what plug in 07 rm85

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powerT

Member

Mar 21, 2007

40

0

• Apr 13, 2007

• #1

it is having fouling problems it came with a ngk br10 should we go to a br9 or br8? i'm at work and can't remember the rest of the number on the plug? It came with some new jets when i got the bike.

We run bel-ray 44.1. The dealer wants us to go to 50.1. will that be to lean?

 

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DannyMoto07

Member

Apr 12, 2007

170

0

• Apr 13, 2007

• #2

BR10ES, NGK... The lower the number (10,9,8) the HOTTER the plug will run.

What's your plug look like? Wet or dry? Black or tan? If it's black, or wet, you're too cool and need to go hotter. If it's white, dry or pitted, you're too hot and need to go cooler.

50:1 is stock for most all 2-strokes. In my experience, you can run up to 35:1 without causing significant carbon buildup. Safest is 40:1... might smoke a little, but you'll never run lean.

When you run rich on oil, you want to run a hotter plug. If you run 40-45:1 you'll need to go with a BR8ES plug.

How thin is Bel-Ray oil? Is it on the same lines as AmsOil Performance 2-stroke, or Motul? Or is it more on the thick-side like Stihl chainsaw 2-stroke oil?

The viscosity of the oil will determine how it's burned in the combustion chamber. Odds are, if you're running rich, and with a super thick oil.. your plugs aren't keeping up. Simple fix.

Also, is there an oil-injection system? or do you simply pre-mix?

Good luck.

 

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powerT

Member

Mar 21, 2007

40

0

• Apr 13, 2007

• Thread starter
• #3

pre-mix
bel-ray is on the same lines as amsoil (i think),it was the oil the dealer had. It was it or motul 800 ($17)
I tried the br9es when i pulled it out it was black and wet, I'll try the 8 next.

 

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snb73

Member

Nov 30, 2003

770

0

• Apr 13, 2007

• #4

DO NOT CHASE A JETTING PROBLEM BY CHANGING SPARKPLUG HEAT RANGES!!!

Pick a premix oil, mix it with the highest pump octane you can find (super), mix at 32:1 then rejet.

Most 85's like a ratio of 32:1

MOBILE MX2T is a fully synthetic oil and can be found at most chain auto stores for $7 a quart. Find the best oil that is in your budget and readily available in your area and stick with it.

Buy a few BR10ES plugs (they are cheaper than BR10EG) and rejet. Once your jetted correctly install the recommended plug.

Here are a few jetting links;

http://www.all-offroad.com/DirtBikes/Beginners/BGNov98.html

http://justkdx.dirtrider.net/carbtuning.html

http://www.keihin-us.com/tune.htm

http://www.keihin-us.com/am/_media/pdf/slide_valve.pdf

http://www.keihin-us.com/am/tuning/

http://www.maximausa.com/technical/lubenews/springsummer2001.pdf

http://www.powroll.com/tech_specs_jetting101.htm

Some Spark Plug Links;

http://www.strappe.com/plugs.html

http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html

http://www.ngksparkplugs.com/techinfo/spark_plugs/techtips.asp?nav=31000&country=US

http://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp?nav=31300&country=US

 

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powerT

Member

Mar 21, 2007

40

0

• Apr 13, 2007

• Thread starter
• #5

Can i just move the clip or do i have to change the mj & pj when i move the clip up one?
the bike came with 2 jets not sure what size they are i'll look when i get home.

 

C

Chili

Lifetime Sponsor - Photog Moderator

Apr 9, 2002

8,062

17

• Apr 13, 2007

• #6

powerT said:

Can i just move the clip or do i have to change the mj & pj when i move the clip up one?
the bike came with 2 jets not sure what size they are i'll look when i get home.

Click to expand...

If you follow up on some of the links snb73 provided you'll find that you should adjust each jetting circuit individually. If your only goal is to stop the bike from fouling plugs and not optimizing it's performance you may be able to achieve this simply by moving the clip or going to a leaner pilot jet.

 

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powerT

Member

Mar 21, 2007

40

0

• Apr 13, 2007

• Thread starter
• #7

we just got it new a week ago right now in in the feeling out stage plugs,oil,that kind of stuff. He stays in the band pretty good but can only just get it in 3rd before he runs out of yard, after a while it starts to foul.Sometimes i'll catch it and ride the bike around the block to clean it out, sometimes that work sometimes it don't.We went to a field so he could go through the gears.he was able to hit 5th sometimes but after a while it started to foul again. Wright now we're more worried about stoping the fouling.

 

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snb73

Member

Nov 30, 2003

770

0

• Apr 13, 2007

• #8

After properly jetting my bike, I ran all year on one plug. I replaced it with my top end because I would feel guilty using and old plug with a fresh top end. I don't need to "clean out" my bike. Bikes are also jetted to a riders style. Ricky or Bubba would probably seize my bike because it's jetted to lean for their wide open style. Conversly, a slower rider could ride my bike and foul the plug. There is no one majical jetting.

You can lean the main jet slightly by raising the clip (moving the clip to the top of the needle) But you will get better results by replacing the main/slow/power jets.

Post your current jetting. Most bikes come from the dealer a bit rich.

 

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terrible

Member

Jun 26, 2006

26

0

• Apr 14, 2007

• #9

I had the same problem with my '04 rm 85. I put in the next-leaner jet that came from the factory with the bike and have been on the same plug for almost a year. Also I have a completely stock bike and run klots R-50 in 40:1 mix.

 

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powerT

Member

Mar 21, 2007

40

0

• Apr 14, 2007

• Thread starter
• #10

here is the current jetting
mj #128
needle in 3rd slot
slow jet #50
air screw 2 turns out
plug ngk br10es
the only thing i've changed is the plug to a ngk br9es

took it to the dealer today. they did a plug check after running it hard through 4 gear then shutting it off. They said the plug looked good that we might could go one notch on tjhe needle for midrange but they recomened not to change a thing but would change the jet if i wanted them to.

terrible
did u just change the one plug or did u change the mj and pj and move the clip on the needle?

 

Last edited: Apr 14, 2007

whenfoxforks-ruled

Old MX Racer

~SPONSOR~

Oct 19, 2006

8,129

2

Merrillville,Indiana

• Apr 14, 2007

• #11

It is your sons bike,do you want it to work properly or hillbillied? Read the threads as posted earlier,Good luck and have fun!

 

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terrible

Member

Jun 26, 2006

26

0

• Apr 16, 2007

• #12

I changed the mj and lef the needle at factory settings. It's best to do one thing at a time. I do run a number 9 plug too. I forgot about that part ;)