plugs

Post by **les** » Tue Mar 02, 2004 9:00 pm

Not sure what to make of this; thought I'd start a service on the pick-up to-nite and when I got to the plugs noticed that number 1 & 2 were blackish, (rich) number 3 & 4 greyish (weak) I did a compression test, 1 & 2 were 190. 3 & 4 were 180. (Standard 1098cc engine) I'd like your opinions!

Post by **Cam** » Tue Mar 02, 2004 9:53 pm

Could be an air leak on the rear inlet manifold to head port leaning the mixture out on cylinders 3&4.

Post by **les** » Wed Mar 03, 2004 7:28 pm

Thanx Cam, that thought was mentioned at work today. Will squirt some petrol in that area to see if the revs rise, might give me a clue.

Post by **catsoup** » Tue Mar 09, 2004 1:26 pm

You sure the blackish colour is due to rich mixture ? It could be oil fouling from it leaking past the valve oil seals.

Post by **les** » Tue Mar 09, 2004 8:37 pm

It's possible I suppose, although I replaced the seals along with the engine rebuild maybe 12000 miles ago. I fitted a new exhaust/inlet gasket Saturday and have yet to check plugs etc again. Noticed that the pipe from carb to oil separator was pretty choked which may not help.

Post by **Kevin** » Wed Mar 10, 2004 8:43 am

Les normally if its oil fouling the plugs have a different look to them, they look more gummy, whereas mixture problems will give a sooty deposit which sounds more like your plugs, have you checked your mixture using Willies simple method, your compression`s are rather good as it should be with a recent rebuild so I would think it unlikely the problem is with the engine. Have you given it a good run or is it just used around town as I have found with town running plugs ect are not always as they should be but after a quick blast all is OK.

Post by **les** » Wed Mar 10, 2004 9:24 pm

Kevin, I would say the plugs were more towards sooty, I initially set the mixture with colourtune so felt reasonably happy with that, but for conformation I will try lifting the piston, although the mystery was having two plugs blackish and the other two greyish. I replaced the inlet gasket as suggested in case of an air leak. I do mostly town work but am able to open up from time to time! Incidently if I park near a wall (side exit exhaust) and start up, I always leave a sooty deposit on the wall, or whatever I park near, come to that!