Boring vm29ss out to 33mm?

[Jpich85]

I'm in the middle of restoring my carbs for my gsxr 750 1985 and have seen a lot online about boring them out to 33mm, I just wanted to ask does it improve the bike much and worth doing?

I thought I might as well do it while they are a part if it's a good improvement to the bike. 

I could machine them at work if it's worth it. 

[Joseph]

More cost effective to fit some BST34 off the 11 or teapot 

[davecara]

1 hour ago, Joseph said:

More cost effective to fit some BST34 off the 11 or teapot 

It really isnt. You wouldnt swap flatties for CV's!

 

Well worth doing 

[Fazz711]

Only ever seen it done on big bore GS. 

Think it may have been done on period race Gsxr slabs. 

Can't remember if it was mentioned in the official hop up Suzuki manual. 

May be worth a look online for a copy of that as it had other good info on tuning 750 slabs

[Joseph]

7 hours ago, davecara said:

It really isnt. You wouldnt swap flatties for CV's!

 

Well worth doing 

Keyword was cost effective. BST34s are cheap and work well 

But lets put it another way. Sell those VM before butchering them and put a set of Mikuni RS34

[Buzuki]

Basically it`s not to complicated to machine those VM29SS carbs (but have to be very very careful !!!)   , since you only need to re-bore only upper side of the inlet plate to about 32 - 33mm diameter , outlet side is already 33mm wide if I remember correctly ,

after this operation you have to play with slightly bigger main jet , and yes IMHO those VM flatside carbs bore widening have sense only if you have full open  4-1 race exaust system , 

btw , that first GSXR750 generation  was from the factory limited to 100HP peak power on the exaust system pipes inner diameter and carbs inlet diameter (29mm) .

[Jpich85]

16 hours ago, Buzuki said:

Basically it`s not to complicated to machine those VM29SS carbs (but have to be very very careful !!!)   , since you only need to re-bore only upper side of the inlet plate to about 32 - 33mm diameter , outlet side is already 33mm wide if I remember correctly ,

after this operation you have to play with slightly bigger main jet , and yes IMHO those VM flatside carbs bore widening have sense only if you have full open  4-1 race exaust system , 

btw , that first GSXR750 generation  was from the factory limited to 100HP peak power on the exaust system pipes inner diameter and carbs inlet diameter (29mm) .

Great thanks for the advice mate, I'll get them off and pop them in the lathe see how they spin, I didn't realise you'll only be cutting off the one edge but I'll have a better look at them tonight, would you know what new jets would be a good starting point to start with?

[Buzuki]

Les or more everything you need to know is explained in three page on these 10 Year old topic : https://www.say what now!?.com/threads/how-to-convert-vm29s-to-tm33s.323315/

[clivegto]

This is a set that has been done. 

[Jpich85]

12 hours ago, clivegto said:

This is a set that has been done. 

Nice Clive, did you bore the face plates out of them? Are you running pod filters too? I'm not sure whether to keep the air box or change to pods, I'll hopefully be getting a fancy yoshi pipe for it by the time the bike is ready, need to save up a bit for it first lol

[Jpich85]

14 hours ago, Buzuki said:

Les or more everything you need to know is explained in three page on these 10 Year old topic : https://www.say what now!?.com/threads/how-to-convert-vm29s-to-tm33s.323315/

Great thanks mate that's perfect