Highway stumble/loss of power

[mrclubike]

After upgrading to LED's I think the up rated charging systems are Obsolete and completely unneeded

It will just make parts more difficult to get 

[Barry]

  --I tried hitting the kill switch briefly while on the road. The slowdown from just turning off the ignition is much smoother than the problem 

I would not do this it could back fire and blow the exhaust apart

It's when you turn the ignition back on that the exhaust goes bang.  It blew the baffle out of my very first bike, a 1970 Ducati single, the baffle was then promptly run over by a truck. I made a new one out of a baked bean can stuffed with wire wool.  Happy days.

[qwerty123]

Hmmmm...yes, well, no more highway kill switch use for me! I seem to have escaped unscathed.

Mrclubike makes a very good point about obtaining parts. It's an especially good point because it saves me the time and expense involved with a new charging system! I feel pretty good about my ability to identify and limp along with failed charging given I've got a volt meter on the dash now and a lithium back-up battery. Unless somewhere REALLY remote an ATV or similar battery that fits can be had at most any auto parts store--I used one for years. Could just alternate batteries, charge both overnight.

[qwerty123]

Well, I thought I'd close the loop on this. After noticing it intermittently for several years, I finally figured out that it's loose-fitting fuel hoses on a jaunt from Boston to St. Louis! The hose going from the tank tap on the LHS to the aftemarket filter, and from there to the tee that splits it so it goes to both carbs, was 5/16 not 1/4 (or the more correct 6mm). I bet it felt pretty tight when new, but age has made it loose. I think that under high-flow situations (e.g. open throttle up a long hill on a highway) it was sucking air through the gaps. I'm not sure exactly what problem that *should* cause, but replacing with new 1/4" ID hose seems to have solved it. And it only took three years!

[dogshome]

Glad you found it.

Not quite sure how air gets in since fuel is under gravity feed and wants to get out! Possible rubberised junk in the pipes or swollen inside?

I had to uprate the fuel lines on my old 250 RD. 220 main jets, Micron MKI expansion chambers and various reed, port, head and case mods plus 30:1 petroil meant fuel consumption was a bit heavy with the rev counter clockwise past the high beam lamp. Lack of fuel on those meant either instant skirt or ring seize near the exhaust port or melting of the plug earth bar and subsequent arcing to the piston crown. The bottom ends were pretty tough and the piston usually destroyed itself in a way that didn't score the barrel or disperse aluminium into the main bearings. i never had the exhaust side of the piston go soft, usually something much more spectacular.

Lifting the front wheel at 40 with the cheery wave of an L plate as you took MGs, Jags, CX500s and CB750s off the island was always fun. Well not so much fun with a CX500.

Memory kicks in that I had to split the fuel pipe to the two carbs just under the tank or something, with bigger pipes and bored out fittings. Suzuki reed blocks and RD400 carbs also now remembering. They had a series in Motorcycle Mechanics or Superbike about how to tune your RD. I was well in front of the curve with that. Been there, blown it up twice already. Still using Yamaha reed blocks? How quaint.