After a 10 mile ride my spark plug looks like this

[renagade281]

So yesterday I decided to buy an aftermarket air filter and when I put it on and went to test drive I immediately realized I needed a bigger main jet due to more airflow. So I went back and bought an 83, 85 and a 90. And also a new spark plug. So I installed the 83 mj and it still ran like crap so I jumped to the 90 and it runs fine. So after a 10 mile wot run I decided to check the spark plug. This is what it looks like. It wasn't wet at all. To me it still looks pretty new but I wanted some other opinions. What do you guys think?

[renagade281]

So after a total of 25 miles the spark plug still looks dry and new. I'm thinking I'm still a little on the lean side. Should I go with an even bigger mj than a 90? I've already moved the needle to the richest slot. It feels as if the scooter is a little hotter than it should be which is another reason I think I need to go a little more rich



Edit: I put the stock air box back on with no restricted airflow and it runs perfect but I notice the there is no fuel building up in my fuel filter. If I close the hose off between the filter and the carb it will fill up but as soon as I open it up the filter drains. The carb is getting fuel bit now I'm wondering with the stock air box and a 90 MJ is it just drinking fuel like crazy? It still runs fine so I guess I'll just leave it alone unless I get good advice that there's a problem

[humanshield]

You would need to post more info about the motor. Is this a 50cc or 150cc scoot?
The main jets you mentioned are typically for 50cc - 100cc scoots

Stock or modified?

But...a quick and dirty assessment......it seems to be running hot as you said.  Why are you using that type of spark plug?
Is it the one recommended for your scooter?

There should be a little bit of tan on the insulator after 25 miles I would say.

[renagade281]

50cc .. It's an irridium plug or however u spell it. Stock engine

[90GTVert]

I rely on tuning runs much more than plug appearance, but I'd try going up a size and see how it does.

[renagade281]

Apr 7, 2016 6:59:31 GMT -5 90GTVert said:

I rely on tuning runs much more than plug appearance, but I'd try going up a size and see how it does.

I was thinking that too but wasn't sure if anything bigger than a 90 was good for a carb that's running a stock engine

[90GTVert]

Whatever gives you the correct air/fuel ratio is good for it, no matter what anyone recommends. I've had up to a 95 in mine in cold weather with a stock airbox minus some restrictions.

[renagade281]

ok. thanks