Single carb conversion thread...

[XSive650]

Well, in theory, it shouldn't require any more fuel. The engine is still going to need a certain amount of fuel to produce power. Optimal air/fuel ratio is generally 14.7 to 1 on internal combustion gasoline engines. And I use the word generally because we are talking theory. Sound reasonable?

I'll be going this route this year myself. Would seem to me that if my carbs are set right on my bike now and I go to a single carb setup running only my left carb that my jetting would still be good. I mean it can only suck air to cyliner at a time right? Or does it require larger jetting because you are doubleing the FPM of air through the carb?

 

[TeeCat]

Well, you might at least have a baseline, so you'll likely at least be able to get the bike running. But a lot will depend on the length of the runners and other such factors. i wouldn't count on a no-touch, straight-up conversion unless you're one of the luckiest people on the planet.

TC

 

[XSive650]

I'm only on page #7 of the thread so far but I have time to waste since we're in the middle of an expected blizzard here in STL today into tomorrow. I'll probably go with a mikuni carb later but I build on a budget so I plan running stock for at least one season.

 

[fishman]

Teecat,

I'm from the Netherlands and i'm doing the same conversion.
Can you tell me what jet needle/needle jet you use?
Mine's got a 6DH3 and it runs way too lean.
Do you have de air jet installed?

Thanks,

Fishman

 

[fishman]

i luv...your set up of the direct pull carby and the bend for the air cleaner... ,i got an email from joe ... about doing 2 into 1 manifolds for 38cv carbys and he said he was looking at that down the track... hopefully not toooooo far down the track ,,i think the standard throttle cable for 38,s would shift side enough to do a good job ... finally i do luv.. the ram set up twin carbs out the front of the head.. although i would tend to ride along watching my carbys ..regards oldbiker

Hi,
At first i used a bs38 on my home made 2 into 1 manifold. I replaced it with a VM36. The outside diametres are about the same. So a BS38 would bolt right up to Joe's manifold.
You can't use the teh original throttle cable. It's too short. I made one of universal bicycle shift cable. Costs nothing!

 

[dr frankensteel]

just wondering if you put any miles on this setup yet? i am very close to ordering the kit meself. any mileage or maintenance or anything info would be swell.....

 

[TeeCat]

I think I have about 125 to 150 miles on it... rough estimate... I know I have 75 on this last tank of gas. I can state with confidence that the bike starts more reliably, idles exponentially better, and accelerates, decelerates, and pulls/runs at speed better than it ever did with twin BS38s. I think the jetting is right where I need it to be. My carb-related issue at the moment is a little weeping at the rear of the bowl, which will hopefully be rectified by changing from phillips to allen bowl screws.

I have made a lot of upgrades to my bike, but the single-carb conversion is on the podium, if not right up top.

TC

 

[XSive650]

I love my single carb set up on my XS. Right side tunnel ram with a n HD CV carb. I'm getting in the 50MPG range.

 

[dr frankensteel]

well now. that is suh-weet.
i can't wait to get me beastie runnin.
gonna have some sheet u all never seen....

 

[Cornish Pixie]

Just read this thread start to finish, thanks to TC for starting the thread and sharing his experience of this conversion and thanks to all contributors, there is a stack of information buried in this thread.

 

[TeeCat]

Cornish, I'm glad you have enjoyed it, and hope you benefit from it. Truthfully, I initially started it in order to make it easier for some highly informed folks here to "help me to help myself", but it seems to have helped others as well, which is the whole point, really, right?

Ultimately, this has been perhaps the best time and money (with comparatively little frustration and effort) that I have ever spent on my bike. "Take it to the bank" starts, stable (though "cammy") idle, pleasing performance off-idle, pulling, during decel, and at speed... I am sold!

TC

 

[mechanicScott]

Changing the screws from Phillips to Allen heads to stop the weaping?
If your taking all the float bowl screws out, you might as well put a new float bowl gasket on.. Seems like its a sealing/ gasket issue, not a screw head

 

[COOPERB27]

do you have a pic of the inside of the intake that we can see?

 

[TeeCat]

Guys, this is a bit of an older topic, but it actually turned out to be the in-line fuel filter that was leaking, and trickling down to the ledge of the carb body, making it appear as though the bowl gasket or screw was leaking. I replaced it with a one-piece metal Purolator and that took care of it.

TC

 

[CitizenJ]

do you have a pic of the inside of the intake that we can see?

I am just starting to do a 2 into 1 mod on like TC's my 1977 . I'm going to give the stock BS38 a patient try. I read this thread and the linked material about fitting aftermarket VMs. When I got the intake I looked at the interior (see pics). Given the advice for the VMs to eliminate "stepups" I've been wondering if some of idle wandering noted might go away if the interiors could be smoothed at the weld locations? I remember as a youth hearing a lot of talk about "port and polish."

I'm greatly encouraged by TC's enthusiam...sounds like what I'd hoped for.

What have folks done with the breathers? Mine has a two tube setup. I saw a reed valve in a Mike's XS catalogue, but I couldn't figure how it related to my breather housing.

 

[joe-wiseguy]

this model has sold about 300 times. never had any issues with port and polish? you are not going to have fuel mix stumble on that ridge where the plenum meets the intake runner. the intake is pulling by vacuum and the mix will follow the pull of flow. polishing long intake ports does not work out like you may think. look up david vizard. "the wizard of horsepower" he explains it much better then i could. if it aint broke dont fix it. and thanks for your sale. and thank you tc for your sale and this thread on how you adapted to your bike. appreciate it Joe Wiseguy.

if anyone ever has questions about any of my intakes or other products dont hesitate to call or email me. i always answer.

 

[mechanicScott]

here's my intake 1 into 2 aluminum intake... using a 40 mm keihin 4 stroke carb off of a honda crf250. works amazing

 

[CitizenJ]

Thanx Joe.

300 happy customers carries the day. And thanks for turning me on to David Vizard. I probably won't buy any of his books or go to his seminars but have gleaned enough from your description and what I can find about his work online to get the drift. Conceptually, that the fuel/air mixture is sucked into the cylinder by vacuum rather than being blow into the cylinder is huge with regard to counter-productive turbulence. It's vacuum cleaners vs. garden hoses. Interesting also to note that introducing beneficial turbulence can enhance performance.

My modification is an old man's mod you might say. I like the XS 650 and would like a reliable ride that doesn't need a lot of fiddling. I am happy to top out at 70 MPH. I'd also like to be able to hop on it and go grocery shopping. That begs docility though we know a beast lurks beneath or within. I try to keep my mods reversible to stock.

My remaining question is: what to do with the breathers? Are they necessary? Can I just cap them?

 

[sluginxlt]

ive read this thread a few times but now that im looking for throttle cable info i cant seem to find it. i just finished making a manifold similar to yours and have a vm36. it seems hard to find a cable with that weird end instead of a barrel for the carb.

 

[itrguy]

Mine was made by motion pro. i use a Vortex throttle too.