Carb Questions

So I have finally gotten around to getting into the carbs, right now I have #1 taken apart, the other three intact and racked as a reference.

I am following my Yamaha service guide as a reference, and taking pointers from the church of clean.


What is the flat head nut next to the Starter Plunger opening at the bottom of the photo, should it be removed and cleaned?

Also what are the two golden nuts (they look similar to the Pilot and Main Jets, they seem to be on the other end of the same passage) in the vacuum chamber? Should they be removed and cleaned, or should they just be probed clean?


I also can not find a reference to what this (brass piece?) is in the back of the photo, it looks bent to me (slightly to the left), it looks like its fixed to the carb body itself (cannot be removed but could be wrong).

What is it, and is it a problem that it is bent. If so what is my best course of action?

Thanks, Troy.

 

Your first question that is the pilot jet yes needs removed there is an O ring on it and a small spring so don't loose it. the other 2 jets need pulled out make a note of location . While carb is split from rack remove butterfly plate and shaft to replace shaft seals ( xj4ever has them) Soak carb is what I recommend Berrymans Carb cleaner 1 gallon container submerge carb one at a time for about 1 hour , then clean in hot water and dawn dish soap , this should get carb clean , and reassemble . The bent tube is what goes into the fuel enrichment in the float bowl. Carefully try to straighten is about all you can do. Cheers

 

Great info, thanks.

 

The other two jets.....assuming h33 carbs....big bottom hole goes in the hole towards the front of the carb body, little hole jet goes in the second....there is also a tiny washer that goes between the spring and o ring on that mixture screw.......I have been able to get by on the last two racks I split by just replacing that idle o ring, it's washer, the throttle shaft seals and the fuel o rings. There is also jets in the back of the carb facing the air box that can come out as well before soaking.

 

Order a set of butterfly screws as well.......on the xj550, I had to grind them to get them off, while with the 750 seca, which the carbs have never been off of, they simply came out with a screwdriver.

 

That would be because of the carbs being made by different manufacturers. Mikuni peened the ends of the threads, Hitachi used thread locking compound.
Replacement screws are a good thing to have regardless. Some will get messed up, and I usually lose at least one on the floor.

 

More info:
http://www.xj4ever.com/inside your carbs.pdf

Carb Video (props to Kmoe for posting this)

 

I upgraded to allen bolts ... looks kool!!!

 

One-time use items at this size though. The heads (no matter who makes them, or how good of a wrench you have) tend to waller out upon removal.
They are easier to get into place than either crosshead or flathead screws.

 

I'm not following. What was it that you had to grind off?

Edit: I believe I know what your talking about now, the screws holding the butterfly onto the throttle shaft, correct? I luckily had no problems removing mine!

 

Very cool, thanks.

 

Correct. The Mikuni carbs (on the 550) had the threads peened, and have to be ground or filed in order to be removed. Thankfully Hitachi chose to not use that method of screw retention. Be sure to use a medium-strength thread-locking compound when reinstalling the throttle plate screws.

 

Some more questions:


Throttle Shaft Diaphragm #1 has a pinhole sized puncture (not shown in picture).
What is the best method of "repairing" this, or would it be wise to purchase new?


The Needle Jet or Emulsion Tube is showing wear.
Its been cleaned up as you can see, should I replace?


So the clumsy; yet industrious PO of the bike has done a nice little repair.


I started to pick at what I thought was gunk, but instead was RTV or some sort.
This is where the pin holding my floats in place calls home, things seem to line up nicely.
Does it seem like a serious issue to anyone if I just secure it back in place?

 

just so we have the same page: grind off the back threads, not the screw head

 

a Diaphragm might be expensive, try a tiny dab of RTV after you clean it.
the Needle Jet can ware oval where the needle goes in it, otherwise that looks good
how tight a fit is that pin in the hole? could you smash the pin enough to make it a little tight? then butter it up with jb-weld and hop for the best.
look for a used carb rack for parts

 

You can repair small holes in diaphragm with a condom or rubber glove and rubber cement . This actually works !!!

 

Isn't a rubber glove the same thing as a condom......

 

Sort of--- one goes over your HAND

 

But the carb shown is a hitachi

 

po would not be the first one to fix float post some jb weld would have been better than rtv, there are a few threads on this subject

 

The bike was running; albeit rough when I got it so I figured as much. Definitely agree with the JB weld.

 

And won't be the last one to have the jbweld dissolve in the gas

 

jbweld gastank repair epoxy ? but do agree a new body is the best way to go.

 

Yeah, he went there... LOL

 

Thought Polock (or was it you Dave?) posted a rather professional float post repair picture not too long ago?

 

Not me-my way of float tower repair is:

Get another carb body that ISN'T bork

 

is this the one

you have no idea what a p.i.t.a. that was

 

Is that a Dove tail? OMG!

 

Yes it is. I was clarifying the differences between the two, and the need for threadlock, after another member mentioned needing to grind the screws (not necessary on Hitachi carbs).

 

Ok

 

Liquid steel is fuel proof it is a two part you kneed it together and push it in place it sets up in about 5 minutes . I have used it to repair my engine case on my VW Beetle and a carb intake it has lasted 6 years.

 

Yea - that's it - Professional Installation Technique Award.

Sure maybe it was a pain, but such a beautiful thing to look at.

 

i still have it, if you want to buy it
i'll even throw in the dried up gasket

 

Have I been using them wrong? Is this why I have 2 kids?