Stripped a Few Screws on my Mikuni Carbs: Options?

[Frank_Hassa]

I bought the recommended JIS #2 screwdriver, but I got it from eBay not Amazon as recommended by the member in a previous thread. So full disclosure, it's possible I got a fake JIS screwdriver, because the head looks EXACTLY like a #2 Phillips. I can post a picture if anyone wants to see it. Looks exactly like the one from Amazon, mostly red and black, same printed words on it, says it's JIS, etc... but it doesn't fit the Mikuni Carb screws any better than a DeWalt #2 Phillips screw gun bit. Flops around in there a little bit.

The first screw I tried stripped out completely. So I went with a cordless screwgun with a brand-new #2 phillips bit and set the torque real low and slowly worked my way up. It started turning the screw at about "18" (out of 20) and the ratched/impact effect of the screw gun seemed to give some time for the screw bit to slip back and "reset" before the next hit, which is why I only partially stripped 2 more screws out of both carbs (which I think is about 16 screws total).

Learned the difference between "Mag" and "PTO" and got clear on the accelerator pump and how it's 4 screws are necessarily longer than the others. Not certain but I think there are 3 lengths of screws.

I have one totally stripped screw and two partially stripped screws that could probably be used again, but now I hate stainless steel screws because I can see how much weaker the metal is than standard steel. The one that is fully-stripped peeled some of the aluminum threads from the body of the carb when it came out. Not much, but some.

I've read about people going with Allen Screws, and I'd like to do that. Looking for a compelling reason not to. Also I'm having trouble finding a replacement screw for the one that is stripped, and the prices are crazy when ordering them as "Seadoo Parts". I know they'd be much cheaper if I simply ordered "M6 x 12 mm stainless steel screw", but that's the problem, I don't know the specifications. Looked all over the parts manual, etc... and I can't find any reference that gives an, uh... "absolute" description of the specs of these screws (thread, length, etc...).

Does such a reference exist? How can I order $3.00 worth of screws and avoid paying $30.00 for them? Is converting to Allen screws a good idea or bad?

Also: Was that loc-tite I was fighting with? There was a hard white substance in the threads. I thought it might have been corrosion since I expect loc-tite to be red or blue, but industrial loc-tite could be totally different. When I reassemble them, should I use loc-tite again? What strength? I'm more inclined to use grease, not loc-tite. How likely is it that these screws will vibrate-out if I don't use loc-tite?

 

[tkarvelis]

The white stuff is a reaction from the stainless and aluminum. Not much you can do, except coat the threads with a light film of grease, but that will change your torque values.

There is no reason NOT to use allen head screws. McMaster Carr should have what you need.

You should have the specs in the parts manual / service manual, I believe. They might not take the carburetor down to the component level. Measure the screw length, and order the same (Pan head, etc) and you should be good to go.

 

[Spimothy Leary]

there is a member here, I forget which one that had complete screw replacement kits for a reasonable price.

when i've needed just one screw I usually just stole a screw from another carb, but I have them laying around here, if you don't have one then maybe just bring a sample to the hardware store and match it up rather than figuring it out online and paying shipping.

 

[Sportster-2001-951C-Stock]

I just press really hard to get a good bite and then twist, I MEAN REALLY hard so the bit doesn't slip. Perhaps some lapping compound might help your bit get a bite, (toothpaste or chrome polish with abrasive in a pinch).

It can be tough getting them out given the galvanic corrosion the occurs.

The bit must be a really good quality hardened bit or else the flutes just fold over. The kind of bit that shatters before it distorts.

Speaking of thread locker, I use only some oil on ALL the screw threads or anit-seize compound for reassembly. Otherwise the threads are easily galled. Never had a screw back off. Some say the mounting bolts will back off on the 787 I believe this motors will due to vibration thus blue thread locker is a must for the mounting bolt threads. Anti-seize on the bottom of the head and non-threaded portion and locker on the threads in this case

There might be something to that, there's a lot of vibration.

I prefer blue if you must, only use red locktite when required b/c that stuff is permanent unless you can apply heat to loosen it hope you don't ever want to take that apart ever again.

Speaking of heat, a butane pencil or high watt (~200 Watt) soldering iron might help you break those screws lose, along with some paraffin wax or ATF as penetrant.

 

[gazza2010au]

Mate don't quote me on this one but i have one of these JIS screws in my hand with a tape measure (caliper is out in the shed 12am here) screw measures 4mm diameter bolt length without the head is 11mm and about 13mm overall length with the bolt head, i don't know the pitch don't have a gauge sorry

 

[hotrodssnova]

On some of the ones I have rebuilt, I had to use a pair of needle nose vice grips to remove the screws. Others, I drilled the head off and used vice grips to unscrew the rest. Ace hardware had the screws in both hex and Philips style in stainless.

 

[racerxxx]

there is a member here, I forget which one that had complete screw replacement kits for a reasonable price.

when i've needed just one screw I usually just stole a screw from another carb, but I have them laying around here, if you don't have one then maybe just bring a sample to the hardware store and match it up rather than figuring it out online and paying shipping.

[MENTION=51350]Jetskigoodies[/MENTION] has them

 

[gazza2010au]

I read last night the JIS screws are metric so that would be a M4 thread pitch :thumbsup: