Carby NT Carb Tuning Basics

Great thread AussieSteve.

Told me everything I needed to know to sort out my 48cc HT's 4-stroking (and possibly detonation?) problem.

Earlier, I figured out that I needed a leaner fuel/ air mixture, but dropping the sliding needle fully and re-jetting from 0.65mm to 0.5mm wasn't quite enough.

Lowering the float's closed position by about 2mm to the correct 21mm hang immediately fixed the problem, and I now have a 'sweet' sounding and more powerful (+economical?) engine.

Thanks!

T :D
 
Great thread AussieSteve.

Told me everything I needed to know to sort out my 48cc HT's 4-stroking (and possibly detonation?) problem.

Earlier, I figured out that I needed a leaner fuel/ air mixture, but dropping the sliding needle fully and re-jetting from 0.65mm to 0.5mm wasn't quite enough.

Lowering the float's closed position by about 2mm to the correct 21mm hang immediately fixed the problem, and I now have a 'sweet' sounding and more powerful (+economical?) engine.

Thanks!

T :D

u got to love steves help . I use it and I like u am orig from good ole perth (floreat pk ),but now I say/live in dirty syd ....
ohh I also have a sbp exhaust I brought from steve ..motor is a rse 48cc hp2 .with more billet than stock even the broken bike was a rse shaft bike ...

brad
 
if I have a thick black coating on my spark plug does that mean its lean?
 
if I have a thick black coating on my spark plug does that mean its lean?
 
I've lost top end power after boostbottle install :-(

Hi folks.
My name is Ryan. I purchased a dual boost bottle kit for my 49cc 2 stroke.
Before the purchase I had near no low end power but decent mid and top end.
After installing the bottles, low end went from mouse to charging bull in comparing power. But top end is now barely a house cat with a bad attitude.
I've adjusted the C clip on the NT carb for better idle (I had to lean it one notch). Still no top end power to speak of :-(
My question is: does any one have a suggestion on how best to tune the carb (specifically jet change) to get my top end back and bring the idle down a little more?
I ordered a set of jets and I'm trying to avoid the trial and error phase...

On a side note: the nut that holds the muffler end cap/tail pipe came loose and bottom end power went through the roof (for such a small motor). I can't/won't run with no exhaust. I'm looking to quiet it more as it is...
Any help in getting my idle down (with out stalling) and getting my top end power back is greatly appreciated :)
 
I bought a couple of jets from sick bike parts sz #64 that solved the bogging at full throttle. I live in long beach, CA.so I'm probably around 75'ASL.I have a question about the float level if you bend the brass tangs down a little to lower the float level will that decrease the amount of fuel in the bowl or do you raise the float to decrease the amount of fuel in the bowl?
 
Thanks for the info, well done. The float height at 21mm, works out to 13/16?does that sound right?
 
float closer to bottom of bowl will mean less fuel in bowl
 
That's what I thought the 21mm or 13/16ths is the spec height? I went to a smaller jet and it ran great for awhile,then it was bogging at wot. I checked for airleak by spraying with water bottle and found a slight leak @ basegasket and I didn't have one handy so I goobered on some copper gasket adhesive it helped a bit. Still won't rev out cleanly so I thought if I lowered the gas height in the float bowl mite help. I know, change out the basegasket
 
forgot to mention

The cylinder head studs started backing out from centercases I took a shortcut and lifted cyl a bit and backed out the studs and put some loctite in the case's and put it back together with copper gasket adhesive. Frustrating
 
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