running on two cylinders

[simongill]

Hi Guys
I took my rebuilt CB750F2 out for a ride yesterday and ended up limping home (already done 200 miles trouble free).
when I finally got back no 2 and 3 exhaust pipes were cool so obviously not firing on 2 and 3.  Went to check it this morning and have a nice spark on 2 and 3 so I assume when its get hot 2 and 3 cut out. what do you think coil breaking down or condenser. I'm sure its an electrickery issue, but any comments would be very useful.

On another note I just imported a mudguard from the states but the sods at customs charged me VAT and handling on the cost of the item plus the cost of carriage. This made a $25 dollar item bloody expensive.

Simon

[Seamus]

Sounds like electrical. 2 and 3 are off a single coil, so just check everything related here.
Look for shorts if there are sparks on those two cylinders. Maybe failing under compression

[bluemouse1006]

There is mention on here about wiring connections from points to loom close to brake
Switch ? I had same prob but I've fitted electronic ignition and had to solder connections in the end

Hope this helps

Amos

[Waggles]

It could be all the things you have suggested but assuming a standard ignition system a grotty contact is most likely. As Amos says I had trouble with the points wire where it joins the loom ( and I am not alone ) the wire is only just long enough and can pull out quite easily, it will then make and break connections at random due to vibration so you could see a nice spark now but it can fail later. Worth checking. I added a little extension wire to take off the tension.

Have suffered at the hands of Customs too, but hey, how else are they going to keep the subsidised prices in the house of commons bars?

[simongill]

Sorry for late reply. Thanks for info guys

[simongill]

Hi
Just for future reference for anyone, I tracked down the problem to the points. I fitted two new sets on rebuild so I didn't go there to start with, however on the set that sparks 2 and 3, as the engine got hot,  the small shaft on the points expands and this was stopping the points from opening and closing. A quick ream through and a touch of grease has sorted it.
I hope this may be useful.  Did I fit another coil and new condensers before I found this.....of course not!!!!
Simon


PS Anyone want a good F2 coil?.......

[Waggles]

Not heard of that one before! assume they were pattern points not OEM?

Know its a bit late now, but if you suspect a coil or condenser etc try swapping them over first and see if the problem swaps sides. ( Can't do that with the points tho! to check them I usually watch for sparks across them )

Sorry, don't need a coil!