Holy jets...jets with holes

[jussumguy]

I need to order some pilot jets for what I think are '79 carbs. The pilots are 25's right now. They don't have the side holes in them, I think when I built them I just put whatever I had laying around

I've got free flowing pipes with supertrapps and foam pods. I think I want 27.5's or 30's
My question is do I want holes in the sides or no? Is the metering hole in the top or bottom? So confused

 

[retiredgentleman]

Your 1979 carbs are the same as my 1978 carbs. My original 27.5 stock pilot jets were real Mikuni and they had no side air bleed holes. They don't need side holes because the pilot jet air is added from the top. Some replacement jets have the holes in the side, but they don't do anything on our 78/79 carbs.

Yes I'd say you need at least #30 pilot jets. I use #30 pilot jets, and I have stock air boxes and stock exhausts, so you certainly need #30, maybe #32.5.

I think I'm right on this, but if not 5twins will correct me, as he has much greater carbs knowledge than myself.

 

[grizld1]

5twins and I addressed this in the Carb Guide. Read it.

 

[jussumguy]

Ok thanks guys

 

[5twins]

The linked BS38 carb sets ('76-'77 and '78-'79 sets) use the VM22/210 type pilot, metering hole on the top .....

But you should really positively I.D. the year of your carb set because re-jetting is based off of what the stock jetting was, and the 2 carb sets mentioned were jetted differently. The '76-'77 set came stock with a #25 pilot, the '78-'79 set with a #27.5.

 

[gggGary]

A look in the throat is a quick 76-77 (3 side holes) vs 78-79 (5 side holes) ID

 

[jussumguy]

I was assuming 79 because of the idle mixture screw style

 

[jussumguy]

Thank you for that information. You guys are priceless

 

[ninskrillz]

What's up with the front end on your bike looks cool!

 

[jussumguy]

Early 90's cbr 1000 with a sportster light. Clorox jugs on the forks to keep the rocks from hitting

 

[gggGary]

I was assuming 79 because of the idle mixture screw style

not sure of the difference?



77 body




79 left 77 right

 

[jussumguy]

I found some 30's in my tool box and put them in. Way better than it was. Need to try some 32.5s also. Thanks again for the help

 

[retiredgentleman]

I found some 30's in my tool box and put them in. Way better than it was. Need to try some 32.5s also. Thanks again for the help

You can tune, with the 30's, using the dead cylinder method, and if you find the mixture screw is at 3 turns or more, you need to go up to a larger pilot jet such a a 32.5. Then you would likely find the mixture screw at around 1.5 to 2 turns.

 

[jussumguy]

I'm at 1.5 on the screws now but I'd like to do a ride to confirm that first. It's always had a tiny hesitation when I'm backing off the throttle going into a corner trying to be smooth. That is almost gone.Should I be raising my needle now?

 

[retiredgentleman]

I'm at 1.5 on the screws now but I'd like to do a ride to confirm that first. It's always had a tiny hesitation when I'm backing off the throttle going into a corner trying to be smooth. That is almost gone.Should I be raising my needle now?

Seems like your pilot jets are about the right size now. I have no experience with adjusting the needle position, as my bike runs perfect with it in the stock position.
I suggest you read and re-read the Carb Guide, as others have mentioned.

 

[jussumguy]

Yes thank you, I did, it's very informative.


(That's where I got the idea!)

 

[grizld1]

Dial in your mains before you mess with the needle position. There will be secondary effects with component changes in any carburetor, and they're especially strong in older designs. If your needle position is a little lean, getting the mains right for your relieved intake and exhaust may be enough to correct it. More often in your carbs the needle needs to be dropped a step for a leaner mix if main jet size is increased 3 or more steps.

BTW, that's a fine looking ride!