Modified clone and 22mm mikuni

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Vtbowhunter3

New Member
#1
#1
My son races a outlaw class with 120 snowmobiles. The only rules are no exotic fuels and max 212cc. I just bought a used modified clone with the following done to it.
Hemi predator block
De-stroked +.17 clone crank
+.20 arc billet rod
Pvl flywheel
Gx200 billet lifters
Chromoly push rods
Nr racing 247 0207 cam
18cc Honda head
Ss 28mm intake 25mm exhaust valves
Milled.80
26lb springs
Champion rockers
This motor was ran with a .650 bored stock appearing carb and nr intake with pulse fitting. I cannot use either because it will not fit in the chassis without serious modifications to the tunnel. As a alternative I have found the inverted intake for a 22mm mikuni. Has anyone has any experience with this intake and also will the 22mm mikuni be sufficient enough for this build? I'm assuming so if a stock appearing carb was used but not sure. Also if it will work well what is a good starting point for jets? Thanks
 
ole4

ole4

#2
#2
Are you talking about the Chinese mikuni with the oval slide venture? It should look like the following pictures. It would work well for your build having a lot more airflow than the .650 SA carb. For starters use a 130 main jet Pilot start with what is in it and see where the idle air bleed setting is for a good idle. If it is more than two turns out then go to a 12.5 if you have to go to almost closed then go to a 17.5 but usually the stock 15 will work. If it does not look like the carb in the picture then I am not sure on jetting.


 
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Vtbowhunter3

New Member
#5
#5
Finally got around to getting this thing in and we are having some issues. Looking for some help here we have tried main jets 100,130,140,165,180 and pilots 15,17.5,30 we have even went as far as trying to drill out a main jet to diagnose and can't seem to get this thing to run right. It is a genuine mikuni with inverted intake and a nr spacer with pulse fitting. I have removed spacer and pulse fitting and tried gravity feeding to eliminate a pulse issue with the pump and no difference. We can get it to start and idle fine but once you begin putting a load on it, it breaks down hard. If I put my hand in front of the carb I can get it to rev up which makes me think we need more fuel but no matter what jets we put in it does the same thing. We didn't set the float height also. Pulling my hair out with this thing. Any suggestions? Thank you
 
trinik7597

trinik7597

Active Member
#6
#6
There are a few things you need to check .... Air mixture screw on the bottom of the carb for one ... But just a quick question .. was it the agk inverted intake you bought ?? If so the problem is probably a bad air leak between the carb and flange ... If you look behind the carb at the flange can you see part of your rubber o ring gasket ?
 
trinik7597

trinik7597

Active Member
#7
#7
Also if you don't need a fuel pump and you can gravity feed fuel get rid of it .... The Chinese mikuni's do not play well with fuel pumps .. it will push fuel right past your needle valve
 
trinik7597

trinik7597

Active Member
#8
#8
I am so stealing these pics to help illustrate what I am talking about [MENTION=31879]CarPlayLB[/MENTION] ... Assuming that the inverted intake is an agk the alignment sucks at the mounting flange and leaves the rubber o ring gasket exposed on the bottom causing an air leak .. this is how a smart person corrected it
 
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Vtbowhunter3

New Member
#9
#9
It's the one from go karts USA. I am going to need a fuel pump I didn't know these carbs didn't work well with one. Are you talking about just the air screw or there's another?
 
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Vtbowhunter3

New Member
#10
#10
Thanks for the pics. I believe that's cause the Chinese mikuni pictured has a different flange then the genuine one. This intake is made for genuine mikuni and it fits the carb well not like what's pictured
 
trinik7597

trinik7597

Active Member
#11
#11
If you have a genuine mikuni then the pump should not be a problem ... If you have a good match at the flange that is not your problem . There is an air screw behind the bowl on the bottom of the carb . 1 1/2 turns out from dead seat is the stock position .. I would go back to a 15 pilot 125 main .. and check pin height . For a base line that should be close
 
ole4

ole4

#16
#16
A 125 or 130 main jet should run without cutting out. A 180 jet would foul out the plug pretty quick. Get rid of the fuel pump if the tank is above the carb. I agree with tim above sound like a air leak. Please post some pictures of your current setup.
 
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Vtbowhunter3

New Member
#17
#17


This is the only picture I have right now. I didn't get a chance to play with it tonight, I will need a fuel pump the tank sits to low


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V

Vtbowhunter3

New Member
#18
#18
I know this intake did call for a 170-180 main jet that's why I had tried it. Thanks for the help guys hope to figure it out soon


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trinik7597

trinik7597

Active Member
#19
#19
That pulse fitting is a little suspect did you take that out of the equation ? I would have drilled and tapped into the intake .. what position is your enrichment lever in ?
 
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