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04-05-2010, 02:18 PM | #1 |
Gone Wild
Join Date: Dec 2009
Location: NE Oklahoma
Posts: 539
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I have Main jet sizes for G2/G9's running modified or no airbox!
I have been messing around with my 1989 yamaha G2's engine performance.
I have removed the airbox to accept a UNI pod filter for an XR100. Similar to a K&N...but cheaper. I have also modified the exhaust by using the stock header flange and running my own header pipe to a used XR250 muffler with a turn down tip. After all the mods I needed to richen the fuel mixture out so it would run properly. At first I drilled out my stock main jet. I didn't have a small enough drill bit but I was anxious so I did it anyway. I new it would be too large, but I wanted to get in the ballpark. The stock main jet size is approximately a #115. After I drilled out my jet it became approx a #150. The engine started right up and seamed to run fine, but was noticably rich. After fouling the plug I went to my local yamaha dealer parts counter with the stock jet. It is a fairly common jet so they had quite a few different sizes. I ended up getting #130,135, and 140 main jets to get me closer to an acceptible fuel mixture. They were $3.00 a piece. After Installing the #130 and a new spark plug the engine runs like a champ. With ALOT better throttle response. (By the way, I also have my govenor completely bypassed and hooked straight to the gas pedal.) I checked the plug after running it pretty hard and it had a good light brown color to it. I went ahead and stuck the #135 in the carb to see what it did and there wasn't much of a change so I went to change it back to the #130 but I misplaced it! Oh well, it hasn't given me any fits yet, and the plug still looks good. Thought I would pass this on becuase I tried to look it up in the search area but NOTHING could be found. I will post pics when I have some more time. Last edited by bansheemxer; 04-05-2010 at 03:03 PM.. Reason: added to post |
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04-05-2010, 04:19 PM | #2 |
Gone Wild
Join Date: Jul 2008
Location: Reddick IL
Posts: 11,217
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Re: I have Main jet sizes for G2/G9's running modified or no airbox!
Pics are good, If you can't hear feel any dif between the 130 and the 135 and the plug is tan leave it alone. The little extra is cheap insurance when its hot out and your neighbor wants to race.
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04-05-2010, 08:54 PM | #3 |
gone yamaha!
Join Date: Sep 2008
Location: ontario, canada
Posts: 1,424
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Re: I have Main jet sizes for G2/G9's running modified or no airbox!
good info banshee! i've found the same thing on my g9 the 140 was too rich. I ended up getting the jet kit from plowmans which includes the new pilot jet too so it runs right up the way through the rpm range.
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04-06-2010, 04:46 PM | #4 |
Gone Wild
Join Date: Dec 2009
Location: NE Oklahoma
Posts: 539
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Re: I have Main jet sizes for G2/G9's running modified or no airbox!
Here are pics of the muffler. I haven't had a chance to repaint it with a quality paint. Engine enamel cooks right off. Anyone know of a good header paint? I thought about wrapping it in header/heat wrap.
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04-06-2010, 04:51 PM | #5 |
maintaining a low profile
Join Date: Oct 2009
Location: SW Virginia USA
Posts: 6,313
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Re: I have Main jet sizes for G2/G9's running modified or no airbox!
Will the heat from the muffler affect the rear end?
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04-06-2010, 05:41 PM | #6 |
Gone Wild
Join Date: Dec 2009
Location: NE Oklahoma
Posts: 539
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Re: I have Main jet sizes for G2/G9's running modified or no airbox!
The muffler itself doesn't get that hot. I figure if it didn't get hot enough to melt the plastic cover/numberplate on the XR250 it was taken off of then I'm sure the rear diff housing can take it.
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04-06-2010, 06:28 PM | #7 |
gone yamaha!
Join Date: Sep 2008
Location: ontario, canada
Posts: 1,424
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Re: I have Main jet sizes for G2/G9's running modified or no airbox!
ya it shouldn't hurt the diff
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04-06-2010, 06:30 PM | #8 |
Admin/Moderator
Join Date: Dec 2006
Location: Ohio
Posts: 18,010
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Re: I have Main jet sizes for G2/G9's running modified or no airbox!
Looks like you may need a new drive belt, should be at the top of the driven clutch.
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Ron
PLEASE VISIT Our Sponsors * BGW GEAR The Store The G2 Project * Swing Arm Drop & Repair * Geep1 Project |
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04-06-2010, 06:30 PM | #9 |
gone yamaha!
Join Date: Sep 2008
Location: ontario, canada
Posts: 1,424
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Re: I have Main jet sizes for G2/G9's running modified or no airbox!
ya i just said that in his other thread ron
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04-06-2010, 06:32 PM | #10 |
Admin/Moderator
Join Date: Dec 2006
Location: Ohio
Posts: 18,010
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Re: I have Main jet sizes for G2/G9's running modified or no airbox!
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Ron
PLEASE VISIT Our Sponsors * BGW GEAR The Store The G2 Project * Swing Arm Drop & Repair * Geep1 Project |
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