Hello Guest User,
Please feel free to have a look around the forum but be aware that as an unregistered guest you can't see all of it and you can't post.
To access these 'Registered Users Only' areas simply register and login.
Please feel free to have a look around the forum but be aware that as an unregistered guest you can't see all of it and you can't post.
To access these 'Registered Users Only' areas simply register and login.
Throat boring Vm26 questions
Moderators: chrisu, paul doran, Taffus, KeithZ1R
- warren3200gt
- Hardcore

- Posts: 3102
- Joined: 13th Jun 2014
- Location: Dartford Kent
Throat boring Vm26 questions
How far can you safely throat bore vm 26's and what is best to do about needle valve seats?
PUM 488 June 2026
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
Re: Throat boring Vm26 questions
warren3200gt wrote:How far can you safely throat bore vm 26's and what is best to do about needle valve seats?
I've seen quite a few sets of bored out carbs. On some the needle valve was trimmed (lowered) and on others it wasn't...
http://www.airevalleyclassics.co.uk
10% discount code Z1OCTEN
Keyster rebuild kits & carburettor spares - airscrews, jets, needles, starter plungers & gaskets.
Also petrol/ethanol proof float bowl gaskets. IMD pistons preferred seller.
10% discount code Z1OCTEN
Keyster rebuild kits & carburettor spares - airscrews, jets, needles, starter plungers & gaskets.
Also petrol/ethanol proof float bowl gaskets. IMD pistons preferred seller.
- warren3200gt
- Hardcore

- Posts: 3102
- Joined: 13th Jun 2014
- Location: Dartford Kent
Re: Throat boring Vm26 questions
Do you know what dia they were bored to ?
Last edited by warren3200gt on Tue May 31, 2022 11:19 am, edited 1 time in total.
PUM 488 June 2026
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
Re: Throat boring Vm26 questions
warren3200gt wrote:How far can you safely throat bore vm 26's and what is best to do about needle valve seats?
I've done this a few times.
You can safely go to 29.5mm and depending on the thickness of the casting in the boot groove area up to 30mm.
All the details start at the bottom of page 15 through to 19 in my cafe racer project thread.
viewtopic.php?f=7&t=14312&start=210
- warren3200gt
- Hardcore

- Posts: 3102
- Joined: 13th Jun 2014
- Location: Dartford Kent
Re: Throat boring Vm26 questions
Perfect ta Rob. Safe upto 29mm then. 
PUM 488 June 2026
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
- Z1streetfighter71
- ZedHead

- Posts: 1031
- Joined: 16th Oct 2020
- Location: Galway-Eire
Re: Throat boring Vm26 questions
zed1015 wrote:warren3200gt wrote:How far can you safely throat bore vm 26's and what is best to do about needle valve seats?
I've done this a few times.
You can safely go to 29.5mm and depending on the thickness of the casting in the boot groove area up to 30mm.
All the details start at the bottom of page 15 through to 19 in my cafe racer project thread.
viewtopic.php?f=7&t=14312&start=210
Have you ever considered taking on a set for some one else.. 2 sets even... hint hint wink wink
Angus.
Too many bikes to list.
Too many bikes to list.
- warren3200gt
- Hardcore

- Posts: 3102
- Joined: 13th Jun 2014
- Location: Dartford Kent
Re: Throat boring Vm26 questions
For your sake, I hope your asking Rob and not me!
PUM 488 June 2026
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
- warren3200gt
- Hardcore

- Posts: 3102
- Joined: 13th Jun 2014
- Location: Dartford Kent
Re: Throat boring Vm26 questions
Rob, have you done a set that had both fuel and air screws? Just wondering how much taper there is on the fuel screw carb body? Bit worried about boring it which might increase the hole diameter.
PUM 488 June 2026
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
Re: Throat boring Vm26 questions
warren3200gt wrote:Rob, have you done a set that had both fuel and air screws? Just wondering how much taper there is on the fuel screw carb body? Bit worried about boring it which might increase the hole diameter.
Yes! The ones i did for the alloy cafe were Suzuki GS750 VM26MM carbs which have both.
No problems.
- warren3200gt
- Hardcore

- Posts: 3102
- Joined: 13th Jun 2014
- Location: Dartford Kent
Re: Throat boring Vm26 questions
Top man. 
PUM 488 June 2026
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
- Z1streetfighter71
- ZedHead

- Posts: 1031
- Joined: 16th Oct 2020
- Location: Galway-Eire
Re: Throat boring Vm26 questions
warren3200gt wrote:For your sake, I hope your asking Rob and not me!
Ha yes was asking Rob but im sure you do good work too...
Angus.
Too many bikes to list.
Too many bikes to list.
-
kev edwards
- Hardcore

- Posts: 2152
- Joined: 3rd Apr 2009
- Location: leverington UK
Re: Throat boring Vm26 questions
If you have a lathe it should be easy enough.
- warren3200gt
- Hardcore

- Posts: 3102
- Joined: 13th Jun 2014
- Location: Dartford Kent
Re: Throat boring Vm26 questions
I'm not convinced that I have enough chuck center line to bed clearance to accommodate the slide body Kev. Need to have a measure up before stripping them down.
PUM 488 June 2026
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
76 Z900A4, 77 Z650B1, 77 KZ650B1, 77 Z1000A1, 82 Z1000J2, ZRX1100R.
- Z1streetfighter71
- ZedHead

- Posts: 1031
- Joined: 16th Oct 2020
- Location: Galway-Eire
Re: Throat boring Vm26 questions
Sorry for resurrecting this thread but the question of the needle valve seats, Rob- did you remove them or bore them out?
Angus.
Too many bikes to list.
Too many bikes to list.
Re: Throat boring Vm26 questions
Z1streetfighter71 wrote:Sorry for resurrecting this thread but the question of the needle valve seats, Rob- did you remove them or bore them out?
What do you mean by needle valve seats ?
Who is online
Users browsing this forum: Google [Bot] and 85 guests