Advice with jetting a high performance/dellorto copy carb.

HumanPerson

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One modification effects another.
I tuned mine for bottom end power, to climb hills in my area. Now you have me wanting to try the NT carb again :D

Ride Safe! :)
 

HumanPerson

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Did you see this thread yet?

 

Leighton

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Wow yours looks like it's had the full treatment. I thought the runtong sealed up nicely esp around the inlet pipe, but I never got it working well. The nt carb just leaked petrol, loads, but it worked pretty well. The new nt not started leaking yet, but it already works better imho.

It actually works at flat out nicely now, the best since I've had it. It just revs loud but no 4 stroking.

The low down speed is pretty sluggish tho. I had the 36 tooth sprocket from the original stock carb and in sure it picked up better before. But the top end was a bit lame. Is that the trade off then? Up hi or down low?
 

HumanPerson

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Oh lord no the runtong has alot of leaky areas that needed to be sealed up.
Yeah that is one major reason i ditched the NT carb was the leaks i could not stop lol it was like my gas just flowed out of the tickler button :D

But you seem to be on a good start and you have alot of good humans here to guide you :)

Ride Safe Leighton! :cool:
 

HumanPerson

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I just like riding around 28'ish but plowing up hills passing the scooter people while i peddle reeeaalllyyy slow :D
 

HumanPerson

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I'd see if i could scan the brain of @RB55 if i needed some NT carb information though.

I hope you get it all figured out :)

Ride Safe! ✌
 

Frogslayer

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You want to get your jet right so it runs great towards wide open throttle first then adjust your needle position to control fuel flow down low through the jet that you need for the up high.
 

RB55

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This is the RunTong carb i talked about: https://www.ebay.com/itm/Runtong-Ra...q-50-2-Stroke-Motorized-Bicycle-/192979852171

It has a slide, a needle clip or needle, i has the emulsion tube and the slide, unlike the NT carb.
@Street Ryderz could tell you more about the NT carb than me.
I used the NT carb for a whole day then went on to the RunTong carb ever since.

Do you have any pictures of your bike and engine?

This HP carb you speak of seems alot like the stock carb :unsure:
I'm in love with it already.
I had the stock carb and it was great, it had a patch if 4 stroking at about half throttle and another patch at about 95% top speed.
It leaked a lot though so I bought the runtong. The STD jet was rediculous so I bought a bunch of jets, it just never felt as good as the nt carb. I went through all my jet sizes and never felt it bettered the nt. I stuck the new nt carb on today (it has 5 needle notches not 4). I'm gonna try all the jets in this but the top speed feels nice with the 66#.

Is it best to set the needle and then do the jets or will changing the jet mean I need to adjust the needle?
I'm thinking I get the needle right and then go up until it starts 4 stroking and go back down one size.
Change jets if you get four stroking above around 3/4 throttle. Otherwise try to use the needle. However you may still need to rejet, the needle is not effective 100% of the time.
 

Leighton

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14 miles later update.
I think the full throttle is maybe one jet too large, it was pretty much perfect today, with only a couple of points where it 4 stroked. Mostly it was just screaming! It's feels soo much better with that rev range alone imho, it feels quicker and sounds better.
I ride it about 7miles to work and about 7 miles back, most of which is WOT, but there are a few points where I have to turn it off and pedal it though. So wot is most important to me.
The Accel low down is still a bit sluggish but I'm moving the pin down the notches (there are still about 2 left until I'm at the lowest) so hopefully that makes it better, it already feels a little better from the other notch lowering yesterday.

I'm getting there tho, thanks all!
 
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