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Boring out my 26mm mikuni carbs to 29mm

  • Thread starter Thread starter Warren
  • Start date Start date
W

Warren

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I have read in my performance Suzuki gs manual that this can be done. Has anyone on here done this?
 
A friend has 26mm's bored out to 28mms on his 79' 1000S. He bought the bike that way though. Looking at them all that seemed to be changed was the intake diameter, no internal changes that I could tell. I'm really not sure if this is an improvement though, the true 29mm smoothbores have a lot of internal changes. There is a company in the states that will aprently change you 26mm's into 29mm but I'd be curious what all is done.
 
hi look at this MAXI-BORE Carburetor Carb Boring Service on e-bay ,251108925818 , they say it better them 29s , I been wounding about it ,
 
damn!
monty cambell is still at it...hehehe
he was/is the "X pipe" guy.
his stuff was never a big seller..."1980's"
oh the memories :)
 
Interesting thread, thanks for posting. Didn't completely understand what he was milling down the slide, he calls it the "recess in the bottom". I'll have to look at a carb body to understand it I guess. This sure seems like a cheaper route. I wonder how a milled set compares to a true set of 29mms ?
 
questions are , Is it worth doing and where can we get it done , and the big one , COST #$$$$
 
why not just buy a used set of VM28's? (as fitted to the UK spec. GS1000S and N models)they measure almost 29mm at the inlet bore anyway (28.8 IIRC)
 
But what are their availability and cost? Whats the cost if this guy is doing it for extra cash on the side?? This is the question I asked him in my PM..whats the cost and is he in business to do them on the side.
 
I've got a good machine shop in town that could do this. Next time I can remember I'll swing by and have a chat with them. I really can't imagine they nearly as much of a performance upgrade as a true set of VM 29mms though.
 
I have a set of spare carbs that I am going to do. I will post how it goes. I believe what he means by recess where the slides go. When you bore out the intake side ID it will push down the material you are cutting off into where the slide has to come down and seat. It actually creates a burr. You need to mill this burr off. If not the slide will not seat all the way down and your needle will not seat at the correct height. This looks to be a very simple process. I believe that this a very easy and quick performance up grade. I have a performance book on the Suzuki Gs750's and it has a small artical on this subject, that the guys racing the Super bikes did this article on this modification.

Cheers,
Hope everyone likes this. I will post how this goes!
 
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Vm26mm boring out to 29mm

Vm26mm boring out to 29mm

Here is the manual that I read this in.
 

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Vm26mm boring out to 29mm

Vm26mm boring out to 29mm

Here is the write up on this.
 

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Vm26mm boring out to 29mm

Vm26mm boring out to 29mm

Here is a pic of the inside recess bore where the slide seats. From what it looks like you need to mill this inside ID down so so the slide will seat below the intake ID that you machined to the 29mm diameter.
 

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ahhhhhh.....it looks as though from the article you posted this mod will give some extra performance but nothing like a proper set of 29mm's.
 
Vm26mm boring out to 29mm

Vm26mm boring out to 29mm

Here is a pic of the intake side of the carb that will be machined out to 29mm. Looking at both photos you can better understand how the material gets pushed down into where the slide seats.
 

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Vm26mm boring out to 29mm

Vm26mm boring out to 29mm

Yes and no, you get the performance gain, but loose on the gas-mileage. Ether way you loose due to the cost of the 29mm. As for the gas Mileage you will have already lost that anyways if you have installed a 4 into one with pod filters and you have re jetted your carb. So for me if it's a performance gain it's a improvement all around. That's why I think they did this in Super sport. As the gas mileage was already gone with all the performance up grades they made. So for them to run the 29mm up grade it did not make a lot of sense as they would not gain anything from it. I maybe wrong, but this is what I am getting from this info.

Cheers,
 
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