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36mm Keihin On 2018 TX300

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I just got a 36mm Keihin from a friend and decided to try it on my TX300.  I really had no issues with the Mikuni aside from the bottom end feeling too smooth and not the power I was used to on older KTM 300's and 250's.  I am starting out with a 40 pilot.  170 main. A needle from slavens that I have no idea what it is, not stock and brass colored.  I plan to try this setup at around seal level which I never ride.  I live at 9000 and usually ride above that.  Anyone have any good tips on jetting for this thing?  I will probably get the zuki needles, but have a bunch of needles siting here so figured Id give them a go first.  Ill keep this updated as I go.

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I would suggest fixing the squish clearance by modifying the stock head, or what I did was a RK head. Incredible how much bottom and mid it got from fixing the squish and bumping up compression. + the bike responds to jetting better. Feels like a smooth less abrupt cr500 now. The carb is not the problem with the bottom end feel.

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3 hours ago, ricky racer said:

I would suggest fixing the squish clearance by modifying the stock head, or what I did was a RK head. Incredible how much bottom and mid it got from fixing the squish and bumping up compression. + the bike responds to jetting better. Feels like a smooth less abrupt cr500 now. The carb is not the problem with the bottom end feel.

Thanks. I do notice more bottom end with the keihin 36 though. I plan to do the rk head at some point also. 

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24 minutes ago, strokemetwice said:

Thanks. I do notice more bottom end with the keihin 36 though. I plan to do the rk head at some point also. 

After talking to Kelsey he recommended raising the cylinder by stacking 1.2mm of base gaskets so a .5mm and .75mm. so it raised the cylinder .029" Which on mine brought the piston flush with the bottom of the exhaust port at BDC. I can not believe what a difference it made! Idles better pulls much stronger. Yeah the 36mm should be stronger feeling down low vs the 38mm.

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On 11/14/2018 at 4:00 PM, ricky racer said:

After talking to Kelsey he recommended raising the cylinder by stacking 1.2mm of base gaskets so a .5mm and .75mm. so it raised the cylinder .029" Which on mine brought the piston flush with the bottom of the exhaust port at BDC. I can not believe what a difference it made! Idles better pulls much stronger. Yeah the 36mm should be stronger feeling down low vs the 38mm.

Good to hear from someone who has actually done the gasket stacking. Heard that Kelsey has been suggesting it. I will try it this winter when I put the 300 cylinder back on. 

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1 hour ago, KTM753 said:

Good to hear from someone who has actually done the gasket stacking. Heard that Kelsey has been suggesting it. I will try it this winter when I put the 300 cylinder back on. 

Now it requires the head to be cut for it. Or your compression will be real low and the squish gap to large. 

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1 minute ago, ricky racer said:

Now it requires the head to be cut for it. Or your compression will be real low and the squish gap to large. 

Also good to know. I figured this much. I am about to send Kelsey a stock head for a "cheater" setup so I will make sure to tell him I plan to stack gaskets when I specify my application. Thanks. 

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I just got a 36mm Keihin from a friend and decided to try it on my TX300.  I really had no issues with the Mikuni aside from the bottom end feeling too smooth and not the power I was used to on older KTM 300's and 250's.  I am starting out with a 40 pilot.  170 main. A needle from slavens that I have no idea what it is, not stock and brass colored.  I plan to try this setup at around seal level which I never ride.  I live at 9000 and usually ride above that.  Anyone have any good tips on jetting for this thing?  I will probably get the zuki needles, but have a bunch of needles siting here so figured Id give them a go first.  Ill keep this updated as I go.
Try a NECJ on the 2nd clip, 38 pilot and 162 main. May have to go to a 35 at that altitude.

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4 hours ago, motocrotts said:
On 11/14/2018 at 7:22 AM, strokemetwice said:
I just got a 36mm Keihin from a friend and decided to try it on my TX300.  I really had no issues with the Mikuni aside from the bottom end feeling too smooth and not the power I was used to on older KTM 300's and 250's.  I am starting out with a 40 pilot.  170 main. A needle from slavens that I have no idea what it is, not stock and brass colored.  I plan to try this setup at around seal level which I never ride.  I live at 9000 and usually ride above that.  Anyone have any good tips on jetting for this thing?  I will probably get the zuki needles, but have a bunch of needles siting here so figured Id give them a go first.  Ill keep this updated as I go.

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Try a NECJ on the 2nd clip, 38 pilot and 162 main. May have to go to a 35 at that altitude.

Any thoughts on sea level?  Nobody ever posts the altitude when they post about jetting. Drives me nuts.

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Any thoughts on sea level?  Nobody ever posts the altitude when they post about jetting. Drives me nuts.
I'd go to a 42 pilot, N3EH #3 and a 175/178 main to start. If cold go richer.

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On 11/14/2018 at 6:22 AM, strokemetwice said:

I just got a 36mm Keihin from a friend and decided to try it on my TX300.  I really had no issues with the Mikuni aside from the bottom end feeling too smooth and not the power I was used to on older KTM 300's and 250's.  I am starting out with a 40 pilot.  170 main. A needle from slavens that I have no idea what it is, not stock and brass colored.  I plan to try this setup at around seal level which I never ride.  I live at 9000 and usually ride above that.  Anyone have any good tips on jetting for this thing?  I will probably get the zuki needles, but have a bunch of needles siting here so figured Id give them a go first.  Ill keep this updated as I go.

does the needle have ring (or 2) machined around it, like another position for the clip..but not that deep

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9 hours ago, highmarker said:

does the needle have ring (or 2) machined around it, like another position for the clip..but not that deep

It might. Its in the bike so i probably won't look soon. 

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23 hours ago, strokemetwice said:

Any thoughts on sea level?  Nobody ever posts the altitude when they post about jetting. Drives me nuts.

Have a 36 pwk in my stock 18tx. I tried a bunch of Suzuki needles but turns out they were to rich and never ran that good. Tried necj, neck, and necl. At 3500-6500’ ~20C. Finally went with the JD jet kit and ran really good with 40pj blue#2 and  162mj. #7 slide. 

Edited by Bigd450
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6 hours ago, Bigd450 said:

Have a 36 pwk in my stock 18tx. I tried a bunch of Suzuki needles but turns out they were to rich and never ran that good. Tried necj, neck, and necl. At 3500-6500’ ~20C. Finally went with the JD jet kit and ran really good with 40pj blue#2 and  162mj. 

Great info. Thanks. 

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Bike ran strong at sea level. There was a mix range studder that i couldn't get rid of. Had to go really rough on main, 175 to get the ping out. I dont love the way this carb fits in the boots. Broke a clamp trying to get tight. May try the mik again

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so you raise the compression with RK,then you lower compression by adding base gaskets???whattttt

On 11/14/2018 at 2:00 PM, ricky racer said:

After talking to Kelsey he recommended raising the cylinder by stacking 1.2mm of base gaskets so a .5mm and .75mm. so it raised the cylinder .029" Which on mine brought the piston flush with the bottom of the exhaust port at BDC. I can not believe what a difference it made! Idles better pulls much stronger. Yeah the 36mm should be stronger feeling down low vs the 38mm.

 

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16 minutes ago, Dirkarider said:

so you raise the compression with RK,then you lower compression by adding base gaskets???whattttt

 

When he machines the stock head or the insert for a cheater or billet head, he will take this additional base gasket into account and adjust the head accordingly to maintain compression. 

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On ‎12‎/‎1‎/‎2018 at 4:14 PM, Dirkarider said:

so you raise the compression with RK,then you lower compression by adding base gaskets???whattttt

 

Not even sure how you could get that from my post! HAHAHAHAHA

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just having fun....add gaskets raises cyl or lowers piston lowering compression.....my bud runs thinnest gasket making the piston above the top of cyl giving it high comp & it rips & no blow ups with a zillion miles on it.Supposed to run flush with top o cyl as per manual:thumbsup:

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I use thickest gasket but don't stack. Stacking is a great way of pulling more top end power but you do lose bottom end.

For a motocross engine which will be reving out more it's ideal. 

Using lower port timing tends to make more bottom end. It's all a compromise.  

Decide where you want the power and machine the cylinder head to suit.

My 14 300 was lifted over 2mm . My current 300 is 0.75. 

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