I have my suspicions, but.......

[RickR90s]

While re-doing the top end on my R90s, I of course have the heads off for de-carboning. Heads were completely gone through about 5 years ago. New exhaust valves, new springs, retainers and a 3 stage valve job.

So I get most of the carbon off with careful scraping and remember what my late brother (who was a pilot and jet engine mechanic) told me about Chevron fuel injection cleaner. It apparently contains Techron, known to loosen/dissolve carbon.

So I take one of the heads, turn it over and fill the combusion chamber to let it soak over-night. (Valves are completely assembled with attached springs) I figger it will take some of the last few desposits off.

but in the morning, I see that the chamber is dry and the F.I. cleaner is now occuping the intake port area, apparently having leaked through the closed valve.

So am I looking at another valve job?

These heads were really coked with oil/carbon so I wouldn't be surprised.

thanks,

RickR90s

[Garnet]

Being a glass half full kinda a guy, I would hope that maybe the valve seat and/or the seating area of the intake valve is carboned up enough to allow the cleaner to leak through. Also keep in mind that a petroleum based liquid will leak through a tiny crack that water would not go through.

Edit: to correct some of the spelling errors.

[mattcfish]

While re-doing the top end on my R90s, I of course have the heads off for de-carboning. Heads were completely gone through about 5 years ago. New exhaust valves, new springs, retainers and a 3 stage valve job.

So I get most of the carbon off with careful scraping and remember what my late brother (who was a pilot and jet engine mechanic) told me about Chevron fuel injection cleaner. It apparently contains Techron, known to loosen/dissolve carbon.

So I take one of the heads, turn it over and fill the combusion chamber to let it soak over-night. (Valves are completely assembled with attached springs) I figger it will take some of the last few desposits off.

but in the morning, I see that the chamber is dry and the F.I. cleaner is now occuping the intake port area, apparently having leaked through the closed valve.

So am I looking at another valve job?

These heads were really coked with oil/carbon so I wouldn't be surprised.

thanks,

RickR90s

You probably only need to lap the valve a little.

[Motorhead]

Mark Degroff is my guy for head work

If the heads were processed with national city

[2valve]

hi to all, hey Rick whats the go with the 3 stage valve job ,what does it involve ? have you any links / pictures / specs for the job to get done ,anything at all would be very usefull , i wouldnt mind learning more about this. thanks

[RickR90s]

thanks guys, I did pull one of the intakes and there is small bits of carbon, oil coking on the face of the valve and seat. So I'm going to have my local head guy do a quick lap and take it from there. I had Leo Goff (Memphis Motorwerks) last do my heads and no issues or complaints. In fact, the light porting he did really opened up the mid-range (where I spend most of my time anyway) so I'm thinking (like y'all) that' a light valve job will go nicely with the 1st overbore and new pistons.

RPG