Hi Everybody, I thought I would post a follow up to my original post here:
Speedster SK one engine dies when other goes WOT
When I searched the forums I never really found an answer that directly helped me so I thought I would post a new thread with what I learned in hopes of saving someone else some time/ headaches.
To recap: I bought a 99 speedster sk with a destroyed engine. I pieced together a replacement and actually got it to mostly run. I ended up replacing the carburetor, after I rebuilt the one It came with but was still having problems like excessive smoking and then horrible backfiring through carbs. I am fortunate enough to have more money than time so it was an appropriate solution for me.
With the the new carb it runs fantastic and I am thinking of replacing the carb on the other motor no too as I am getting about 5-10% better performance on the new carb/ motor depending on throttle position.
The backfiring was the last straw for me with the old carb but when I searched the forum, I wasn't able to find a good answer for what the issue might be and it seemed others had similar problems but no solutions. Here is what I discovered:
I learned from the forum that a backfire through carbs was a symptom of a lean condition. I pulled the plugs and discovered they were fouled with oil. OK looks lean then. I made sure spark arrestor and air box were on correctly and everything sealed and mated correctly. No change. started it at 0 throttle: No backfire. Moved throttle to 1/3: No backfire. Moved throttle to 1/2: BANG! Hypothesis: High speed jet issue. Solution: pull (in my case replace) carb and inspect. Sure enough High speed jet looked fine but after running a fine wire through it discovered it had some varnish as well as obstructions in the carb machining itself (this thing sat for years with fuel in it before I bought it) An ultrasonic cleaner might have cleared it up but I don't have one readily available.
Now for next issue: the carb I bought was a BN40i off amazon. https://www.amazon.com/dp/B01BHI97RA?psc=1&ref=ppx_yo2ov_dt_b_product_details
This carb comes with the pump integral to the carb so I had to do some replumbing of the pulse line and delete the existing external pump. Next winter I will probably pull the motor completely and relocate the pulse outlet from the crankcase to tidy things up a bit but for now - good enough.
Please if anybody with more experience has anything to add (or correct) please let me know! I have found this forum to be a wealth of knowledge and experience and was hoping to add to it for those of us just diving in.
Speedster SK one engine dies when other goes WOT
When I searched the forums I never really found an answer that directly helped me so I thought I would post a new thread with what I learned in hopes of saving someone else some time/ headaches.
To recap: I bought a 99 speedster sk with a destroyed engine. I pieced together a replacement and actually got it to mostly run. I ended up replacing the carburetor, after I rebuilt the one It came with but was still having problems like excessive smoking and then horrible backfiring through carbs. I am fortunate enough to have more money than time so it was an appropriate solution for me.
With the the new carb it runs fantastic and I am thinking of replacing the carb on the other motor no too as I am getting about 5-10% better performance on the new carb/ motor depending on throttle position.
The backfiring was the last straw for me with the old carb but when I searched the forum, I wasn't able to find a good answer for what the issue might be and it seemed others had similar problems but no solutions. Here is what I discovered:
I learned from the forum that a backfire through carbs was a symptom of a lean condition. I pulled the plugs and discovered they were fouled with oil. OK looks lean then. I made sure spark arrestor and air box were on correctly and everything sealed and mated correctly. No change. started it at 0 throttle: No backfire. Moved throttle to 1/3: No backfire. Moved throttle to 1/2: BANG! Hypothesis: High speed jet issue. Solution: pull (in my case replace) carb and inspect. Sure enough High speed jet looked fine but after running a fine wire through it discovered it had some varnish as well as obstructions in the carb machining itself (this thing sat for years with fuel in it before I bought it) An ultrasonic cleaner might have cleared it up but I don't have one readily available.
Now for next issue: the carb I bought was a BN40i off amazon. https://www.amazon.com/dp/B01BHI97RA?psc=1&ref=ppx_yo2ov_dt_b_product_details
This carb comes with the pump integral to the carb so I had to do some replumbing of the pulse line and delete the existing external pump. Next winter I will probably pull the motor completely and relocate the pulse outlet from the crankcase to tidy things up a bit but for now - good enough.
Please if anybody with more experience has anything to add (or correct) please let me know! I have found this forum to be a wealth of knowledge and experience and was hoping to add to it for those of us just diving in.
