Triumphrat

jimmyj900 · 08-12-2005, 11:14 AM

I've had a dozen experimental carb needles made up and I wondered if anyone would care to test a set.

The characteristics are similar to the Factory Pro titanium needles but lack adjustment clip positions and are intended to be a drop-in replacement for the stock needles.

There are a few necessary prerequisites:

1) You have to have Keihin CVK carbs. The needles won't fit Mikunis.

2) You have to be able to remove the carbs and open them up so they'll have to go to folks that have already changed their jets successfully.

3) Modifications to exhaust or intake are irrelevant but must be documented.

4) It would be pretty senseless to replace a set of FP needles with them.

The test I need is as follows:

1) Install the needles (without shims!) and record your first impressions.

2) Ride the bike for a week or two

3) Replace the stock needles and record your impressions of any changes.

4) If you like the new needles better, keep them and enjoy them. :-D

I realize swapping the needles twice is a PITA, but it's the only way I can figure to back up first impressions beyond "new gadget" enthusiasm.

Jim

Saigon5 · 08-12-2005, 11:31 AM

Jim,

You will get me to start thinking like Spooner and consider that you could be an alien.

I will put my name on the list of candidate for the needle test. No problems to remove the carbs. I am getting to like it.

I am just wondering why you want me to remove the carbs to change the needles. I remove them with the carbs in place so I can add a few more test on the needle.

Stock needles
Stock needles with shims
Jim needles
Jim needles with shims.

denny · 08-12-2005, 11:43 AM

I am definately interested in trying these needles out.
I have stock needles with 2 shims in there now, and mostly good. jut a little rich in the midrange. I had the dynojet needles before, I had troubles adjusting them to work well with mine.

Thanks, Denny

fbird · 08-12-2005, 03:49 PM

Hey Jim,
If your still looking for volunteers I'd love the chance to try them out. Might get rid of the lean spot I have in my lower mid range. My bike is basically stock with drilled mufflers, modified airbox and a rejet. Shawn

Wombat · 08-12-2005, 04:46 PM

If you offer is still open. I would be very interested as I am about to do a rejet and aiebox/exhaust mods.

Bob

jimmyj900 · 08-13-2005, 01:34 AM

OK. Home from work, off tomorrow and just had a large Irish coffee. Those Bushmill folks sure do turn out an excellent muscle relaxer for my sore old back....

Quote:

No problems to remove the carbs. I am getting to like it.

Saigon5, that kind of masochism deserves a set... :-D

As far as removing the carbs, I didn't want to be in the position of having to write a procedure step by step for somebody who hasn't done it before... or listen to the griping about Triumph's design!

Quote:

I have stock needles with 2 shims in there now, and mostly good. jut a little rich in the midrange.

Denny, you got 'em but don't try and put them in the '96, OK? Also, NO SHIMS on the first pass. If you shim them you're going to be a bit rich.

Quote:

Might get rid of the lean spot I have in my lower mid range.

Fbird, only if the lean spot is on full throttle. If it's at small throttle settings the needles shouldn't make much difference but it's worth a try.

Quote:

...I am about to do a rejet and aiebox/exhaust mods.

Sorry Bob. I've only got three sets of needles left, but the disqualifier was that you're planning to make a whole slew of changes at once. That makes it impossible to determine whether the needles or the other changes made a difference in performance.

So... e-mail an address and I'll get the needles sent out in the next couple of days.

Thanks guys,

Jim

Blaine · 08-15-2005, 12:20 PM

Jimmy,

I admire your tenacity. Having needles made is the sign of a very dedicated (some would say seriously obsessed :-D ) tuner. My bike's cams are not stock Triumph pieces nor is my exhaust common. I have tuned my Keihins with FP needles but I too have run into a part throttle problem. The straight section of the FP needles are smaller than the stock needles. Is the diameter of your experimental needles somewhere between the two? If so, let me know if you produce them as I am interested in purchasing a set.

As an aside, some Mikuni needles (5xx) will fit the Keihin carbs if the straight section is reduced in cross section area (surface grind opposing flats) to increase fuel flow at part throttle and can be used to prototype new needle characteristics.

Blaine

jimmyj900 · 08-15-2005, 11:29 PM

Quote:

...some would say seriously obsessed...

Jeez, Blaine. If YOU are calling ME "seriously obsessed" I guess I must be in real trouble... :-D

Right now I'm more concerned with the behavior when the needle takes over from the pilot circuit than the straight portion of the needle, so I'm working on the taper and overall needle length. It should be pretty close.

The straight is very close to the FP needle so there's no joy there, but I'll keep you posted if I make any changes to that part.

Grinding flats on the straights is really clever though, and come to think of it I've seen that done on a metering rod in a proportional hydraulic valve. If I had access to a suface grinder I'd give that a shot. That would also effectively change the angle at the end of the taper and give a two-step taper...interesting... Thanks for the tip!

Jim

Blaine · 08-16-2005, 10:06 AM

Jimmy,

The straight section of the needle functions as a transition between the pilot and needle jet circuits. As the throttle is opened from idle, fuel flow initiates through the needle jet, one; before the pilot circuit reaches full flow and, two; before the slides begin to lift. In my experience, this transition largely determines fuel flow between 1/8 and 1/4 throttle openings which is where most normal riding occurs. On my bike, for example, average fuel mileage at 60 mph changes from 51 mpg with the stock needle to 46 mpg with the FP needle with no other tuning changes. I need a leaner small throttle needle while retaining a taper similar to the FP needle for acceleration. So far I have been unable to come up with an alternative tuning scheme that is satisfactory. Good luck with getting your ride "just right." :wink:

jimmyj900 · 08-16-2005, 01:53 PM

That's what I was figuring: the straight portion basically functions in parallel with the pilot jet and the mixture screw and then becomes most active in the transition range.

At this point though, I'm having more difficulty with full throttle operation so that's where I've been putting the most effort -- getting the taper and taper start nailed down.

I guess this is why most tuners won't bother with the CV carbs -- too many "automatic" things going on independent of throttle.

Jim