New to XS w/carb question.

[2Diverse]

Hi all! I bought a 1977 XS650 last week. It ran ok but I thought I'd take a look at the carbs. They are dirty. I purchased a rebuild kit from Mike's that, hopefully. might come today.

I'm guessing that they are BS38s as I can not find any marking on them that shows the model number.

I have limited mechanical skills but I'm fairly confident that I will be able to work on them to have them operate correctly.

I've watched numerous YTube videos on how to rebuild them. All pretty much the same. However mine are different than any I saw on YT. Mine have a vent tube on the inside at the top of the carb. The left carb was leaking gas when the bike was on the side stand. My mounting flanges do NOT have a vent/vacuum tube. The tubes vent to the ground behind the engine case.

Here are my questions please.

1) What are these tubes designed for?
2) Are they supposed to vent to the ground or be connected to each other?
3) Are they supposed to be blocked off?
4) Do I need vent/vacuum tube mounting flanges?

Any help here will be greatly appreciated.

 

[Wingedwheel]

If it’s a ‘77 you don’t have vacuum fittings on the boots. I also DO NOT recommend that rebuild kit unless it’s genuine Mikuni parts. Most of those kits are generic and cause more issues than they fix. Usually cleaning up the OEM parts works just fine.Read the carb guide in the tech section then read it again.you will be glad you did. Those tubes you question are not connected and vent to the ground.

 

[2Diverse]

Thank you so much for the reply Wingedwheel. You answered the questions I had.

Being new to the bike I've been trying to buy what I THINK I should get for it. Turns out I've bought a few things that I didn't need. I did plan to reuse the original parts, as long as they are the correct (stock) ones, I can clean them up to be reused and they aren't boogered up. If it runs well then I'll leave it at that. If not I'll try the Mike's parts.

I've left them on the bike til the parts arrive. Seems safer to me for now. I have a plan to keep the parts separate between the two and if I do it correctly I won't "misplace" any parts. Add that my garage is 40 degrees today. I'm old and hate being cold. Tomorrow should be in the low 50s which is tolerable. I think I have this.

I'll read and reread the carb guide. Thank you again for the prompt and clear advice.

 

[Its been a long time]

Thank you so much for the reply Wingedwheel. You answered the questions I had.

Being new to the bike I've been trying to buy what I THINK I should get for it. Turns out I've bought a few things that I didn't need. I did plan to reuse the original parts, as long as they are the correct (stock) ones, I can clean them up to be reused and they aren't boogered up. If it runs well then I'll leave it at that. If not I'll try the Mike's parts.

I've left them on the bike til the parts arrive. Seems safer to me for now. I have a plan to keep the parts separate between the two and if I do it correctly I won't "misplace" any parts. Add that my garage is 40 degrees today. I'm old and hate being cold. Tomorrow should be in the low 50s which is tolerable. I think I have this.

I'll read and reread the carb guide. Thank you again for the prompt and clear advice.

History suggests those carburettor kits cause more issues than they solve. Shouldn't be any problen using the gaskets, O rings etc out of the kit. But not the jets etc. There's lots of information here regarding correct carburettor parts and set up. I recently overhauled the carbs on my 77 XS650D and took the stuff out that a previous owner had installed to put the carburettors back to factory settings. Once I have it running, that'll be the time to think about whether I need to change from factory settings or not.

 

[Jim]

Two good (US based) sources for genuine Mikuni parts... Agree, the MikesXS kits are about worthless save for the gaskets and such.

https://jetsrus.com/

http://www.nichecycle.com/ncs/categories/carburetor.html