boreing out carbs ???

[unclemark]

Hi i need to bore out some 900 cat carbs and the ?? are whats the biggest and the best way to do this ? rifle bore,taper bore or just a regular bore ??? I heard you cant go all the way to 42mm on the cat carbs so whats a safe mm to go to ?? and what else should i know be for doing this

Thanks

 

[Pebs]

Are you having a shop do it? Also, I've only heard of one way of boring carbs. Rifle bored? Really?

 

[KAWGRN]

I have some 42 TMX that I used on a 1220 ET motor in a CMX for sale 400$ with cables and evey tunning jet needle and needle jets

 

[longhairfreak]

If I remember correctly 41.7mm is max.

 

[4Z]

Down side of boring is that is gives less side support for the slide. I had a motor that on it's second season the slides started to send chunks through the motor. After that all my bored carbs I just put new slides in each year and it solved it.

You can bore them on a lathe. Very simple....... or send them to Fastrax....

 

[unclemark]

Are you having a shop do it? Also, I've only heard of one way of boring carbs. Rifle bored? Really?

yea their's a guy here in AK theta puts a dremel tool to them makes them a Little bigger and makes 4 screw like groves in them claims they make a world of difference !!!

Down side of boring is that is gives less side support for the slide. I had a motor that on it's second season the slides started to send chunks through the motor. After that all my bored carbs I just put new slides in each year and it solved it.


You can bore them on a lathe. Very simple....... or send them to Fastrax....

so any one with a lathe can do the boring ???

If I remember correctly 41.7mm is max.

thats what i remember i think

 

[unclemark]

How about the taper bore ?? how exactly is this done ?? some one on here said that a 42mm taper bore carb gets more air than a 48mm i don't see how thats possible ??


any thing else should i know ?? any thing special when re assembling them ??

THANKS

 

[4Z]

UM, I am not a machinist, nor even remotely pretend to be. But, I have bored my own on a buddy's lathe....... many times......

 

[fredw]

i just dod a set of skidoo 40mm flatslides, i had local machine shop bore them out to 42mm, and they seam to work fine, had to raise pilot up one for normal idle

 

[Thunder101]

Aaen says taper bore is best, and flow high cfm as a straight bore but no ill effects with low speed rpm which seems to be everyones prob with straight bore.

 

[Fredrik]

Anyone tried kehin pwk 41 pro carbs.

 

[svensdream]

I bore carbs on weekly basses and those carbs can go to just over 42mm, a strait bore or a taper bore is best, I have heard from several mod shops that riffle boring is ill advised

 

[itsallgood]

riffle bore

why is riffle bore ill advised?

 

[krom]

how much of a taper is reccomended? I have a lathe (with a taper attachment)and a set of 40 mm racks to do, but it will be the first I've done, hate to ruin them, so was going to stop at 41.5, any suggestions?

 

[svensdream]

why is riffle bore ill advised?

the biggest reason is that it is done by hand which is not symmetrical and conducive to flow. why would you want to get the air spinning anyway, it's just going to straighten back out when it hits the reed cages

 

[Scott]

Down side of boring is that is gives less side support for the slide. I had a motor that on it's second season the slides started to send chunks through the motor. After that all my bored carbs I just put new slides in each year and it solved it.

You can bore them on a lathe. Very simple....... or send them to Fastrax....

REALLY?
Brass chunks?

I wonder if that's what happened to me two weeks ago?
It wasn't enough to notice anything, but my EGTs started running about 65° on the PTO side.
Got pits on piston top, dome, and am getting cyl re-nic'd right now.
HMMMM.

 

[Thunder101]

according to Aaen , for example, a 38 taper bored to 42 will flow so so very close to a straight 42 ,like 134cfm for a straight and 130 for a taper, the benifit is the attomization at low speed with the taper over the straight. And yes I read a few times rifle boring is a myth. dont do it, just think about it the air is flowing straight then you going to make it spin then go straight again when it hits the r cage. the idea of the taper , in my mind, it acts like a velocity stack after the jet and slide, decrease in friction.

 

[4Z]

REALLY?
Brass chunks?

I wonder if that's what happened to me two weeks ago?
It wasn't enough to notice anything, but my EGTs started running about 65° on the PTO side.
Got pits on piston top, dome, and am getting cyl re-nic'd right now.
HMMMM.

Not brass, aluminum (slide material).

 

[Scott]

I had "brass" colored bits in my exhaust cans and little rectangular pits in my piston top and dome.

 

[the fix-it guy]

That was the zipper off your cart-harts.