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Post by jimkerruk on Nov 22, 2014 15:48:13 GMT
this forum, but I'm needing some help. I have built an engine to go into my px. I have malossi 221 kit, 60mm bell shaped crank, mbd reed block and manifold with the rd350 reed valve, 35mm mikuni tmx carb, standard gearbox but with t5 fourth gear, and RZ mark one expansion chamber. I'm looking for a ball park figure for jetting the carb to get me set off. I appreciate that it will need tweaking, but just want to get started. If anyone could help I would very much appreciate it. Thanks.
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Post by henri on Nov 22, 2014 16:57:33 GMT
just a guess ,but a px150 runs 96,an a 200 116 ,so up ten for 50cc+ , your up half of that so upto a 121 ,then coz of bigger carb (ya dont say which filter used) an rz exhaust your going to need roughly 10% on that ,that takes ya to 133 , i think i'd start around 135-137 ,an work down on the main ,sorry thats all si carb thoughts
which bike is carb off/meant for , an what needle/slide an clip position has it got , i thought the 35mm was meant for 125cc moto-crossers an the 38mm was for 250cc, i think i'd jet for a 38mm to start with ,a 370 main 20 pilot an a 6ej12-ss needle on the highest clip position ,ie one furthest from end ,an drop the needle as needed to lean it up ,
this is all guess work as ive never used a mikuni tmx prefering keihin pkw , the mikuni has a rep for hard to get a good idle or low speed pick up, together ,one or tother but not together ,who supplied the carb ,was there any advice given on jetting , ya could try the sip forum , H
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Post by jimkerruk on Nov 22, 2014 17:39:21 GMT
Thanks henri, will have a look on sip forum. The filter I have is a ramair sponge filter. I bought the carb from sip but no jetting info supplied. I'm not sure which bike uses it as standard though. Thanks for the reply. Jim.
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Post by jimkerruk on Nov 22, 2014 20:54:33 GMT
Thanks very much, there's a lot of info there. I'll try and use some of it and tweek as I go. Thanks.
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me
High Number
Posts: 105
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Post by me on Nov 22, 2014 22:03:23 GMT
Easiest thing is to tell us what jets are in the carb.... including the needle.
Ive done a few of this style of engine - carburation is never exactly the same from engine to engine - you really need to see what its doing so know what to change, is it a proper Mikuni or a OKO copy? the both share jets and needles and jets but obviously the pattern parts are much cheaper.
Also remember the mikuni original jets are rated by flow and not dimension (mm hole).
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Post by jimkerruk on Nov 23, 2014 0:07:49 GMT
Hi, yes it is a genuine Mikuni carb. I'm not sure of the jets in it as standard. I am away for the weekend, but I'll check when I get home tomorrow. Thanks for the reply. Jim.
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Post by jimkerruk on Nov 23, 2014 17:22:55 GMT
The jetting in the carb when I bought it are,
Main jet 350
Needle jet 53
Pilot 30
Cheers, Jim.
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me
High Number
Posts: 105
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Post by me on Nov 23, 2014 21:10:21 GMT
Mikuni a very responsive to the needle adjustments, a 53 seems rich - but - you really need to get it going 1st to see what and how it responds - even on the stand you'll work out if its rich or how it picks up, with years of experiance i can usually tell from the sound and smoke it makes.
Once you get on the road you'll soon tell what and where it needs adjustment - the air screw is very responsive to small adjustments and 1/4 a turn can make a big difference.
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