Advice with jetting a high performance/dellorto copy carb.

HumanPerson

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Where the throttle cable goes in, i seal mine with allseal, sometimes just electrical tape will suffice and get ya going.
Another small leak area is where you tighten the carb collar to the intake, again, sealall has been a good friend,
combined with either an o-ring or a sleeve to go over the intake.
 

RB55

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This is just my opinion (feel free to contradict or add to this!)

A tuned NT is the best carb for stock engines. Realistically and theoretically speaking, the so called "HP" or cheap "upgrade" carburetors do nothing to increase HP. Honestly there should be more info for beginners warning them not to use these rip off carbs. They're worthless.

I don't give a crap about temperature for these MB engines. Bikeberry keeps spreading this false rumor that you need a cool down period after 20 or 30 mins of riding. Lol the people at Bikeberry are the dumbest people I've ever seen, all they can do is sell you boost bottles and banana "expansion" pipes and "high performance" colorful Chinese junk. That's complete BS. I rode my stock MB for 3 hours and 30 minutes straight once, full throttle with no breaks on a 44T so i was hitting 9K RPM the entire time and it was 91 degrees outside. That thing got as hot as it could ever get. Stock exhaust as well which definitely does not help cool the engine due to its restrictive nature. Opened up engine afterwards, no damage at all. Cylinder and jug looked great. Compression test, exact same PSI. Later I was experimenting with carb jetting and ran the bike (still stock) FAR too lean (barely running) for two hours on a hot day. And the same for the next few days. Same story, no damage to jug/piston, engine great inside. That engine now has 600 miles on it and runs to this day, although I've scrapped it due to bolts stripping and clutch issues.

So if I were you I wouldn't be afraid to go lean. Sounds like you're a too lean right now however with the NT or you have an air leak. That #66 may be a bit too small. Try a #67 or #68 and see if you get a linear throttle response with it. It's all about patience at the margin with tuning carbs. I personally hate tuning carbs but the gain is worth it.

also, water should boil if you drip it onto your exhaust pipe...no such thing as an internal combustion exhaust below 220F! ;)
 

HumanPerson

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Those RunTong/HP carbs are pretty simple in my opinion.
I had more problems with the NT stock carb :D

This is all i did to my RunTong/HP carb,
After i sealed where the throttle cable goes into the carb i still noticed i had a leak somewhere.
Upon inspection i noticed it seemed to be leaking from the carbs collar, where the slots are.
I sealed the slots with SealAll then no more problems, i run a #69 jet.

That was with the stock intake manifold.
I made a manifold and had to use the 0-ring method even with the sealed carb collar slots.

I can never touch my cylinder or head after a 5 mile ride, sleeved cylinders seem to be ready to take the heat a bit better than the chromed stock cylinders, in my opinion.

Although there is another guy with another MB in my town and he swears by the NT carb lol

Good Luck and Ride Safe! :)
 

Leighton

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I think that's what mine is, a ripp off racing nt carb haha. It doesn't have not on the red plastic bit. My original stock one was a runtong, and the tickler dissintergrated. It always leaked around the float bowl and the screw at the bottom of the bowl. It did rip with that stock jet bit it had 2x 4 stroking zones. When I went for the hp it just felt like it lost something, it never leaked at all and it looks cool hit it just seems to make your engine slower.
Ive not tried all the jets on the nt (I was using the hp when I bought those). I will maybe start going up a few jets then...

With the needle clip. Does that setting (upto 3/4 throttle) change as you go up or down jets.
E.g say I'm currently on a #66 jet, with the needle clip at the bottom (rich) and I need to go richer, when I go to the 67# jet do I need to adjust the needle clip up to make it a leaner setting? Then work.your way down the clip until you're richest and then go to the next jet up?
Or is it find the right spot on the needle and leave it regardless of jet size?
 

HumanPerson

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Leighton

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Oh s**t, I had it wrong, you're right. I have the fake nt carbs (it has Chinese letters not "nt"), they are the ones I like.
I started with the stock one which the tickler broke on and it leaked petrol. Then I had the hp (which is actually stamped runtong) and I didnt have much luck with that, so went back to a nt carb. But I got the red one.
 

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HumanPerson

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I understand now. I was confuseled :ROFLMAO:

I really should have given the NT carb a chance, but i decided to go with the RunTong carb, so just
really dealt with those problems if that makes sense :D

The RunTong carb certainly has had the problems to fix right out of the box for me but once dialed in, everything seems to be really good now.

If you don't mind me asking, what problems were you having with this carb> https://motoredbikes.com/attachments/15822354753246493240803793767179-jpg.92962/ ?
 

Leighton

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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.
 
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