Carb Parts

[OC Hoosier]

So I've been attempting Jaime's 'power increase' techniques and things have gone well so far. The needle shim provided a little more mid-range grunt, and I have a new main jet and k&n ready to be installed. My problem is that the float chamber screws are installed so tightly, and the metal is so soft, that the heads just want to round off when I try to unscrew them. Has anyone else had any issues like this on their Mikuni? I don't have an issue with drilling them out, so long as I can find replacements. Does anyone know of a dealer that carries replacement bolts, even if it involves buying a whole rebuild kit? The company from which I purchased my jet doesn't appear to carry them.

[Water Warrior 2]

Are you using the factory screwdriver ?? Believe it or not it is a metric screwdriver and most people just grab a normal SAE tool which will strip the head of the screw. They are a slightly different design but look the same at a glance. Try the screwdriver tip from an impact driver which is metric specs. The whole impact driver make a great but heavy/bulky screwdriver. You can also use an extension from a socket set to get into tight spots.

[Easy Rider]

Has anyone else had any issues like this on their Mikuni?

Yes, it's a common problem for most all bike carbs. Don't know why exactly.
A machine shop probably could get them loose for you in just a couple of minutes and for only a few pennies. They might also be able to tell you where to get replacements (or supply them) if they end up too damaged to re-use. Hopefully drilling won't be necessary.

[OC Hoosier]

OK, thanks guys!

[Moedad]

There's metric screwdrivers?? :??: A screw is not a screw?? :whistle:

[Quimrider]

they're just a metric screw, nothing special. My trick to getting them out is to let them soak in a little PB Blaster, use some locking vice grips on a screwdriver bit. I push up as hard as I can while turning. Just make sure your screwdriver bit is a good fit for the screw head so you don't strip them. If you still can't get them out and decide to drill them I'll take one of my screws out and go to the hardware store and see what size they are.

[Easy Rider]

Just make sure your screwdriver bit is a good fit for the screw head so you don't strip them.

I think you missed the point. I've heard it said that the phillips-type head on metric screws is slightly different and a standard Phillips bit is not a perfect fit. I believe that to be true, gauged only by feel, as I have never actually tried to FIND a metric X-head screwdriver.

So.....who knows for sure? Is there such a thing ?? Are they different ??

[patrick_777]

http://www.centralhobbies.com/Tools/jis.html

[Quimrider]

I think you missed the point. I've heard it said that the phillips-type head on metric screws is slightly different and a standard Phillips bit is not a perfect fit. I believe that to be true, gauged only by feel, as I have never actually tried to FIND a metric X-head screwdriver.

So.....who knows for sure? Is there such a thing ?? Are they different ??

Nope. no point missed. You more or less said what I meant; If it doesn't feel like a good snug fit then don't use it. I had a fresh new #2 Phillips bit that was a perfect fit for the metric screws on my carb. Until reading this thread I never heard of a Phillips head on a metric screw being different from a Philips head on an english screw. Personally I'm somewhat skeptical, but I don't claim to know everything, so maybe they are slightly different.

[patrick_777]

Okay then...try THIS link instead.

http://www.moodytools.com/MTI_CATALOG_PAGE_11.pdf

What’s the difference between Phillips and JIS?
These cross-point drivers appear deceptively similar to one another. Phillips is the type with which most people are familiar. JIS (Japanese Industrial Standard) drivers will always fit Phillips fasteners, but because of slight design differences, Phillips drivers may not fit JIS fasteners (see illustration on page 11 of our catalog).

[Badbob]

The important thing is that the bit must be a good/tight/snug fit for the screw. The tighter or more difficult to remove the screw the more important the fit becomes. Sloppy fitting screwdrivers will cam out of the screw and damage the head, you, and/or the part. Using the wrong size or type of screwdriver can be very expensive.