XS650SE Carbs

[Bullnose]

I’m rebuilding a set of pretty nasty carburetors and want to completely disassemble and vapor blast. I need to remove the screws from the butterfly throttle valves and remove the throttle shafts. I see the screws have been factory crimped to prevent loosening and dropping into intake ports. Good idea, until you need to take them apart, especially with aging and additional rust. Could someone with experience with this situation comment on removing the screws? Thanks!

 

[650Skull]

Carefully file the back end of the screw

 

[5twins]

Yes, I grind it away some with a Dremel.

 

[jetmechmarty]

Use a JIS screwdriver to back them out, after following the previous instructions.

 

[Bullnose]

Thanks, guys. All good stuff. I’m thinking a variable speed tool with a larger sanding disc might be the easiest to control. I use my JIS bits with a T-handle for extra torque. Hope they didn’t use Loctite, too.

 

[jetmechmarty]

Thanks, guys. All good stuff. I’m thinking a variable speed tool with a larger sanding disc might be the easiest to control. I use my JIS bits with a T-handle for extra torque. Hope they didn’t use Loctite, too.

I’ve been able to back those screws out with a JIS screwdriver and no grinding. If the screw head is already boogered up, all bets are off.

 

[Jim]

I’ve been able to back those screws out with a JIS screwdriver and no grinding. If the screw head is already boogered up, all bets are off.

Same here. Never had to resort to grinding the crimped area if, like Marty says, the heads are good. A well fitting driver is essential here...

 

[Bullnose]

They’re not pristine, that’s for sure. Some corrosion and rust. I’ll get em. Don’t wanna have to drill them out. Bike last titled in ‘97…

 

[Jim]

Hope they didn’t use Loctite, too.

A heat gun goes a long way toward softening Loctite.

 

[Bullnose]

A heat gun goes a long way toward softening Loctite.

“Heat can be your friend!”

 

[5twins]

The T-handled J.I.S. bit should do the trick. You might want to seat the bit in good first with a couple light hammer taps. I've never encountered any thread locker on these screws. A little penetrating oil soak time prior to removal helps too. I use a ball cutter in the Dremel to grind a little of the staked end off.

I would do my best to save this carb set. I think the '78-'79 carb set is the best of the 38s.

 

[Jim]

A few light hammer taps is good... emphasis on light.
Just keep in mind that the shafts are brass with a slot machined into 'em.
They'll bend if you ask 'em too.

 

[jetmechmarty]

A few light hammer taps is good... emphasis on light.
Just keep in mind that the shafts are brass with a slot machined into 'em.
They'll bend if you ask 'em too.

I keep a 2 oz hammer for stuff like that.

 

[Jim]

I keep a 2 oz hammer for stuff like that.

If I'm not mistaken, @gggGary made a special tool to back up the shaft just for tapping and reefing on the screws.

 

[gggGary]

Second version is made from oak.
clamp it in the vice heel resting on the vice screw, slide the carb down over it. solid support for your unscrewing efforts. As a rule the later (BS34) throttle shaft screws come out easier. The early BS38 usually need some grinding or that mashed steel screw will strip the threads out of the brass shaft.

 

[Bullnose]

Yeah. Yamaha Special Tool #OAK2100. I like it. A light rap always seats the bit and loosen the screw.

 

[Bullnose]

So, a couple screws put up a fight but all is well. Additionally, there is a vertical brass tube in the venturi that appears to originate in the float bowl. Removal is necessary to slide butter valve inboard. In good times, perhaps it ships into the float bowl but currently it’s corroded and unmovable. I’d love to hear comments on the brass tube.

 

[gggGary]

Brass tube IS fixed, Note the slot in the #2100OAK special tool. butterfly comes out toward front, do NOT sand buff edges of butterfly it's a bit futzy removing it, PATIENCE grasshopper.

 

[Bullnose]

Thanks you, Master. Priceless information. Seemed logical to remove from the front but also seemed solidly stuck. I’ll revisit.
That’s probably a cricket, grasshopper NA

 

[gggGary]

A bit of carb cleaner or WD type spray help loosen some deposits, make everything slide a bit easier (including your fingers) LOL