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Cleaned carbs now have a hanging rpm issue
- Thread starter dman1049
- Start date
The first thing I would try is making sure the idle mixture screws are out at least 3 turns, then see how it runs.
hardtailed77
Never Finished
We've all pretty much came to the conclusion that the manual is wrong on the idle screws. Houghmade is right on the money, and that's where I would start from, and just adjust from there. Also, as BC mentioned, having the filters off the bike while tuning is just going to make you tune twice. Set the bike up the way it will be while riding (filters on, baffles in (or maybe out), etc.), then do your tuning.
monkeyboy
XS400 Enthusiast
check to make sure that both carbs are synced,the screw in the middle of both of them,which makes both carbs close and up the same amount at the same time
def too lean, you need to clean
if you want to ride your mean machine
the carbs are old
so now your told
check out the rubbers
for open cracks and others
I'm a poet and didn't know it
if you want to ride your mean machine
the carbs are old
so now your told
check out the rubbers
for open cracks and others
I'm a poet and didn't know it
I'm at 4.5 turns out on the mixture screws and the bike starts better now. Still have the hanging rpm. I synced carbs before i reassembled everything. I put the filters back on. Im around 1000 feet elevation. The jetting is stock. Whats good for checking air leaks?
hardtailed77
Never Finished
Thank you for my new signature! hahaha Drewpy, you kill me!def too lean, you need to clean
if you want to ride your mean machine
the carbs are old
so now your told
check out the rubbers
for open cracks and others
I'm a poet and didn't know it
hardtailed77
Never Finished
Spray some WD-40 on the carb boots and see if the engine idle changes.
You're always going to be too lean on stock jets if your filters are off; you can unscrew the idle air screws until they come off, but the stock pilot jet can only deliver so much fuel. Is this problem happening with the air filters on? mikesxs.net has every size you could ever want for the bs34 carbs.
Ok, wait, before you jet you need to confirm there are no air leaks. Everything is stock, right? If everything is stock you probably have an air leak and jetting is not the solution to that problem. Are the tips on the idle air screws intact or broken off? I wouldn't trust the manual for jet sizes because the figures in the haynes were definitely wrong for my bike. I would pull the jets out of your carbs and read the size off of them; it will be imprinted somewhere. Just order a set 1 and 2 sizes up and you should be good to go. Mine dont, but some of the bs34 carbs on the 650s have rubber o-rings on the idle air screws that apparently disintegrate over time.
everything is stock. it even has the baffles in. i sprayed the intake into the cylinder, i sprayed around the filters and the idle didnt change. i guess ill check again. the needles looked fine. i guess it is weird that it runs the same from 3/4 to 8.5 turns out and still backfires and still hangs on rpm.
Have you tried restricting airflow at the intake port on the air filters? Maybe duct tape over the some of the opening and see if idle improves. I wonder if smoke would be useful for finding air leaks or if operating the bike itself would disturb the air too much. What did you set your float height to? My jets are way too small for my current setup, but when I had my floats set so high that they nearly started pouring gas out the air filters I could rev the engine fine; once I fixed the float height I could not open the throttle at all without the bike shutting off. My point is that it can have a dramatic affect on performance.
i left the floats alone. There were relatively the same height so i didnt touch them. It idles fine, as soon as it sees a little throttle the rpm hangs. you can start the bike let it idle a little and just twist the throttle a hair and it will go to 2000-2500 rpm and stay there 5 to 10 seconds and then drop back down.
If you have the carbs apart again measure them. The recommended setting in the manual from haynes is way too low for my bike; trying to set it to what they recommended would actually fully close and seal the float needle 
