Disappointing RB20.

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10 inch Terror
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Sat Jul 16, 2016 6:08 pm

Hi all, I finally got one of my recent projects on the road today and I was left very underwhelmed. It's an RB20 with transfers matched but otherwise standard. I'm running 17/47 sprockets on a Italian Pacemaker box, NK Rally, 30mm Dellorto and mid weight flywheel. 1st and 2nd seem fine but in 3rd and 4th is completely gutless and will literally die at anything over half throttle. I got the carb supposedly already jetted to suit. Would a badly set up carb cause these symptoms? I'm pretty gutted by it all if I'm honest I was really hoping it'd be a fun ride. Any help greatly appreciated. Thanks in advance Pete.

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drunkmunkey6969
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Sat Jul 16, 2016 6:12 pm

What is the jetting spec?


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10 inch Terror
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Sat Jul 16, 2016 6:20 pm

drunkmunkey6969 wrote:What is the jetting spec?


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I got it from a dealer a few years ago and as far as I know it's as per standard RB20 spec. I just fitted it and never checked what was in it. I just put the scoot away earlier and haven't looked at anything. Do you think I should strip it down and check?

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wack 63
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Sat Jul 16, 2016 7:22 pm

I've just fitted a VHSH30 on an RB20 that is supposed to be jetted to suit from AF's. It has
U16 needle
DQ267
170 main
60/B48 idles
60 choke
3.0 float valve
50 slide
I've not rode it yet but it starts and revs fine although the main seems large plus the jetting is not the same as in the RB instructions?

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Donnie
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Sat Jul 16, 2016 7:39 pm

There's no such thing as a carb jetted right out of the box, at best it's going to be in the ballpark!
Donnie.

10 inch Terror
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Sat Jul 16, 2016 7:48 pm

Donnie wrote:There's no such thing as a carb jetted right out of the box, at best it's going to be in the ballpark!
I agree, and was expecting to have to adjust, or swap bits. This though seems a million miles out.

hendy
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Sat Jul 16, 2016 8:02 pm

I bought a phbh30 jetted for my gt186.

I've come down from 135 to 125 on the main and it's still too rich.

It did run though.

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Donnie
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Sat Jul 16, 2016 10:56 pm

10 inch terrors runs too though, so like you he will need to make adjustments.
Donnie.

10 inch Terror
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Sun Jul 17, 2016 1:28 pm

I've had the plug out, and although I didn't do many miles yesterday, it seems a pretty good colour. The photos don't really show it, but it's between a chocolate colour, and black. This suggests to me that it's not that far out?
Image
Image
Thoughts, please.

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HxPaul
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Sun Jul 17, 2016 2:25 pm

It looks rather rich.

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