XS 1B Carburetors

Manic

Manic

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Okay, first of all, I’m not trying to stir the pot here. I’m just looking for some advise.

I purchased two Keyster carburetor rebuild kits from Mike’s XS. I followed the instruction and ordered two different kits (one for the left carb, one for the right). I received the kits and although they had different parts #’s and and the instructions indicated one was for the right carb and the other was for the left, there didn’t appear to be any differences in the kits. Also, they both contained parts for the ‘plunger’ style choke. The type with a pull knob vs. the type with a lever. But having read that many rebuild kits contain parts for various carbs and that some may not be applicable, I figured that must be the case here.

However, the choke gaskets were close for one carb but didn’t quite line up right. And was totally off for the second carb (the one on the right that doesn’t have a lever. Both kits basically contained the gasket for the left carb.

After reaching out to Mike’s and providing the requested pictures showing the problem, I received a reply email saying they “could see the problem. Your carbs are off an XS 2”.

But if that’s the case, then why doesn’t my carbs set have the plunger style choke knob? Also, like I said, the gasket for the choke is very close for the left carb. It just doesn’t line up perfectly at some of the screw holes and ports. I’m thinking I ordered the right kits, these are just poorly made & assembled kits.

Anyone have any suggestions or insights on this? If it’s just that the Keyster kits are not very good, any suggestions where I could source these parts?

Thanks all for your input!
 

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XS2 carbs only have a chock plunger on the left carb there is a crossover between the carbs. XS2 carbs do use a lever to operate the chock.
 
Manic said:
Doesn’t look like they have rebuild kits, but do have some gaskets. Looks like they have a lot of other good stuff though.

Thanks!!!
Click to expand...
There’s the thing, to get the right parts you pretty much have to build your own kit.
IMG_3292.png
Use this chart, check the carb guides under the tech tab and use Genuine Mikuni.
 
The choke on both the XS1B and the XS2 is operated by a single lever which lifts a plunger(s).
The XS1B lever lifts a plunger on both carbs.
The XS2 lever lifts a plunger on the left carb only.
How about some over-all pics of your carbs.
It looks to me like one or both of the choke gaskets, while not lining up exactly, will still line up good enough to work. Or, order the thinnest bulk gasket material you can find at the auto parts store, and make your own gaskets.
 
DogBunny said:
The choke on both the XS1B and the XS2 is operated by a single lever which lifts a plunger(s).
The XS1B lever lifts a plunger on both carbs.
The XS2 lever lifts a plunger on the left carb only.
How about some over-all pics of your carbs.
It looks to me like one or both of the choke gaskets, while not lining up exactly, will still line up good enough to work. Or, order the thinnest bulk gasket material you can find at the auto parts store, and make your own gaskets.
Click to expand...
Thanks DogBunny, from what you’re describing, it does sound like I have the XS 2 carbs. Strange, I would think it was the opposite, where the newer model had both enriching circuits
DogBunny said:
The choke on both the XS1B and the XS2 is operated by a single lever which lifts a plunger(s).
The XS1B lever lifts a plunger on both carbs.
The XS2 lever lifts a plunger on the left carb only.
How about some over-all pics of your carbs.
It looks to me like one or both of the choke gaskets, while not lining up exactly, will still line up good enough to work. Or, order the thinnest bulk gasket material you can find at the auto parts store, and make your own gaskets.
Click to expand...
Thanks everyone for your input. It appears I do in fact have the XS 2 carbs based on what you’re all saying. However, the problem I have is the Keyster kits don’t seem to be properly put together? Maybe different markets had subtle differences. i.e. European models had a plunger rather than a lever for the choke? But what gets me is their directions say you need two different kits, indicating there are different parts between the left and the right carbs, yet both kits had the exact same parts, including a choke plunger valve?

On top of that, the choke gaskets are close, but will not work the way they are and there’s not enough material to modify them (see pictures). Seems to me like a pretty crappy kit. I will follow others advise and do my best to piece together the parts.
 

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On some of the pictures I placed the stock gasket that came of the carbs, in place so you can see how it lines up. I also overlayed it on the replacement gaskets. I suppose their could be a subtle difference between the 1 & 2 carbs choke housing. But it doesn’t seem likely. I feel, based on these kits not being as advertised, Mike’s should give me a refund on them. But I doubt that will happen. So I will try and piece together my own parts.

And before anyone says “but you ordered kits for a 1 instead of a 2.” That doesn’t explain why the kits were identical even though they had different part numbers and both had choke plungers for a knob type choke?
 

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It's unlikely Mike's will refund you. I wouldn't waste the time.
Your terminology is confusing. The only knob choke was on 1980, which uses BS34s, a completely different carb. All BS38s have plunger(s) operated by one lever.
The plungers from the kits are for later year carbs.
Your original plunger and gaskets are probably fine. I'd smear an extremely thin coat of MotoSeal on both sides and re-use the gaskets. Permatex MotoSeal is on the shelf of auto parts stores. Assuming you don't already have Three Bond, or Yamabond, or HondaBond, or similar gasket maker.
 
By “knob choke” I mean one with a pull knob, not a lever. And yes, that’s what is confusing in these kits. They claim to be for a 71 XSB1, yet they appear to be for a carb that had a pull knob vs a lever.

Yes, I have both yamabond & threebond. It would just be nice if the kit had good parts. Oh well, live & learn.
 
Manic said:
Looking at the VIN decoder, it does appear I have an XS 2. Not sure where the guy I bought it from got it was a B?
Click to expand...

Very common, (production date spans 2 years), If the bike is built, Aug-Dec of the previous year

Found a pic of your XS1B.....😉
IMG_5844.jpeg


Pics solve problems faster 99% of the time.
 
Last edited:
650Skull said:
Very common, (production date spans 2 years), If the bike is built, Aug-Dec of the previous year

Found a pic of your XS1B.....😉
View attachment 340369

Pics solve problems faster 99% of the time.
Click to expand...
Yes, that’s my bike! But apparently mine is an XS-2. It’s all very confusing what Yamaha was doing back then with this model. I’m still not sure what the big difference between the TX & XS 650 were. Maybe trim level?

I had a TX 750 back in the early eighties. It was a great bike and the engine was very different than the XS design. I know they had the issue with the chain driven counterbalances and oil cavitation problems, which doomed future sales. But the only problem I ever had with it is it broke the shift shaft return spring twice? But that was an easy fix. Just had to pop the clutch cover off and replace it.

So, what were the differences between the XS-1B and the XS-2?
 

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