stock/nt carb rejetting: how much lower than the stock 70 have you ever had to use?--or heard of someone else using?

I'm running a #64 in mine @ 900 ft altitude. Please don't do the drill mod, it's a crapshoot and if you have to buy the bits, heat source, and solder, a helluv lot more expensive than a 3 dollar jet.
I have never bought jets because I have everything needed to do it in my shop, I soldered and drilled jets often when I worked as a contractor for the local gas company. I know a lot of people don’t have the tools was just giving my methods. As for the OP’s post it almost sounds like a crack or hole in the carb that is passing fuel.
 
interesting take,...greg58. I will re-re-inspect the carb again for casting defects/cracks/holes. I saw nothing out of the ordinary the last 3 times I had it apart,....but I was not looking for that.

….and thank you gary 55 for explaining the jet number-to-mm meaning. I totally get it now. I actually DID suspect it had a direct correlation to mm.

..well...now im feeling 120 percent better and my optimism has been renewed in regards to this issue being resolved by further down-jetting. further down-jetting is now not an excersize in futility imo.

come on bicycle motor works ship my low 60's jets!!!!!
 
One thing that has happened to me is the needle jet or jet base has loosened up and caused four stroking, this happened on a eBay nock off nt, since you have had yours apart it probably not the problem but thought I'd mention it. I have heard of the jet falling into the bowl so jets loosen by vibration.
 
I have also heard of that. I will say that I removed my muffler and noticed the exhaust gasket was just a hair in the exhaust stream so i trimmed it,...reassembled it,...giddy,....my heart all aflutter thinking I found the problem.

NOT. ------sad face.

I also discovered my fuel inlet nozzle/float needle seat was not tightened down fully. same scenario. tightened it,...ran around the house 3 times laughing thinking I found it. WRONG. god dammit.

waiting for these low 60's jets to arrive
 
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final (hopefully) prognosis: 63 jet.

this NT carb is a knock-off,..the float depressor button looks like a spring-loaded pop rivet sliding inside a blue plastic "jacket" that plugs/fits into the hole to the bowl. VERY different-looking than the gold plastic kind. but,.. it does what it says on the tin. (I never, ever used it,..once,..ever.)

this carb says NOTHING on the entire outside. not "speed" ,....not nothing. just some hokey Chinese symbols indicating the choke lever positions. that's all.

today will be spent riding to determine what fine tuning remains to be done if any. I think my crankcase is loaded with unburnt fuel and needs a long sustained hot ride. same with the muffler.
 
final observations:

63 too rich,..61 still too rich but soooo close,....running WAY better, plug getting lighter,....exh. drippage reduced.

threw in the 60 and that's all I have. done for the day. will update tomorrow.

--does light 4 stroking cause damage? any? short/long term?
 
It fouls plugs, and maybe might plug up your exhaust over time. No engine damage will occur.

well then a little extra popping and noise is what they will get. its only the increased volume of the popping that had me worried about possible wrist pin bearing wear.

I retarded my timing a little with the magneto rotor keyway filedown mod. smoother.

insane power to **about** max revs then she sputters. with a 61 jet. so the 60 is in,...we'll see tomorrow.

im ready to get the micro drills and a soldering iron from harbor freight if it don't go right.

methinks my test ride in the am will be straight to harbor freight
 
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been down to a 0.5mm. bit grumpy on start ups, but once it gets warm... hang on!

all stock but the pipe. only one engine would take that though.

if drilling jets isnt your cup of tea, try soldering a strand at a time of super fine wire in there. just slip it in the jet and tack it on lightly. it wont escape...

once it starts running bad from leaning out too far.. remove the last TWO strands.

headphone/charger leads are a good source of fine wire.
 
I had to resort to soldering the stock jet and drilling it out.

I have never bought jets because I have everything needed to do it in my shop, I soldered and drilled jets often when I worked as a contractor for the local gas company. I know a lot of people don’t have the tools was just giving my methods. As for the OP’s post it almost sounds like a crack or hole in the carb that is passing fuel.

i drilled it with a .45,...and THAT was too lean imo. started,...idled,...wasnt really wanting to be running....got hot,...zero pulling power at wot. way too lean. got home,...took my drill bit and used it to file out the hole some,...boom. full power all the way to screaming. still the slightest hint of 4 stroking at cruising,..(1/4 throttle,....not really pulling) but im ok with it. oil is good. but the noise sucks.

----anyone know a good source of thick wall 1/2 inch ID silicone rubber tubing for my exhaust???? I KNOW that works miracles with noise levels...…...

im also ok with **MILD** 4 stroking because this motor is JUST broken in,....unt will prob. lean out further as miles go by. plus I like knowing that chintz-ey,...half-a millimeter plating layer is wet with top-of-the-line synthetic. (opti-2)

--i'd say this jet is in the neighborhood of a low 50. my best estimation is around a .52-.53

---will do a final plug inspect after I get a whole tank of this opti-2 mix through her. will post results.

THANK YOU EVERYONE WHO SOUNDED OFF
 
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