this was the dirtier of two
(02-10-14, 10:57 AM)Falcon 269 link Wrote: I think the coils are a red herring In which case they should probably be upgraded with electric eels, but cod knows I'm probably talking pollocks :rollin
Sorry :o
Can't do any more as my sides have split!
well that's mine ok again.....new plugs fitted
I took tank of again , I have thoroughly cleaned the white block. I also found a bunch of 4 terminal blocks in a large plastic cover . one of these had green pins , cleaned all these and WD'd . Bike starts every time now but , again pick up is not clean! Can't get my head round how last night it ran 30 miles perfectly. Might even treat it to new plugs as the last ones only a month ago were e bay cheepos possibly NJK copies. clutching at straws now. whats an ignitor ? re A faulty Ignitor would effect 2 or 4 cylinders. (Unfazed)
Bwizz, I must apologise the pick up coil connector is under the right hand side cover, it is the TPS connector which is under the tank.
The pick up coil is linked to the EXUP motor, TPS, Speed Sensor, emergency stop switch and ignitor.
When I had the sudden stop problem I traced it to the dreaded green corrosion in the pick up coil connector.
Ignitor is Yamaha name for the the electronic ignition system and is the box under the seat next to the fuse box with Denso label, also known as ECU, CDI or ECM
Ok ta I thought you meant .The "what I thought of as the CDI unit" I'll have a geek behind the side panel tomorrow. i think the RAC man checked it though. Uneven running fault seem to be affecting 1+4 both these plugs are showing signs of fouling
Did you use the plug caps on the replacement coil? A few replacement coils I have bought in the past had corrosion in the caps.
Swap the plugs caps on Cylinders 1 and 4 with the plug caps on cylinders 2 and 3 and see if the fault follows the caps.
03-10-14, 10:36 AM
(This post was last modified: 03-10-14, 07:18 PM by bwizz.)
I tried some kawasaki plug caps " from the temporary coil" on 1 and 4 , did not make any difference ! I took of the side panel , lots of terminal blocks there! pulled every one apart and cleaned +WD'd result no difference! Not died since though!
I hung a plug on both no1&4 , massive spark on both. Two thoughs now , either these two plugs break down under load.
Or two cyclinders are flooding intermittently (Mikes suggestion area ), I'm going to try two plugs from my 600 tomorrow , not quite the same heat range , but might be interesting
I fitted the 2 plugs from the 600, started up fine then within minutes ,I lost no 4, This would seem conclusive that no 4 is flooding constantly and no 1 intermittently. This will have to wait till i'm in a better state of mind to thake the carbs of,
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