General jet questions

[Cylon]

Hey all I just put a pocket bike exhaust on my bike and it seems like it leaned it out a bit at WOT it bogs a bit but will still pull if I stay about 6 mm from WOT. I have a bunch of jets I bought from bicycle motor works and I'm having a hard time eye balling the stock jet it looks to be about .70 I think?

So I know I need a bigger jet and I'm at 118 feet elevation. Anyone have a idea what the stock jet size is? Also I think I'm just going to slap in a .75 jet to test later, not really looking forward to having to pull the carb apart over and over to get it right but I know running lean isn't ideal. Any recommendations from people around my elevation and mods?

Here's a picture to show mods and the pipe. Very mild porting to intake and exhaust ports, no transfer porting just cleaned up the casting so it was smoother.

 

[2door]

Jet 'size' doesn't mean much to me. I've seen too much inconsistency in the numbers vendors apply to them. I'm a solder and drill guy. Yes, it means some experimentation (pulling the carb apart) but in the end you get exactly the right size jet orifice for your application with no guesswork.

Tom

 

[YesImLDS]

I'm going to have to go with tom on this one. I bought a .66 jet from a vendor because I wanted to have a back up for tuning and it was the exact same size as my .70 jet that came with the bike. Obviously not a problem for my use but that could screw somebody else over pretty quick.

 

[Moto]

I got a full set of http://www.treatland.tv/dellorto-main-jets-part-1486-p/dellorto-main-jets-moped-1486.htm from 60-90 its a lot of money but lets you perfectly tune your engine. However thats for jetting all sorts of different stock and heavily modified engines with different carbs. I would recomend getting 65-75 to start. and yeah the stock jet is a 70

 

[Cylon]

Hey all, wanted to post a update. I pulled the jet out of my NT speed carb and it looked very small maybe .60 to .65. I went ahead and installed a .75 jet and it worked great the first time, I was super happy I didn't need to pull it apart again. No more worries about blowing the motor to a lean condition.

 

[2door]

You can look at a jet and tell the size? Man, your eyes are better than mine.
Glad you found the right dimension for your engine.
Have fun and ride safe.

Tom

 

[Cylon]

Yeah I'm only 25 and good better then normal vision. It's not 100% but I can see slight differences using a bright light. I lucked out. Thank you.

 

[Venice Motor Bikes]

I'm also a 'solder & drill' guy with the small carbs... With real carbs (such as Mikuni), I use real jets.

I always jet 'by ear'... I start by jetting it large & drop down until you can just feel the engine starting to sound crisp.
If you jet too small, it will feel real powerful but will actually be burning up the engine, so it's best to keep it a little on the fat side.