Sorry so many posts! Help me I'd my mikuni kogyo carbs?

[Jake Violando]

I have a 1980 xs650 I just pulled the motor off to get ready to change the front Cam chain guide. My carberuators are mikuni kogyo but that's all they say and I want to get a rebuild kit for them. The Rh carb passes the "lift diaphragm and cover hole, see how long till it drops" took about 25 seconds. Perfect. The Lh side drops in 3. I want to get these running right.

 

[Jake Violando]

Sorry for posting so much I'm an 18 year old who's ripped 2 stroke dirtbikes apart and old cars with carbs and rebuild car carbs. I have somewhat of a mechanical background hahaha. Don't know much about these bikes but I'm learning a lot and really like this bike, just want jt to run right. With 17 /32 gearing it tops at 65mph. Rant over lol

 

[weekendrider]

gggGary is traveling but if you can wait till he gets home he can probably hook you up with parts. Dogbunny is also a good source for parts.
I'd hold off on the "rebuild kits". It isn't going to be what you need.

 

[Jake Violando]

Pics

 

[650Skull]

JBM industries sell Carb diaphragms http://jbmindustries.com/Yamaha650.html

Your carbs are BS34's..................Usually jets and needles don't need replacing, they aren't really a wear item as such, unless the bike has done a million miles or the PO has poked the jets with no 8 wire to clean them. Buying separate gaskets and throttle shaft seals is a cheaper option.

 

[B Burdine97]

Those are stock bs34 carbs that come on the later model bikes. Mikexs sells rebuild kits for those. All the rebuild kit includes is a bowl gasket, a new float needle and o ring I believe. If your having issues with the carburetors a good cleaning could possibly help alot. Also if your newer to the sight the search function is your best friend..

 

[5twins]

As I mentioned in your other thread, the reason the bike won't go over 65 could be bad diaphragms. Well, it appears you have one. These are vacuum powered carbs, vacuum makes the slides lift. Only one of yours is working. That's why it will only go so fast. Pop the tin top off that bad carb and inspect the rubber diaphragm. I bet you find holes in it.

 

[Jake Violando]

Right on the money my man! I'm gonna get new ones. The holes are were the cap sits on the diaphragms. Hopefully I don't have to pull any more of it apart as the PO messed up the Phillips heads bad

 

[fredintoon]

Right on the money my man! I'm gonna get new ones. The holes are were the cap sits on the diaphragms. Hopefully I don't have to pull any more of it apart as the PO messed up the Phillips heads bad

Hi Jake,
Some have reported making a temporary diaphragm fix by dropping superglue on the holes.
I don't suppose it's a long term fix but it may work for long enough to see if replacement diaphragms are all the cure that's needed.
And beware the crosspoints! They ain't Phillips heads they are the allegedly better JIS (Japanese Industrial Standard) heads which need JIS screwdrivers
to turn them because Phillips screwdrivers crater them out.
What most folks do after removing a JIS head or a Phillips head fastener is throw it away and use an Allen head fastener in it's place.

 

[MaxPete]

Hi Jake:

I'm NOT a carb expert - and there are lots of folks on the forum who are - but I did notice that in the photos of your carbs, the slides are no all the way down. On my carbs (BS38s - but very similar to your BS34s), these slides are essentially all the way down when the carbs are off the bike.

Otherwise, I commend you to the able expertise of the other folks who know waaaayyyy more than I about these things.

Pete

 

[fredintoon]

Pics

Hi Jake,
check out the slow running needles.
They are down the little openings one of which is under your thumb in photo #3.
If you can see screwdriver-slotted needles down there just screw 'em out when you do the complete teardown clean those carbs will need.
If what you see is a brass plug with a hole in it, that's the EPA-mandated seal that stopped the buyer from adjusting the idle settings away from extra-lean.
Rip those things outa there! Not just because extra-lean is a bad thing, but because if the seals are still there the carbs ain't been fully cleaned since they left the factory.

 

[Bob Kelly III]

Well stated Fred !
that hole in the diaphram you showed the light going through looks like it's supposed to be there at the very least you could seal it with silicone gasket stuff when putting it back in.... what your looking for in the diaphram is a ragged rip or a frayed hole of some sort somewhere between the lip of the seal and the carb slide..... I don't think you've found it yet ! 5Twins doesn't miss too much if he says that hole means it's bad then I'll go along with him but it looks stamped out to me, and it's in the ring seal not in the vaccuum part ! so I don't think that hole you showed is it buddy !
look close around the carb slide area and see if the diaphram seperates from the slide...
....
I fought my carbs for what seamed like forever the things I learned was the idle circuit is a convoluted mess ! it's extreamily hard to get clean if it's clogged up... carb cleaner is our friend ! ...do what Fred said and pull the pilot air screws... and save the tiny o-ring and washer.... and clean that pilot circuit real good with the carb cleaner nossel ( watch your eyes)
the float bowl has a hole in the outer rim that changes direction and enters the bottom of the float bowl.... that must be clear and open
both of mine were closed ! (what's the odds of that ?) and it kept the choke from working...... and on these bikes you need the choke !!!!!
.....hope this helps !
keep after it Jake you can do it just don't brake anything or have a hart attack it can be flustrating indeed !!!!!
Bob..........
edit ....Note when putting the CV slidesback in there is a bulge or indicator on the diaphram rim that must go in the proper way into the carb body don't mix the parts up... keep all the parts from one carb seperate from the other one !