Author Topic: Jetting Question  (Read 2213 times)

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Offline Big Yac

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Jetting Question
« on: August 02, 2010, 08:35:58 AM »
I have a question concerning my jetting.  I'm in Ohio, elevation from 900 to about 1000ft.  The needle and needle clip position are stock, air screw is 1.5 turns out, 155 main jet, and 55 pilot jet.  The plug is alittle on the dark side but the bike runs great, doesn't foul plugs or anything.  Theres a mix of woods and open areas where sometime I can get up into 4th or 5th gear.  With the stock jetting the bike would foul plugs even when opening her up.  When I first got the bike I ran MC1 @ 50:1.  After changing jetting and the advice of a friend who owns a local shop I switched to Maxima SuperM @ 50:1 and like I said, haven't fouled a plug since but have a darker than normal plug.  My question is, if I raised the clip one position would this lean out the carb over the entire range?  I really don't think my jetting is that far off, don't feel any blubbers or anything, just the plug color.  Maybe I should leave well enough alone?  Thanks for any help.

Offline Jopiz

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Re: Jetting Question
« Reply #1 on: August 02, 2010, 11:03:33 AM »
Raising needle clip makes your mixture leaner from 1/4 to 3/4 throttle. Main jet from 3/4 to 1. Pilot jet from no throttle to 1/4.

Belray MC1 is a very "heavy" oil. Its very similiar to motul 800 but known widely for gumming up the whole engine. Racing oils need high flow velocities to leave the engine. Lighter viscosity 2 stroke oils dont. Thick oil covers the crankcase and eventually spark plug which leads to fouling. Stick to ligher viscosity oil and jet correctly.

-J

Offline Friar-Tuck

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Re: Jetting Question
« Reply #2 on: August 02, 2010, 11:33:42 AM »
  Don't forget about the high temps and high humidity,  here's some jetting pages.  There is tons of info on jetting, and you could theoretically re-jet all day.  Most of us have found a happy medium.
http://www.kxriders.com/coppermine/displayimage.php?album=lastup&cat=1&pos=52
   If the bike runs well, have you considered a hotter plug?
  If your running an NGK 9 series try a 7 for 15 or 20 min and check your plug.
Just get a few of the cheapies until you find what range keeps your plug clean. If the plug doesn't get hot enough it won't burn off the oil and carbon.
  Tuck\o/
"The Truth Has No Agenda"

Offline Big Yac

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Re: Jetting Question
« Reply #3 on: August 02, 2010, 03:26:52 PM »
I don't ride it at all in the winter but I do ride from spring until the snow begins to fly then it gets winterized for a few months so yeah changing temps and humidity and all come into play but other than the one time I have never played anymore with the jetting.  Like I said, the bike runs fine, hasn't fouled plugs and only has a plug color that's alittle darker than normal.  I currently use a BR8ES, maybe I'll try a BR7ES and see if that lightens it any.  I will stick with my SuperM @ 50:1, it seems to work fine and keeps the top end and powervalve mostly clean.

Offline Friar-Tuck

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Re: Jetting Question
« Reply #4 on: August 03, 2010, 06:12:48 AM »
  Sounds like a Plan!  :-)
\o/
"The Truth Has No Agenda"

Offline Roostmad1

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Re: Jetting Question
« Reply #5 on: August 17, 2010, 10:22:27 AM »
Raising needle clip makes your mixture leaner from 1/4 to 3/4 throttle. Main jet from 3/4 to 1. Pilot jet from no throttle to 1/4.

Belray MC1 is a very "heavy" oil. Its very similiar to motul 800 but known widely for gumming up the whole engine. Racing oils need high flow velocities to leave the engine. Lighter viscosity 2 stroke oils dont. Thick oil covers the crankcase and eventually spark plug which leads to fouling. Stick to ligher viscosity oil and jet correctly.
Don't know where you heard synthetic motual 800 gums up the engine?thats a load of rubbish!!,its the best oil for KX,s mate,i've used it for years at 32:1 on all my KX's and jetted correctly never fouls a plug even when putting around and also keeps the powervalves mint with superior lubrication,try some even smells nice

Offline greencannon

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Re: Jetting Question
« Reply #6 on: August 19, 2010, 05:45:16 AM »
If it runs good, doesn't foul plugs and doesn't smoke badly - dont fix it..... Friar is right you could change jetting constantly and never be completely satisfied... find that happy medium
I used to run super M, if i remember correctly it is very dark oil with a spash of castor in it.  My bike ran great on it other than the dark plugs and spooge at the silencer. I now run
Yamalube R with same performance, lighter color plug and hardly any spooge, same jetting.
Be careful with a 7 plug. They work good for woods riding but I think they are too hot of a plug at wide open throttle.

Offline Big Yac

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Re: Jetting Question
« Reply #7 on: August 20, 2010, 11:23:32 AM »
I really don't get alot of wide open throttle times, its mostly woods here with the occasional blast across an open field.  I did get a BR7ES.  By the way, whats the difference between the BR8ES and BR8EG?  The G says racing but what else does it mean?

Offline Friar-Tuck

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Re: Jetting Question
« Reply #8 on: August 20, 2010, 01:43:04 PM »
Everything you wanted to know about Plugs :-D
http://www.ingfatrygg.se/Spark_plug_diagnostics.html
 \o/
"The Truth Has No Agenda"