1973 TX650 Chopper
XS650 Member
Okay guys, I'm a newb here so I'm hoping for a little advice on a problem I'm having. I bought a 1973 TX650 that was 95% completed by another owner. I knew it needed a little work but I'm having an issue I can't figure out.
This TX650 is a custom chopper/bobber with a lot of aftermarket parts. It has aftermarket open exhaust and pod air filters. When I purchased the bike it started easily but ran a little rough, though it would go down the road and was driveable. It would start right up and it would drive, but it would run rich and poorly (no acceleration) for the first 10 blocks or so. Then it would stop running so poorly and the acceleration would return to normal and I drove it like that a few times. It seemed to run okay once the initial no acceleration problem disappeared. But then after the bike ran better and warmed up, it wanted to increase the RPMs on it's own and surge rather high. I've had to shut it down a few times to avoid it racing to dangerous RPMS. A few times I activated the choke temporarily and that seemed to keep it from RPM increasing. Also, I could feel it wanting to rev up while it was in gear, but if I left it in gear while I slowed down the RPMs would drop back down low enough it would usually not surge, until it reached a high enough RPM and then it would want to surge again. I originally thought the carbs were junk since they were the original ones. I ordered new Mikuni VM Roundslide 34mm Carbs by TC Bros and I installed them along with a new throttle cable and new intake manifolds. Once I replaced those parts the bike started right up and I was tinkering with the idle screws and making minor adjustments to the carbs. I took the bike down the block and back and it seemed to run well, but then the exact same thing happened with the RPMs increasing dramatically and I had to shut it down to avoid damage. Now, I'm not sure what to check. The carbs are brand new and tuned for my set up out of the box by TC Bros.
Can anyone point me in the right direction? I have the owner's service manual and the Clymer's manual for the bike and I do have a fair amount of mechanical aptitude, but I'm not certain how to troubleshoot this occurrence. I wanted to test ride some more, but I live in the upper midwest and it's really cold here now. The TX650 has an updated charging system I believe, but it still has the original points type set up. Any help would be appreciated. Thanks for your time.
This TX650 is a custom chopper/bobber with a lot of aftermarket parts. It has aftermarket open exhaust and pod air filters. When I purchased the bike it started easily but ran a little rough, though it would go down the road and was driveable. It would start right up and it would drive, but it would run rich and poorly (no acceleration) for the first 10 blocks or so. Then it would stop running so poorly and the acceleration would return to normal and I drove it like that a few times. It seemed to run okay once the initial no acceleration problem disappeared. But then after the bike ran better and warmed up, it wanted to increase the RPMs on it's own and surge rather high. I've had to shut it down a few times to avoid it racing to dangerous RPMS. A few times I activated the choke temporarily and that seemed to keep it from RPM increasing. Also, I could feel it wanting to rev up while it was in gear, but if I left it in gear while I slowed down the RPMs would drop back down low enough it would usually not surge, until it reached a high enough RPM and then it would want to surge again. I originally thought the carbs were junk since they were the original ones. I ordered new Mikuni VM Roundslide 34mm Carbs by TC Bros and I installed them along with a new throttle cable and new intake manifolds. Once I replaced those parts the bike started right up and I was tinkering with the idle screws and making minor adjustments to the carbs. I took the bike down the block and back and it seemed to run well, but then the exact same thing happened with the RPMs increasing dramatically and I had to shut it down to avoid damage. Now, I'm not sure what to check. The carbs are brand new and tuned for my set up out of the box by TC Bros.
Can anyone point me in the right direction? I have the owner's service manual and the Clymer's manual for the bike and I do have a fair amount of mechanical aptitude, but I'm not certain how to troubleshoot this occurrence. I wanted to test ride some more, but I live in the upper midwest and it's really cold here now. The TX650 has an updated charging system I believe, but it still has the original points type set up. Any help would be appreciated. Thanks for your time.