Plug read

[Rob406]

Hey all. 84 Aero 80. Could someone tell me if this plug is just right, or is it lean? Brand new plug out of the box, about 5 minutes of runtime, ripped down the road WOT, turned around, hit WOT again and then parked it and pulled the plug. Unfortunately I have just the one plug along with the old one.

[motormike]

Are you suspecting the scooter to be running lean ?
I see nothing on the plug that indicates lean.
Any other issues pointing toward lean?

[Rob406]

Hi Mike, no it runs good. There is a slight hesitation somewhere around 1/2-3/4 throttle before hitting a noticeable power band but all in all it runs good. I leaned it out (needle clip 1 setting and also air screw 1/2 turn. Initially using existing plug but it looked wet - hence deciding to start leaning it out ) and it runs a little better maybe. The plug in pic is a result of this. I dont want to find out the hard way that its too lean.

This is on a new polini 21 mm out of the box, larger intake and I also fitted a v8 pipe (off a dio or spree, cant remember) had to cut and weld to make it fit. Not trying to make a rocketship but one thing led to another. Really just like having the cable operated choke. I did not expect to have to lean things out is why i ask.

[Rob406]

I actually chopped the above plug and this is the pic. I expected the ring to be darker but either it is too lean or not enough run time. Im not sure i can actually perform a legit plug chop on a scooter or maybe i have to run it down the road further? I have ordered a cyl head temp gauge with an eyelet that goes under the spark plug. Still would appreciate any input.

[Wheelman-111]

Greetings:

Yeah, a legit plug chop on a bike with a clutch means cutting Ignition as you pull in the clutch. On a CVT scooter, the engine keeps spinning after you hit the kill switch, and the unburnt fuel "washes" the plug for at least a few thousand cycles before you pull to a stop and unscrew the plug to read it.
We've learned to "read" the plug despite this. But yours needs a good long ride to be able to say anything more. Your plug basically looks brand-new.

[bonesv]

Hi Rob, I suggest you test for lean condition this way. Buy a CHT gauge like you said, and you can more easily tell if your carburetor needs a larger or smaller main jet by the temperature reading but it has to be with the ring under the spark plug and you remove the crush-washer first. If you get the temp above 380 and climbing while running down the road, then you need an upjet to next size. 400 is max and if it got that hot it would have shut off by itself soon after that. But check it again and if it still climbs above 380, well, you might have an air leak somewhere. But you said it ran good without any issues? or you didn't suspect you have a lean condition?
On the exhaust, kudos for making it fit! Be sure it is not leaking at the flange! You will know if it is by looking at that connection and see if you see oil all over that area? If so, you better adjust it or re-weld it, or use a different gasket but be sure it doesn't leak! You do not want any leaking at that connection. Then re-test for lean if you had a leak there. I could not tell you anything by the pic of your spark plug. Wheelman said it perfectly.

[Rob406]

Thanks guys unfortunately the cht gauge was just shipped so it will be in to next week until i can resume tuning.

[Rob406]

So cht gauge is installed. My understanding is the following for temps:

Idle: 190-220
Cruise: 260-310
Wot: 350-370

Could someone confirm??

If the above is correct, i am golden. My wot is low so i will lean it out but need to get some jets.

[Meatball]

400 is seize territory. Good rule of thumb is to never let it pass 380 and only ever get that hot on constant wot for 10 minutes. However, the speed of which the temps climb is also very telling. If its climbing very rapidly (300>330>360) stop immediately because its mega-lean. One of my builds can cruise wot all day at 360-365 and is perfectly happy. On big hill climbs it will warm up to 375 but the degrees slowly creep up…not rapidly.

[Rob406]

400 is seize territory. Good rule of thumb is to never let it pass 380 and only ever get that hot on constant wot for 10 minutes. However, the speed of which the temps climb is also very telling. If its climbing very rapidly (300>330>360) stop immediately because its mega-lean. One of my builds can cruise wot all day at 360-365 and is perfectly happy. On big hill climbs it will warm up to 375 but the degrees slowly creep up…not rapidly.

Thank you. So are the temps i listed “target temps” i should aim for? Right now the highest i could get temp @ wot was 313. So I want to lean out the main correct? For cruising i am in the 260-270 range if i am on the throttle steady so i think i am good there. Might lean out the needle 1 setting. There are a lot of hills here and it will climb going up a steep incline but nothing that seems alarming. Thoughts?

[Meatball]

If you are not fouling plugs and have crisp throttle response, you’re golden. You could try leaning out the jet and/or needle for better mpg or less smoke but temps are only one indicator when jetting. I have a build thats perfectly jetted and never gets above 310° no matter how much I hammer on it. It depends on what makes the motor happy. Ive even had two identical builds that wanted different jetting.

CVT tuning is just as crucial as jetting. Playing with clutch springs, roller weights, variator shims, contra springs, etc…will unlock performance you didnt know you had. However, Im not sure how much of this stuff is available for the Aero 80.

[Bear45-70]

Don't wanna hurt anyones feeling but that plug looks lean to me and I would go up at least 2 sizes in main jets. Oh and I really don't care who's feelings I hurt.

[motormike]

Don't wanna hurt anyone's feelings but that plug looks lean to me and I would go up at least 2 sizes in main jets. Oh and I really don't care who's feelings I hurt.

First time I see you purposely trying to hurt someone's feelings Bear45-70, moderating action WILL be taken.

[Bear45-70]

Ha,Ha!