Tuning Heiden / XS Performance Needles: What worked for me.

Here's a pic of the Heiden needles with a pair of stock '80-'84 BS34 needles for starters. I have the stock needles set to show how big of a tuning range is available on the Heiden's and just how bluddy long the things are. I also have a suspicion these needles are meant to work with their 2-into-1 exhaust.

Here's my setup: 653cc (stock), Shell #1 cam (Hoos mis-grind), BS34's, Heiden/ XS Performance 2-into-1 pipes into a 1.75" Cherry-Bomb muffler (It's loud, but the muffler gives me a lot of pipe length 'after the collector' and keeps exhaust velocity and inertia up.)

6/28 edit: Finally have made good progress with these needles. It turns out, I was running my valve lash wide (.006" int/.012" exh). When I set it a little closer to normal (.004" int/.007" exh) the added duration and overlap made the mix a bit richer. The last few changes I've made have been with a #47.5 pilot, 142.5 main, and I worked the needle leaner from its richest position. These guys have six tuning slots, and I've finally chased away the off-idle stumbles by lowering them to position #4. This puts the top of the taper about where the stock needles should be, but I know I'll have a mid-range lean bog once the temperature goes below about 70*. I'm hoping to be proven wrong about that, but I doubt it's going to happen.

Ultimately I think I'm going to end up with either the stock needles or the Canadian needles and a #140 or 137.5 main jet. I'm pretty sure these things are just too damn long in the low-speed taper. Going to re-visit the pilot jets and see if getting the lash closer to factory made those richer, too. Stay tuned.

This was all crap.

6/28: added some valid information, I'll hopefully be able to get some verification about the pilots after a little road trip this weekend. However, after a quick ride I can tell you this is the first real usable carb set-up I've had.
I have my suspicions about these needles, hopefully we can once-and-for-all-time figure out how to run them or just reject them wholesale.

7/7: 180 mile road trip last weekend, the bike ran well except for a rich stumble in the 4-6k range. It made 46.4mpg with a LOT of horseplay and did an admirable job keeping up with a DL1000 Vstrom. Today I lowered the needles to notch #3 and cleared up the midrange stumbles. Final jetting combo is: #47.5 pilot, #142.5 mains, Heiden/XS Performance/Mikes XS needles at #3. I still need to double-check the pilots, but it idles well, the revs don't hang high or drop-and-recover when you blip the throttle. Pretty sure the pilots are fine. I'll hopefully be able to do a mileage run sometime this week and see what I've got.

I'm convinced these needles were developed to go with the XS Performance 2-into-1 exhaust, and I'm pretty sure the needles are a critical necessity with ported heads and a hotter cam with that exhaust. The 2-1 exhaust makes a serious change to the vacuum signal at the carburetors, raising the slides higher, faster. This has to be why the XS Performance needles are so bluddy long, to keep that vacuum signal from sucking more fuel than the mass airflow can burn.

These needles will probably never work with a 2-2 exhaust system.

Those needles were developed in Europe. I know from over 30 years of riding Euro twins that tuning parts developed over there don't always work here. If you want to try something that might work, 650Central has a similar BS34 needle tuning kit that was developed here. The jets supplied in the kit are genuine Mikuni and the needles are made of titanium.

Is that the kit with the exact same picture as the one on mikesxs.com and the Heiden page? I thought the board consensus was they were the same kit...

This just in from Heiden tuning:re needle kit:

Hello
It can work with the Y0 and also with the 336 Y0 (needle jets)
The kit must work with the 2-1 exhaust.
Regards
jerry

It sounds like he's saying it was developed for the 2-1 exhaust kit that Heiden developed and Mikes XS sells. This fits with what I've learned tuning the 2-1 with the needle kit and with stock needles.

OK!! Huge update today. I'd had some lingering issues with mis-balance between cylinders, all due to some dummy (me) making a mistake the first time he assembled his carbs and gouging one side of the throat in a needle jet. Somehow, met someone that thought it would be fun to repair the needle jet. So he did, it's in the bike, and it's finally running just like it's supposed to be.

Other changes:
- Running the foam UNI pods. They're messy and I hate touching them, but they've cleaned up most of the 4-5k ugly spot.

- Dialed in fuel level in the carbs to where it's supposed to be. I'd messed around with level last summer, and I do NOT recommend it to anyone. Set it like it should be.

Today's ride was 123 miles on 2.247 gallons. 54.7mpg. I'll take that all day long.

EK