Stripped Internal Carb Screws

[riwaverunner]

Went to do a carb rebuild on a gifted ski, and a few of the screws are either rusted or stripped out. Specifically one of the two that holds the metal cover for the jets, and the one that holds the small bracket for the seat. Any ideas on getting them out? Or any leads on a good place to pickup a replacement carb if I can't (carb for a 951, the Mikuni BN46I)?

 

[NickCawks]

Unfortunately if you can't get those off you can't complete the rebuild. If the carb isn't functioning then you won't be able to fix it.

First step would be to soak it in PB for a few days and see if that helps at all.

If that doesn't work it's time to look into a replacement. I'd give Nick over at Westside Powersports a shout he can likely hook you up with a good condition carb(s)

https://www.westsidepowersports.com/Nick - 612-743-9311

 

[riwaverunner]

Unfortunately if you can't get those off you can't complete the rebuild. If the carb isn't functioning then you won't be able to fix it.

First step would be to soak it in PB for a few days and see if that helps at all.

If that doesn't work it's time to look into a replacement. I'd give Nick over at Westside Powersports a shout he can likely hook you up with a good condition carb(s)

https://www.westsidepowersports.com/Nick - 612-743-9311

Thanks man! I've also heard of ATF/acetone as a penetrating lubricant, any opinion on that vs. PB?

 

[j.harris]

Were you using a JIS screwdriver? Usually that makes a big difference on these carb screws. If you can get an impacting screw driver that will help the most.

Also there is a stainless screw kit available on ebay, I would buy one for each carb.

https://www.ebay.com/itm/Mikuni-Car...886282?hash=item2846f0ed0a:g:KVYAAOSwkgxew0Pg

 

[ezgoin92]

AKnarrowback left me a good suggestion in a previous request I had when I had a similar issue. I was able to get mine out with JIS and the impact screwdriver like pictured above. Yours looks a little more stripped than mine. I replaced with the stainless kit that j.harris showed above and it was a good way to go. here is what AKnarrowback suggested which might help you:

Pretty much all of us have run into this.

I'll share how I have dealt with it. I use a small center punch with a VERY sharp point. I do an initial tap, straight down onto the screw head 2/3 of the way out from the center line of the screw head, and then angle the punch in the pit I just made and gently work the screw out. Each hit barely turns the screw, it takes patience, but I have been succesful every time I have done this (so far).

It is my personal preference since I hate the idea of drilling and trying to use an "easy out" since the head on these screws is much wider than the actual thread and I don't want to damage the carb threads.

The screws do not have any loctite on them from the factory but they do compress the rubber seal under the block so it takes a couple of turns to get them to spin freely.

As long as the head is not buggered up too bad you can probably reuse the screws, just don't crank them down as tight as factory. I have always reused mine without a failure yet (so far).

The problem you, I and many others have hit on is the screws in the Mikuni carbs take a JIS (Japanese Industrial Standard) screw driver that locks on solidly into the grooves on the head. Most "other" screw drivers do not seat properly and end up getting the results you have there.

 

[val-e-vue]

Not to worry. Just drill those screws out using a 3/32" bit deep enough to drive a torx T10 bit into the hole. Don't drill very deep because you don't want to snap off the screw head. You just need enough depth for the torx to get grip. If you do snap the head off, you can probably remove the screw with small vice grips.

The T10 will grip the screw very well and you will get it out. You can order some new screws to replace them. M4x14mm 316 Stainless Steel Flat Head Phillips Machine Screws are a perfect replacement for the the manifold.

Gregg

 

[riwaverunner]

Not to worry. Just drill those screws out using a 3/32" bit deep enough to drive a torx T10 bit into the hole. Don't drill very deep because you don't want to snap off the screw head. You just need enough depth for the torx to get grip. If you do snap the head off, you can probably remove the screw with small vice grips.

The T10 will grip the screw very well and you will get it out. You can order some new screws to replace them. M4x14mm 316 Stainless Steel Flat Head Phillips Machine Screws are a perfect replacement for the the manifold.

Gregg

Hey Gregg, I'm a little confused here. I'm drilling a round hole, then basically forcing the T10 bit into it until it bites and can spin the screw out without further stripping the screw?

Also, which of the screws would you recommend this for? The larger one holding the metal cover over the jets? or the one holding the bracket for the seat?

Thanks for the help, really appreciate it!

 

[val-e-vue]

Hey Gregg, I'm a little confused here. I'm drilling a round hole, then basically forcing the T10 bit into it until it bites and can spin the screw out without further stripping the screw?

Also, which of the screws would you recommend this for? The larger one holding the metal cover over the jets? or the one holding the bracket for the seat?

Thanks for the help, really appreciate it!

Yes I think you have the picture. Torx has a slight taper by design, so they will drive into a hole and bind up nicely. This method works perfect on the flat head screws that hold the cover (aka manifold) over the jets. Start with a size under 3/32" and try the torx. If it won't wedge then go with 3/32" drill. I believe that is the perfect size for the T10

The other screw for the needle/seat hold down, is probably classified as a pan head. This method may not work as well there. I think I would lean toward @ezgoin92 method for that screw.

Gregg

 

[riwaverunner]

Yes I think you have the picture. Torx has a slight taper by design, so they will drive into a hole and bind up nicely. This method works perfect on the flat head screws that hold the cover (aka manifold) over the jets. Start with a size under 3/32" and try the torx. If it won't wedge then go with 3/32" drill. I believe that is the perfect size for the T10

The other screw for the needle/seat hold down, is probably classified as a pan head. This method may not work as well there. I think I would lean toward @ezgoin92 method for that screw.

Gregg

Thank you! Really appreciate it!

 

[riwaverunner]

Thank you to all who helped on here. Finally got all 3 screws out!!