Analyze this spark plug

[Speedgoat]

236145236146236147Just finishing my build on a 200s. Trying to improve the throttle response. Right now has stock carb and stock plug. Put this brand new plug in, ran it wide open for about 1000yds. This is what it looks like. A good friend, who know a lot more than me about engines, told me it looks lean.
What are your thoughts and what adjustments could I make.
(It starts first pull, idles fine, throttle response is very slightly delayed when taking off from stop, pickup and response is a little slow in higher gears. Top speed 43.0)

[rocks]

You are running super lean. Not good.
Adjust the air screw. Try to close it all the way down then test. I am not sure how many turns out it needs to be, but give it a try. Better run rich than lean.

[Speedgoat]

Do I mess with the needle at all or just start with air screw?

[yaegerb]

Way to lean.

Are you running OEM airbox with OEM filter?

What model carb? PD62B?

[TwiZ]

Do I mess with the needle at all or just start with air screw?

Air screw,front of carb engine side..Gently seat it if you screw all the way in. I usually go 2 turns out and go from there,i think book says turn n a half. Wanna try and get it where its in between dying when screwing in and same screwing out,wanna get it where it idles the higest between these two positions,if that makes sense

[RubberSalt]

Based on that. It looks lean. If you ran WOT for 1000 yards, and that's the results, your main jet may be to small.

Try pulling the choke and see if it gets any better. Partial choke/full choke. This will richen it up and give you an idea.

The only way to get a "true" reading is to cut the threads on the plug off and look at the insulator between the threads and the porcelain. This part changes color first.

[AK47KID]

Omg I 'bout fell over!! Lean very lean! Do what twiZ said

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[RubberSalt]

AK47kid, the fuel screw adjust the low end circuits of the carb. He's running WOT and seeing that. WOT is determined by the main jet. At WOT, the pilot circuit on contributes about 2% of the fuel. The main jet does the rest.

Air screws are on 2 stroke carbs. They adjust the air going into the circuit. These are near the Air filter side of the carb.
Fuel screws are on 4 stroke carbs. They adjust the fuel going out of the circuit. This is on the engine side of the carb.

[TwiZ]

AK47kid, the fuel screw adjust the low end circuits of the carb. He's running WOT and seeing that. WOT is determined by the main jet. At WOT, the pilot circuit on contributes about 2% of the fuel. The main jet does the rest.

Air screws are on 2 stroke carbs. They adjust the air going into the circuit. These are near the Air filter side of the carb.
Fuel screws are on 4 stroke carbs. They adjust the fuel going out of the circuit. This is on the engine side of the carb.


You are absolutly correct,and i was sloppy by calling it a air screw,and i was using it as a generic term and should have called it a fuel screw,my bad. I was explaining this to him due to the slight delay and off line response.When i tune a carb i start with setting fuel/air mix,thats just me. Ive been doin this stuff for years just dont explain well sometimes. Thank you for catching that.
Check and see where the clip for the needle is,should be in the middle,drop your clip down and it should richen it. If not enough try the last notch. If its better id get a little bit bigger jet. If i remember right it has a 108 in it,38 or 40 pilot

[Speedgoat]

Way to lean.

Are you running OEM airbox with OEM filter?

What model carb? PD62B?

OEM airbox with a moose faom filter over the OEM metal screen tube

carb is PD85C, main jet is 100

[Speedgoat]

Air screw,front of carb engine side..Gently seat it if you screw all the way in. I usually go 2 turns out and go from there,i think book says turn n a half. Wanna try and get it where its in between dying when screwing in and same screwing out,wanna get it where it idles the higest between these two positions,if that makes sense

yes that makes sense. that is exactly what i did initially to get the results in the pictures

[Speedgoat]

AK47kid, the fuel screw adjust the low end circuits of the carb. He's running WOT and seeing that. WOT is determined by the main jet. At WOT, the pilot circuit on contributes about 2% of the fuel. The main jet does the rest.

Air screws are on 2 stroke carbs. They adjust the air going into the circuit. These are near the Air filter side of the carb.
Fuel screws are on 4 stroke carbs. They adjust the fuel going out of the circuit. This is on the engine side of the carb.

my understanding is the needle only affects about 1/4 throttle to 3/4 throttle. at WOT, the main jet is the only factor.Is this accurate?
if my main jet is not clean, could it cause it to run lean?
Will adjusting the air/fuel screw change anything if I am only doing plug checks at WOT?

[yaegerb]

I would change the main to a 108, leave your pilot alone for now and drop the clip one groove on the needle. Also leave your pilot screw setting where you have it.

[Speedgoat]

I would change the main to a 108, leave your pilot alone for now and drop the clip one groove on the needle. Also leave your pilot screw setting where you have it.

any recommendations on where to get new jets without dropping a lot of cash?

[yaegerb]

any recommendations on where to get new jets without dropping a lot of cash?

Jetsrus. But get the genuine jets, don't get the OEM equivalent.

[TwiZ]

I know my local honda shop has em for like $5. I cant remember what size main the s has, i know that the 200x some were 108 and some were 110. Generally the 40 pilot is standard. Try what yaeger and i suggested and drop the clip down a knotch,if still lean go to bottom,provided its on middle slot now. Every one does things different,but if i have to drop or raise the clip i do this to get a better idea what size main i need.Like with my 200x,when i put uni filter and dg pipe i had to go to bottom clip to get close with a 110,ended up with a 112 to get me back to middle slot. Just last week i installed a 10.25-1 weisco stock bore,xr cam and xr carb. The factory jetting is lean for me so i gotta go get some jets. Im on bottom notch and still lean

[Rob Canadian]

Is the carb clean? Why throw jets at it. IMHO

A clean carb is a good carb. Clean carb take note of jet sizes and elevation of where you are at.

[TwiZ]

I guess we assumed it was,at least i did,when he said just got finished with the build,and his mechanic buddy was there,and fresh plug. But u know what they say about assume.....lol

[Speedgoat]

Is the carb clean? Why throw jets at it. IMHO

A clean carb is a good carb. Clean carb take note of jet sizes and elevation of where you are at.

This was my thought too. The guy I got the engine and carb from said he cleaned the carb. I might take it apart and clean it again before buying a new jet. I also have the exact same carb I could try cleaning and using but it's really dirty

[Speedgoat]

Twiz,
The guy I got it from had the most immaculate and clean garage I have ever seen. He said it was clean. All the parts I got from him were clean. I opened the carb and it looked spotless. I have never cleaned a carb so I trusted the guy I got it from probably could clean it better than I. I will take it apart this weekend and try cleaning it. If no improvement, then try new jet and all th other advise you have given. Thanks.

[TwiZ]

Twiz,
The guy I got it from had the most immaculate and clean garage I have ever seen. He said it was clean. All the parts I got from him were clean. I opened the carb and it looked spotless. I have never cleaned a carb so I trusted the guy I got it from probably could clean it better than I. I will take it apart this weekend and try cleaning it. If no improvement, then try new jet and all th other advise you have given. Thanks.
I kinda figured it was,as a good mechanic would have done the cleaning.Wont hurt to do it again,taking it completely apart,spray carb cleaner in all passages(ill easily use 2 cans) and blow compressed air thru all ports. I use a torch tip cleaner to get the jets good then use carb cleaner and comp air again,maybe even get a good rebuild kit.Be surprised what a teeny bit of scale or dirt will do.You never did say where the position of the clip on needle was. Unless someone changed it or engine has been modded the stock jetting with clip in middle should be good.

[Speedgoat]

I will take it apart and clean it in the next few days and adjust the needle clip one notch. I lwill update you once it's done. Might not get to it till this weekend.

Thanks for the advice

[yaegerb]

I will take it apart and clean it in the next few days and adjust the needle clip one notch. I lwill update you once it's done. Might not get to it till this weekend.

Thanks for the advice

Just FYI, I don't believe the needle alone will do it. If you were truly wide open for xxx yds. then you were on Main (3/4-WOT). I am just trying to get you richer then you can fine tune down the road.

[Speedgoat]

Just FYI, I don't believe the needle alone will do it. If you were truly wide open for xxx yds. then you were on Main (3/4-WOT). I am just trying to get you richer then you can fine tune down the road.

Thanks, I think the consensus is fix main jet problem first...as you have mentioned.

[Speedgoat]

I pulled the carb and cleaned the jets tonight. Also adjusted the needle. The clip was one notch up from middle so I put it back to middle notch. Put everything back together. Idles great. I live In town so I couldnt take it out for a rip. I will on Saturday.
I also noticed I had a slight kink in fuel line. I am doubtful this had any affect but of course I fixed it as well.

[Speedgoat]

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[muthey]

when you go and put in the new main jet, also make sure your air filter is oiled a dry air filter can also help cause a lean condition, not that bad that is definitely jetting, but even so stock jetting is with a wet air filter.

[gimmeamidget]

I would also pull the fuel line and turn on fuel for a few seconds and make sure gas rushes out and not just a slight trickle. My 350x was so lean when I first got it that the pipe would glow red at high rpm's and I started replacing jets before realizing the petcock was partially clogged and fuel was just trickling out causing lean condition.