Running on one cylinder

Brooking 850 · Jan 22, 2015

Any luck Iain?

ntst8 · Jan 26, 2015

Day 3 of ride from Osorno (Chile) to Ushuaia at the moment.
Returned the bike to Dr Lex before i left and understand it is now running. Something about a dodgy earth wire.
Bit confused though as i had tried bypassing the loom with a temporary earth to see if loom had a problem.
Won't be back until mid Feb to get the full story.
Cheer
iain

Bernhard · Jan 26, 2015

Always check rubber “O” ring at carb body face is good.
Also check that you have a “spark “ on both plugs.

kerinorton · Jan 28, 2015

ntst8 said:
Day 3 of ride from Osorno (Chile) to Ushuaia at the moment.
Returned the bike to Dr Lex before i left and understand it is now running. Something about a dodgy earth wire.
Bit confused though as i had tried bypassing the loom with a temporary earth to see if loom had a problem.
Won't be back until mid Feb to get the full story.
Cheer
iain

Hi Ian, hope you are having a good time riding in the deep south. I would be a bit confused as well, because I would have thought with a faulty earth, both cylinders would be affected. I will chat with Lex at the rally.
Dereck

ntst8 · Jun 21, 2015

Finally had the bike on the road today starting well and running on both pots, 200km trip around the back roads. :mrgreen: :mrgreen:
The misfire seems to have been due to one high tension lead being not quite perfect and the Altair has proved to be very sensitive to rotor alignment. Unlike some other ignitions the rotor is only located by the taper, there is no shoulder resting against the end of the cam so it is not hard to have it very slightly off square.
Part way through the process of sorting out the misfire the Alton starter slipped on the crankshaft, shearing the woodruff key. It seems that the starter relies on the friction between the rotor/sprag, the spacer and the front sprocket so the torquing of the nut on the crankshaft is crucial. Still not sure why it loosened (the nut was only finger tight after the slip and had been torqued correctly) but this time i will be retorqueing the nut once or twice after a few uses.

Brooking 850 · Jun 21, 2015

Hi Iain, sounds good how did the SAmerican trip go?
Ride over to Hampton Downs on the 19th July to catch up at the HMCC winter series.
Regards Mike

ntst8 · Jun 21, 2015

Hi Mike, Sth America was great, highly recommend the trip. Southern Andes very like Alpine Sth Island - only there is way more of it.
Sadly i will be out of town on family duty weekend of 19th.

kerinorton · Jun 21, 2015

Hi Iain, I can sympathise with the problems you had, Have just been through all that myself last weekend after having the bike in bits for 2 months or so. Finally diagnosed the Boyer has packed up. Went through everything again, including swapping over the float bowls then I invented a new problem and ended up replacing a bowl that had been ok. Replaced a buggered multi connector in that big one under the tank and thought I had fixed it. Got my son down to help with the timing and the bloody thing started and died and that was it. 12v to the unit. no spark when turning key on and off and no spark when clicking the 2 leads from the sender unit together. diagnosis. Boyer U/S.
Dereck

ewgoforth · Jun 21, 2015

ntst8 said:
Finally had the bike on the road today starting well and running on both pots, 200km trip around the back roads. :mrgreen: :mrgreen:
The misfire seems to have been due to one high tension lead being not quite perfect and the Altair has proved to be very sensitive to rotor alignment. Unlike some other ignitions the rotor is only located by the taper, there is no shoulder resting against the end of the cam so it is not hard to have it very slightly off square.
Part way through the process of sorting out the misfire the Alton starter slipped on the crankshaft, shearing the woodruff key. It seems that the starter relies on the friction between the rotor/sprag, the spacer and the front sprocket so the torquing of the nut on the crankshaft is crucial. Still not sure why it loosened (the nut was only finger tight after the slip and had been torqued correctly) but this time i will be retorqueing the nut once or twice after a few uses.

A good diagnostic tool for investing misses is a set of longer than normal sparkplug wires. Install them, if the problem goes away, the problem was your sparkplug wires. Then, assuming you have a spare spark ignition, try reversing the wires. If it changes sides it's probably a coil, or the wiring to the coil.

Running on one cylinder

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