Hey all. My motor has like, no power, and often stalls at low rpm and boggs and sputters. I put in new gas mixed at 52:1 using Golden Spectro Synthetic. I put in a new plug, after running for 20min, i pulled the plug and it is black. I took apart the carb, cleaned it inside and out. I put in all new valves, floats, gaskets everything. Now, the stock Main Jet was 190, and on the Needle Jet, the clip was all the way at the top. I Put the clip on a the 3ed position, and put in a new needle. I was wondering what my Mainjet should be? Should i go down to a 160? or a 170? any Help is great, thanks in advance. Plus, The 36MM carb is stock carb bored out to 35.6mm

Ben

 

If your problem is at low rpm, then the main jet has nothing to do with it. Check and see what size pilot is in there and read this article. A few things that might help you....

- The needle jet (not the needle) on the stock mikuni carbs tends to wear causing your low end to run too rich.
- You're running a very thin gas/oil mixture which makes your air/fuel ratio richer.
- By switching from the top position on the needle to the middle you made it alot richer. Try to set it up so that it's jetted properly with the clip closer to the middle.
- Your bored out carb and ported cylinder are going to require a fatter main than stock, not leaner.

 

ok. Im going to go get a 175MJ and see how it runs... I dont get it because my manual says stock runs from 190- 210MJ.. and im running really really rich with the 190.. the carb is just re-built to. I replaced the needle jet so i know it isnt worn, ill tell you what happens when i switch the jet. also, your artice dont work.

 

well, now my motor wont even start... thanks for all the help....

 

That's probably a good thing cause with a 175 main it woulda gone BANG once it got up to high rpm. Reread my first post....... The main jet has nothing to do with low rpm bogging
http://ericgorr.com/techarticles/carbtuning.html

 

ok, well so you know, i Put in a 180MJ and The Needle Jet on 3ed clip, it wouldent start. Didnt even sound like it wanted to start. when i kicked it, it just had a deep thud. Also, i put the 190MJ back in, and it isnt starting either. I think it might have something to do with my Piolt. But also, the last time i ran it, the motor wouldent spin over 4,000RPM, and when i went full throttle it just sputtered and broke up, with a lot of smoke.

 

Ok, right now i have: 190MJ, 45Piolit, and Needle Clip On last Position... Ill see if it will run.

 

why has only 1 person responded????? i know alot of people know about jetting!! I have a 45 Piolit, 190MJ and Needle Jet on Last Clip! It has ran with this jetting befor, but now it wont even start!! even when i put feul right in the carb, it just has a deep thud!! i dont get it! some one helP!

 

change the plug, or at least make sure you have a spark...thats always the first place i start when she wont start...make sure you float level is correct too since you said u replaced your floats. That did wonders for mine...

 

I checked the float level, they were Excatly 11mm. Which is perfect. Also, the spark plug is new, and when it out and kick over the motor, their is a spark. Also, when i put my finger over the sparkplug hole, their is alot of compression. Also after kicking the motor over alot, the plug is wet...