BS34 Float Help

[Jim]

Oh... and there's a spring inside that barb plate. Careful... if it launches itself high enough, the jet stream will send it my way.

 

[Jim]

OK.... sumpin' kept nagging at me so I opened one up. I stand corrected. Both the cavity drain plate and the barb plate will clock (only) two ways.... 180° from each other. Leave the cavity plate as is and rotate the barb plate 180°
Phew....

 

[5twins]

Jim, is there an internal passageway or something that requires the vent to face the rear?

 

[Jim]

Yes, the diaphragm actually consists of two sheets of rubber, one on each side of the cavity plate. I suppose that's to give extra protection against a pinhole leak allowing fuel into the vacuum barb. The passageway leads in between the two rubber sheets. It needs to be on the bottom for drainage in case of a leak.

 

[bul_racer]

Thanks guys! Not sure I understand the terms cavity plate and drain plate though. I guess I'll figure it out when I get into it. Hoping I can just turn the back around but sounds like I'll need to move some other things as well.

So when I took apart the tank cap, though it looks OK from the outside, it is pretty rusted inside. That's all in the 3 weeks since I last had it apart and cleaned everything real well. Not thrilled with the idea of just putting it back together knowing it will quickly rust all over again. Not sure what I can do to prevent that short of sealing the tank and that's a big hassle.

 

[Jim]

Hoping I can just turn the back around but sounds like I'll need to move some other things as well.

The back (barb plate) is all you need to turn around. Leave everything else be.

 

[Xs650911]

Hi All,
I'm a newbee trying to rebuild carbs on my 1980 XS650G. I know there's a LOT of previous discussion about this but after reading a bunch of it I'm just confused. Some say confused is just another word for stupid & maybe I am bc I don't know how to proceed. The bike ran when I parked it years ago, but poorly.

One of my floats makes a funny noise when I shake it and when I place it in water it floats with that side lower than the other so I'm pretty sure there's gas inside. Maybe this was the problem way back in 2004. I tried to find a hole or evidence of a leak but can't see anything. I placed it in hot water but no bubbles appeared. I don't know how to repair a leak I can't find. Some posters say I shouldn't try bc heating to solder is likely to create additional leaks or at least cause them to become more open.

I'd hoped that it wouldn't be a major project to get this bike running as I already have several projects taking up my garage floor space. My inclination is to just buy a new float but I've tried and tried to find a source for a replacement float. Hard to believe that Mikuni wouldn't provide the part since there seem to still be a lot of these bikes on the road. Mike's shows one but reading the detail my bike is not among those listed. Saw a post where someone said they ordered this and it seems to be for bs38, not bs34. I don't want to order a part that won't fit.

It seems that some folks are using plastic floats to replace the brass but I don't know which ones to get. Is there one that fits or would it need to be modified? Also not sure if there's a float height spec for the plastic or if I'd have to hook up a gas line to the bottom of the float bowl in order to visually check float height.

Any help would be appreciated.

Can you help me tell the difference between a B34 and a B38 carburetor? I have a huge fuel problem and I was told to tell a member here which I have. I don't know which.

 

[Xs650911]

Hi All,
I'm a newbee trying to rebuild carbs on my 1980 XS650G. I know there's a LOT of previous discussion about this but after reading a bunch of it I'm just confused. Some say confused is just another word for stupid & maybe I am bc I don't know how to proceed. The bike ran when I parked it years ago, but poorly.

One of my floats makes a funny noise when I shake it and when I place it in water it floats with that side lower than the other so I'm pretty sure there's gas inside. Maybe this was the problem way back in 2004. I tried to find a hole or evidence of a leak but can't see anything. I placed it in hot water but no bubbles appeared. I don't know how to repair a leak I can't find. Some posters say I shouldn't try bc heating to solder is likely to create additional leaks or at least cause them to become more open.

I'd hoped that it wouldn't be a major project to get this bike running as I already have several projects taking up my garage floor space. My inclination is to just buy a new float but I've tried and tried to find a source for a replacement float. Hard to believe that Mikuni wouldn't provide the part since there seem to still be a lot of these bikes on the road. Mike's shows one but reading the detail my bike is not among those listed. Saw a post where someone said they ordered this and it seems to be for bs38, not bs34. I don't want to order a part that won't fit.

It seems that some folks are using plastic floats to replace the brass but I don't know which ones to get. Is there one that fits or would it need to be modified? Also not sure if there's a float height spec for the plastic or if I'd have to hook up a gas line to the bottom of the float bowl in order to visually check float height.

Any help would be appreciated.

I hope you are getting more support than I am. I would help if I knew what to say but I'm inexperienced and would probably just cause more problems for you. So was your carburator leaking to?

 

[Xs650911]

.041" safety wire or a paperclip is just the ticket here.


View attachment 194711

Nice...

 

[bul_racer]

I hope you are getting more support than I am. I would help if I knew what to say but I'm inexperienced and would probably just cause more problems for you. So was your carburator leaking to?

Hi 911,

Sorry you're not getting support on this forum. I've been fortunate to have great support from the many experts here. Unfortunately, I'm not one of them.

I'm not sure the differences between the BS34 & BS38, as I just have the BS34. You should be able to tell which you have by measuring the spigot where it connects to the motor. If it's a BS38 it should measure 38mm.. No, my problem wasn't leakage, but just a bike that sat out unattended for 17 years.

There's quite a bit of info in this forum. You should do some searches. Here are a couple of links you might find useful:
Yamaha XS650 Model ID
XS650 Garage Carburetor Guide

The fellows here seem to like pictures so maybe you can pique their interest with some graphical stimulation. Good luck with your project!

 

[bul_racer]

Oh... and there's a spring inside that barb plate. Careful... if it launches itself high enough, the jet stream will send it my way.

Haha! I don't think you'll be receiving the petcock spring but one of the little zerk fitting balls I was using for the choke rod might still be in orbit.

 

[Adamc]

911 what a tosser!

 

[grizld1]

As Jim pointed out, 911 was already banned once under another handle. As I pointed out, his tale of woe and plea for help are phony. He's a chronic loser whose only sense of accomplishment comes from getting others to buy into his act.

Be a good troll, Bubba; crawl back under your bridge and suck algae.

 

[bul_racer]

Trying to reinstall the carbs. After many, many twisting, contorting attempts I simply have not been able to get them in that little space with the metal covers on the rubber intake manifolds. When I removed the covers I did get the carbs in place. Sure, the covers provide support against vibration but are they really necessary since the rubber seems pretty sturdy?

If the metal covers are necessary I hope someone has some nifty tricks for getting the carbs in. I thought maybe I'd try putting the carbs into the manifolds & then see if they'll fit but if I do that there'll be no way to get an Allen wrench in to tighten those bolts. Jeez! It almost seems like Yamaha designed it to be difficult. If they'd moved the downtube back half an inch it would be a completely different story.

Anyway, looking at the manifolds in between wrestling bouts I noticed that the one for the left carb does not align with the intake opening. Maybe I can fix it by hogging out the bolt hole in the manifold but wondering if I ought to just get some better manifolds. These were cheap Chinese parts so not a big loss if I don't use them. On the other hand, I'm not crazy about waiting another week and then finding out that the new ones don't work any better than what I have.

Here's a pic of the manifold's attempt to turn my 34mm carb into a 30mm.

As always, I appreciate any insight.

 

[Jim]

Even on good manifolds it can sometime be a bear to get the carbs in. And yes you need the metal cages. Otherwise the carbs will sag and stretch the rubber 'till it starts cracking.
Looking at that "Chinese offset"... I'd trash 'em. Look for some ARS branded ones. ARS made the originals for Yamaha. Don't remember where I got mine. Lemme do a little digging....

 

[Jim]

Look here. TourMax branded... made in Japan. These'll be the ARS intakes.

 

[bul_racer]

Look here. TourMax branded... made in Japan. These'll be the ARS intakes.

Thanks Jim! Well, for that price they had better be good. If they're not at least a little bit easier to get the carbs into I'll probably be posting on here for someone to come help me get them in. Looks like I'll need 2 men and a boy to do it...

 

[Jim]

I've installed 'em both ways... forcing the carbs on... and putting the the carb in the boot first then installing the boot/carb on the head. Both are doable.... neither way is easy.

 

[5twins]

To wiggle the carbs into the frame with the manifolds mounted on the engine, you need to remove that top butterfly shaped bracket from the carb set and take the acorn cover nut off the cam chain adjuster. It's still tricky but they'll go in.

 

[bul_racer]

I've installed 'em both ways... forcing the carbs on... and putting the the carb in the boot first then installing the boot/carb on the head. Both are doable.... neither way is easy.

Jim, I sure don't see how it's possible to access the Allen head bolts if you put the boots on first. Maybe if I discard the Allen bolts & replace them with hex head bolts. Then I could reach them with a wrench.