So ive been messing with carbs and jetting for a month or so now and i still cant figure it out. i have good compression but its still acting weird. after it warms up (Sometimes) the rpms will hang and stay at 3k then come back down on their own after like 15 to 20 seconds. i cant reproduce it and i dont know how to stop it. and at about 65 mph in 5th it seems like its done accelerating. It will surge a little then bog slightly. just back and forth. i might be able to get to about 70. Plugs are still white, even at idle and im waaaaaay big on my mains. i think i put a 145 in today and its still the same. going back to 137.5 or 140 tomorrow. I cant make the plugs turn black even if i wanted to. i dont get it...
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Blown head gasket? Maybe I have bike hypochondria?
- Thread starter Jawknee21
- Start date
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- carburetors engine
If it was me, I'd look for an air leak in the intake on the downstream side of the throttle plate, or could be the throttle shaft seals leaking. Is the vacuum on the right side capped off? Left side connected to petcock? I once had a very tight exhaust valve give symptoms like an air leak on a single cylinder bike.
Push on things around the intakes and see if you can get it to rev up. While it's in that condition, spray carb cleaner around suspect areas and see if the revs go down; there's your leak.
Push on things around the intakes and see if you can get it to rev up. While it's in that condition, spray carb cleaner around suspect areas and see if the revs go down; there's your leak.
ippytattoo
Just another grumpy old hack.
If it has the stock carbs (BS34's) each of the intake boots, the rubber boots in between the head and the carbs, have a vaccum barb that points up and out from the boot. Just by what you are describing I would check that the throttle cable is not binding, moves smoothly and returns to the idle position consistantly. Then check that the boots are not cracked or torn as this will cause an air leak, or lean condition, and the RPM's to hang. Check and see if the blind plug, the little black or colored cap on your vaccum barb, is cracked or sealing correctly. You could buy a section of vaccum hose that is long enough to connect the 2 vaccum barbs together and run the bike with the petcock in the prime position, if you have the vaccum operated petcock, or to replace the blind plugs, if you have a non-vaccum operated petcock.
They are. Jeez. If I get money this year I would like to send my motor to Hugh. I really want to keep this bike but I can't seem to make anything better. It just gets worse. But I'm learning a lot from it..,
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New plugs on the vacuum barbs, new manual petcock and I sprayed carb cleaner around the boots and no change.
Maybe I'll try a new throttle cable. It only seems to do it when it's warmed up. After about 10 miles of riding...
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Maybe I'll try a new throttle cable. It only seems to do it when it's warmed up. After about 10 miles of riding...
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CDNTX650
XS650 Guru
did you spray around the throttle shafts?
littlebill31
Smells of Raw Fuel
Make sure you ckeck those throttle shaft seals as CDNTX650 suggests. Watch this little video I made, it shows you where they are and how to check them with the carbs on, bike running. It's at minute 2:30 to 3:15. They will cause a bad air leak too.
If you crack the throttle at idle, and it hangs then drops, that is the pilot circuit/pilot jet. Also check your diaphragm for tears. That is another cause of power lose.
Check to see what position your throttle is in when things are amiss. Like half throttle, at idle, wide fucking open, ect. That's how they work.
If you crack the throttle at idle, and it hangs then drops, that is the pilot circuit/pilot jet. Also check your diaphragm for tears. That is another cause of power lose.
Check to see what position your throttle is in when things are amiss. Like half throttle, at idle, wide fucking open, ect. That's how they work.
hotrdd
XS650 Junkie
I went through something similar for a few weeks but after rebuilding the Carbs for the third time they are now fine. I guess I thought I cleaned them enough the first time but missed something. Follow the carb rebuild specs. Line for line.
No and take this with love.... It's a skills (patience) pit. No one has said the sync word, are the carbs sync'ed? A prime symptom of out of sync carbs is a hanging high idle. Have you read and UNDERSTAND the carb guide. Somewhere in those carbs is an unsolved problem waiting for that eureka moment. have you removed the plugs and the idle jets new or good condition rubber washers in the proper order with the washer? Intact rubber caps on the pilot jets?
Brand new idle jets and o rings in correct order. New rubber caps on pilots. I have read it quite a few times. It's gotta be something dumb that I didnt think of. I have checked the floats 3 times, new needle and seat, I didn't do the throttle shaft seal so I'll check that in a few mins. I am not going to take it to a shop cause they probably don't work on stuff this old very often. I'll figure it out if I don't get rid of it first...
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This video looks like garbage and you have to click on it to see it. The sound is really quiet too.
Does this look like I need to replace the throttle shaft seals? That's what's in the video isn't it? Maybe I'm wrong. I sprayed carb cleaner and i couldn't find anywhere that was making it die. It did a few times but it couldve been overspray to the pods. Anyone live in SoCal that knows what they're doing?
Does this look like I need to replace the throttle shaft seals? That's what's in the video isn't it? Maybe I'm wrong. I sprayed carb cleaner and i couldn't find anywhere that was making it die. It did a few times but it couldve been overspray to the pods. Anyone live in SoCal that knows what they're doing?
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When you open the throttle the butterfies are what open inside the carb. The shafts that turn to open the butterflies have seals around them where they go through the body of the carbs.
If those seals leak then you willget a lean condition.
At an idle when you spray carb cleaner or starting fluid, WD40 you won't kill the engine just cause the idle to change, go up or down a second or two.
Leo
If those seals leak then you willget a lean condition.
At an idle when you spray carb cleaner or starting fluid, WD40 you won't kill the engine just cause the idle to change, go up or down a second or two.
Leo
CDNTX650
XS650 Guru
not true, mine were so bad it would kill the bike. i used contact cleaner.
if you spray it where the shaft is, inside (not inside the carb throat itself as in between the 2 carb bodies) and out i bet it will die. use the straw. aim it directly at the pivots and give it a good blast, like 3 seconds. Do the right side carb as there is nothing in the way of the seals. Left has the throttle cable linkage.
I can almost guarantee they need to be done. 2 sets of my bs34's were completely shot.
if you spray it where the shaft is, inside (not inside the carb throat itself as in between the 2 carb bodies) and out i bet it will die. use the straw. aim it directly at the pivots and give it a good blast, like 3 seconds. Do the right side carb as there is nothing in the way of the seals. Left has the throttle cable linkage.
I can almost guarantee they need to be done. 2 sets of my bs34's were completely shot.
