81 cb650c backfire on downshift/cruise at 4k rpm
Posted: Fri Jul 26, 2019 11:26 pm
Hello new friends,
ISSUES: backfiring on the downshift or around 4k rpm, a little lag when you want to give her the beans, and when the bike is hot idle is at or above 2k.
BACKSTORY
After two years of owning my bike (name tbd, suggestions welcomed) I finally got her on the road this May. I received the bike with a rusted out tank and carbs split into 4 ziplock baggies. After a very frustrating winter, carbs we're back together with all genuine Honda rebuild kits and factory setting Jets. Tank was treated pretty successfully with a por-15 kit and some aircraft grade fuel puddy to fill the pinholes.
Spark advance was replaced and gapped to specs. Intake boots, spark plugs, and pretty much every gasket you could think of was replaced. After we figured out the idle screw was turned in almost all the way, the bike finally idled normally.
After stripping a screw on the cylinder head cover, and replacing said cylinder head cover, valves we're gapped, timing and carb sync were accomplished.
Essentially, two aircraft maintainers went head to toe and replaced everything we could think of.
The bike starts great cold, runs through the gears like a champ, and rips the New England back roads like you read about.
Only issues thus far are: backfiring on the downshift or around 4k rpm, and there's a little lag or studder when you want to give her the beans. And the high idle after riding 30mins
The bike came with a MAC 4into1 and k&n air filter. Filter has been cleaned but not reoiled.
I was thinking of tinkering with pilot screws a little before going to bigger Jets.
Thoughts...
Sent from my LM-G710VM using Tapatalk
ISSUES: backfiring on the downshift or around 4k rpm, a little lag when you want to give her the beans, and when the bike is hot idle is at or above 2k.
BACKSTORY
After two years of owning my bike (name tbd, suggestions welcomed) I finally got her on the road this May. I received the bike with a rusted out tank and carbs split into 4 ziplock baggies. After a very frustrating winter, carbs we're back together with all genuine Honda rebuild kits and factory setting Jets. Tank was treated pretty successfully with a por-15 kit and some aircraft grade fuel puddy to fill the pinholes.
Spark advance was replaced and gapped to specs. Intake boots, spark plugs, and pretty much every gasket you could think of was replaced. After we figured out the idle screw was turned in almost all the way, the bike finally idled normally.
After stripping a screw on the cylinder head cover, and replacing said cylinder head cover, valves we're gapped, timing and carb sync were accomplished.
Essentially, two aircraft maintainers went head to toe and replaced everything we could think of.
The bike starts great cold, runs through the gears like a champ, and rips the New England back roads like you read about.
Only issues thus far are: backfiring on the downshift or around 4k rpm, and there's a little lag or studder when you want to give her the beans. And the high idle after riding 30mins
The bike came with a MAC 4into1 and k&n air filter. Filter has been cleaned but not reoiled.
I was thinking of tinkering with pilot screws a little before going to bigger Jets.
Thoughts...
Sent from my LM-G710VM using Tapatalk