32mm flat slides or 34mm round slides, which is better? Why?

[Sir Real Ed]

Looks like the latest pile of parts I acquired does not include carbs.

It appears the choices are:
1. Stock carbs
2. 32mm flat slides
3. 34 mm round slides

What is best, and who are good venders to frequent.

 

[azman857]

What do you want the engine to do? Cam and exhaust used?

 

[grizld1]

Which 32 mm. flat slides? If you mean the Keihin PWK knockoffs, there has been more than enough written here about the trouble they cause, and instead of wasting time restating why they were a bad idea to begin with for 4-stroke use, I'll refer you to the search function, which works very well indeed. If you mean Mikuni 32 mm. flat slides, they should work quite well. What signifies in venturi diameter is unobstructed area. Since the venturi of an OE BS-series carb is obstructed by the throttle shaft and butterfly, a 32 mm. open throat carb should have an effective area somewhere between an OE BS34 and an OE BS38. There's nothing wrong with the VM34 either, and there's a wealth of information available on setup and tuning, if a person takes the trouble to look for it. Best vendors are Michael Morse of 650 Central and Gary Hoos of Hoos Racing.

There's nothing wrong with OE vacuum operated carbs either, particularly if you leave the air box in place. One advantage is that carbs with vacuum operated slides respond to changes in altitude.

 

[Sir Real Ed]

Thanks for the replies.

Grizid1 - Agree on using the search function. Just wanted to get the short answer for now. Just starting the research process. You've given me some good info to follow up one. Grumpy old men are the best.

azman857 - Don't really have a performance goal in mind yet. Engine(s) are stock. Carbs are missing. Looking for a decent base line at low cost.

For now, my plan is to find a stock airbox. Goal is to avoid the giant vacuum cleaner sound I remember from bikes with modified intakes.

 

[azman857]

I'd start with stock carbs then.

 

[Muckroot]

I live at 6,035 in Colorado Springs, and plan to ride my bike all over the place, from Denver (5,280) to pueblo (4,692) to buena vista (7,965) on a semi-monthly basis. I also plan to take the bike on road trips across the continental United States as well as down into Mexico. I have no problem tweaking a carb screw every 500 feet of elevation, but I'd rather not be draining the carbs to swap a jet that often.
Which carb offers the most reliability, altitude lenience, and gas mileage? this is an old style chopper, and while it'd be nice to take off like a bat out of hell it's a straight up cruiser, so throttle responsiveness isn't a huge issue. I plan to use either cylindrical foam filters or air stacks with mesh screens, depending on the environment I'm traveling to.

 

[GLJ]

Which carb offers the most reliability, altitude lenience, and gas mileage?

There's nothing wrong with OE vacuum operated carbs either, particularly if you leave the air box in place. One advantage is that carbs with vacuum operated slides respond to changes in altitude.

Stock carbs and foam filters would be my choice.

 

[jetmechmarty]

With some help from this forum, my XS11 CV carbs are dialed in. Yes, it can get expensive fixing them. They work! For a street bike, the CV operation is smooth. I noted it was difficult to maintain steady throttle on an old Triumph with Amal carburetors on a bumpy road. The CV carburetor was a great advancement for a street bike. Going racing? Not so much. As long as quality replacement parts are available, I’m fine with maintaining the CV carburetor.

 

[XSLeo]

I'm running the Kawasaki Ninja EX500 carbs. I run the Uni-filter 4 inch foam pods. They work well, easy to tune, get great mileage. Very smooth through the transitions from low speed up through WOT.
A lot of this carbs advantages are from it being a more modern design and easy to get parts for.
Leo

 

[Sir Real Ed]

Hey Leo,

I'd like to see some pictures of your bike. From your signature, seems like you have done some sorting. I grew up west of Rochester NY, so I know where Lebanon is.

Thanks to all so far for the good info. Just what I was looking for. Right now I have two rolling chasises consisting of only frame, engine, suspension, wheels, and handlebars. Originally I wanted a stock 1976 XS650C, but might just stick with a project bike due to costs. Both bikes have 1.75" head pipes, one is down swept, on the other, both exit on the right side of the cylinder. Anyone with the parts I am missing, please contact me.

Currently leaning towards EX500 Carbs due to newer-ness and availability. Possibly with a stock airbag if one pops up.

thanks again.