needle groove tuning question

[bultaco4ever]

My Keihin carb on my 220 has a needle with five grooved clip positions. My question is this:

When comparing an 1172 needle with an 1173 needle, would it be safe to say that an 1172 with the clip in the top groove is still richer than an 1173 needle with the clip in the bottom groove?

 

[bultaco4ever]

bump...I know that someone out there knows the progression of settings. I changed my needle and went with the leaner 1173 and just experimented by putting the clip in the middle position. I'll keep experimenting. Just was looking for someone to validate my reasoning. Next time I go riding I'll take note of how the performance changed. I was getting some heavy exhaust smoke and spooge was spitting out of the pipe.

 

[RM_guy]

I don't know what those numbers mean but some needles are just a half of a goove different and others change the taper of the needle. Without knowing which of those changes are on those needles it's hard to awnser your question...again, not being familiar with those neeedles.

 

[julien_d]

no, not at all. Checking the charts now, and there's only the slightest difference between 1172 and 1173 needles. Not even half a clip position worth. Running both needles in the same clip position and the 1172 has just a tiny bit more fuel flow from 0 - 3/16ths throttle. The peak of this increase is a bout 2% @ 1/16th throttle, tapering to 0% at 3/16th throttle. After that point the fuel curve is identical between the two needles all the way to WOT.

 

[bultaco4ever]

These are Kawasaki designated needles. I think officially they are 1172L and 1173L. The larger number indicates a larger diameter needle. I think the L indicates the taper and the 11 indicates the lengths of the straight portion of the needle up by the grooves. I think the only difference in these two needles is the diameter. A fatter needle will allow less fuel to get by and thus lean out the mixture. But changing the clip position may allow the needles to overlap the range of this mixture change.

 

[julien_d]

Yes, I know this. The kawi KDX needles are r1172n/r1173n. For these needles, the R11 is the taper, the 72/73 is the diameter, and the N is the L1 length.

R1173n needle is a equivalent to a keihin BGP, and the r1172n needle is equivalent to a BGN needle. A small change in diameter will only really affect fuel flow over the straight section of the needle, which is roughly 1/4 throttle or less.

Here's the relative fuel change when going from 1173n to 1172n needle, using same pilot/main and 5th clip position. As you can see, the difference is not what you might think it should be...

 

[bultaco4ever]

So, dropping the pilot jet might give me the more leaner mixture that I am seeking.

 

[julien_d]

Indeed. Let me know your current jetting and we'll do some comparisons.

Oh, while we're on the subject, might I suggest a cek/dek needle? You'll need to go down on the jetting considerably to compensate for the richer needle, but the fuel curve with these needles is overall much better than the 1172/73 kawi needles. What year is your bike? I forgot....

 

[bultaco4ever]

97 KDX 220, stock pipe, boyesen reeds. 42 Pilot, 145 main, now 1173 needle, middle groove clip. I've already purchased a 40 pilot in anticipation. Also a 38. Also picked up 142 and 140 mains. Near Chicago...600 feet above sea level.

 

[julien_d]

wow. I would think that jetting would be pretty close at that elevation. What oil are you running, and at what ratio? What's the condition of the bottom end? Are you sure both main seals are good? Top end is in good condition and providing good compression? Forgive me if we've gone over this stuff at another time, my short term memory is for crap these days....

 

[bultaco4ever]

The tech section on this website recommends 40 pilot and 140 or 142 main if then engine and pipe are stock with the addition of Boyesen reeds, stock 1173 needle, too. The PO told me he had just put a new piston in the bike before I bought it. Cranks seals...I don't have a clue about. I'm prepared to follow this website's recommendations. But, I always makes jetting changes one step at a time. The PO had put the 1172 needle in. Don't know why.
Oil is Golden Spectro at 50:1.

 

[julien_d]

You should really make sure the compression is good, and that both crank seals are good before you start jetting. A deficiency in those areas will throw your jetting all out of whack.

With that said, you really need to figure out which sections of the throttle are rich, and which ones are lean. The stock kawi needles create big fat sections throughout the throttle range. You can fix some of this with jets, but there are certainly better needle options out there. You can start checking it by marking your throttle in increments. 1/4, 1/2, and 3/4. Ride it using the full RPM range but one of those throttle positions exclusively. Pay attention to how it runs in each area. Once we know which area's are blubbery rich, we have a better idea what jetting adjustments to start with.

 

[bultaco4ever]

Great recomendation. I have done exactly that same thing on one of my Bultaco's last summer. I had forgotten about that technique. How would you go about checking compression?

 

[bultaco4ever]

I've only been riding this bike for the last month and the jetting is close. It runs great with great low end power and adequate top end (for me). It's just a little too smoky for my taste. And the spooge is nasty. I baptized my wife's car last night when I started it in the garage with the pipe aimed at her rear quarter panel.

 

[bultaco4ever]

The 1173 needle did seem to help the smoke and spooge issue a little. Only ridden it half a block. I'm taking this bike on a 30 mile dual sport ride through the woods this Sunday. I'll get a good taste of it after that. I heard 'zero' from any Illinois KDX riders when I called out about this run. It's going to be heaven.

 

[julien_d]

Sweet :). If it's running well with the jetting you posted, it should be close. To test compression you'll need a cheap compression tester. Hit up your local auto parts store for one in the $25 - $30 range.

A leak down test is necessary to diagnose the crank seals though. If there's no signs of leaking behind the stator cover, and you're not burning tranny oil, chances are the main seals are fine though. The oil on the wifes fender kinda throws me, lol. Have you cleaned the silencer?

 

[bultaco4ever]

No, never looked at the silencer. It's deadly quiet, though. None of my Bultaco's were ever this quiet.

 

[julien_d]

It's not rebuildable really, and no replaceable packing, but there is a drain bolt on the bottom. Warm it up, shut it off, and take that bolt out. See if a bunch of spooge runs out of there. Shoot me your email addy....

 

[bultaco4ever]

did you get the email I sent you?

 

[julien_d]

Yeah, it went to my junk mail folder! Stoopid hotmail.....

 

[reepicheep]

Interesting thread. My 200 with the Eric Gorr big bore kit needs that clip in the second slot to run well, which feels a bit extreme.

 

[bultaco4ever]

Reep, mine is stock everything, except boyesen reeds. I like how it performs in stock form. Don't need any fire breathing dragon. Just trying to clean up the smoky exhaust issue. I'll drop the pilot jet one size in my next experiment.

Juliendogg, dropping the pilot jet looks like the next step in the spreadsheet that you sent me. Thanks. If the pilot jet is the answer, I will be set exactly as the 'Tech Section' on this website recommends.

 

[julien_d]

Yep, sounds like a logical next step. I had best luck cutting down on smoke and spooge by going down on the pilot. If I leaned out the needle enough to help, I got a nasty lean bog.

 

[bultaco4ever]

Put the 40 pilot jet in for my 35 mile dual sport ride through the woods and cornfields. I liked the performance. Much less smoky exhaust and tons of low end torque. Really fun. Starting to really love this bike.

 

[julien_d]

Excellent!