Need help with carb ID and kit for 1970 XS-1 650

[skooch]

I have a 1970 Yamaha XS-650 XS1 with 16K miles that my father bought brand new when I was 7 years old. We rode different bikes for years, but we always kept the XS. It's still a beautiful machine. Dad passed away 2 years ago, and I've been taking it out only to start it and warm it up and then wheel it back under covers. We've always used fuel stabilizer for winters and kept the tank full and changed the fuel every year in the spring, but beyond that, never drained the bowls or put it away like it was going to be down for a while. This year, I decided to put it on the road as it really needs to open up and breathe as only the 650 can. I love that bike.

Anyway, the bike starts first or second kick when choked. It always has. Lately, when I take it off choke, it struggles to idle and eventually stalls. I read and read many posts and also read through the original Yamaha Service Manual which gives a pretty good basic reference in a 1970 kind of way. I decided to pull the carbs and take a peek as I don't think that's ever been done and the symptoms seemed to justify a closer inspection. Plus I'm bored and curious. Anyway, they're in really good shape physically, but there is clearly some gumming and cleaning that would be in order. Additionally, one of the bowls looks like it hasn't been wet for a long time. I found that interesting. I've also done some other very minor fuel related fixes like rebuild the petcocks with a kit and replaced the dried out fuel lines. I've also tweaked around with some other small things but the bike needs almost nothing.

In fact, this post isn't about helping to solve a "the bike won't this or that"kind of problem. This is about helping me solve a conflict in identifying which carb is on the bike and ordering the right kit.

My confusion come from conflictions I'm seeing between the service manual/original carb (yes, I am 100% sure they're the original, like everything else on the bike) and what Mikes XS is showing as rebuild kit options.




Issue 1: Choke Body Gasket
This is from MikesXS.com (Part #48-2010)
Carburetor Choke Body Gasket Mikuni BS38 CV carb TX650 XS650B

Carburetor Choke Body Gasket - 7 Hole - Fits: TX650A, XS650B (74-75) Stock Mikuni
BS38 CV Carburetor.
Note: 1970-73 650's did not use a choke body gasket

I have attached a picture of the choke assembly from the carb and it obviously has a gasket. Secondly, the gasket Mikes lists that looks identical to the one on the carb, is a 7 –hole, and Mikes shows that not only did the 70-73 not have a gasket, but the bike is a 1970 not a 74-75 which had this specific gasket.

Issue 2: Correct Carb Rebuild Kit?
This is from MikesXS (Part #48-1919) (THIS "LOOKS"LIKE THE RIGHT KIT)

Carburetor Rebuild Kit XS650B TX650A Mikuni BS38

Carburetor Rebuild Kit - Fits: TX650A/XS650B (1974-75) BS38 Mikuni Contains - Slide needle Y-22 (40mm needle) & clip, Pilot jet #42.5 BS30/96, Main Jet #130 Small round N102/221, Float
Needle assy 2.5, Air screw with spring, 7 hole choke cover gasket, Float bowl
gasket 256.

Again, this kit matches the service manual (2.5 on the fuel valve seat, 7-hole choke gasket) but there is one conflict in that the manual shows a pilot jet of 45 not 42.5. Not sure if I need to be overly concerned about that.

Next, is this kit below. According to Mikes, its for the 70-71 XS1 and XS1b. But the specs conflict with the service manual (comes with a fuel valve seat of 2.0 not 2.5 as in the manual, and it also comes with a 42.5 pilot, not the 45 that's in the manual).
Carburetor Rebuild Kit XS1/XS1b Mikuni BS38 CV

Carburetor Rebuild Kit - Fits:XS1/XS1b (1970-71) BS38 Mikuni (Solex) Kit Contains: Slide needle Y22 & clip, Pilot Jet BS30/96 #42.5, Main Jet - #130 Small round N102/221, Float Needle & Seat assembly #2.0, Air Screw with spring, Choke Plunger & spring, float bowl Gasket ( 256). Made in Japan - 1 kit required per carb.

OEM Reference #
- 306-14901-00-00

So, the short questions are: Which kit? Despite that I know for a fact that this bike is a 1970 XS1, the carb kit for the 74-75 seems like the right one as all the parts (gasket/fuel seat..) seem to match the service manual and the carb itself? How can that be? Did Yamaha use a variety of carbs on one of the earliest of the 650s? FYI, the VIN serial number is "XS650-1008". What am I missing here?

Thanks for any and all help. This site is awesome.

 

[wesleyonoel]

Why not carefully disassemble, clean and reassemble? Did that with my '73 TX - no rebuild kit - and it runs like a champ! If the carburetors were functioning properly - just gummed up a bit - it could be no rebuild parts will be required............

 

[XSLeo]

Carbs like yours were used on many bikes not just an XS650. Each bike used slightly different internal brass parts.
The kits come with a generic set of brass that fits a lot of bikes but not neasarily yours. It's best to tear down, clean and inspect your carb.
Once torn down and inspected you can buy just the parts you need. Yamaha used very robust gaskets. Often reusable several times. The brass parts wear very little, they can be reused. And you know they are the right parts. Why buy a $20 kit when you only need a $3 gasket?
www.amckayltd.com/carbguide.pdf will help with your tear down, clean, inspect. It also has a section on carb tuning.
Leo

 

[skooch]

I thought about doing exactly that, except for one very small rip in the choke assembly gasket, and the bowl gasket is also a little dried out and rough in a few spots. Both would probably be ok, but given the way things go, I'd probably get some fuel weeping I guess I was thinking "while I'm in there I might as well", but your point is valid. Thanks for the feedback.

 

[5twins]

Most of the rebuild kits are incorrect. They have been for years. I don't recommend even using them. Just replace any individual parts you may need. As mentioned, you usually don't need much in the way of replacement parts if you're careful with the original stuff. If you do ignore my advice and get the kits anyway, don't use any of the jets or that generic Y-22 needle. All that stuff is repro junk and there's no way to know if it is flowing correctly. The float needle and seat is also repro junk and may or may not work. If your originals are working (carbs not leaking or overflowing gas), reuse them.

Personally, I rarely, if ever, pull the choke bodies off carbs. There's no need to. The holes and passageways through them are huge by carb passageway standards and pretty much never clog up. I pull the choke plungers out of the housings and inspect/clean them, that's all. I also swab out the hole for the plunger in the choke housing and blow air through, but like I said, these things really never get plugged.

So, since I never pull the choke housings, I never encounter the notorious "choke gasket mystery". And believe me, this is a mystery on the early carbs. Nobody seems to know for sure what gaskets are correct or if gaskets are used at all. From what I've seen, any choke body gets a gasket. Carbs with one choke that feeds both carbs use a gasket for that choke but no gasket under the blanking plate on the other carb.

 

[skooch]

Well, based on what you guys are saying, I'm going to take the advice and give it a go with a reassembly after a good cleaning. None of the parts are bad enough to justify replacement especially if there's a good chance what I buy will be wrong. Besides, with the help of this forum regarding disassembly tricks, getting the carbs in and out is no big deal anyway. Thank you all, and Happy Memorial Day!

 

[5twins]

Record all the jet sizes, needle and needle jet numbers, float needle seat number, etc. you find in there for future reference. As mentioned, most parts can be reused if you're careful with the disassembly. The original Yamaha gaskets are very robust and long lasting. I still have all the originals in my '78 carbs and they work fine. What you will probably find needs replacing are the needle jet o-rings. I find them bad in pretty much every set of 38s I go into. The needle jets should be a very snug push fit into the carb body. If they're loose in there, easily pull out (or even fall out), or wiggle in the body, the o-rings are toast.

 

[hard_y_rd]

I'm having the same luck with the choke body gasket on my early carbs. I called my Yammie dealer. They don't know. I know the 7 hole gasket at Mikes doesn't work. I think maybe the 8 hole gasket will work. I'm going to order it once i get another parts list together.

 

[TwoManyXS1Bs]

Hey, skooch, noticed you have the original XS1 shop manual. What a rarity! What you need to do is find and download (biker.net 's pdf files) or buy (off eBay) the 70-73 BIG manual. It includes service notes in appendix 'c', which describes no less than 3 different carb configurations in the introduction year. Best to not grand-slam replace everything from a kit. Only exception I would suggest is the main bowl gasket and the needle jet o-ring.

I have this bad habit of going out, turning on the fuel, firing it up for awhile, shutting it off, letting it set for a couple days, "without draining fuel from the bowls"! Worse thing you can do, don't know why I do that. Dain-brammage? But, what that does is increase the amount of fuel/varnish that accumulates in the bowl, and clogs up the pilot jets every time...

 

[hard_y_rd]

Hey, skooch, noticed you have the original XS1 shop manual. What a rarity! What you need to do is find and download (biker.net 's pdf files) or buy (off eBay) the 70-73 BIG manual. It includes service notes in appendix 'c', which describes no less than 3 different carb configurations in the introduction year. Best to not grand-slam replace everything from a kit. Only exception I would suggest is the main bowl gasket and the needle jet o-ring.

I have this bad habit of going out, turning on the fuel, firing it up for awhile, shutting it off, letting it set for a couple days, "without draining fuel from the bowls"! Worse thing you can do, don't know why I do that. Dain-brammage? But, what that does is increase the amount of fuel/varnish that accumulates in the bowl, and clogs up the pilot jets every time...

I don't think you nee to drain the fuel from the bowls on a running bike after a few days. That seems like a huge pain in the ass. Varnish doesn't set up after a few days. If it does you should change gas stations.

 

[TwoManyXS1Bs]

Per Skooch: "*I’ve been taking it out only to start it and warm it up and then wheel it back under covers.*"

Per me: " I have this bad habit ..."

Yeah, it won't varnish the first time, but my world is not a normal world anymore. After 4-5 months of this (which seem like a week to me), it's varnish time...

 

[hard_y_rd]

I hear ya. I don't even want to test the engine for that reason. Fuel sitting idle in the carbs for a year. Besides, it's sitting in my basement. I don't need the fumes down there. I guess i'll test it at some point. Maybe when it's closer to being roadworthy. Dying to hear it run though.

 

[5twins]

Well, a year is a another matter. I routinely let some of my bikes sit a month or so during the summer between runnings. There's no problem with gunk and "varnish". But then again, I'm speaking of my Euro twins which, even though I love my 650, are much higher quality bikes. I guess they can take it, lol.

 

[skooch]

First off, thanks to all for the great advice. I've got the carbs cleaned up and ready to go back in. Pretty happy. So glad I didn't order the kits. You guys were right on.

I started reinstalling them, and noticed that the equalizer tube "L" fittings (see red arrow in pic) are "less than tight" in both carbs. I can move the U-shaped EQ hose back and forth without a lot of effort. It might hold gas, but it really doesn't seem right to have that kind of wiggle. I searched for "equalizer tube" in the forum here, but thought I might just get greedy and throw this out in this thread. I pulled the carbs back out and gave the L-fittings a tap or two to see if I could get them to want to stay better. I'm concerned because they're 40+ year old plastic so my taps are somewhat conservative. Thing is, I think the stems on the fitting ends that go in carb-side (not hose-side) might be bottomed out. But maybe not. I didn't measure but I'm not sure smacking them harder is a good idea anyway. I don't think they'll hold fuel very well and/or for very long in that hi-vibe area. Any suggestions as to making them less loose before I put it all back together? Can't thank you guys enough.

 

[TwoManyXS1Bs]

Hey skooch, here's some banter on those 90° crossover barbs:

http://www.xs650.com/forum/showthread.php?t=27040&highlight=nylon

 

[skooch]

Hey skooch, here's some banter on those 90° crossover barbs:

http://www.xs650.com/forum/showthread.php?t=27040&highlight=nylon

Thanks TwoMany! I went through that thread and decided to just press them in, give em' a few taps and reassemble. Like one guy said, that's the way it's been done for years. Nothing fancy. So, turned on the petcocks, waited a few minutes, choked it, and 2 kicks later she was running good as new. No leaks and no trouble. Set the carb idles according to the book, and she's just like herself again, thanks to lots of great help from this forum. Otherwise, I'd be waiting on kits instead of riding. Thank you all!

 

[TwoManyXS1Bs]

Skootch, congratulations!
You've just 'skootched' up a couple of notches in the "members who know what they'e doing" roster...

 

[gggGary]

Dracu-thread.
70 -71 float valves.
NEEDLE VALVE ASSEMBLY
168-14190-15-00

Other than a bunch of snowmobiles only lists 70-71's
Yamaha Motorcycle 1971 XS1B CARBURETOR (XS1 - XS1B)
Yamaha Motorcycle 1970 XS1 CARBURETOR (XS1 - XS1B)

Then 168-14190-20-00 fits basically all other years and a bazillion other carbs.

I threw generic "kit" needle valves in WJL the 70 and it seems quite happy. My guess is the 1.5 stamped refers to the passage size and IIRC the later needles are 2.0 or 2.5. I figger long as the floats are set to the correct height it doesn't hurt anything to use the later needles.
Looking at the part numbers seems to confirm this.
168-14190-15-00
168-14190-20-00
Any other opinions?

 

[TwoManyXS1Bs]

Dracu-thread...

It certainly is.

...Looking at the part numbers seems to confirm this.
168-14190-15-00
168-14190-20-00
Any other opinions?

Another mystery here.
I'll give you all I got, Gary.

This montage of the early XS1-XS2 parts manual shows both a #1.5 and #2.5 valve.
Part number 3.

This manual excerpt shows using only the #2.5 (fuel valve seat).

This excerpt from our Brit member's Mikuni spreadsheet shows the 70-71 valve parts vs the 72-79 valve parts. He has the wrong p/n for the 70-71 valve assy.

Something to watch for, as experienced by another member, is the possible physical differences of the valve parts, lengths and valve tip angles.

That's it, all I got...

 

[gggGary]

Money gun fired, just sent $75 to Niche supply for needle valves, mains, and pilots.
This is mostly for the set of early carbs I got from Jim.