I forgot to mention that the carbs I bought last year came with a shorter set of springs for the slides. Tonight I took those out and put in the longer springs that I had in my original carbs, thinking that maybe it just didn't have enough spring force to return the needle to idle when I closed the throttle. Has any one ise ever seen these shorter springs?
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Engine Has Gone MAD!
- Thread starter Fergie
- Start date
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- Tags
- carburetors jetting
I've used shorter springs, and it won't make much difference on return for idle, just makes it richen up quicker from roll-on.. The faster the needle gets back into the needle jet, the faster it is running on only the pilots, which isn't going to have much affect on your popping problem, or maybe make it a little worse.
Before thinking about rejet, try a 1/4 turn further out on both mix screws and see what happens. You might need to go 1 size up on the pilots (but pods by themselves seldom need it - if you use aftermarket/modified exhaust + pods.. that's another story).
Before thinking about the mains, you need to get out and ride it and look for flat spots in acceleration, and unless that flat spot is at WOT, then you'll want to try and shim your needle first.
Rejetting is a process... nobody can tell you for certain what exact jets you need and have it come out right. It might be close enough to ride on, but it won't be right on. Your spark plug color can tell you a lot about what's going on too, and many even use it as a tuning guide once jetting is very close.
Before thinking about rejet, try a 1/4 turn further out on both mix screws and see what happens. You might need to go 1 size up on the pilots (but pods by themselves seldom need it - if you use aftermarket/modified exhaust + pods.. that's another story).
Before thinking about the mains, you need to get out and ride it and look for flat spots in acceleration, and unless that flat spot is at WOT, then you'll want to try and shim your needle first.
Rejetting is a process... nobody can tell you for certain what exact jets you need and have it come out right. It might be close enough to ride on, but it won't be right on. Your spark plug color can tell you a lot about what's going on too, and many even use it as a tuning guide once jetting is very close.
Yea I played with lengthening and shortening the spring for quite a while until I finally decided that Mikuni got them right.........the shorter spring advances the slide and causes trouble and lengthening it is just the opposite ...at least that is what I found.........both springs being the same length is the only thing I check now......and that no one has dicked with them...........
xsjohn
xsjohn
Sundie
Jabroni
No. ride it around. Go on a 2 hour highway run. Clean it out. Don't cane the crap out of it, but get it running up in the more than 1/2 throttle range for a while.
THEN come back and fiddle with it, a little bit at a time.
THEN come back and fiddle with it, a little bit at a time.
Alright. I took it out for a ride this afternoon, and I was happy with it. I kept it pretty tame for the first 15 miles, then took it on the high way and opened it up. It's the first time I rode in over a year, so it was pretty exciting too.
When I first started it up, the idle was crap, so I let it warm up for about 5 minutes. The exhaust was still making a popping sound, but pretty low decibles. I turned the idle mixture screws about 1/4 turn out, and it seemed to fix it a little bit, but not perfect. When I got it on the road, above 2500rpm the engine was smooth. I rode it in 4th gear and got the revs to about 5500rpm, and there was a small flat spot, but not too bad. I don't normally run there any ways, so that doesn't concern me.
After I rode it around for about an hour, I pulled into a gas station and the idle was up around 2000, so I turned the set screw down until I was in the 1200-1400 range. I then rode it home and the idle was about 1000rpm. I don't know what that's about. I made sure the chokes weren't sticking, or open at all, and the throttle plates were returning to the set screw. After the bike cools down, I'm going to check and set the over head, because I haven't done that since the rebuild. I'll also warm it up again and go through the dead cylinder test again. I'll try to post another video again so guys can hear it.
When I first started it up, the idle was crap, so I let it warm up for about 5 minutes. The exhaust was still making a popping sound, but pretty low decibles. I turned the idle mixture screws about 1/4 turn out, and it seemed to fix it a little bit, but not perfect. When I got it on the road, above 2500rpm the engine was smooth. I rode it in 4th gear and got the revs to about 5500rpm, and there was a small flat spot, but not too bad. I don't normally run there any ways, so that doesn't concern me.
After I rode it around for about an hour, I pulled into a gas station and the idle was up around 2000, so I turned the set screw down until I was in the 1200-1400 range. I then rode it home and the idle was about 1000rpm. I don't know what that's about. I made sure the chokes weren't sticking, or open at all, and the throttle plates were returning to the set screw. After the bike cools down, I'm going to check and set the over head, because I haven't done that since the rebuild. I'll also warm it up again and go through the dead cylinder test again. I'll try to post another video again so guys can hear it.
OK, I reset the over head, but it's wasn't off by much, and was probably with in tolerance. I did set the intake just a smidge on the tighter side of the tolerance.
I checked the mixture screws, and the LB was 2 1/2 turns from a soft seat, and the RB was 3 turns from a soft seat.
Here is the spark plugs. They don't look too bad, but RB does look a little bit richer than the LB.
I checked the mixture screws, and the LB was 2 1/2 turns from a soft seat, and the RB was 3 turns from a soft seat.
Here is the spark plugs. They don't look too bad, but RB does look a little bit richer than the LB.
It's unbelievable. I put the plugs back in, did the dead cylinder adjustment, started the engine up and it was nothing but smooth. It held idle perfect at 1200rpm; no back fires or popping. I took it out for a night spin, and it felt great...the best it's ever felt. I've gone 50 miles on about 1 gallon of gas, so the fuel economy is right on. I'm taking it to work tomorrow, even if it is going to be 45 deg F when I wake up in the morning.
I'm guessing a combo, John. He got the floats and the mix screws set up right. I had to go through dead cylinder twice to get it on the money too.. Seems like I've had to do most things on this bike twice.
Congratulations on a great repair!
Congratulations on a great repair!
