1981 xs 650 air fuel mixture not right? Help!

[Bruce Wayne]

So I've got a 1981 xs 650 that is getting turned into a cafe, I've rejetted both main and pilot jets a couple sizes up, chopped the pipes, and put on airfilter pods to replace the stock airbox.

After I rejetted the bike it ran awesome for about a week, then It started acting up. I would go to start it and while the choke was on it would sound great and run like a champ, but when i turn the choke off the bike loses almost all of its power and sounds like a cap gun. I think its something to do with the air/fuel ratio because when the chokes out it runs great, then i push it in and it's crap.

Let me know what you guys think. Im thinking its gotta be something to do with the carb... maybe just a minor fix like adjusting the air or fuel screw?

Thanks!

 

[Bruce Wayne]

Also...sometimes the bike will fire right up and act like there is nothing wrong with it. it will run great if I take the choke off and I can ride for hours without any problem. but then other time i'm not so lucky...

 

[TampaSVT]

Also...sometimes the bike will fire right up and act like there is nothing wrong with it. it will run great if I take the choke off and I can ride for hours without any problem. but then other time i'm not so lucky...

Hmmm...

Rich

 

[retiredgentleman]

When you need to keep the choke on in order to run, usually means the pilot circuit in the carb is partially blocked. The choke is feeding extra fuel to overcome the lack of fuel from the pilot circuit.

Look in the Tech section for the "Carb Guide" and read it thoroughly. You need to educate yourself on how these carbs work.

 

[Bruce Wayne]

The bike runs with the choke off, just not very good. So should i take the carbs apart and check for clogs?

 

[retiredgentleman]

Yes..................pilot jet is one of the usual suspects.

Remove carbs, turn upside down and remove the rubber plug to reveal the pilot jet. Only use a screwdriver that fits very tight in the jets slot to prevent damaging the pilot jet slot.

 

[Bruce Wayne]

I replaced the pilot jets maybe 3 months ago, you still think this could be the problem?

 

[retiredgentleman]

As I first mentioned, the problem area is likely the pilot circuit , and the pilot jet is only part of that circuit. Read the Carb Guide, study the diagrams to see what is what.

There are bypass holes in the carb throat..............are they clear?
Has the factory cap been removed from the air/fuel mixture screw access ?
Is the mixture screw adjusted as listed in the Carb Guide?
Have you blown carb cleaner through the passage ways in the pilot circuit?

 

[littlebill31]

It takes one tiny piece of crap to block the carbs, that's it.
I rebuilt a set for a guy last spring, gave them to him and a week later he brought back the whole bike. I guess I forgot to tell him a rusty gas tank isn't good for carbs.

 

[Bruce Wayne]

Just took the carbs off ill check out the jets and look over the screws and let you guys know what i find

 

[Bruce Wayne]

so i took it all apart and found that I could see through one of the pilot jets, but not the other. It looks like there's a bunch of crap in it i tried poking it out with a needle, didn't seem to work. Should I soak it in some carb cleaner or boil it to try and dissolve the stuff that's in there?

 

[5twins]

Got compressed air? That's what it usually takes to do a proper carb cleaning. Besides the jet, you need to blow air and cleaner through the hole it screws into and watch for it to come out the holes in the main bore.

 

[Bruce Wayne]

boiled all the parts and got it all cleaned up. there was just a bunch of dirt blocking it. runs great!

 

[retiredgentleman]

Congrats.................you are now a certified carb repair dude