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Guest
Guest
Hey Everyone!
I recently traded one of my Sportsters for a buddies 1982 GS850. I’ve loved the bike since we helped him buy it last year. He was a new rider, so the bike went down a couple times in rookie mistakes, both he and the bike were okay, just a little worse for wear. My plans are to restore the bike, and turn it into a longer range bike than what the peanut tank on my sporty will allow.
Enough with the backstory, here’s what’s going on.
So the carbs were rebuilt and synced twice last year, once for a freshen up as the old girl had sat for 20 years, and again because of leaking fuel between the carbs. The bike started dumping fuel and stopped running well about January this year. I got it 3 weeks ago. I took the carbs off and found the floats out of spec per the service manual, so I adjusted them into 22.4mm +- 1mm, including the lip where the gasket sits. I then found the petcock had failed, and constantly dumped fuel in the vacuum line, so I blocked off the vacuum line to the carb with vacuum caps brand new from O Reillys. I adjusted the air fuel mixture by turning the mixture screws 3 turns out from seat and turning them in slowly until the idle decreased and then turning them back out 1/8 turn. This is where I started to notice something weird. Cylinders 3&4 gave a very noticeable idle decrease, while cylinders 1&2 barely took an adjustment. Then I adjusted the idle into approx 1050ish per the bikes tach. On a 3 mile ride around my neighborhood afterwards, I noticed that the motor would rev seemingly normally, but with no power and top speed in 4th and 5th was 60, per my GPS speedometer app on my phone. The bike would die if I pulled over and stopped, but would refire normally and strong. On a stupid whim, while stopped and running I slightly touched cylinder 1 and then 2 exhaust pipes, noticed they were warm, rather than hot. I could hold them without burning myself, while 3&4 seemed at normal operating scalding hot temperature. My buddy and I pulled the plugs, 3&4 had strong spark to the cylinder head, 1&2 had weak spark. 3&4 plugs looked like normal running plugs. 1&2 were wet, but not overly. Plugs are gapped to approximately .025. Performed compression tests, warm bike and wide open throttle. All cylinders were over 110 psi, with 1&4 over 150 psi. My compression tester is a cheap Oreillys special and I could not get the best seal on cylinders 2&3, but they read 110 and 120 respectively, but I believe them to be higher.
Based on the weak spark at 1&2 cylinders I’m believing to start there, but I’m at a loss.
Thank you in advanced, sorry for the information dump!
I recently traded one of my Sportsters for a buddies 1982 GS850. I’ve loved the bike since we helped him buy it last year. He was a new rider, so the bike went down a couple times in rookie mistakes, both he and the bike were okay, just a little worse for wear. My plans are to restore the bike, and turn it into a longer range bike than what the peanut tank on my sporty will allow.
Enough with the backstory, here’s what’s going on.
So the carbs were rebuilt and synced twice last year, once for a freshen up as the old girl had sat for 20 years, and again because of leaking fuel between the carbs. The bike started dumping fuel and stopped running well about January this year. I got it 3 weeks ago. I took the carbs off and found the floats out of spec per the service manual, so I adjusted them into 22.4mm +- 1mm, including the lip where the gasket sits. I then found the petcock had failed, and constantly dumped fuel in the vacuum line, so I blocked off the vacuum line to the carb with vacuum caps brand new from O Reillys. I adjusted the air fuel mixture by turning the mixture screws 3 turns out from seat and turning them in slowly until the idle decreased and then turning them back out 1/8 turn. This is where I started to notice something weird. Cylinders 3&4 gave a very noticeable idle decrease, while cylinders 1&2 barely took an adjustment. Then I adjusted the idle into approx 1050ish per the bikes tach. On a 3 mile ride around my neighborhood afterwards, I noticed that the motor would rev seemingly normally, but with no power and top speed in 4th and 5th was 60, per my GPS speedometer app on my phone. The bike would die if I pulled over and stopped, but would refire normally and strong. On a stupid whim, while stopped and running I slightly touched cylinder 1 and then 2 exhaust pipes, noticed they were warm, rather than hot. I could hold them without burning myself, while 3&4 seemed at normal operating scalding hot temperature. My buddy and I pulled the plugs, 3&4 had strong spark to the cylinder head, 1&2 had weak spark. 3&4 plugs looked like normal running plugs. 1&2 were wet, but not overly. Plugs are gapped to approximately .025. Performed compression tests, warm bike and wide open throttle. All cylinders were over 110 psi, with 1&4 over 150 psi. My compression tester is a cheap Oreillys special and I could not get the best seal on cylinders 2&3, but they read 110 and 120 respectively, but I believe them to be higher.
Based on the weak spark at 1&2 cylinders I’m believing to start there, but I’m at a loss.
Thank you in advanced, sorry for the information dump!
.
