Ima gunna throw these carbs out the window!

[slapfrog]

I've been having the hardest time getting these carbs jetted and adjusted right. They are 1979 BS38's

Symptoms: Falls flat when throttle is cracked open at idle, spits and sputters when driving around and throttle is cracked open, runs good and pretty torque when riding with choke on, but take the choke off and the bike spits and spatters and chokes out. Idles good with good throttle response when mixture screw is 6.5 turns out.

I'm running open pipes, mikesxs knock off k&n xs pods, #30 piolet jet, #140 main jet, i lowered the needle (clip is set at #2), freshly rebuilt carbs 3 weeks ago, and new intake boot.

I've just about had it with these dam carbs, I'm new to the bike world and This is all new to me. I'm at the point where I just want to throw these carbs out the window!

 

[MechNewb]

I may be wrong as I have more experience with the BS34s but I suspect your pilot jet is way too small.

 

[5twins]

Buy a new bike with fuel injection - problem solved. These old bikes aren't for everyone. Yours seems to be causing you more grief than it's worth. So many things could be wrong with it I don't even know where to start. Then I see your avatar and realize you're dealing with a sawzall special. That means 10 times the problems of a stocker - if it was built right. Most aren't.

 

[slapfrog]

I thought it was the pilot jet too, I went one up to a #30 but lowered the needle. By lowering the needle could that be messing up the idle and causing the hesitated throttle response?

 

[CDNTX650]

Try putting your needles back. Welcome to owning an old bike. Hacked off mufflers and pods make shit even worse. Mikes pods are junk to start with.

 

[timbeck]

Hey Frogslap---Summer will soon be over, bite the bullet and send them to Rick at Old Skool Carbs, problem over. That is if your ignition and compression , air leaks at manifolds, etc is good. The other avenue , like 5twins said , is get a newer Honda. Good luck---tim

 

[gggGary]

So much good info is available here with a little searching. That time and sanity saving trick is ignored SO often. Sorry you haven't done that that because with an hour or two of reading and another hour or two of work you would be out riding.
I actually feel for you, I am fighting a "customized" 79 myself, it is even further out in the wilderness than your bike. I could write a book on what I have done so far but that's a different thread. Summer is slip sliding away at a fantastic rate.

 

[79xs]

The #1 rule of carb tuning is:

ONLY MAKE ONE CHANGE AT A TIME!

If you change two things, you don't know the effect of each change individually and it makes it easier to cover up problems, or pass over real solutions.

In general, if turning the choke on helps, you're too lean. Bigger pilot jet is a good place to start... but you might need to change other things a well...

Make sure you do not have in intake leak!

 

[5twins]

I'm thinking your freshly cleaned carbs may not be as clean as you think they are. It sounds like the pilot circuit is still plugged or at least partially plugged. Sometimes it takes several tries to really get these carbs properly cleaned.

 

[TwoManyXS1Bs]

What about the diaphrams?

 

[slapfrog]

I've been busy with work and fixing all the little things that tend to go bad on a new build. So I took the bike to a friend that is fairly good with these old bikes. Turns out that the bike was running really lean. So we had to go up on the pilots and the mains, this guys a wiz at figuring out what size jets need to go in. He started out by checking for air leaks and found that I needed new intake gaskets, replaced the gaskets and bike instantly stared running better. He then replaced the spark plugs, started the bike and went about adjusting the air mixture screw. We would then turn the bike off and check the plugs. After he was happy with the pilot jet he decided to take it out for a test drive to check for correct idle and dead start acceleration. He did this proses a few times until he was happy with the pilot jets he picked out of his case of at least 100 jets (no kidding). Then he decided on the size of the main jet by driving pretty fast down a long road a few blocks from my house and then he would kill it. After he stopped he would take the plugs out and inspect them. It was pretty cool watching him do all of this, the initial adjustments that were made to both the pilot and main jets were decided on pretty quick but to watch him fine tune the bike was defiantly a skill that I do not have yet. The process was cool to watch, the one thing that I learned was to start with the pilot and once you have it dialed in go on to the next part (I think it was the needles) and then the main jets.

 

[jd750ace]

From what you described my first thought was wondering if you had the correct style of pilot in place. 2 will fit, only one works. Actually, he started with the pilot because he could not get past it to do the top end. Typical methodology is working from the top down, main jet, needle type and setting, pilot, then mix screw.
Only requires patience and information. Having the information in your head speeds things up a bit, but you could slog through his process with the carb guide. High speed "throttle chops" are not done frequently anymore. That's old school tuning there. Sounds like you found the right guy though. Get all of your jet sizes and settings down on paper for future reference. I write them in my manuals.

 

[Paulrxs650]

Try reading this - http://www.amckayltd.com/carbguide.pdf

Very good and helped me a lot!

 

[slapfrog]

This guy is for sure an old school tuner, he's an old semi pro flat tracker. Cool guy and has a lot of knowledge. He likes to shake his head at me when I tell him my ideas because I'm not really a mechanic, I'm pretty good at sheet metal and fab work but I like to think outside the box. My next project is going to be hot Rosing this motor and adding fuel injection to it, he will be the one making sure I don't mess something up. I have an 81' XS that I want to supercharge but my buddy just looks at me with a look that says "you don't know how." It's kinda funny.

 

[slapfrog]

That's a great read on jetting your carbs! I think I'm just too impatient to to do it.

 

[racerdave]

hot Rosing?

 

[timbeck]

Ya racer dave, it's all the rage in Spokane--- tim

 

[chopit25]

Ya racer dave, it's all the rage in Spokane--- tim

Hmm, I'm in Spokane Washington and I do not recall hearing about this?

 

[650Skull]

That's a great read on jetting your carbs! I think I'm just too impatient to to do it.

Don't make any sense??????. Want the cool factor then complain about the carbs and haven't the patience to work on them.

Looking at the neck brace, i see it is welded to the center of the top tube of the frame. A big no no because it will be prone to brake where the brace ends at the tube.

 

[weekendrider]

Hmm, I'm in Spokane Washington and I do not recall hearing about this?

For those wondering, this is a hot Rosing.
And she can do anything she wants with my motor.