Bs34 carb, need help

Hey peanut, i will check those header gaskets and muffler joints, I have done the diaphragm test and there was no leaks, I took carbs back off last night and going to take a close look at everything, thanks for your input, will check those things out.
 
Took out pilot jets size is 42.5 is this the right size for this bs34? Btw had loose clamp on muffler (thanks peanut).
 

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good luck Richard.:thumbsup:

They are damn frustrating these carbs. No matter how meticulous you think you've been they still seem to have problems once fitted.
Perhaps some 'carb' issues are actually a problem elsewhere with valves, timing, advance etc.

I'm taking mine off again today to try and eliminate this hanging idle problem once again. This time I'm also going to adjust the valves adjust the cam chain tensioner check the Boyer advance setting etc but its just desperation because I'm sure they are all fine.
 
Your right peanuts, they are frustrating :banghead: Now I did found a loose muffler clamp on the side it was backfiring, hopefully that's fix now and I did notice that the wire going through the end of my pilot jets gave my some résistance, but got it through and everything is now opened and clean, got to put them back on. I re-checked my floats and they are good. O btw, good luck to you also.
 
Peanut
I had the hanging idle problem on my rebuilt motor and carbs (BS34). I had completely stripped and rebuilt carbs with new Yamaha throttle seals, yet the RHS one was leaking. When replacing this, I noticed it was sitting flush with it's housing. When I put in the new one I made sure it was pushed well into the housing (small bit of tube over throttle shaft) because I concluded that when I originally re fitted the throttle shaft, the seal must have moved outwards and because of this would not seal correctly. So far so good - just an idea


Martin
 
Thanks Martin for the suggestion.:thumbsup:

funnily enough I did notice that one of the throttle shafts did have a lot of float on it and the plastic spacer had quite a big gap between the throttle shaft bush and the carb (difficult to describe in words)

I think I will try to find some replacements and see if I can reduce that gap. My shafts do not appear to have any significant wear but it really doesn't need to be much excess air to cause a hanging idle.
 

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funky said:
My engine bogged dow when i when to lean on the needle I.E top notch from second notch it did not like that at all.
Click to expand...

surprising what a difference it can make isn't it.

I checked my main jets the last time the carbs were off with a view to fitting some new 140 jets that I bought to supposedly upgrade from the standard 135 due to my straight through exhausts.
i was surprised to find I had 145 fitted :wtf:

Although the bike was pulling like a train through the entire throttle range I changed them from 145 to 140 and immediately noticed the engine bogged from 3/4 to WOT so I'll switch them back tomorrow (weather permitting):thumbsup:
 
Hey guys just an update: took cRbs off and made sure all passages and jets are clear, pilot jets too, still dying wth throttle. Found to exhaust leaks, fix them and still dying, did the float test with tube, but notice as gas stating to fill tube, it ran out, has to be the floats, i thought I had them set right (confused). Where we go Again.
 
its very frustrating isn't it.:doh: you just want to be able to go out there jump on the bike and go for a blast :bike:

Good news for me ....I have finally cured my hanging idle problem at least for the time being. Tonight I went for a short ride through the village with the idle at 1000rpm at last!

Don't give up you'll get there soon.

When you recheck the float levels make sure that you lower the floats down onto the float valves really gently so that the float valve spring isn't compressed giving a false reading. Don't forget to check both ends of the floats
Also ...check that the float tangs are horizontal (parallel with the carb body base) when inverted otherwise the float tang might press the float valve more to one side maybe causing friction :shrug:



let us know how you get on:thumbsup:
 
Hey peanut, glad you got your bike running right, yes its frustrating:doh: maybe its just me, but it is hard to see in there, I need to line those carbs up so I can see and make sure they are right.
 
what do you mean it ran out .... what out of the tube or what ....make sure your floats "FLOAT" have they got holes in them.you can take the floats of and put them in a small tub of fuel submerge them see if they are fully bouyant.if theres holes in them you will hear it sloshing about when you shake the floats
if the fuel ran out of the top of the tube then that float in not floating or its getting stuck so you have a constant feed of fuel to the carb it will flood the circuits and when you touch the throttle it will cut out
 
I know floats are good. I did shake them and hear nothing, I did noticed a fuel line going a crossed half the floats, so I rechecked and adjusted the floats, the only other thing I did was replaced the o rings,maybe there not right, put them back on and choke to start and use the throttle it dies, I'm totally at my wits end.
 
Ultimately my issue were the floats. Unless I missed I haven't seen mention of the diaphragms. Have you tried the slide test to make sure the slides are gong up and down correctly?
 
Are your floats brass or plastic? They use different levels. 27 mm on the brass, 22 on the plastic.
If brass draw a cup of hot water, submerge the floats in the hot water, As the floats warm up the air inside expands, any leaks will show up as air bubbles.
They can be replaced with the plastic.
Leo
 

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