Will these rebuild kits work on my stock 78 special?

[mwp309]

http://www.ebay.com/itm/TWO-Yamaha-...Parts_Accessories&hash=item19d1cf6499&vxp=mtr

Any detail oriented folks out there know if these will work on my brand new to me vintage stock 1978 xs650 Special? Thanks for any input

 

[XSLeo]

On a carb rebuild kit like those they come with generic internal parts which are seldom right for your bike. The gaskets, the float valve and the rest won't hepl. The Y22 needle is wrong you need a 502. The main jet is wrong, you need a 135 or bigger. The pilot jet is wrong, you need a 27.5 or 30.
Generally you can tear down your carbs, clean and reassemble with the parts you have, just be careful with the float bowl gaskets and you won't have leaks.
When you get it apart you can inspect for wear and damage. Buy just the parts you need.
www.amckayltd.com/carbguide.pdf will help on the teardown, cleaning, reassembly and tuning.
Leo

 

[xjwmx]

I agree. I was reading something by a bike carb rebuilder and he said he couldn't remember the last time had to replace a part that was too worn out to work or make work. That assumes the part hasn't been destroyed by somebody of course. Possibly in taking it off to clean it.


I can think of an exception, which is the bs34 float valve seat o-ring. After all this time they're likely to be loose and leak due to shrinking and dissolving. If you can lift it out with your fingers it's too loose. If you put a new o-ring don't destroy the seat getting it all back in.

 

[mwp309]

Thanks Leo and xjw. They are still on the bike, I blasted all the brown goop off them with some throttle body cleaner and they seem to be in good shape. Looks like some brass bolts on the bottom of the bowls, heads rounded off and chewed up. I'm sure these are important and impossible to obtain, LOL
Hope the carb cleaning will address the backfires and sputtering on deceleration!

 

[5twins]

Yes, that kit is totally wrong for your carbs, it's for earlier ones and even then, not totally correct for most of them. As mentioned, don't get rebuild kits at all, just replace any needed parts. The thing I find that needs replacing most of the time on the 38s is the needle jet o-rings, occasionally a float needle seat assembly or float bowl gasket.

 

[5twins]

Those brass bolts are your float bowl drain plugs, also the access cover to the main jets. Not sure if Mike's sells those or not. They were used on many models over the years so finding some good used replacements shouldn't be too hard.

Edit - Yes, Mike's has them.

 

[mwp309]

Woo Hoo, there's hope for this old scooter (and me) yet! I'll have an order for Mike's soon enough, I'm sure. Thanks for your input! Ok, time to check the tech section on carb cleaning/rebuild!

 

[XSLeo]

One thing about Mike's stuff, most are good parts, some are crap. Rubber parts are the biggies. When in doubt just ask and someone will tell you if it's something to be wary of.
Leo

 

[mwp309]

Thanks Leo, hopefully just need new bowl gaskets and the drain plugs. I'll give everything inside a good cleaning with that Valvoline throttle body cleaner I got. Also new fuel line to replace the 34 year old rubber lines. Soon as I pull the gas tank they will break in half, they are so brittle!

 

[5twins]

Mike's fuel line is excellent, so is his breather hose. The 11.5" fuel line length they sell may seem rather odd but cut it exactly in half and it makes 2 perfect length lines for the 2 petcock tanks.

 

[mwp309]

Thanks 5twins, good info to know. I'll certainly need those fuel lines. Inside of my tank is pristine, so I'll forgo the in line fuel filters at this time.