Grey coloured plug

[HxPaul]

I have a Casa 210.About three months ago I burnt a hole in the piston.I have rebuilt the engine.I did a leak down test and the engine remained without a leak,so I re-fitted engine.Yesterday I went for a run of about 40 miles,when I got home I checked the plug and it was grey in colour.I would like to know if this was rich or weak.

[Mel K]

Weak

[coaster]

Weak

+1, grey is definitely not good

[CHRIS in MARGATE]

Not good. Definitely running weak at some part of the rev range. Exhaust gasket leaking?
Got to richen it up to just below the point it starts 4 stroking on you.

[MickYork]

ignition too far advanced, jetting/carb' issue ?

Air leak caused by heat expansion/fine when cold........unlikely, but still a possibility.

[coaster]

Did you re-torque your head after a hundred or so miles?

[HxPaul]

Thanks for the answers.I've re-jetted the carb and put a richer needle in,I'm going for a ride,so I will see how it goes.

[Mel K]

Best of luck

[HxPaul]

Went out for a ride with new settings.The plug is a black to deep brown colour,which means the scooter is running rich(safe)I'll alter the jettings till I get a nice chocolate brown colour on the plug.Thanks for all the advice.

[HxPaul]

Back to grey plug colour again,dont know what to look for now.I've done a leakdown test,checked the timing,17 degrees before tdc.Changed spark plug,plug lead,cdi and carb.I usually use a dellorto phbl 25 carb with-main jet 98,pilot jet 47,atomiser aq 268, needle d29 on top clip,choke jet 60.Tried it with a scootopia sh2/22 with same result.It feels like its running rich with 4 stroking but when I get back from a run,which is usually about 10 miles,and check spark plug colour its always grey.By the way the carb is a rubber mount with a new rubber connector.

[CHRIS in MARGATE]

You will need to do plug chops at 4 throttle openings.

When the engine is warm, what happens when you put the choke on? It should be too rich and stall. If it doesn't then you have a problem.

[Scooterdude]

Looks to me like your carb set up is all to cock with the PHBL25, seems to be to rich on the atomiser but to lean elsewhere hence why you were getting a black plug but then chocolate brown then grey.

Try an aq266 atomiser with a d22 needle, a 50-52 pilot and a 105-110 main jet (or maybe even a 112-115) but as has been said above plug chops at ALL throttle positions, easiest to put masking tape around throttle and mark up the positions then find a long gradual incline to do the plug chops.

[HxPaul]

Thanks for the reply's.