nickh
50 Special
Posts: 27
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Post by nickh on Feb 21, 2023 12:28:36 GMT
hi folks,
I have fitted a procup 3 to my PK and am struggling to get the idle mixture correct. I am using an shb20mm carb with a 94 main jet and a 50 idle. even with the screw 4 turns out it still acts weak even more so when warm. The exhaust is a BGM banana race and the cases are matched to the cylinder with the timing set at 16 degrees as per the sheet that came with the kit. I have pressure tested it and it held 6 psi for 15 minutes.
Anyone got a base setting I can work from. I am going to put a 98 main in and swap the idle jet for a 55 or even 60. After a couple of miles of easy riding on the flat it appeared to soft seize at idle whilst on the drive on its current jetting.
TIA
Nick
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Post by henri on Feb 21, 2023 17:58:09 GMT
a 52 idle with filter , a 55 if running no filter . an a bigger main , say 97-98 is where i'd start . an knock timing back to 15btdc aswell , the sheets for italian conditions an fuel . an tho where all supposed to be on the same "standards" , italian an german fuel often exceeds the min standard ,uk fuel sadly often at the pump fails to meet bare requirements . for a base line 19mm carb i start 48/95 , a 24mm its 52/105 , both with filters , so you with a 20mm ets carb are in the middle . a picture of plug in daylight would help , you want a nice carbon black outer ring ,thats ya idle jet read ,where you seem to have troubles .H
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nickh
50 Special
Posts: 27
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Post by nickh on Feb 26, 2023 20:19:23 GMT
Cheers H. Eurocarb only do a 55 or 60 long idle jet. I am running with a filter but will get one of each
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nickh
50 Special
Posts: 27
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Post by nickh on Mar 6, 2023 7:59:14 GMT
I ended up using a 55 long type idle jet and a 98 main. there is probably room for improvement but I got cold and bored riding up and down the road.
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nickh
50 Special
Posts: 27
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Post by nickh on Apr 13, 2023 10:46:07 GMT
I ended up using a 55 long type idle jet and a 98 main. there is probably room for improvement but I got cold and bored riding up and down the road. ended up with a 93 main and just over 1 and a half yurns out on the mixture screw and it is sweet as. happy days. |
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Post by jonnysnatchsniffer on Apr 29, 2023 19:46:06 GMT
id consider using a larger carb on that kit, it will only improve it
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nickh
50 Special
Posts: 27
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Post by nickh on May 3, 2023 8:49:14 GMT
JSS, I have a 25mm to put on it. I just need to get my arse into gear and do it.
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nickh
50 Special
Posts: 27
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Post by nickh on May 15, 2023 18:32:54 GMT
JSS, I have a 25mm to put on it. I just need to get my arse into gear and do it. so I put the 25mm carb on it today and am now grinning like a cheshire cat. what a massive difference. I used a polini manifold and matched the opening of the manifold to the gasket as there was a sizeable difference. I should really have added some meat to the manifold using the TIG but it will do for now. is the malossi manifold any better? it wants to be given the difference in price. |
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Post by henri on May 16, 2023 6:01:53 GMT
not a fan of malossi manifolds so much ,particularly the barrel inlet ones .there more curved,less straight than others an prone to fuel up at low revs/tickover an bog down .H
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Post by jonnysnatchsniffer on May 23, 2023 12:11:58 GMT
yes and you also should have enlarged the pad to its maximum, and from there the walls of the inlet should be straight to the gasket face.
the back of the inlet on the drive side will need filling as you will deffinately break through, it needs to taper inwards, but not like a trumpet
id not weld there as you have a bearing seat so yr personal choice of epoxy or chem metal will do, lot of gains here hp wise, you can also cut the crank for more inlet timing
around 190 degrees is good
ive got a modified polini manifold to fit a 35mm keihin, it works rather well, keep it rotary and get a franz pipe for it, yr have even more of a chesh on
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