LanarkXS
XS650 Member
OK, here goes, first post......
Early in the summer I picked up a stock 1980 XS650 Special with 24,000 kms on it. It looks to be in very good condition.
It was running fine when I acquired it. The second day after it was licensed I took it for an "inaugural"ride. It ran fine for 60 kms. I came to a stop at an intersection and when I went to pull away the motor bogged badly and I thought it was going to quit altogether. However it kept running and got me home.
Since then I have done a number of test rides in the neighbourhood to try to observe how it behaves. It starts easily hot and cold. In a "steady state"constant throttle the motor runs fine under load at any speed. The problem arises when starting off from a stop. Some of the time it runs normally and pulls away cleanly. However, more often than not the motor will bog and go back and forth between wanting to accelerate and wanting to die – it rides like a bucking bronco. If one is persistent it will get past this behaviour and run strongly until the next time one gears down to a stop and then start over again as one pulls away.
I was wondering if the vacuum actuated petcock might be the culprit but it does the same thing if the petcock is put in the prime position. Gas flows freely on prime as I drained the tank on prime.
I checked the compression and got 150+ pounds using the kickstarter. The spark plugs look fine.
I am thinking that this is a carburation problem of some sort and now that I have time I want to get it sorted. I was wondering if it might be diaphragm problems. I removed the tank and airbox thinking I would tear down the carbs. The slides move freely. I tried the "quick check"of the diaphragms by lifting the slides, blocking the top port and watching the descent. Both slides move down slowly and drop quickly once the port is unblocked. This would suggest that the diaphragms are ok.
So before I go any further with a carb tear-down I thought I would ask here for diagnostic advice on what to look for carburation-wise or otherwise.
I have the XS650 Garage Carburetor Guide and the CV Carburetor Rebuild Tutorial.
I welcome your thoughts and suggestions and thank you in advance.
mike
Early in the summer I picked up a stock 1980 XS650 Special with 24,000 kms on it. It looks to be in very good condition.
It was running fine when I acquired it. The second day after it was licensed I took it for an "inaugural"ride. It ran fine for 60 kms. I came to a stop at an intersection and when I went to pull away the motor bogged badly and I thought it was going to quit altogether. However it kept running and got me home.
Since then I have done a number of test rides in the neighbourhood to try to observe how it behaves. It starts easily hot and cold. In a "steady state"constant throttle the motor runs fine under load at any speed. The problem arises when starting off from a stop. Some of the time it runs normally and pulls away cleanly. However, more often than not the motor will bog and go back and forth between wanting to accelerate and wanting to die – it rides like a bucking bronco. If one is persistent it will get past this behaviour and run strongly until the next time one gears down to a stop and then start over again as one pulls away.
I was wondering if the vacuum actuated petcock might be the culprit but it does the same thing if the petcock is put in the prime position. Gas flows freely on prime as I drained the tank on prime.
I checked the compression and got 150+ pounds using the kickstarter. The spark plugs look fine.
I am thinking that this is a carburation problem of some sort and now that I have time I want to get it sorted. I was wondering if it might be diaphragm problems. I removed the tank and airbox thinking I would tear down the carbs. The slides move freely. I tried the "quick check"of the diaphragms by lifting the slides, blocking the top port and watching the descent. Both slides move down slowly and drop quickly once the port is unblocked. This would suggest that the diaphragms are ok.
So before I go any further with a carb tear-down I thought I would ask here for diagnostic advice on what to look for carburation-wise or otherwise.
I have the XS650 Garage Carburetor Guide and the CV Carburetor Rebuild Tutorial.
I welcome your thoughts and suggestions and thank you in advance.
mike