Afternoon everyone
I recently finished a ground up cafe build on a 1975 CB550F. It’s been running like a top and pulls like a small train. I’ve ridden about 150 miles since I finished the build and I’m extremely pleased with the way the bike has been performing, until last night.
Details about the Bike:
1975 CB550 F
Stock Engine internals
Carbs are from a ‘76 550 K (rebuilt and jetted for pods)
Unit foam pod filters
4into1 exhaust w/ high flow muffler
Motogadget M-Unit electronics w/ new wiring
Factory points ignition
Shorai 210cca lithium battery
Regulator-rectifier (eBay special)
Factory style coils (eBay special)
So here’s what happened:
Out for a ride last night and the bike was behaving perfectly. About an hour into the ride I downshift on a quiet bit of road and gave it the beans. The bike pulls normally then suddenly give me a short burst of extra power, like it got a short shot of NOS. I decelerated and everything went back to normal. About 10min later I lost all acceleration, I downshifted and tried to accelerate and the bike was still running but the power delivery was completely flat. I let off the throttle and the engine died.
Pulled over and diagnosed.
Fuel flows from the tank to the carbs (pulled the line off the carbs and observed fuel flow) carbs are filling (checked the drain plug on the #4 carb ((furthest from the fuel inlet to the carbs)). Battery had plenty of power and the starter turned over the engine strongly but wouldn’t start. Pulled the seat and saw the ignition terminal LED is flashing on the Motogadget M-Unit (that indicates, or should indicated a fault in the ignition circuit). Checked all connections on the coils and overall condition and everything seems fine. I pulled the power wire (ignition wire) from the M-Units Ignition Terminal and plugged it into the AUX 1 terminal and the bike fires back up and idles normally. The AUX 1 input supplies the same power as the “ignition terminal” but does not have a “kill switch” feature, so this was only a “get home fix”. I pulled back on the road and acceleration was poor and flat, no power. I got up to about 40mph and when I opened the throttle the bike surged and bucked like the ignition was only sometimes firing. In fear of causing further damage I pulled over and called the wife to scoop me up with the trailer.
I suspect faulty and failing coils and will be starting my full diagnostics with the ignition points and moving through the charging system when I get back home as I’m currently on vacation with only basic tools at hand.
What are your thoughts? More brains are better than one.
Cheers everyone and hopefully everyone had a great 4th of July.
I recently finished a ground up cafe build on a 1975 CB550F. It’s been running like a top and pulls like a small train. I’ve ridden about 150 miles since I finished the build and I’m extremely pleased with the way the bike has been performing, until last night.
Details about the Bike:
1975 CB550 F
Stock Engine internals
Carbs are from a ‘76 550 K (rebuilt and jetted for pods)
Unit foam pod filters
4into1 exhaust w/ high flow muffler
Motogadget M-Unit electronics w/ new wiring
Factory points ignition
Shorai 210cca lithium battery
Regulator-rectifier (eBay special)
Factory style coils (eBay special)
So here’s what happened:
Out for a ride last night and the bike was behaving perfectly. About an hour into the ride I downshift on a quiet bit of road and gave it the beans. The bike pulls normally then suddenly give me a short burst of extra power, like it got a short shot of NOS. I decelerated and everything went back to normal. About 10min later I lost all acceleration, I downshifted and tried to accelerate and the bike was still running but the power delivery was completely flat. I let off the throttle and the engine died.
Pulled over and diagnosed.
Fuel flows from the tank to the carbs (pulled the line off the carbs and observed fuel flow) carbs are filling (checked the drain plug on the #4 carb ((furthest from the fuel inlet to the carbs)). Battery had plenty of power and the starter turned over the engine strongly but wouldn’t start. Pulled the seat and saw the ignition terminal LED is flashing on the Motogadget M-Unit (that indicates, or should indicated a fault in the ignition circuit). Checked all connections on the coils and overall condition and everything seems fine. I pulled the power wire (ignition wire) from the M-Units Ignition Terminal and plugged it into the AUX 1 terminal and the bike fires back up and idles normally. The AUX 1 input supplies the same power as the “ignition terminal” but does not have a “kill switch” feature, so this was only a “get home fix”. I pulled back on the road and acceleration was poor and flat, no power. I got up to about 40mph and when I opened the throttle the bike surged and bucked like the ignition was only sometimes firing. In fear of causing further damage I pulled over and called the wife to scoop me up with the trailer.
I suspect faulty and failing coils and will be starting my full diagnostics with the ignition points and moving through the charging system when I get back home as I’m currently on vacation with only basic tools at hand.
What are your thoughts? More brains are better than one.
Cheers everyone and hopefully everyone had a great 4th of July.