Valve Guide wear.

bobnorton · Post by **bobnorton** » Mon Jan 03, 2011 12:33 pm

Guide wear is apparently an issue with these motors, I am considering a change to cast iron guides and chrome stem valves, any one with any thoughts on the subject?.

Ray O'Donohue · Post by **Ray O'Donohue** » Mon Jan 03, 2011 12:41 pm

I'll be curious to see what folks say re iron guides. I don't think you can beat a properly fitted bronze guide at about nil+ clearance,sealed or un-sealed.Bronze guides are said to be somehow "self lubricating".

Ray O'Donohue · Post by **Ray O'Donohue** » Mon Jan 03, 2011 12:41 pm

I'll be curious to see what folks say re iron guides. I don't think you can beat a properly fitted bronze guide at about nil+ clearance,sealed or un-sealed.Bronze guides are said to be somehow "self lubricating".

Ray O'Donohue · Post by **Ray O'Donohue** » Mon Jan 03, 2011 12:41 pm

I'll be curious to see what folks say re iron guides. I don't think you can beat a properly fitted bronze guide at about nil+ clearance,sealed or un-sealed.Bronze guides are said to be somehow "self lubricating".

sevicke · Post by **sevicke** » Mon Jan 03, 2011 6:19 pm

cylinder heads will be the least of your problems, with one of these don't worry about things that havn't happened.

wdietz186 · Post by **wdietz186** » Mon Jan 03, 2011 8:20 pm

You need to fit some good quality silicon/bronze guides not the recycled butter type that Ducati supplied. Here in the states a company named Kibblewhite Precision make an excellent guide and valves to go with them but I don't know if anyone in the UK carries them. Something from air cooled Porsches might be adaptable if you have access to a lathe or a patient machinist friend.

bobnorton · Post by **bobnorton** » Tue Jan 04, 2011 12:13 am

Cast iron barely needs any lube at all, I think bronze is favoured as its easy to machine and more forgiving if a valve is hit.I understand that the cast/chrome combination is hardwearing , I dont think the head was designed for adjusters ,maybe shim type rockers would give better action.Iron guides will also need a tighter fit in the head.I only intend to build this motor once so i'm hoping to cover all the weak points.Hi Ray, glad i'm not the only one who F----ks up the posts!!.How does one delete???.

wdietz186 · Post by **wdietz186** » Tue Jan 04, 2011 6:41 pm

Bob, The purchase area in the head for the guide is pretty small and I think problems might arise due to expansion rate differences. I've had Kibblewhite guides in my 750 GT for about 20k mi. and last I checked the wear isn't noticable. The originals lasted about 4k. The inherent problem with the guides is they are really too short for proper support and the spring engines wear them more quickly I guess because of oscillations and side loads being greater than in the desmos. Properly set up I think you will be ok with good quality bronze guides.

sevicke · Post by **sevicke** » Fri Jan 07, 2011 10:22 pm

"quote: I only intend to build this motor once so i'm hoping to cover all the weak points

good luck on that one LOL that so funny hahahahha best joke Ive heard in a long while.

bobnorton · Post by **bobnorton** » Sat Jan 08, 2011 3:18 am

We will see!! , other classics i built are still up and running after 20 years light use , I have to agree that bevels are needy beasts, however the weak points are well known and these bikes are cosseted and not abused ,my 250 took ages to sort out all the problems caused by others mistakes but now starts and goes like a rocket , Rita ignition, good oil, carefull use and crossed fingers!!.

machten · Post by **machten** » Sat Jan 08, 2011 6:32 am

I only intend to build this motor once so i'm hoping to cover all the weak points

good luck on that one LOL that so funny hahahahha best joke Ive heard in a long while.

As a Duc owner of some 32 years I don't see anything at all wrong or funny with Bob's approach to researching options, particulary to adding to engine life using newer technology. Improvements in metallurgy alone are good reason to use a modern bottom end as opposed to an original Ducati part, for example. These engines are expensive to rebuild. If the service life might be extended, surely that's worth thinking about?

The approach of innovatingly eliminating the factory weak points and improvement of inital factory engineering are two of the key factors that led to Phil Schilling and Cook Neilson's privateer triumph at Daytona in 1977.

'nuff said, I reckon.

Kev

abmartin · Post by **abmartin** » Sat Jan 08, 2011 8:29 am

My SS has never been apart and I've only ever taken one cylinder head off because of my own foolishness. In all, for a bike that gets used every year, I've had very few problems in my 26 years of ownership.

It probably is time for new valve seals and possibly guides though. Its drooling a bit through the exhaust port and the oil level is dropping more quickly than I like to see.

Bruce

Steve Foster · Post by **Steve Foster** » Mon Jan 10, 2011 2:34 pm

Here in the states a company named Kibblewhite Precision make an excellent guide and valves to go with them but I don't know if anyone in the UK carries them.

Doesn't look like they have a UK distributor. See:
http://www.kpmivalvetrain.com/distribut ... ocator_top

I'm now interested in getting some of the Kibblewhite 750 GT guides myself. See (copy the link as I can't seem to get the last bit included in the URL):
http://valvetrain.kpmivalvetrain.com/vi ... |1065|1066

The Kibblewhite catalogue shows no difference between intake and exhaust guides for the 750 GT, but the factory parts catalogue gives different numbers for intake (0755.92.393 standard size for later engines) and exhaust (0755.92.413). (Same part numbers for the 860 GT.)

Based on wdietz186's positive experience with the Kibblewhite guides I assume that any difference between the intake and exhaust guides is insignificant, but I'm curious to know why there are different parts listed in the factory catalogue. Can anyone shed some light on this?

Thanks,
Steve.

wdietz186 · Post by **wdietz186** » Mon Jan 10, 2011 6:18 pm

My recollection of the factory guides is the exhaust guide was a bit shorter and didn't have a taper at the end like the intakes. The last thing the springer heads need is shorter guides.

Ray O'Donohue · Post by **Ray O'Donohue** » Tue Jan 11, 2011 6:08 am

Changing the subject just a bit,here is a related suggestion: whatever guides are used,paint a sealant into/onto the guide-rocker box juction of the guide bore. I have seen well built engines suck oil down the outside of the guide bores and smoke like crazy.(Easy to fix,once you find the cause,but a pain in the butt..) The short guide bore of the Ducati is quite prone to this,as is any engine which has had the guide removed by coarse methods.