Bs34 carb, need help

richardthemotorcycle1

richardthemotorcycle1

XS650 Guru
Messages
1,119
Reaction score
16
Points
38
Location
Vintondale Pa.
Hey guys, I'm about ready lose my mind. I've clean my carbs many times and had the bike running pretty good twice, today started having trouble again, have to choke it to start, when using throttle it Boggs down, just put new reverse cone mufflers on bike and when running the exhaust seem strong, like its burning too rich, mixture screw 3 turns out.
 
No. The oring that seals it to the carb body. It's in the guide. They do go bad. Clear tube float check will tell you what the level is doing.
 
Hey guys, had the carb off and check out the float valves, left side good, right side s Lille play, put carb back on and it running better, but still piping out right exhaust and when riding and gearing down backfiring, would a bad o ring cause that?
 
Being 3 turns out on your mixture screws makes me think you are lean on your pilot jets.
I went one size bigger than the stock ones on my 83 and it seems happy. As I recall you shouldn't be more than 2 turns if your pilots are in the ballpark
 
Did you actually remove the float valve bodies and check the o-rings???? This is a must do on BS34s. They are nearly always bad, letting gas bypass the valve.
 
Yes I did Gary, they didn't look bad, but the right valve didn't fit as tight as the left, Ivan you buy just the o ring? But I did discover the right muffler clamp wasn't tight,
 
did you remove the o-rings from the body? They ARE crap, trust me on this. I kinda can't believe you got THAT close and didn't just change them. The local auto store has a replacement that will fit use a touch of grease to help them go back in easy. Odds are high that is your rich issue on that carb.

IMHO when you go to remove the o-ring it will break and fall apart or just be rock hard.
Please report back.
 
Hey Gary, replaced those o rings. You were right. One o ring under sized because of wear and brittle and broke easy.
 

Attachments

  • image.jpg
    image.jpg
    266.1 KB · Views: 313
Last edited:
Ok replaced o rings and still having trouble. Will start only with choke on, use the throttle it dies, while it running every once in a whole backfires, pulled put, looks dry, what I'm i doing wrong?
 

Attachments

  • image.jpg
    image.jpg
    259.5 KB · Views: 288
Hi Richardthemotorcycle1 With regards to loosing your mind I can only prescribe olanzapine 5mg I am mental health practitioner :D with regards to your carbs :doh: I have the same issue with the reverse cones I have replaced my float valves and seats and "o" Rings. I also weakened the main jet needles to position 2 and 1 but this did not help:banghead: i am now waiting on main jets stepping down from 132.5 in increments of 2. Make sure......
If you have brass floats to set them at 26.5mm hight from the base where the gasket sits in :thumbsup: do not go above 27mm hight. once you have done this fit the bowls back on dont forget the gasgets,:laugh: use clear tubes to check the levels by fitting tubes to drain holes on the bottom of your carb bowls undo the drian screw but making sure your tubes are secured up the side of the carb body with a elastic band this will give you a clear visual on the float and fuel level ,,, if the carbs are off the bike as i assume they are you will have to feed fuel into the carbs using a large serynge or funnel necked down to fit the fuel line going into the carbs make sure they are level I used a small spirit level ,,, No Smoking :thumbsup::laugh: see my poats "what do you think" pics available http://www.xs650.com/forum/showthread.php?t=42783 it may help you .:thumbsup: Will let you know how i get on with the jets
All the best Funky
 
Last edited:
richardthemotorcycle1 said:
Ok replaced o rings and still having trouble. Will start only with choke on, use the throttle it dies, while it running every once in a whole backfires, pulled put, looks dry, what I'm i doing wrong?
Click to expand...

Have you actually removed the pilot jets, and confirmed they are fully clear? Did you read the number on the pilot jet, so you know if its the correct size?
 
Yes I have removed the pilot jets and they are clear, now I didn't look for number on the pilot jets, so But I will do that, is the size I need in my Manuel book? I just bought a metric ruler too today to check the floats, I had a slide type but hard to read.
 
Richard there would appear to be two seperate but related issues here

Backfiring is frequently caused by fuel mixture being ignited in the exhaust system due to valves not seating or timing being too advanced or air being drawn in the exhausts or headers somewhere so I'd go over all the exhaust joints really carefully and make sure that they are all fitting snugly. You can fit new header gaskets and use some exhaust jointing compound to seal muffler joints.

Backfiring can also be caused by timing being too advanced and exhaust valves not seating properly so it would be worth checking the advance mech and timing and definitely recheck that the valve settings are spot on.:thumbsup:

Regarding the bogging issue ..when your engine is idling and you roll on the throttle it is governed by the pilot jet air screw and throttle valve (slide diaphram) .The needle and needle jet have no effect at this point of the throttle range nor of course does the main jets.

Have you checked that both diaphrams are sealed and not leaking ? I'm not familiar with the BS34's but presume the diaphram intakes are centre top of the venturi mouth. If you cover the air intakes with a finger and raise the slides they should stay up or at the very least take a few seconds to fall .

Check for air leaks everywhere even the choke bodies where I recently found leaks on mine.
The fact that the starting issue seems intermittant when you remove and refit the carbs might suggest an air leak at the stubs/cylindrer joints or carb /stub joints
 

Similar threads

G
750 Tripple carb tuning help
Replies
16
Views
3K
VikingBeard
V
lumbee
Carb Woes...
Replies
12
Views
1K
lumbee
lumbee
devildrums
Tuning help needed
2
Replies
34
Views
2K
Paul Sutton
Paul Sutton
Astrolite
Need advice on two starting issues
Replies
12
Views
747
bosco659
bosco659
J
XS500 carburetor problem.
2
Replies
21
Views
1K
arcticXS
A
Back
Top