2 into 1 intake

darrenlindy78 · Full Member Joined: Mar 05, 2008 Posts: 52

i'm building a 72 chopper want to build a 2 into 1 intake. i think i got a good plan but do the intakes have to be the same length?

darrenlindy78 · Full Member Joined: Mar 05, 2008 Posts: 52

any info from anyone that has done this would be great

xs1961 · Posted: April 11, 2009, 7:00 am Post subject: Re: 2 into 1 intake

Wouldnt the fuel/air mix & velocity would be down on the longer intake ?

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

How do the bikes run wiht a 2 into 1 intake? Anyone have this set up?

xs1961 · Posted: April 11, 2009, 9:37 am Post subject: Re: 2 into 1 intake

I did see one once on an XS motor fitted to a Norton featherbed frame..If its as good as the single carb conversion I had on my Commando it would be well worth doing, it ran a lot sweeter than with two !
Cant be done easily with a standard XS frame because the rear downtube is right where the single carb would sit!

penn71911 · Posted: April 11, 2009, 9:48 am Post subject: Re: 2 into 1 intake

Last summer I owned a old GL1000 (gold wing), It had been sitting forever and I could never get the 4 carbs all workijng at the same time... so after numerous cleanings disassembly/reassemblies... I had enough. I pulled off the factory carb setup, fab'd up an intake manifold, basically a steel box with tubing welded to it in the right spots... and bolted on a 2bbl weber carb (off of a 76 BMW car that I scored at the local boneyard)... the bike ran it's a$$ off after some tweaking...

A single carb setup will work, it's a heck of alot easier to tune... I've seen a pic or two of a single setup on XS's... do a google search. Ideally both intake runners should be the same length... and you will probably lose some top-end power unless you step up to a bigger carb.

xs1961 · Posted: April 11, 2009, 9:51 am Post subject: Re: 2 into 1 intake

Best thing I ever did with the Commado (apart from selling the F****r !) Id sacrifice top-end popwer/speed for smooth running any day of the week if it could be easily done

Retiredgentleman · Posted: April 11, 2009, 10:45 am Post subject: Re: 2 into 1 intake

xs1961;
Don't let Barbara catch you talking that way about Nortons. Smile

xsjohn · Posted: April 11, 2009, 10:54 am Post subject: Re: 2 into 1 intake

In order to create more horsepower the runners become shorter in length allowing the air a more direct path, and when torque is desired the pipe length is extended

The extra length of the intake tubing to the right cylinder acts as a larger plenum resulting in uneven air distribution between the left and right cylinder…."A smaller plenum gives you more torque, while a bigger plenum makes more power at high rpm."

Smaller volume gives faster air flow for power.

Larger volume gives better torque.

Y TAKE………since the right cylinder already runs 25 degrees hotter than the left any intake modifications that would increase this situation would "not" be good at all….

I read for a couple of hours on this subject………seems the air filter may have to be on the right to reduce the plenum ……not much room there with the kick start and all….and I don't know that this is even true....you would needl to research it to understand what effects the extra plemum has on mixtures....if you leaned the right any don't do it....if you richened the right that would be good ...........

I couldn’t find much information on intake length and plenum size and its effects on mixtures….but air speed and vacuum pressure on these carbs would have an effect on drawing fuel up and out of the carbs I would think….lower atmospheric pressures due to the slower moving air at lower rpms with a larger (uneven) plenum WILL EFFECT SOMETHING…..and if it effects the right cylinder temp anymore than stock it wouldn’t go on mine….and you will loose the ability to directly effect each cylinders mixtures in order to balance cylinder temperatures…….And I do know something about that on these....

OK class dismissed....... Laughing

xsjohn

blackwidow · Posted: April 17, 2009, 7:05 pm Post subject: Re: 2 into 1 intake

They sell 2 into 1 intake setups on ebay for the xs650 and it sticks out the right side of the bike and both tubes are the same size

BiffTirkle · Posted: May 14, 2009, 5:23 pm Post subject: Re: 2 into 1 intake

i saw that link, i talked to joe at wiseguyschoppers.com i asked how the setup has been running. and he said it was doing great! i asked about the temp of the right cylinder. and he said he didnt notice any problems.
i doubt he measured the temp on each cylinder though. i didnt ask directly. i will next time i talk to him. i am interested in this setup. and, i dont really know why. ive already got a set of round slides that work perfect. but this would be for my other bike. which, has a set of carbs that also work perfect. maybe i just like wasting my money.

could be worse, i could be hooked on going to strip joints, and cocaine.

xs1961 · Posted: May 14, 2009, 6:26 pm Post subject: Re: 2 into 1 intake

Soon as I can lever my 650 motor into my spare 750 frame (which has twin rear down-tubes)Im going for a single carb set-up, from past experience with my Brit-bikes single carb wins every time !

darrenlindy78 · Full Member Joined: Mar 05, 2008 Posts: 52

any idea what jet sizes to use?

woodman · Full Member Joined: Oct 12, 2008 Posts: 256

Look at the runner length differences in a carbed 6 cylinder car or truck engine and it seems to work OK ? IM sure its not going to run as well but it will run. Personally if I tried it Id use a Keihin 40mm CV carb like on my Harley, they seem to be as easy to work on and trouble free as any Ive seen. But Im not trying it, Im happy the way it is.

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