BS38 Single Carb Application

[Hombre Verde]

BS38 Single Carb Application Question

I am thinking of trying to run a single BS38. I realize that there is a lot of factors that go into this but I am looking for ideas on a baseline for the main jet and pilot jet sizes to start to tune with. Should I start with 2 or 3 up from stock? If you have tried this and figured it out, even better.
Thanks for the input in advance

 

[XSLeo]

Start with the same jets as you had when using two carbs. In the two carbs, one fed each cylinder. 360 degrees apart.
On the single carb, the carb feeds one cylinder, then 360 degrees later it feeds the other cylinder.
So one carb will need the same jetting as two carbs. One carb feeds one cylinder, that stays the same.
Leo

 

[Hombre Verde]

I figured that would be the case. My problem is that the engine I have has yet to run. It was in need of a rebuild when I picked it up. I will be running a pod filter and custom exhaust with 4 inch baffles. Do you think 2 steps up from stock would be a good starting point?
Thanks

 

[CDNTX650]

stock. Then decide on jetting.

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[Hombre Verde]

That is what I will be doing of the next few weeks. I will dig deeper into the Carb Guide and get it figured. Was hoping someone had done about the same and could give a baseline.
Thanks

 

[XSLeo]

Start with what you got, let the engine tell you what it needs.
Read this www.amckayltd.com/carbguide.pdf print it out and read it.
Oh yea, read the carb guide.
Did I mention read the carb guide?
Leo

 

[bluebikerblan]

I am thinking of trying to run a single BS38.

Ok.....I give.....I'll bite.....again! Can somebody please run it by me one more time?

Why? What's the point? The geometry's wrong as is the engineering that went into the
match ups? It sure seems like a to me?

Blue

 

[blackbetty]

Gonna have to agree^

TeeCat must have sprouted a few greys hunting down his 2-1 issues. Seems like a totally unnecessary headache to a problem that doesn't exist.....if it aint broke, don't fix it.

 

[TeeCat]

Gonna have to agree^

TeeCat must have sprouted a few greys hunting down his 2-1 issues. Seems like a totally unnecessary headache to a problem that doesn't exist.....if it aint broke, don't fix it.

To be honest, I was locked in mortal combat with my stock BS38s for the better part of 3 years. Whether the carbs had vacuum issues, a problem with the enrichener circuit, throttle shaft leak... I don't know. What I do know is that nothing I tried yielded a stable idle, and the bike would fire on the first kick one day, and refuse to cooperate at all the next. I did everything to those carbs except light votive candles and sacrifice a lamb. Having addressed every other issue I could think of (ignition, timing advance, etc.), I just decided to change the rules of the game completely. Sure, I ran into a few issues, but with the help of griz, twins, joe wiseguy, and a few others who were willing to entertain my "spirit of adventure" (and let's remember that I did not pioneer this idea), my bike has been running and idling better than it ever did with those possessed BS38s. So I suppose the answer to your question, in my case, was abject exasperation with the stock carbs, and a desire to try something a bit different. If thine carbs offend thee, pluck them off.

Now, conceding that the performance gains netted by us one-mixers are not on quite the same level with the scenario I'm about to allude to, I wonder if anyone ever asked Carrol Shelby, when he wanted to shoehorn a small block V8 into a British AC... "Why?".

'Cause he had an idea. And we all know how that story continues...

TC

 

[Hombre Verde]

Having messed with multiple bikes with dual and quad carbs it is a pain in the $#*! to get them dialed in when you change things like intake and pipes. The process of taking everything off to get to the carbs after the fifth time makes me want to walk into traffic. May be easier on the XS seeing as how they are not jammed under the tank between the cylinders. Either way I have no desire to deal with it, plus I need the room under the seat for other stuff that does not include the box. Plus different is what it is all about.
TC, a Cobra fan? Then again how could you not be?

 

[TeeCat]

Having messed with multiple bikes with dual and quad carbs it is a pain in the $#*! to get them dialed in when you change things like intake and pipes. The process of taking everything off to get to the carbs after the fifth time makes me want to walk into traffic. May be easier on the XS seeing as how they are not jammed under the tank between the cylinders. Either way I have no desire to deal with it, plus I need the room under the seat for other stuff that does not include the box. Plus different is what it is all about.
TC, a Cobra fan? Then again how could you not be?

Wanting to walk out into traffic is a good characterization of how I often felt with those '38s. In my case, I have a lot of interests and other obligations, and when those carbs were basically dictating my mood on a given weekend or evening, I removed them without a shred of remorse. I'd simply reached "critical mass" with those carbs.

Yup... I love Cobras. There was a documentary on the Speed Channel last night about Carrol Shelby and the Cobra/Daytona Coupe/GT-40 programs. I didn't get to see the end of it, so I hope it's rebroadcast.

TC

 

[hotrdd]

I'm in the process of getting my Carbs setup and running and agree that it's a painful process. The question is WHY isn't everyone using a single carb if it makes life that much easier. What's the down side?

 

[TeeCat]

I'm in the process of getting my Carbs setup and running and agree that it's a painful process. The question is WHY isn't everyone using a single carb if it makes life that much easier. What's the down side?

Well, I agree there are downsides - some might not like idle characteristics of unequal runner lengths, for instance, or the fact that a single-carb problem could knock the bike out, where on a dual-carb setup, it might just limp - but I think this question is subject to overthinking. A lot of it just boils down to personal preference, married with individual curiosity and capability. I think that's the essence of modification.

TC

 

[Hombre Verde]

There was a cobra program on last night? How did I miss that? Ever since I was little the Cobra was it for me. So, I have done a lot of reading and what not on his life and the cars that he has worked with. I have always wanted one but I will never be able to buy one. I hope to build a "kit" car some day. It is one bad ass car no matter what!