Bevel help - Ducati.ms

vt450scr · Jun 1st, 2011, 10:19 pm

Made the mistake of entering the following as my intro message: My bad.
While I've dealt with Duc bevel top ends since my first real street bike ('65 250 SCR, back in '77), things change, and new info comes along. Any advice would be greatly appreciated. As originally posted:

Hi There...

Getting ready to finally (after almost 30 years ownership) put my 450 SCR on the road. I'll be asking for opinions on various details as I go, seeing as there are many.
I'm about ready to close up the head, having lapped the valves and inspected the associated gear.
I have three different types of valve guide seals at my disposal, all of which were bought back in the day (1980s) as spares. These are:

A. Black (neoprene, I suspect)
B. Green (teflon compound?)
C. Milky white (sure look/feel like silicone)

Which are you're favorite for intake/exhaust, and how do you prefer to lube the valve stems when installing same?

Duccout · Jun 2nd, 2011, 12:28 am

Well, all the early seals were black, then later Ducati began using both the green seals and the white. I seem to recall that the new Ducatis use different colours for inlet and exhaust - maybe someone here knows more. I always use plenty of oil on the stems and a squirt down the guide, although there are specialist engine greases for this job too.

Bevel-Heaven · Jun 2nd, 2011, 12:50 am

I don't know about white caps but the 8mm 2V ones I get from DUCATI which I sell to my customers are black and green - black for intake and green for exhaust.

remery · Jun 2nd, 2011, 4:40 am

Hmm, my '68 350D is smoking a bit (lot!) on startup, I'll have to take you up on some black and green stem seals. Its been a while since I looked in there, will I have to take the head off?

machten · Jun 2nd, 2011, 6:43 am

The desmo singles don't use them. They use an 8x1mm o-ring inside the valve guide. It's not uncommon for these to get a nick in them either at installation or even later on if they get installed with a twist in them.

You have to take the head off to replace them, but it's an easy job. I've got the same problem with my MK3D and will be doing mine in the next few weeks too!

Kev

vt450scr · Jun 2nd, 2011, 6:57 am

Duccout - Thanks for the response. I was wondering if a dab of molybdenum disulfide, along with oil, on the stems would be helpful. My concerns in doing this would be possible deposits on the valve seat (intake) and/or possible seizure of the exhaust valve from the heat cooking same. Decisions, decisions...

Good riding - Cliff

vt450scr · Jun 2nd, 2011, 6:59 am

Thanks Steve.

vt450scr · Jun 2nd, 2011, 7:09 am

Remery - Machten's got you covered. I'll just add that there is the possibility, albeit less likely with a Desmo, that either guide may be worn, but you'd have checked that before replacing the sealing rings.