Tap vs helicoil on carbs

[Bobby Joe]

So one of the mounting holes for the carb bowl on my 71 CB500F stripped out the other night. It was almost there previously...and just went. Now I am wondering if I should tap it or use a helicoil. The debate is 1) is there enough metal to apply a helicoil vs 2) will a tap just mush the soft metal around??

Opinions?

 

[Matts69cbproject]

Speaking from experience, trying to tap aluminum is very tricky. You can do it, but its tricky. As for the helicoil, you should have enough metal to sink one in. You just really have to be carefully when trying to cut into aluminum if you're hoping to get a straight hole. Aluminum likes to stretch.

 

[carnivorous chicken]

You can always get a smaller bolt and lock nut. Pain in the ass to get done and undone, but if you're not working on your carbs when they're on your bike, it's an easy, quick fix.

 

[xb33bsa]

aluminum stretches less than steel
cheapo 4 fluted taps are the enemy
you need a good quality sharp 2 or 3 fluted gun point tap and use light oil,correct hole size, keep it straight,blo out chips often keep the tap wet,any light oil penetrating,atf,wd40 whatever works well with ali
nothing wrong with a helicoil if done correctly very important to tap those threads accurately as well

 

[johngofast]

Helicoil or not, you're going to have to tap it. I don't think a coil is necessary for this though. Never had an issue tapping aluminum.

Like already said, drill to the correct size, use a good tap, use tapping oil or some kind of lube, keep it straight, every few turns in, turn out 1 or two and blow out the shavings.

 

[Bobby Joe]

You can always get a smaller bolt and lock nut. Pain in the ass to get done and undone, but if you're not working on your carbs when they're on your bike, it's an easy, quick fix.

not too sure there would be enough room to get a lock but in there.

 

[Rich Ard]

Re: Re: Tap vs helicoil on carbs

aluminum stretches less than steel
cheapo 4 fluted taps are the enemy
you need a good quality sharp 2 or 3 fluted gun point tap and use light oil,correct hole size, keep it straight,blo out chips often keep the tap wet,any light oil penetrating,atf,wd40 whatever works well with ali
nothing wrong with a helicoil if done correctly very important to tap those threads accurately as well

This guy.

 

[Bobby Joe]

I guess I will stop by Grainger and see what they have in stock. I assume staying away from HF taps are obvious for this job. What is a recommended brand of taps?

 

[xb33bsa]

nice thing about a gun point tap with a short,thru hole(not blind) is that the tap tends to keep the chips pushed ahead and as long as you keep it lubed reversing the tap is usually not needed
certainly doesn't hurt to blo them out as you go

 

[Bobby Joe]

I've borrowed a set of craftsman taps. I hope this does the job. I may be able to increase the hole from a 4mm x 0.7 to a 5mm

 

[johnu]

Kerosine (sp) is an excellent cutting fluid when tapping aluminium also.

 

[fresh_c]

Good ol' WD40 works pretty good as tapping fluid. Just remember to break your chips after every turn and you should be good.

 

[Bobby Joe]

Why won't my pics upload anymore!?!?

 

[Bobby Joe]

Nvm. Off to get some fluid. Thanks guys. I'll keep ya posted.

 

[Bert Jan]

just tap it. Aluminium on such a small hole is no biggie for a hardened tap. Ive had the same problem and just used a nut on a slightly longer bolt.

 

[johnson_steve]

Ditto on the wd40; I use wd40 as coolent when i cut aluminum on the lathe or mill, it leaves a nice surface, blows the chips out of the way and the smoke from it evaporating leaves a pleasent smell in your garage.

 

[johnu]

Ditto on the wd40; I use wd40 as coolent when i cut aluminum on the lathe or mill, it leaves a nice surface, blows the chips out of the way and the smoke from it evaporating leaves a pleasent smell in your garage.

You are right except for the pleasant smell part... at least my wife doesn't agree, I know because I've done it!

 

[Tugboat]

+1 on using a slightly longer bolt with a nut & lock washer on the end if the hole isn't blind, and if you can get to it.

 

[Bobby Joe]

Summary:

Not enough room for the longer bolt and nut option.

Tried cleaning out the threads with a 4mm...none left.

Retapped to a 5mm and drilled out the cap to fit the larger bolt. I used ATF for the cutting fluid by just dipping the tap in the fuild before each cut. 1 turn in, clean...2 turns in, clean...n turns in, clean. Looks good. I went with a hex bolt to prevent stripping the bolt and figured that one day I will change them all out. I think they look a lot better too.

 

[Rich Ard]

Glad you found a fit - but a earning, those black bolts will rust quickly.