'82 Carb Jetting Opinions

[Renegade600]

Hi all, I've built a bobber from an '82 Heritage and have been messing with the jetting on this thing.

I have put some curved drag pipes on From Gordon Scott (thanks Gordon they sound awesome). And have bassically just thown the bike together to run out the bugs then i will blow it back apart for paint.

This weekend I fired it up for the first time. I had cleaned the carbs and installed the Canadian needles and jets, and also added the 137.5 mains to replace the 132 (stock BS 34). I did not have the pods yet (which are still coming, but justr was running open carbs to see how it ran.

Problem I had was it kept beaking up on the top end, I figure rich, so i slip the 132's back in and everything cleans up nice. Running the needles 2nd notch from the top.

I plan on bumping the pilots, one step to see how it runs.

To my question. This thing runs so nice now, good power, etc. I can't see needing much of a change. But.... everyone says that these carbs are so lean from the factory logic twells me that I'm running lean with open carbs, and long open pipes....???

Opinions? I plan on one step on the mains but once I get the pods on i know it will change again....possibly my chokes leaking and offsetting the stock mains?

I've done lots of jetting on sleds so i'm not a total rookie, just wanna avert a meltdown...
Tom

 

[5twins]

Compare the working length (top clip groove to tip) of those Canadian needles to your stockers and you'll see they are different. The Canadian needles will be shorter (richer) when run in the center groove. They're about the same as the stockers when in the top groove (50mm). You probably won't need mains as big with them if you run them in position #2 or #3 (middle).

Then there's that Canadian needle jet. MikesXS says it's richer too but they say a lot of stuff that's not true, especially when it comes to carbs. The only difference you can really see when comparing the 2 needle jets is the # of holes down the sides. Now, those are air feed or bleed holes that add air to the fuel being pulled up through the main. You would think more holes would make for a leaner jet, right? I haven't messed with these enough to know yet so all you can do is experiment I guess.

 

[Renegade600]

Thanks 5twins. I do have the needle jets in addition to the needles, but like you when i looked at them they really did not seem different.

I didn't know how rich the Can needles would step up, but it sounds at least one jet size?

I'm running about 4 to 4-1/4 turns out on my idle jets, so I'm hoping that a bigger pilot may bring me more in line with about 3 turns out and richen up the mid range some. Trial and error.....hopefully more trial than error....
Tom

 

[5twins]

Yes, step up your pilots. Four turns out on the mix screws is really too much. You can also change the air jet on the BS34s to fine tune the idle circuit. For instance, if one pilot size is too lean but the next one up is too rich, you could step up the air jet with the larger pilot in place and get somewhere between the 2 pilot sizes (or step it down with the smaller pilot).

I'm not sure exactly what the effect on main jet size is for the Canadian parts. As I said, I don't have that much experience with them. So far on the BS34s I've tuned, they worked OK by just changing mains and pilots with the stock needle and needle jet. If the Canadian parts continue to give you tuning problems, you might try the stock stuff again.

 

[Renegade600]

Thanks 5twins...I have some new pilots on the way...I'm close, justg not quite there...thanks for your help...
Tom

 

[kvanderploeg]

Hey, Tom. Just ordered the Canadian Needles, Needle Jets, 135 & 137.5 Mains, and 45 Pilots for my BS34's. I'm running POD filters and Gordon Scott's Curved Drag pipes as well. How did that larger pilot work out for ya? I see you were at 4-4.5 turns out on the mix screw. That calls for a larger pilot in my book as well. Thanks and any update info is welcome as well!

Kent

 

[sivarTi]

I'm running 137.5's and 45's and just ordered in new canadian needles. I'm running about 3 turns out with pods and Mikes Headers with short cocktails. We're at 2200 feet or so. When I open the bike up it starts to cut out a bit and quits pulling around 4500, maybe earlier if I'm on it real hard. Seems like fuel delivery but I don't know. Parts will be here Tuesday but I ordered new brake parts too. Putting them on first, going to worry about more whoa before I add more go.

 

[gentlemanjim]

A rule of thumb on pilots if you are turned out more than 3 turns you need bigger pilots if are turned out less than 2 turns you need a smaller pilot jet.

 

[mrkwaka]

Hi have a 79 with cv34s 45pilots cdn needles and jets 135mains.Runs brill up to mains fell flat.changed to 137mains.wont go past 75mph.do i need to go higher on mains.pods high level exhaust with cans.in england

 

[gentlemanjim]

you are going the wrong way try 132.5 mains

 

[joebgd]

Its been a while and now I forget, is it always bigger number jet more gas gets through?

 

[gggGary]

Yes a bigger number means a bigger hole.
I suppose an exception is the air jet on BS34s a bigger hole in an AIR jet would lean the mixture.

 

[mrkwaka]

OK will give it a try.forgot to say exhaust is 1.75 with torque converters.will make any difference u recon