1971 Build for Dad

[5twins]

Beware of rebuild kits, they often contain the wrong size jets. Most of us don't use kits. The jets are aftermarket and we prefer genuine Mikuni ones. About the only useful item in the kit is the float bowl gasket, lol, but most of the time you don't need it because the original is still good. Original gaskets are very robust and can usually be re-used if not damaged during removal.

I don't disturb or remove the choke housings, so no need for a new gasket there. I just pull the plungers out of the top.

There are only 2 o-rings in this carb, one on the needle jet and one on the mix screw. Neither will come in most rebuild kits. For the needle jet, a 1mm x 4mm is a suitable replacement. For the mix screw, we've found this size to be perfect .....

 

[Rhy650]

Awesome, thanks for the feedback. I did find a couple of bags of small O-rings in the shop and I bet this was the intended application. Dad did advise me against the use of the new brass in these kits. I did need the gaskets so it wasn't a total waste. I also need new throttle shaft seals - it looks like the consensus is to get OEM on these, if possible? Lastly will need some new main/pilot jets as this bike will have pods. I read in an old post that you would start with 140, 142.5, and 145 for the mains and 30 and 32.5 for the pilot. Still sound about right?

One more question, as I need to do this to the '80 now that the weather is getting nice. Would you recommend starting with the smaller jets and work up or the bigger jets and working down - or is it just a crap shoot?

 

[Downeaster]

T'was me, I'd start in the middle and run it for a bit, pull the plugs and based on what I see there decide if it needs to go up (richer) or down (leaner).

 

[5twins]

For the '78-'79 carb set, I doubt you'll need as large as a 145, maybe not even as big as the 142.5, so I would suggest getting 137.5 and 140 to start. Pilot sizes are good. I'd start out with the 30 pilot and 137.5 main. Depending on how free flowing your exhaust is, you may be able to use the 32.5 pilot and 140 main, but only running and experimenting will tell you that. Also, you will need to lean the needle clip setting a step. The '78-'79 carb set needs this with any increase in main jet size. Start with the mix screw set at the stock 2.25 turns out and fine tune from there. It might be good there but could require 1/8 to 1/4 turn either way to make it perfect.

The BS34 carbs will be similar but not quite the same. You should only need one up on the pilot (42.5 stock to 45) but the mains will require at least 2 up maybe even 3 (132.5 stock to 137.5 or 140). You can't fool with the needle setting because there is no adjustment (it's "fixed"), but it's usually not required anyway. This carb set comes set up so lean from the factory that the added richness bleeding over into the midrange from the larger main and pilot just seem to make the midrange right. There is one more jet you can play with on the BS34s, an air jet in the bell mouth that feeds the pilot circuit. This has less of an effect than changing the pilot jet size so can be considered as a way to "fine tune" the circuit. Going down one size (135 stock to 132.5) will make the pilot circuit a tad richer, but not as rich as going up another size on the pilot jet. The mix screw is normally set at 3 to 3.5 turns out. With the richer pilot jetting, you can reduce that to around 2.5 turns out, and fine tune from there.

Yes, O.E.M. butterfly shaft seals are best and actually the cheapest, if you use the Suzuki equivalent. This is the exact same seal but priced much better. Here's the Yamaha offering .....

https://www.partzilla.com/product/y...?ref=0c2514270f638cfd80aa2c78e639f3d5a7971cda

..... and the Suzuki equivalent .....

https://www.partzilla.com/product/suzuki/13651-51010

I don't buy my parts from Partzilla anymore because I recently discovered a better, cheaper place called Partshark. Here's that same Suzuki seal from them. On my recent order from them, I bought a dozen, lol .....

https://www.partshark.com/oemparts/p/suzuki/13651-51010/seal

 

[gggGary]

Partshark.

Tried them for the clutch plates, then they didn't ship, when I asked they said only stock in Japan warehouse So I ordered from Partzilla who had stock, then Partshark shipped the next day (also), good thing I'll need lots of plates.. Just went there now cuz I need some valve seals and Partshark site is acting flaky, Member sign in not working, parts cart not displaying correctly. I'm using firefox. as my browser. Got it hammered out now, ordered valve seals and more throttle shaft seals but site seems a bit unresponsive. Shrug.

 

[Rhy650]

Depending on how free flowing your exhaust is, you may be able to use the 32.5 pilot and 140 main, but only running and experimenting will tell you that. Also, you will need to lean the needle clip setting a step. The '78-'79 carb set needs this with any increase in main jet size. Start with the mix screw set at the stock 2.25 turns out and fine tune from there. It might be good there but could require 1/8 to 1/4 turn either way to make it perfect.

Good lord, thank you for the insights. I will do my best to put it to good use. I gave Partshark a chance and ordered genuine Mikuni jets from Niche cycle via eBay. Those add up quick... feel sorry for the 4-cylinder guys...

 

[5twins]

Indeed. The only saving grace for those guys is that Mikuni packages and sells their jets in 4 packs and you do get a slightly less per jet price. Since I do a lot of carb tinkering, this is what I shop for and buy.

https://www.ebay.com/itm/Mikuni-N10...252083&hash=item5b87c655f5:g:VbwAAOSwjXxgGiod

 

[Rhy650]

Made some good progress on the carbs this past week. Having now built a set of BS34s and BS38s I have to say that I really prefer the BS38s. Seems like a simpler, more robust design. What I started with:

And where I ended up, after much cleaning...

Given that these will be hard to pull off the bike I really tried to get them put together right the first time. Carb bodies went through the ultrasonic, then a carb dip, were blown out with compressed air, and finally were soda blasted. All rubber components were replaced and they were jetted per @5twins recommendations. I did have one question before I put them on the bike... is there a special function to the plastic spacers on the throttle shafts? Mine were very beat up so I made some new ones out of brass:

Only to think later that maybe the plastic had a function I was unaware of. Any problems with using brass here?

I was also able to get the headlight put together. Sucks to have to spend that much on a ring, but I think it was worth it:

I have been staring at that bucket full off wires for long enough, am glad to see it starting to look like a motorcycle! Trouble is I am running out of excuses to not paint the gas tank...

 

[5twins]

I don't foresee any issues using brass for the spacers as long as you got the lengths correct of course.

 

[Mailman]

Really nice work on those carbs, they look beautiful!

 

[cra-z1]

Carbs look great.

 

[TwoManyXS1Bs]

Concerning your throttle shaft spacers, have a look at Mailman's 60th birthday thread,

http://www.xs650.com/posts/511934/

Plus the following 4 pages.
Actually, the entire thread is worth reading...

 

[Rhy650]

Concerning your throttle shaft spacers, have a look at Mailman's 60th birthday thread

First of all, this was one of the funniest things I have seen in a while...

That was some good information, thank you. I just had a feeling that there could be more to the story - glad I didn't Loctite my butterfly screws quite yet. My mind was screaming something about man hole covers, circles, and old geometry classes. Thinking about my situation, I am confident that the brass spacers I made are the same length as the originals, at least within a couple of thousandths... That being said, they have crisp, freshly turned edges that are not reflective of the wear in the original spacers, so there is undoubtedly going to be a small difference in the play of the butterfly shaft.

A couple of questions/clarifications...

-Am I correct in thinking that as long as the butterfly is making good contact along it's entire circumference I should be in good shape? My carb bodies show only minimal wear where the butterfly makes contact.

-What kind of play (if any) is expected to be in the throttle shafts? Has anyone quantified it? Factory spec?

-Should I not temp fate and just install the original spacers? I could also turn new ones from a variety of material. I almost used Delrin or HDPE...

-I used white lithium grease on my shafts. Would something like a silicon grease be a better choice?

 

[Mailman]

My two cents....
I would think that your butterfly is good if it’s making contact all the way around. I think you read that link 2M gave you about my carburetors worn body where the butterfly had worn it. During the course of that discussion we realized that many carburetors are often not perfectly round in their bores, I don’t think it’s a dealbreaker. Even with the gaps I had, that bike actually ran pretty well. These old carbs aren’t super precision instruments.
Regarding the spacers you made, I have come to realize you are pretty meticulous in your work and I’m sure you were careful in your measurements, I’m sure they will work fine.
As for your question about lithium grease or silicone? I’ve used both, I think whatever you use will work. I personally have come to like silicone, I feel it’s a little more slippery and dust and grit doesn’t seem to stick to it as much as the grease. ( Where I live has lots of dust and grit )
Carry on....you’re doing great!

 

[Rhy650]

Carry on....

Ah man... I was gearing up for a deep dive into the sea of over-engineering, which is of course fed by the estuaries of over-thinking and neuroticism...

Thanks for the perspective, always appreciated! I'll wait and see how it runs before going too far with it.

 

[5twins]

You did center the butterfly plates before the final tightening of their screws, right? You have to do this because the return springs naturally pull the butterfly shafts towards them during operation. That can bind the plate against the side of the bore.

 

[Rhy650]

I have not torqued them down yet, but was aware that they needed to be centered. Found some good stuff on the forum about what to look for when I do tighten them up.

5twins, I rejetted the '80 per your advice and took it out today for about 30 miles. Still had stock airboxes, so 1 up on the mains and 1 down on the air jet. What a difference! It started easier, accelerated smoother, was more responsive, and even seemed to sound better. Thanks for the advice!

I could tell the pipes didn't get as hot, but since they are already discolored I don't think they will be the best indicator moving forward.. I'll clean the plugs and pull them after the next ride.

 

[5twins]

Yes, once the pipes discolor, you're kinda stuck with them like that. Hopefully your tuning will keep them from getting any worse. At one time the BS34s were kinda looked down on and the BS38s were considered more desirable. But, with some minor tuning to overcome their lean factory settings, the BS34s can be made to run quite nicely.

 

[Rhy650]

I think I have hit the end of the road in terms of putting off the gas tank. I would appreciate any feedback you guys might have as to a color selection. The "candy orange" was already decided by Dad, as the side covers and bucket are already painted. That color is HOK Solor Gold 0104:

I am having a hard time picking the base white coat, complicated by the fact that I have never actually seen an XS1B in good condition. From reading it seems that it was not a flat white, but had metallic/pearl element to it. So.. was it more silver or white? This is what I am considering for the base, but wanted to get your feedback due to the insane cost of this paint and the sheer number of hours involved in painting...

HOK Snow White Pearl:

Alternatively, if the original base was more silver in color there is HOK Silver-White Pearl:

Any thoughts?

 

[Jim]

Based on recent experience with a gold XS1-B, here's what I've found..... the order of application.
1. Primer. Looks to be a light grey.
2. Silver base. This silver was applied over the entire tank.
3. Gold candy. Not positive, but it looks like the candy was applied to the entire tank also.
4. White striping. This was applied over the gold.
You can see from the pic below that the entire tank was silver. The white has faded/disappeared from UV leaving some of the candy underneath. The silver you see is from the UV removing the gold... that make sense?

In the second pic (red circle) you can see this. At least I hope you can... it was obvious looking in real time. There's a light grey primer, then the silver... then the gold.
So... contrary to popular opinion, the base was silver and not white. The white was only on the stripes.
Gimmie a min. and I'll find a link to the paint I used.