This is a little weird, I know, but the P.O. shipped an 850 to me from Chicago fall of 2008. I rode it around a parking lot and put it in storage. A year later, Chris G. reinstalled the twin Mk1 Amals that came with the bike in a box of takeoff parts (a single Mk2 Amal had been installed previously). Chris had the bike running fine in his shop. I put the bike back in storage (tank and bowls drained). Fast forward to the present – I’d never ridden the bike on the street during seven years of ownership. I know, I know…
So, two weeks ago, having retired, I pulled the bike out of storage. Bowls and tank looked good. New battery, coils ohm’ed good, spark good. Did a bunch of other stuff – cleaned and adjusted chain, flushed the brake, fresh oil. Carbs wouldn’t tickle – no start. Shot of starter fluid, she cranked and ran – Yowzah! Got out on a back road and it ran fine for five miles, smooth & good power cracking it to 70 mph. Then it started missing and popping, pretty bad. Managed to get home.
Figured the he carbs probably needed cleaning, so I put the dissassembled parts through a couple sessions in an ultrasonic cleaner, plus blowing carb cleaner through with compressed air. All seemed squeaky clean, including the pilot jet passages (didn’t have anything the right size to poke through the pilot jet though). Installed new Stayup floats and float needles. Adjusted the float tabs to get the obligatory 0.21″ fuel level below the lip of the bowls. Back on the bike, the carbs now tickle well.
Bike started on the third kick, using choke and holding about half throttle – great! Still popping and missing when revved through 2K to 3K rpm – not so great. Also didn’t want to idle. This is with the air screws at the nominal turn and a half out. Slides synced and held up a little by the throttle screws.
My thought was to now check the ignition timing. Thing is, what could happen with timing so that it ran five miles just fine and then deteriorate? The Boyer’s contact plate and rotor are snug, and I’d cleaned the coil connections, coil ground and frame ground earlier. I’d rather not get into the whole degree wheel, piston stop process if I’m just chasing the problem. My gut tells me the timing probably didn’t just drift off after initially running good, and that it’s more likely there’s still crude in the carbs (but really?). I’d think the only likelihood there is the pilot jet passage – but could that be affecting fuel delivery above 3K? BTW, both needles are in the top notch, slides are 3.5. All jet and needle numbers are correct.
I’ve gathered a number of tech articles from online research, but I guess I’m looking for any hunches as to the most likely things to check next. Any advice much appreciated. I’m kind of in Norton desert down here in Lynchburg.