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3 Plugs Black One Grey !

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#1 Minitransition

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Posted 16 May 2018 - 03:49 PM

So - after a few hundred miles of running the 998 auto - just having a look around and checking all is well. Leaks, mixture, odd rattle etc. Plug no 1 is perfect grey and brown, mixture about right I thought. Remainder are all black and a bit sooty.

 

So - if one is right the mixture is right ?? yes??

 

How do I tell if it is over rich or oil burning? No signs of smoke from exhaust.

 

Anyone else had this odd experience?

 

Thanks...

 

 



#2 CityEPete

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Posted 16 May 2018 - 04:29 PM

Vale clearances all correct?

#3 Mervyn

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Posted 16 May 2018 - 04:32 PM

I'd say it's running rich and one cylinder is burning water

Merv

#4 Minitransition

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Posted 16 May 2018 - 04:49 PM

Thanks, can check valves, are you thinking cylinder 1 is wrong or cylinders 2 - 4 ?

 

No water loss over 300 miles so hopefully head is good. It was a new head at rebuild.



#5 CityEPete

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Posted 16 May 2018 - 06:14 PM

Hard to say, needs to be the first thing you check anyway before altering any tuning, you might find one too tight or too loose or three too tight or too loose, get them all right and the same then see how the plugs look after a few runs out.

#6 Minitransition

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Posted 18 May 2018 - 05:09 PM

so - tested compression, all around 170psi. Checked tappets - all fine. Put in colortune and mixture looked a bit rich but same all cylinders. Weakened mixture to get blue burn with orange when revved up. 

 

May be an oil control ring?? Have soaked overnight with reddex in bores and will report back !



#7 MIGLIACARS

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Posted 19 May 2018 - 12:56 PM

try 4 new plugs and leads and start from there







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