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Author Topic: Jetting Q's on the Micarb  (Read 623 times)

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blasphemous

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on: September 07, 2018, 01:20:12 pm
Hello Gentlemen,
I have a 1999 500, last year I installed the S&B air filter and free flowing exhaust. As part of this I moved up from the stock jetting (Main 110, Pilot 25, needle clip on last but one on the richer side) to the following jet sizes (Main 115, Pilot 30, needle clip on the lat groove on the richer side). I ran with this setting for a while to understand how the bike was performing and while it ran fine, I realized that sometimes
a) when the bike starts from stationery on a slight incline, I have very little power,
b) When the temp drops I find the engine response very sluggish.

To remediate this I moved the Pilot jet from 30 to 32.5 and left the rest of the jetting same and noticed the following:
a) I feel the engine runs better with the new pilot size.
b) still have the issue of loss of power on starting from stationary on an incline.
c) bike has better response when cold temps than before but still not satisfactory.

So I now have the following Q's:
a) Should I go up another level on the Pilot? (35?)
b) Should I go up on the main jet to 117.5 ?
c) Should I go up on the needle jet the next size up from stock?

A lot of people I spoke to said usually you don't have to change the needle jet at all although that seems counter-intuitive to me as most of the riding is 1/4 to 3/4 throttle. Help me understand why this is the case.

I live at 4000 feet above sea level.

Hitchcocks has the following recommendations, although not sure for what altitude:
Standard stock: M: 110, NJ: O8, PJ: 25, Slide: 3
S&B air filter with open silencer:  M: 125, NJ: P2, PJ: 30, Slide: 2.5

Thanks for the help!
« Last Edit: September 07, 2018, 01:41:39 pm by blasphemous »


cyrusb

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Reply #1 on: September 07, 2018, 02:04:41 pm
I had a similar situation with my 05. Too much clearance between the slide and the body of the micarb made it unusable. Don't waste your time with that piece of rubbish (like i did). PWK 30mm and never look back. Great performance right out of the box, and an actual fast idle on the cold start enrichener .


cyrusb

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Reply #2 on: September 08, 2018, 04:41:45 pm
BTW your icon is truly frightening


blasphemous

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Reply #3 on: September 09, 2018, 04:28:14 pm
I had a similar situation with my 05. Too much clearance between the slide and the body of the micarb made it unusable. Don't waste your time with that piece of rubbish (like i did). PWK 30mm and never look back. Great performance right out of the box, and an actual fast idle on the cold start enrichener .

I know, thats the easy way out though right? I don't know, don't wanna invest in an expensive carburetor for such a low tech bike. I know this can be tuned to be just right, so want to give it a shot.


blasphemous

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Reply #4 on: September 09, 2018, 04:29:48 pm
BTW your icon is truly frightening

haha he was an Indian film actor called Shakthi Kapoor, did comic-villain type of roles. Although recently got caught in a casting couch episode and let a lot of people down with his behavior.


blasphemous

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Reply #5 on: September 10, 2018, 11:46:20 pm
nobody even wants to hazard a guess? I'm certain we have depth of experience here, why the silence? Thanks!


Adrian II

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Reply #6 on: September 11, 2018, 05:48:19 am
Possibly the C.I. Bullet enthusiasts are getting a bit thinner on the ground these days as more and more EFI Bullets and Himalayans proliferate, with the twins to follow. Sometime. Zzzzzzzzzzzzzzzzzzzzzzzz

As an AVL Bullet fan (and therefore not much help with 28mm Micarbs, sorry!) I think I may also be a member of an endangered species.

A.
Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


cyrusb

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Reply #7 on: September 11, 2018, 11:15:53 am
Possibly the C.I. Bullet enthusiasts are getting a bit thinner on the ground these days as more and more EFI Bullets and Himalayans proliferate, with the twins to follow. Sometime. Zzzzzzzzzzzzzzzzzzzzzzzz

As an AVL Bullet fan (and therefore not much help with 28mm Micarbs, sorry!) I think I may also be a member of an endangered species.

A.
Not thinner, but smarter. To still be running a micarb thats from 1999 is truly amazing. These things were junk from the factory, built with the  tolerances  of an aluminum ashtray. I believe at 19 years old that has to be some kind of record!  Mine had huge slide to bore clearances. So, it has nothing to do with the proliferation of the Major Appliances the R.E now sells. The question is can you live with antique technology or not?


tooseevee

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Reply #8 on: September 11, 2018, 11:47:42 am
So, it has nothing to do with the proliferation of the Major Appliances the R.E now sells. The question is can you live with antique technology or not?

      Ooo Ooo Ican Ican  ;D Can I stay. Can I stay  ??? ???
2008 AVL Classic.Extensive head work by Ace.Ace canister/TM32/Ace manifold.Small open bottle/hot tube removed.Pertronix Coil.Bobber seat.Fed mandates removed.Battery in right side case.Decomp&all doodads removed.'30s Lucas taillight/7" headlight.


cyrusb

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Reply #9 on: September 11, 2018, 12:16:59 pm
You sure can! No disrespect but really that is what it comes down to.  Also, it's easy to loose sight of peoples abilities in 2018. Even lawnmowers have electronic ignition so there is quite a few generations that have not dealt with points, ever. Same goes with valve clearances, and even carbs. In fact, knowing about these things automatically makes me an old fart.
« Last Edit: September 11, 2018, 01:04:38 pm by cyrusb »


Adrian II

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Reply #10 on: September 11, 2018, 03:31:45 pm
Quote
In fact, knowing about these things automatically makes me an old fart.

You leave me with no choice but to raise a glass of dark beer* in your honor and drink to your health.

A.

* possibly Fuller's London Porter or Theakston's Old Peculier, haven't decided yet.
Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


tooseevee

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Reply #11 on: September 11, 2018, 03:50:04 pm

A.

* possibly Fuller's London Porter or Theakston's Old Peculier, haven't decided yet.

       Ya' know, it's no wonder Monte Python was so incredibly funny and successful. Just look at the amazing verisimilitude of the names of the beers & the porters & the ales & the darks & the lights. Just that alone not to mention the names of the villages  :D ;) :)
2008 AVL Classic.Extensive head work by Ace.Ace canister/TM32/Ace manifold.Small open bottle/hot tube removed.Pertronix Coil.Bobber seat.Fed mandates removed.Battery in right side case.Decomp&all doodads removed.'30s Lucas taillight/7" headlight.


portisheadric

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Reply #12 on: September 12, 2018, 05:32:54 am
Hi, Hitchcocks are only 350ft above sea level so their results can be taken as 'at sea level' for tuning purposes.

Abnormally increasing the pilot jet size is only masking the problem created by the free flow exhaust and filter. You would normally need a richer slide together with a larger needle jet to compensate for those changes along with a slightly larger pilot jet and main jet to deal with the change in fueling elsewhere in the range between a closed and fully open throttle.

A 115 should be okay but if you can see all the way through the exhaust you could try a 117.5 main jet. 
Increase the jet needle to a P2 it should work well for your higher altitude.

Your current oversize 32.5 pilot jet along with the richer P2 needle jet may be enough to provide sufficient overlap where you can  keep the stock throttle slide, otherwise fit the required richer slide and go smaller on the pilot jet. 



blasphemous

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Reply #13 on: September 12, 2018, 05:35:05 pm
Thank you for the pointers good Sir !


finbullet

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Reply #14 on: September 16, 2018, 03:12:34 pm
If you can't get the micarb dialed in, and you don't want to buy an expensive carb there's the option of a chinese PWK copy. I have one in my bullet and it works great (just 35$ from aliexpress). Just get the one that uses those hex headed jets. The one I ordered they promised AAA quality and it proved right.