Joined
·
132 Posts
OK, I need some help from the carb gurus on this board.
Background: I bought a non-starter in Feb from a guy who apparently parked the bike in late '07 after a fall and had not ridden it since. Expecting carburetor nastiness, I removed the carbs and, not surprisingly, there was a lot of green gunk on everything. I went through all the points in the carb sticky in this section, scrapping and shrubbing as best I could. I used carb cleaner liberally on the metal bits and hit every orifice I could find with compressed air.
After an unsuccessful attempt at just running with just cleaning the jets and other bits, I bought new main and pilot jets (152.5 mains, 17.5 pilot) and installed them yesterday. Went for a ride and low throttle/rpm performance was good; not stumbling or backfiring now. Got on the highway and the bike topped out at less than 90mph. I checked the letters on the tail of the bike and it is a 650 and not a 250.
I was in too big a hurry yesterday to sync the carbs before the test run, so I did that last night. Way out of sync, so I evened them up and put everything back together and hit the hay thinking I'd solved the problem.
Well, not so. Took the bike out for another spin this afternoon and while it is running much smoother at all rpms, there is no pull past about half throttle. On the highway, with the throttle pinned, I topped out a 80mph, even worse than before the sync! :angry1:
I checked the throttle cable adjustment before reinstalling everything and it is opening the throttle to the stop.
The bike is hard to start cold, stalls and dies at first, but after warmed up she purrs at idle.
Before all this carb work fun, I pulled the plugs and they looked fine but I replaced them anyway.
Have not checked compression, but it pulls strong under half throttle, so I don't think that is the problem. Other: Stock gearing. K&N filter. Micron exhaust with mid-pipe (headers looks stock, not sure though.) Previous owner jetted, looks like Factory Pro needle?
So, two things I can think of:
1) I haven't gotten all the green varnish out of all the fuel passage ways. I suppose the only way to get this is to tear it down again and soak the body in carb cleaner. I really want to avoid this if possible.
2) Throttle position sensor bad? I tried to check the resistance when I had the carb apart, but I'm not sure I understood how to read it. I don't suspect this because I can rev the engine in neutral all the way up to the redline.
So, fuel starvation sounds like the most likely scenario.
In and around town, the bike is fine. But this is to be my track tool, so top speed of 80-90mph and no response past half throttle is unacceptable.
Background: I bought a non-starter in Feb from a guy who apparently parked the bike in late '07 after a fall and had not ridden it since. Expecting carburetor nastiness, I removed the carbs and, not surprisingly, there was a lot of green gunk on everything. I went through all the points in the carb sticky in this section, scrapping and shrubbing as best I could. I used carb cleaner liberally on the metal bits and hit every orifice I could find with compressed air.
After an unsuccessful attempt at just running with just cleaning the jets and other bits, I bought new main and pilot jets (152.5 mains, 17.5 pilot) and installed them yesterday. Went for a ride and low throttle/rpm performance was good; not stumbling or backfiring now. Got on the highway and the bike topped out at less than 90mph. I checked the letters on the tail of the bike and it is a 650 and not a 250.
I was in too big a hurry yesterday to sync the carbs before the test run, so I did that last night. Way out of sync, so I evened them up and put everything back together and hit the hay thinking I'd solved the problem.
Well, not so. Took the bike out for another spin this afternoon and while it is running much smoother at all rpms, there is no pull past about half throttle. On the highway, with the throttle pinned, I topped out a 80mph, even worse than before the sync! :angry1:
I checked the throttle cable adjustment before reinstalling everything and it is opening the throttle to the stop.
The bike is hard to start cold, stalls and dies at first, but after warmed up she purrs at idle.
Before all this carb work fun, I pulled the plugs and they looked fine but I replaced them anyway.
Have not checked compression, but it pulls strong under half throttle, so I don't think that is the problem. Other: Stock gearing. K&N filter. Micron exhaust with mid-pipe (headers looks stock, not sure though.) Previous owner jetted, looks like Factory Pro needle?
So, two things I can think of:
1) I haven't gotten all the green varnish out of all the fuel passage ways. I suppose the only way to get this is to tear it down again and soak the body in carb cleaner. I really want to avoid this if possible.
2) Throttle position sensor bad? I tried to check the resistance when I had the carb apart, but I'm not sure I understood how to read it. I don't suspect this because I can rev the engine in neutral all the way up to the redline.
So, fuel starvation sounds like the most likely scenario.
In and around town, the bike is fine. But this is to be my track tool, so top speed of 80-90mph and no response past half throttle is unacceptable.
