XS650 build.

[Northerner]

Just brought this home and it will be the starting point of my first real build, looking for advice and guidance along the way. The first thing I want to do is get it running and then I’ll work on getting it to be rideable and then I’ll plug away at the details. I have a set of carbs that came with it but unassembled the motor turns and I was told it will produce spark. What would you all do at this point?

[datadavid]

[ATTACH=CONFIG]98899[/ATTACH]

Just brought this home and it will be the starting point of my first real build, looking for advice and guidance along the way. The first thing I want to do is get it running and then I’ll work on getting it to be rideable and then I’ll plug away at the details. I have a set of carbs that came with it but unassembled the motor turns and I was told it will produce spark. What would you all do at this point?

Clean out and reassemble the carbs and try firing it up, i guess.

[Tattooo]

Clean out and reassemble the carbs and try firing it up, i guess.

Yep what he said...... The first thing is to make sure it will run........... No need wasting money on it if it doesn't............

[Northerner]

Looking into the carbs now. Pretty sure they are BS38’s I’m missing the float bowl screws and I’m not sure if they are supposed to be connected when mounted up so I’m doing some digging on the internet and ordered a Mikuni Carb tuning/rebuild manual from XS650 direct.

[Northerner]

The engine cranks and when the coils, plugs etc are connected it can produce a spark. I’m going to pick up a compression gauge this week and test that out as well.

[Tattooo]

You will also need a manual if you don't have one already.............

[TriNortchopz]

To help give you an idea of what parts are what, a parts book is a good reference; Bike Bandit is a good site where you can search OEM parts with exploded parts images with reference to the identify the part and gives part numbers; here is the carbs for a 1980 xs650 for example (you didn't say year of your bike so i guessed):

https://www.bikebandit.com/oem-parts/1980-yamaha-xs650-xs650g/o/m147153#sch219544

You can plug in year, make and model of your bike, select OEM, or aftermarket, or universal parts to look at.

[datadavid]

Looking into the carbs now. Pretty sure they are BS38’s I’m missing the float bowl screws and I’m not sure if they are supposed to be connected when mounted up so I’m doing some digging on the internet and ordered a Mikuni Carb tuning/rebuild manual from XS650 direct.

Its easier to have the float bowls on the carbs before installing them. Also make sure your intake rubbers arent rotten and cracked!

[Northerner]

Thanks guys! From the numbers on the engine I’m pretty sure it’s a 70-71 and some internet digging seems to confirm this with the type of carbs. This is definitely the first hurdle, I have ordered the Mikuni carb tuning manual by Sudco which has exploded views and parts numbers

[Northerner]

Here’s a picture of the carbs as they came. I believe they are Mikuni BS38’s. The 90 degree fitting on the bottom of the float bowl was busted on the one, I have pulled it out. I cannot find anything like this online. All the parts I can find are jets gaskets and basic rebuilding stuff. Does anyone know if I can get a replacement for this or use something else? I know there’s a lot more missing on these carbs as well but while I wait for the manual and parts book to come I figured I’d ask about this specific piece. Thanks again.

[TriNortchopz]

You need to know what carbs you have before you start ordering parts.
The wheels are Yamaha mags, which started in 1980,which is why i guessed your engine as that - you say 1971, so you got a bitsa, bits of this and bits of that.

This may help you to figure out what you have for carbs; new or old and which size:

The XS650 Garage 37-page Carburetor Guide
We've tried to gather the most frequently-requested information into a single reference.
In the process, we've cannibalized our own posts ruthlessly. We do not offer this guide
as the last word on XS650 carburetion; references online and in print that we've found
valuable have been recommended, and we hope you find them useful.

http://www.amckayltd.com/carbguide.pdf

and look here:

XS Model ID Guide:

https://www.mikesxs.net/pdf/XS_Model_ID_Chart.pdf

oh, wait, there is still more...just gotta LOOK:

The following table and descriptions outline the evolutionary changes to the carburetors used on all XS/TX 650 Yamahas., (including body model numbers)

http://www.xs650.org.au/Technical%20Info/XS-TX650%20Carburetor%20Evolution.htm

[Northerner]

Thanks for the info.
I had already looked at most of it before and identified the carbs as BS38 Mikuni from 1970. The 125 stamp on the butterfly valve the 90degree fittings I’m looking for and the Solex bodies confirm this.
I totally have a bunch of parts from different years. The number on the engine (s650 123153) tells me it’s a 1970 XSA from what I can find on the internet and the type of carbs would line up with this as well.
The number on the neck of the frame (447 900944) dates it to 1974, again from what codes I can find.
So I’m not surprised if my wheels are 1980! Haha.

Anyways, the guys at Mikesxs650 told me these fittings are irreplaceable. Not sure why I didn’t think of just asking a supplier in the first place. They are the vent/ overflow lines and they seem to think you don’t really need them........ I’ll just focus on rebuilding the rest of the carbs for now.

[datadavid]

Thanks for the info.
I had already looked at most of it before and identified the carbs as BS38 Mikuni from 1970. The 125 stamp on the butterfly valve the 90degree fittings I’m looking for and the Solex bodies confirm this.
I totally have a bunch of parts from different years. The number on the engine (s650 123153) tells me it’s a 1970 XSA from what I can find on the internet and the type of carbs would line up with this as well.
The number on the neck of the frame (447 900944) dates it to 1974, again from what codes I can find.
So I’m not surprised if my wheels are 1980! Haha.

Anyways, the guys at Mikesxs650 told me these fittings are irreplaceable. Not sure why I didn’t think of just asking a supplier in the first place. They are the vent/ overflow lines and they seem to think you don’t really need them........ I’ll just focus on rebuilding the rest of the carbs for now.

If the parts cost for those carbs pile up, consider buying a new pair of round slide carbs instead.

[Northerner]

Man, that’s what I’m weighing in my mind right now. As cool as it would be to rebuild these carbs the time and money it will take, that’s becoming more and more obvious the deeper I look into it, is making a new pair seem pretty sweet.

I did a compression test on the engine which seemed normal, so if I get new carbs I’m not buying them for a junk engine.

Anything else I should look into before dedicating to new carbs? I can’t purchase anything until after the Christmas season here.

[datadavid]

Man, that’s what I’m weighing in my mind right now. As cool as it would be to rebuild these carbs the time and money it will take, that’s becoming more and more obvious the deeper I look into it, is making a new pair seem pretty sweet.

I did a compression test on the engine which seemed normal, so if I get new carbs I’m not buying them for a junk engine.

Anything else I should look into before dedicating to new carbs? I can’t purchase anything until after the Christmas season here.

Go through the electrics and clean up any corrosion, try and make that spark as fat and blue as you can��