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FightingRed

ShiftUp Spartan Head - Best carb?

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Just realized I'm a dummy and the "200X" ebay carb I've had for awhile is a Mikuni (22mm and I think it might be fake) Looks like the OEM Honda ATC200X came with a Keihin PD. Looks like I will pay about as much for an old Keihin than a Mikuni VM26 and adapter. BBR 58mm piston, TB cylinder, Kitaco cam, ShiftUp spartan head on XL bottom end, pipe ID will be 25-28mm. Bike is used as mini dual sport/trail bike/beer run scooter, not a race bike. Whats the best bang for the buck on carbs for this setup? Also, I'm at 6500ft so I'm leaning towards a Mikuni VM28 to get even more air in but don't want to have an off idle bog with full weight flywheel.

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In my opinion the best bang for the buck is the OEM 83'-85' 200x carb.  Plus, they are super easy to jet.  (at least close below 2000' it is)

 

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Most of the 2 valve sub 250 Honda motor carbs should fit. Any XR200/R carb will be 26mm, some of the XL and TLR versions are smaller. Don't know about the other ATC carbs.

I recommend using jetting recommended for the carb version rather than the engine it is installed on.

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What's nice about the 1983-1985 200x carb is the intake matches the intake on the intake manifold of the XR100, and it also fits the airboot perfectly.  Jetting will very from set-up to set-up.  The main difference on your is the Shift-up head.  The main could literally be any from a 112 for a basic 120, to a 130 for a super modded 120 in a CR85 chassis with a big airbox.  Plus your at 6500', so that will cause a whole other variable.  The XR200 has a slightly different intake port than the intake manifold, so it's a bit off, and it's a tighter fit on the airboot, if memory serves right.  Plus, it's taller.  We ran the 200x carbs for 30+ years.  They rip.  Remember, this is best bang for the buck.  That's why I'm not saying get a Yoshimura carb. 

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Great stuff, guys. Thanks! I also have a Dekni PZ27 that uses keihin jets but it seems like it is also a knockoff or repop like the OKO stuff. 

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On 1/29/2019 at 8:28 PM, FightingRed said:

Just realized I'm a dummy and the "200X" ebay carb I've had for awhile is a Mikuni (22mm and I think it might be fake) Looks like the OEM Honda ATC200X came with a Keihin PD. Looks like I will pay about as much for an old Keihin than a Mikuni VM26 and adapter. BBR 58mm piston, TB cylinder, Kitaco cam, ShiftUp spartan head on XL bottom end, pipe ID will be 25-28mm. Bike is used as mini dual sport/trail bike/beer run scooter, not a race bike. Whats the best bang for the buck on carbs for this setup? Also, I'm at 6500ft so I'm leaning towards a Mikuni VM28 to get even more air in but don't want to have an off idle bog with full weight flywheel.

I am gathering parts for a similar build. I have the shift up head, tb120 kit on a 2001 xr100r bottom end. Which cam did you choose? And will you be able to run pump gas with the bbr 58mm piston? 

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37 minutes ago, Larkin Nick said:

I am gathering parts for a similar build. I have the shift up head, tb120 kit on a 2001 xr100r bottom end. Which cam did you choose? And will you be able to run pump gas with the bbr 58mm piston? 

Kitaco “step 1” hollow core cam. No clearance isssues and I haven’t actually done the calculations but I estimate about 9.5 to 10:1 compression and I live at 6400ft elevation so regular grade pump gas is 85 or 86. I run ethanol free 92 octane with no issue. Still tweaking the tuning and I’m finishing up the exhaust pipe soon. Running a 15 pilot and 100 main with the fuel screw 2 turns out.

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Cool thank you, I will be running 92 ethanol free or 93 octane premium. Much lower elevation for me below 1000ft. Would you consider your cam choice to be conservative, radical, or somewhere between? I’d like one that does not create any clearance issues so I am leaning towards the one you mentioned, but I am just curious.

Did you use the stock camshaft holder or the billet one offered by Spartan for that head? This is my first 4 stroke build I have tons of questions.

I also plan to build an exhaust as the motor is going in an xl75 chassis with dual rear shocks so fitment will be custom. I am wondering if there is a method for figuring out diameters and lengths and if I should make a stepped pipe or power bomb or something closer to the original.

Thank you!

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The crf150f carb is the same as 200x. May be able to find one in better condition. My buddy bought a Chinese clone carb that is identical  and was cheapIt works great  

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PWK/OKO oval slide carb, 24 or 26 mm will work extremely well and be inexpensive. The needle and needle jet will be right and the main and pilot jets are available in 10 sets for cheap on Ebay. They are very compact which can be a great help. 25 mm bore pipe (1.125" OD)  or smaller. The 28 mm up (1.25" OD) stuff is far too large. 25mm  bore will support well over 20 hp.

 

 

Edited by Momus

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On 3/21/2019 at 6:28 AM, Momus said:

PWK/OKO oval slide carb, 24 or 26 mm will work extremely well and be inexpensive. The needle and needle jet will be right and the main and pilot jets are available in 10 sets for cheap on Ebay. They are very compact which can be a great help. 25 mm bore pipe (1.125" OD)  or smaller. The 28 mm up (1.25" OD) stuff is far too large. 25mm  bore will support well over 20 hp.

 

 

Cool thank you I will be building my exhaust in the next couple weeks and I already have a few 25mm ID sections I can use. I will be purchasing one of the carbs mentioned as well. 

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