Hi, I've already benefited a great deal from the resources on this site. Thank you! I'll do this in point form to be as brief as possible.
What it is:
- recently acquired '79 650 Special.
- PAMCO ignition
- rebuilt rotor, new stator, and reg/rectifier.
- BS38 carbs
Symptoms:
- easy start, then idle races up to 3000+ RPM while the bike jackrabbits across the driveway on the center stand.
- Copious smoke from the left pipe.
- left plug soaked, right sometimes. dried out, bowls drained and primed, and bike fires up again ok.
- engine runs pretty reliably off right side alone, idles around 1500. Only once did it seem to take off on RHS alone. No/little smoke on right.
Investigation:
CARBS
- carbs pulled (twice), clean as a whistle, probably done by PO.
- jet sizes can't be identified. Main pilots taken out inspected and blasted out. Airways blasted with compressed air and free of obstructions and varnish.
- float heights set and double checked externally with tubing. Fuel meniscus level about 2mm below edge of carb body, both sides.
- one float valve pulled and inspected, no evident groove
- idle screws set to 2.25 turns out each side. Bike won't behave long enough to do dead cylinder method. Was 1.75 on right and 2 on left.
- needle jet O-rings seems done, loose. New on order.
- left idle mix screw O-ring toast, split. New being sourced.
- airbox carb boots ossified, but reconditioned a bit with Renu and adjusted as best as possible. Probably some leaking here. New on order.
- airboxes cleaned, was sand in the left side pre and some POST
filter. Coupling rubber between airboxes toast. New on order.
- fuel petcocks not checked, nor filters screens nor tank. Much gas flowing freely from float bowls the many times they've been drained after flooding. So opted to leave that alone for now.
ENGINE (broadly)
- advance springs replaced, mechanism visibly working
- solid spark both sides, new plugs and caps
- cold compression 135psi per side
- valve clearances checked, set. (model ID still a bit ambiguous and hence intake clearance)
- mild exhaust header leak left side, meh
- some bad crud on the engine walls past the manifolds. This bike sat for a long time before being worked on by the PO.
CHARGING SYSTEM
- a wildcard here. new components and wiring throughout. The bike won't settle long enough to take a measurement to see if the battery is charging, but a quick look seemed to indicate not.
- salvage rotor tests good, brand new stator and rectifier/regulator. Wired in by PO.
The machine has a mind of it's own. One time you can start and it will race. The next time it will sit and idle like it ought to for 10 or 15 seconds, and then take off. The next time it will race for a while, flood itself and die.
I would be grateful for any suggested next steps here. Thanks!
What it is:
- recently acquired '79 650 Special.
- PAMCO ignition
- rebuilt rotor, new stator, and reg/rectifier.
- BS38 carbs
Symptoms:
- easy start, then idle races up to 3000+ RPM while the bike jackrabbits across the driveway on the center stand.
- Copious smoke from the left pipe.
- left plug soaked, right sometimes. dried out, bowls drained and primed, and bike fires up again ok.
- engine runs pretty reliably off right side alone, idles around 1500. Only once did it seem to take off on RHS alone. No/little smoke on right.
Investigation:
CARBS
- carbs pulled (twice), clean as a whistle, probably done by PO.
- jet sizes can't be identified. Main pilots taken out inspected and blasted out. Airways blasted with compressed air and free of obstructions and varnish.
- float heights set and double checked externally with tubing. Fuel meniscus level about 2mm below edge of carb body, both sides.
- one float valve pulled and inspected, no evident groove
- idle screws set to 2.25 turns out each side. Bike won't behave long enough to do dead cylinder method. Was 1.75 on right and 2 on left.
- needle jet O-rings seems done, loose. New on order.
- left idle mix screw O-ring toast, split. New being sourced.
- airbox carb boots ossified, but reconditioned a bit with Renu and adjusted as best as possible. Probably some leaking here. New on order.
- airboxes cleaned, was sand in the left side pre and some POST
filter. Coupling rubber between airboxes toast. New on order.- fuel petcocks not checked, nor filters screens nor tank. Much gas flowing freely from float bowls the many times they've been drained after flooding. So opted to leave that alone for now.
ENGINE (broadly)
- advance springs replaced, mechanism visibly working
- solid spark both sides, new plugs and caps
- cold compression 135psi per side
- valve clearances checked, set. (model ID still a bit ambiguous and hence intake clearance)
- mild exhaust header leak left side, meh
- some bad crud on the engine walls past the manifolds. This bike sat for a long time before being worked on by the PO.
CHARGING SYSTEM
- a wildcard here. new components and wiring throughout. The bike won't settle long enough to take a measurement to see if the battery is charging, but a quick look seemed to indicate not.
- salvage rotor tests good, brand new stator and rectifier/regulator. Wired in by PO.
The machine has a mind of it's own. One time you can start and it will race. The next time it will sit and idle like it ought to for 10 or 15 seconds, and then take off. The next time it will race for a while, flood itself and die.
I would be grateful for any suggested next steps here. Thanks!
