Hi all
Well need some help with my 77` Mk3 850, went out today for a ride everything was fine until I got up on the 80 - 90 speed and then she just cut out until I came back down the revs then she is fine again so opened up got to the same speed and she done the same thing, she is fitted with premier carbs.........my first thought is fuel starvation I must admit I had one fuel tap open....but surely that was not the case...........cant remember what the size main jets are in the carbs but is there any other thing that can do this.
Regards Mo
Speed or Revs ?
- Log in to post comments
Thanks Guy`s I will take on…
Thanks Guy`s I will take on board everything you have said so when I get a chance I will try all them things .....but just seems strange that if you are saying you are sitting on 70 and then you open up and get beyond 80 thats when it happens as soon as you come back down to 70 it`s fine again, it seems like petrol starvation ...but like you both say it could be a electrical problem as well..... so I will check it all out thanks again..
Mo
- Log in to post comments
Cutting out.
Could be the air filter is blocked or main jets are too big.
Dave
- Log in to post comments
Petrol tap screens?
Have you checked the petrol tap screens?
Maybe they are partially blocked???
Mike
- Log in to post comments
Easy
Easy sort out if it is the pickup plate as Richard says.. Start the bike with the pickup cover removed, Wait till the tick over settles, move the ignition wires at the pick up plate, it will soon stutter/stop if such wires are to blame. A lot of years ago I had a rev limit of 75 then to 70 when it came down to 65-enough-found a broken earth wire on the ignition, but very funny how it fires up and runs around town for ever but won't have the 'big roads'.
- Log in to post comments
Hi well today I done what…
Hi
well today I done what Francis said about the kill switch and found that the leaver that moves the switch is held by two small rivets of which one of them had come out so after fixing that I then went and cleaned the contacts on the switch itself and took her out for a run got to 90 and only then did she played up a bit but nothing like before, but also I had both petrol taps open, so I will check also what Alan say about the pick up wires and just try that as well.....also I am going to look at the timing as at 90 she did not seem to have much left speed wise....Now I know I was running into a real strong head wind as I was getting blown all over the place but I thought she world have had more go than that................we will see :-(
Mo
- Log in to post comments
Those pickup wires..
.. are awful especially as they use crimped pre-insulated connectors. I took ages to track down a misfire on my Commando caused by them.
- Log in to post comments
Fuse
May be, the fuse-holder can cause those irritations, but mainly misfire at higher revs. Either the bajonet-type or, as I've experienced, the "horseshoe"-like ones, as used in cars. The metal part of the fuse could be under tension here, cutting the current under (vibration) stress. Everything fine when at rest. Just discovered this failure by thoroughly inspection, not to be measured by a voltmeter or so. Only a small "burnt" aerea on the "fuse-bridge". Fell into two parts, when casing was broken up.
- Log in to post comments
Does it do the same thing in every gear ?
A failing wire to the points / ignition pickup can cause those symptoms...as the engine leaps around at certain revs, it can cause an internal breakage in the wiring to open and close and run quite happily elsewhere in the rev range.
It's a cheap and easy replacement to try.
Otherwise maybe a vibrating ignition switch or bad fuse holder could do it. If you're running with lights on, do they go out ?