From 3 Carbs to 1

Use this area for posts and questions that don't seem to fit anywhere else.
Post Reply
Jeff L
Contributor
Posts: 687
Joined: Fri Oct 28, 2011 5:09 pm
SELF INTRODUCTION: Hey...I live in South Jersey (the Super Fund State) work as an Operating Engineer local825.Besides bikes I love to fish the surf.I have my current & seemingly endless project a BSA 750 Rocket3, a 72 Honda CB750,79 Kawasaki KZ1000, 48 Simplex, & a 62 Norton Atlas engine
Location: South Jersey

From 3 Carbs to 1

Post by Jeff L »

Thinking about building a Manifold to run a single Carb.Is there a Formula to determine what size I will need?
Changing the shape of the Earth...1 bucket at a time...IUOE local 825 top of the food chain
User avatar
Customize IT
Contributor
Posts: 992
Joined: Thu Sep 19, 2013 7:54 am
SELF INTRODUCTION: I am a young punk kid that needs some help building himself a chopper!!

I am sorry I only have a hotmail account???

Tell me what I need to do I need help with my girder!!!

PLESE HELP????


[url=http://imgur.com/8saXkqN][img]http://i.imgur.com/8saXkqNl.jpg[/img][/url]








[url=http://imgur.com/pXJZqQ0][img]http://i.imgur.com/pXJZqQ0l.jpg[/img][/url]









[url=http://imgur.com/T3Q4Ev4][img]http://i.imgur.com/T3Q4Ev4l.jpg[/img][/url]









[url=http://imgur.com/fsXGYQw][img]http://i.imgur.com/fsXGYQwl.jpg[/img][/url]
Location: Ohio, USA

Re: From 3 Carbs to 1

Post by Customize IT »

Page 10

https://www.dropbox.com/s/1xc1ux8hgnn12 ... %20101.pdf

But really as long as there is equal runners no cyl will starve then set your carb to that!
User avatar
curt
Long in the Tooth
Posts: 1068
Joined: Tue Oct 25, 2011 11:36 am
SELF INTRODUCTION: hi everyone its me from the old bord hopeing to see everyone come here and all the newcomers . lets make this as good as the old one or even better . lookin foreward to seeing everyones projects continue and ill be continueing mine too
Location: utica new york

Re: From 3 Carbs to 1

Post by curt »

unsure about formulas but food for thought if your switching to single carb maybe a carb with accelerator pump . I been thinking about it for my triumph i remember back in the day used to run a mikuni was thinking if I could still get a manifold modern sporty carbs have the same mount and an 883 is close to 750 so jetting should be available an accelerator pump should have many benefits no bog off the line jumping on it too hard , easier starting no fuel pouring on the engine from hitting the ticklers . only thing I worry bout is the squirt being too much for the twin but a triple might handle it better but I bet playing with the length of the rod for the pump could control the squirt . I am going to try no matter what but your a lot closer than I am and its just food for thought
ever notice when you hit somethin or someone with a hammer you feel instantly better
Jeff L
Contributor
Posts: 687
Joined: Fri Oct 28, 2011 5:09 pm
SELF INTRODUCTION: Hey...I live in South Jersey (the Super Fund State) work as an Operating Engineer local825.Besides bikes I love to fish the surf.I have my current & seemingly endless project a BSA 750 Rocket3, a 72 Honda CB750,79 Kawasaki KZ1000, 48 Simplex, & a 62 Norton Atlas engine
Location: South Jersey

Re: From 3 Carbs to 1

Post by Jeff L »

Been thinking....(no my Brain doesn't hurt)...Since only one Cylinder is firing at any given time,seems like I wouldn't really need a Carb bigger than what's on each Cylinder now.The amals are 26mm..I'm gonna try a 30mm. mikuni.
Changing the shape of the Earth...1 bucket at a time...IUOE local 825 top of the food chain
User avatar
Customize IT
Contributor
Posts: 992
Joined: Thu Sep 19, 2013 7:54 am
SELF INTRODUCTION: I am a young punk kid that needs some help building himself a chopper!!

I am sorry I only have a hotmail account???

Tell me what I need to do I need help with my girder!!!

PLESE HELP????


[url=http://imgur.com/8saXkqN][img]http://i.imgur.com/8saXkqNl.jpg[/img][/url]








[url=http://imgur.com/pXJZqQ0][img]http://i.imgur.com/pXJZqQ0l.jpg[/img][/url]









[url=http://imgur.com/T3Q4Ev4][img]http://i.imgur.com/T3Q4Ev4l.jpg[/img][/url]









[url=http://imgur.com/fsXGYQw][img]http://i.imgur.com/fsXGYQwl.jpg[/img][/url]
Location: Ohio, USA

Re: From 3 Carbs to 1

Post by Customize IT »

It will need jetted up but one carb will work from stock.

the needle will needed shimed.

I have also seen manifolds made not equel runners work ever seen one on a striaght six engine? Same concept!
spidr
Stalker
Posts: 151
Joined: Mon Feb 10, 2014 2:21 pm
SELF INTRODUCTION: I own a custom fab shop, and build choppers in my off time. I like to build differant from the norm, no cookie cutter stuff, no bolt ons, foot clutch, hardtail, and loud. My kids help me build, they learn how to run the equipment, and we get quality time together while they build some skills.

Re: From 3 Carbs to 1

Post by spidr »

I had a whole response typed up aboout CFM needed, and such, based on my own experiance, and then accidentally closed the window.

But then I stumbled oon this, and it would help you tons.

http://www.csgnetwork.com/cfmcalc.html

The only number you may not know is the volumetric effiency, Usually I crunch the numbers based on about 70%, 99% of motors dont get over 90 unless they're boosted(turbo or super.) It will at least get you in the ball park for cfm.

For the sake of argument, If I run the numbers on a 750 3 cylinder running stock 30mm carbs, the carbs each flow approx 70cfm.

At 70% effiency and a 7000rpm ref limt, the engine requires 64cfm and you';d be fine. At 100% effiency though, you'd 92 and the motor woruld starve. Raise the rev limiter, and you wouldnt have enoough to hit redline under load.

I pulled the cfm #s off the net, and just used that as an example, but you get the idea. Its worth crunching the numbers before hand to know what to expect, never know what you might come across.
neale
NewB
Posts: 22
Joined: Tue Jun 19, 2012 12:04 pm
SELF INTRODUCTION: I have had an interest in choppers from the '70's when I was in high school, reading custom chopper mag etc, I have never had or built a chopper to date, I'm trying to learn, I am acquiring equipment (tube bender, oxy torch etc) and am trying to get started building up the skills and information I need to get started on building a chopper.
My current bike is a Yamaha XV1000, I would class it as a mild custom rather than a chopper, a lot of the useless (to me) bits have been removed and I am trying to modify and chop a few more things off to get it to a longer, lower, leaner machine with better performance (custom shortened rear shocks, refabricate forward controls and drag bars, try and get raked cups working on it etc), but IMHO it doesn't have the right type of frame to build a "proper" chopper on, so I am looking for a more suitable donor bike for the project.

Re: From 3 Carbs to 1

Post by neale »

That's great info, thanks for that.

The bike I'm playing with at the moment is a Viagra XV1000 (previous generation to the XVS1100 donk in your chop), and one of the cafe boys found that it's possible to fit the XVS1100 barrels, heads and internals to the XV1000/XV1100 cases as a simple bolt in operation. I've been hunting a donor XVS1100 to do this, and want to do pretty much the same PCS upgrade as you're doing, but I've got a Mikuni HSR42 on a single carb manifold on at the moment, it was interesting to see that even if I got 95% efficiency and ran an 8000 redline, the numbers still come well inside what the HSR42 will deliver.

Cool, ta ;^)

Neale
Jeff L
Contributor
Posts: 687
Joined: Fri Oct 28, 2011 5:09 pm
SELF INTRODUCTION: Hey...I live in South Jersey (the Super Fund State) work as an Operating Engineer local825.Besides bikes I love to fish the surf.I have my current & seemingly endless project a BSA 750 Rocket3, a 72 Honda CB750,79 Kawasaki KZ1000, 48 Simplex, & a 62 Norton Atlas engine
Location: South Jersey

Re: From 3 Carbs to 1

Post by Jeff L »

Thanks Spidr...I plugged in 8000rpm @ 80% ( digging around found Numbers that state most stock Engines run between 75 -85% efficiency)& got 85cfm.At 100% the cfm required is very close to the rating for the 34mm.(The only ratings I could find had the 34mm Mikuni flowing at 109cfm)..Not sure if later down the Road I'll put bigger Cams in or not,It will probably be better to be over Carbed than under Carbed.I'm thinking this might be a good Size to start...thoughts????
Changing the shape of the Earth...1 bucket at a time...IUOE local 825 top of the food chain
spidr
Stalker
Posts: 151
Joined: Mon Feb 10, 2014 2:21 pm
SELF INTRODUCTION: I own a custom fab shop, and build choppers in my off time. I like to build differant from the norm, no cookie cutter stuff, no bolt ons, foot clutch, hardtail, and loud. My kids help me build, they learn how to run the equipment, and we get quality time together while they build some skills.

Re: From 3 Carbs to 1

Post by spidr »

Just make sure you leave yourself a bit of a buffer. Something as simple as a wet filter in the rain could screw you up. Your intake needs to flow free enough to evenly distribute the air, etc.

Last thing would be to make sure that you can jet that carb biig enough to work. depending on the model, jets only go so big without drilling them custom, if you cant put enough fuel into that air soo that the ratioo is right, you'rre still up the creek.
Jet numbers are based on MM, a 100 jet is 1 mm. You need to consider square area of the jet, if it was running an 80 main on each carb, you would need too step up to a 140 main to triple the amount of fuel. Tuning is always a bitch, but its just one mroe thing to consider.
Jeff L
Contributor
Posts: 687
Joined: Fri Oct 28, 2011 5:09 pm
SELF INTRODUCTION: Hey...I live in South Jersey (the Super Fund State) work as an Operating Engineer local825.Besides bikes I love to fish the surf.I have my current & seemingly endless project a BSA 750 Rocket3, a 72 Honda CB750,79 Kawasaki KZ1000, 48 Simplex, & a 62 Norton Atlas engine
Location: South Jersey

Re: From 3 Carbs to 1

Post by Jeff L »

I put a call into Mikuni & was trsnsfered to a Co.that dustributes for them (guess they don't have Tech support...odd).I told the Guy what I was planning to do & using a 34mm.Carb.He told me there was a single Carb convertion for the Norton 750 that uses the 34mm.Carb,but because the Bore on my Engine is smaller His suggestion was stepping down to a 30mm. Or 32mm. Carb.
Changing the shape of the Earth...1 bucket at a time...IUOE local 825 top of the food chain
neale
NewB
Posts: 22
Joined: Tue Jun 19, 2012 12:04 pm
SELF INTRODUCTION: I have had an interest in choppers from the '70's when I was in high school, reading custom chopper mag etc, I have never had or built a chopper to date, I'm trying to learn, I am acquiring equipment (tube bender, oxy torch etc) and am trying to get started building up the skills and information I need to get started on building a chopper.
My current bike is a Yamaha XV1000, I would class it as a mild custom rather than a chopper, a lot of the useless (to me) bits have been removed and I am trying to modify and chop a few more things off to get it to a longer, lower, leaner machine with better performance (custom shortened rear shocks, refabricate forward controls and drag bars, try and get raked cups working on it etc), but IMHO it doesn't have the right type of frame to build a "proper" chopper on, so I am looking for a more suitable donor bike for the project.

Re: From 3 Carbs to 1

Post by neale »

Jeff, I'm no expert by any means, but as Spidr said, you should allow yourself a buffer, this comparison that I dug up when searching for the CFM of my carb (HSR42) shows that pretty well.

http://www.nightrider.com/backup2/biket ... irflow.htm

FWIW

Neale
Jeff L
Contributor
Posts: 687
Joined: Fri Oct 28, 2011 5:09 pm
SELF INTRODUCTION: Hey...I live in South Jersey (the Super Fund State) work as an Operating Engineer local825.Besides bikes I love to fish the surf.I have my current & seemingly endless project a BSA 750 Rocket3, a 72 Honda CB750,79 Kawasaki KZ1000, 48 Simplex, & a 62 Norton Atlas engine
Location: South Jersey

Re: From 3 Carbs to 1

Post by Jeff L »

I wish they would publish Tests like that for all thier Carbs.I could only find cfm ratings for 34-38mm.Carbs.Unfortunately I have to start somewhere.I picked up a 32mm. cheap, so I can start on the Intake.If it turns out it's not big enough,I'll step up...time will tell.
Changing the shape of the Earth...1 bucket at a time...IUOE local 825 top of the food chain
Post Reply

Return to “General Technical Matters”