Drilling main jets bigger

Discussion in 'Thumpers' started by domains, May 2, 2012.

  1. domains

    domains Been here awhile

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    I'm working on a xr650L motor and biggest jet I can buy is 155 but I want to go 160

    Is there a drill bit I could buy for 160?
    #1
  2. domains

    domains Been here awhile

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    Can I buy a 0.60mm. drill?
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  3. PistonPants

    PistonPants Crankcase Scavenger

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    I might have a 160 from out of a dynojet kit. The kit comes with 155 and 160 mains.

    Piston
    #3
  4. Beezer

    Beezer Long timer Supporter

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    there is a bit that size.... but I'm not sure thats what you want to do.... mostly because I'm not sure how they measure the jet size. I do know that Mikuni, Dynajet, and Kehin all have different sizes for the same number:




    Width------Kehein # -- DynoJets # -- Mikuni #
    0,0350---- 92,5--------- 92----------- 86,3
    0,0360---- 95----------- 94----------- 88,1
    0,0370---- 97,5--------- 96----------- 90,0
    0,0380---- 100---------- 98----------- 91,9
    0,0390---- 102,5------- 100---------- 93,8
    0,0400---- 105--------- 102---------- 95,6
    0,0410---- 107,5------- 104---------- 97,5
    0,0420---- 110--------- 106---------- 99,4
    0,0430---- 112,5------- 108--------- 101,3
    0,0440---- 115--------- 110--------- 103,1
    0,0450---- 117,5------- 112--------- 105,0
    0,0460---- 120--------- 114--------- 106,9
    0,0470---- 122,5------- 116--------- 108,8
    0,0480---- 125--------- 118--------- 110,6
    0,0490---- 127,5------- 120--------- 112,5
    0,0500---- 130--------- 122--------- 114,4
    0,0510---- 132,5------- 124--------- 116,3
    0,0520---- 135--------- 126--------- 118,1
    0,0530---- 137,5------- 128--------- 120,0
    0,0540---- 140--------- 130--------- 121,9
    0,0550---- 142,5------- 132--------- 123,8
    0,0560---- 145--------- 134--------- 125,6
    0,0570---- 147,5------- 136--------- 127,5
    0,0580---- 150--------- 138--------- 129,4
    0,0590---- 152,5------- 140--------- 131,3
    0,0600---- 155--------- 142--------- 133,1
    0,0610---- 157,5------- 144--------- 135,0
    0,0620---- 160--------- 146--------- 136,9
    0,0630---- 162,5------- 148--------- 138,8
    0,0640---- 165--------- 150--------- 140,6
    0,0650---- 167,5------- 152--------- 142,5
    0,0660---- 170--------- 154--------- 144,4
    0,0670---- 172,5------- 156--------- 146,3
    0,0680---- 175--------- 158--------- 148,1
    0,0690---- 177,5------- 160--------- 150,0
    0,0700---- 180--------- 162--------- 151,9
    0,0710---- 182,5------- 164--------- 153,8
    0,0720---- 185--------- 166--------- 155,6
    0,0730---- 187,5------- 168--------- 157,5
    0,0740---- 190--------- 170--------- 159,4
    0,0750---- 192,5------- 172--------- 161,3
    0,0760---- 195--------- 174--------- 163,1
    0,0770---- 197,5------- 176--------- 165,0
    0,0780---- 200--------- 178--------- 166,9
    0,0790---- 202,5------- 180--------- 168,8
    0,0800---- 205--------- 182--------- 170,6
    0,0810---- 207,5------- 184--------- 172,5
    0,0820---- 210--------- 186--------- 174,4
    0,0830---- 212,5------- 188--------- 176,3
    0,0840---- 215--------- 190--------- 178,1
    0,0850---- 217,5------- 192--------- 180,0
    0,0860---- 220--------- 194--------- 181,9
    0,0870---- 222,5------- 196--------- 183,7
    0,0880---- 225--------- 198--------- 185,6
    0,0890---- 227,5------- 200--------- 187,5
    #4
  5. Tosh Togo

    Tosh Togo Long timer

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    #5
  6. debaisley

    debaisley Long timer

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  7. Weldit

    Weldit Been here awhile

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    160 actually is very close to a drill size in the mega drill index - the one with number and letter drills
    if you have a set or access to a set like that then give it - what can you hurt the 155 is not right
    I have drilled jets with good luck - just file off the original # or scratch it out so you know it has been modified
    if you have a digital vernier caliper you can measure the drill and get the one that is the right size
    --------------------------------------------------------------------------------------------------------------------------
    but jets are cheap so buying a 160 is only going to cost $5.
    -------------------------------------------------------------------------------
    I was working on an old scab xr and didn't want to spend any $$$
    160 is .160 mm or something like that - it will be obvious when you measure the drill that fits in your 155
    ----------------------------------------------------------------------------------------------------------------------------------
    now drilling out pilot jets is a much more involved process !!
    as they are only .6mm = very small hole - had to use a torch tip cleaning file & strands of wire for measuring size
    not recommended - except for the really impossible to find jets - and then get your self a set of jet files. :D
    -------------------------------------------------------------------------------------------------------
    but the old scab XR runs like a scalded dog now and cost Nothing but time and patience ! :1drink
    #7
  8. elsalvadorklr

    elsalvadorklr southern xr rider

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    i used acetylene torch cleaners/reamers used to clean the tips of the soldering torchs.

    with mixed results,

    I used it to ream a few small pilot jets I had on my 88 xr600....they are the same(close) to the jets in the xrl cv carb

    the issue I had was not the reaming part but actually guessing what size I had after reaming and in the end I had some jets shipped to me while I played aroud with my jets here with the reamers.

    the main jets you could use a jewelers drill as the hole sizes are bigger

    again I used the jets I had and reamed the small ones to the size I thought I wanted.

    In the end it wasnt as useful as I would of thought,

    My recomendation is to use keihin jets and buy a bunch so you can play around with them.

    cheers
    #8
  9. elsalvadorklr

    elsalvadorklr southern xr rider

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    jaja we did the same thing use the torcj cleaners then find dffernet wire gauges to gauge what size you had reamed to...I did this with a 58 pilot jet, very small and wanted to get a 61 or so approx jet size...

    its very hard to do since the reamer does not leave a smooth finish and THATS the issue, I tried to polish the hole with nylon wire gauge after and some polishing compound but the result was a size 62 or so pilot or more which I had already.
    #9
  10. hotwheels

    hotwheels Adventurer

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    I've been drilling jets, both main and idle for years with great results ! You need to get two sets of drills both numbered, #'s 1 to 60 and #'s 60 to 80. The #'s 60 to 80 are very small you can't chuck them in a drill. I hold the drill in a small vice and spin the jet in my fingers to drill the hole. I go slowly I find the smallest drill that WON'T go thru the jet and drill with that one, if the mixture screw won't tune, I go larger until it does. You need to learn to tell when the mixture tunes properly, one way too rich, the other way too lean. When the screw tunes both ways the idle jet is the right size. The main jet is differnt and you need to tell when the mixture in either too lean or too rich by how the engine sounds at wide open throttle. Remove the burrs after drilling the jet by taking a much larger drill, but that fits into the jet and lightly dress of the burr caused by the original drilling. This method is quite useful when jets are just not available (Yamaha SRX250).
    #10
  11. markk53

    markk53 jack of all trades... Super Supporter

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    As is clear it is all about surface finish in the jet as to the flow gained. The fuel is fluid and fluid dynamics come into play. A rough jet hole surface could actually cause less flow than the size where the jet started. Example, a 2" corrugated plastic tube used on a defroster system in a piece of heavy equipment actually had a functional flow rate about 1/2" diameter due to the speed of the system and the turbulence of the corrugation of the tube along with other minor factors. With a smoother manifold the flow was significantly increased. (Thus the reason for the K&N tubes used on cars vs the accordion type tubing.)

    Best is if you can find a jet of the size needed on-line. But if drilling is necessary, be very aware of he ID surface condition after drilling. Use a magnifier to look at it if you can do so.
    #11
  12. Beezer

    Beezer Long timer Supporter

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    if you look at my post #4 you'll see a chart that equates brands by size. This is very handy if you know the manufacturer. years ago I discovered that the guy behind the parts counter will sell you jets without knowing what they really are. This will drive you nuts if you are trying to jet and buying different brands. Long and short of this story is that I had a mix of jets. I ended up sorting them by flow with a home made checker. The first was a 20cc pipette & I simply timed the flow 5-6 times and averaged the result. Then later I used a differential pressure tester (leak down) rigged to a block. Put in 80 psi & see what the other gauge says. It only gives relative results, but thats better than shooting blind.
    #12
  13. markk53

    markk53 jack of all trades... Super Supporter

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    Quit making sense! :rofl


    Good idea. It would let you know if you hosed up when drilling a jet too. :clap
    #13
  14. Hurricane Bob

    Hurricane Bob Long timer

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    [​IMG]


    what your looking for is called a hand operated pin vise using wire gauge drill bits. available at a jewelry supply house.
    #14
  15. tkent02

    tkent02 Long timer

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    Or you could just drop $2 and buy a jet. How silly.
    #15
  16. elsalvadorklr

    elsalvadorklr southern xr rider

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    its a bit futile to argue...but the above post is true!

    UNLESS

    you have to wait a month or more to get the jets and you're not in a big civilized country like the us or a countty in europe...

    it has to do with thinking outside the box a bit and understanding that not everybody has access to $2 jets! in a day or so...or over the counter

    the second to last post is exactly what you need to ream jets well, a jeweler can probably get you what you want, in my case I reamed them with torch cleaners, same thing except you dont have the nifty handle...

    cheers
    #16
  17. Hurricane Bob

    Hurricane Bob Long timer

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    Knowledge is not silly. It can be applied in other endeavors.

    ....and he did state he could not purchase the size needed.


    :lurk
    #17
  18. tkent02

    tkent02 Long timer

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    I bet those fancy ass drill bits grow on trees in the Amazon, too.
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  19. elsalvadorklr

    elsalvadorklr southern xr rider

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    dude?

    I said torch reamers...and that those jeweler reamers/drills are exactly what you need, and yes in fact you can get them here, they are expensive though...

    now getting jets over the counter or quickly thats another story

    bro youre not the only person in this world...

    there are others:norton
    #19
  20. tkent02

    tkent02 Long timer

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    Like the next poor sap who buy this bike?
    It's high on my list of stupid PO tricks, right up there with jamming SAE screws into metric threads, using Scotchlok connectors and using globs of permatex or RTV to seal a leak from the outside. It's hardly thinking outside the box, they've been doing this for decades. Sure for the guys who's stranded in the Andies, you do what you've got to do.
    For the rest of you, buy the jets.
    #20