Motoscrubs.com

Helping build a 250 up Ser.# DM25089558, a scrambler engine with a "road/race Hot road grind "cam. Because the new cam has less material opposite the lobe than the stock cam the rocker clearance (solid rocker) to the top of the unshimmed winkle cap seems excesive to me. I measure 1.8mm which means to shim it anywhere near where it shouuld be the winkle cap would be barely hanging on to the valve stem. Don't want that coming off! It almost seems to me that that cam requires a longer valve stem or a winkle cap that is longer. Can anyone shed some light on this for us? Thanks

Nice to see someone use an old fashioned term like winkle cap.
Apart from a correct thickness shim (are they available that thick?), a threaded rocker might provide the needed adjustment.

Jordan

I experienced something similar on my 250 desmo. I found different valve stem lengths and even different distances from the valve stem end to the collett ring. Some info down near the end of this page. Look for pics of valves...

http://www.motoscrubs.com/forum/viewtopic.php?f=3&t=459&start=50

Kev

Could you add the existing clearance (1.8mm) to the current shim size (minus the target amount of clearance) to get the necessary shim size and check availability? I think the largest is 4.2mm. You can check availability with Lacey and I understand they are also available from Ducati dealers as they are the same as the 2 valve twins with 8mm valves, or so I have heard. I know that this may not be the proper way to solve this one, but it will give you an idea if you are still in the ball park. If the needed shim size is larger than anything even available then you'll know that a longer valve stem is needed.
-Jim

Thanks for the responses guys. Iv'e never run into this problem before because I've always gone stock cams but I'm going to just shim it up to spec and see how it looks. Threaded adjusters are not an option as the contact angle is way out of line with correct clearances.Machten is there a list of valve stem lenghths that you know of? I would have thought all 250's would be the same. thanks again for the help and heres a pic of my latest project, I know, not Italian but I'll put up with it for runs to the store.

> Threaded adjusters are not an option as the contact angle is way out of line with correct clearances.

Curious - is that a problem?
For longer valves, I'm told blanks can be bought, then machined as needed.

Nice Honda.

Jordan

kevin wrote:Helping build a 250 up Ser.# DM25089558, a scrambler engine with a "road/race Hot road grind "cam. Because the new cam has less material opposite the lobe than the stock cam the rocker clearance (solid rocker) to the top of the unshimmed winkle cap seems excesive to me. I measure 1.8mm which means to shim it anywhere near where it shouuld be the winkle cap would be barely hanging on to the valve stem. Don't want that coming off! It almost seems to me that that cam requires a longer valve stem or a winkle cap that is longer. Can anyone shed some light on this for us? Thanks

____ Seems that you just need to do as most others do when presented with ANY valve-clearance issue... obtain a valve-shim/winkle-cap which will provide the desired clearance.
I've found them anywhere between 60 & 190 thousandths -(1.5 & 4.8mm),
(and the bevel-twins use the same shim-caps!).
__ I believe Monza-type valves (made to work with the screw-adj.rockers), are near 2mm longer, (although all Monza-valves haven't always been exactly the very-same length, varying by 1mm.)
Another possibility is that you might also consider a valve-job at this time, so as to help reduce your more excessive jump in v.clearance.
____ How about providing us with some info on the odd camshaft you've installed !? _ (This kind of info has always been of much interest to me !) _ Do you have the base-circle size ?
How about the valve-lift and timing figures, etc. ?
I have lots of experience with this stuff, and can give you a good idea of what to expect from whatever cam-specs.

____ As for your posted-pic of the 305 Super Hawk,, my-own opinion is that it's about as pertinent here at this w.site, as a Chinese-made moped would be, at a Harley-site,, (sorry to say). _ (IOWs, sorta like finding a noodle in ya'r bowl of premium ice-cream.)


Duke-Cheers,
-Bob

Thanks for the advice, I promise no non Ducati pics in the future.

Oops.

kevin wrote: I promise no non Ducati pics in the future.

____ Well, I-myself could reasonably find pix which INCLUDE non-DUKE bikes, to be acceptable, within whatever pic.shot,, so long as there is also at least something that's DUCATI-Single related, within the view-shot as well. _ So while we really don't wish anything that's ENTIRELY nonDUCATI-related to be posted here at THIS w.site, allowance of INCLUSION of something that's not DUCATI-related is not so obtrusive so as to raise an eyebrow (as your chosen pic did !).
__ Such as this situation has happened to occur once before (with a Brit.single), and I much wanted to put some damper on it but just didn't get-around to posting my non-positive thoughts on the issue before Jim-himself (surprisingly) posted his-own praise on it.
So anyway here in this case, I felt the need to somewhat point-out that we have a weed which ought not be nurtured, before others might begin further petting it into a full-fledged branch of undesired OFF-Topic mater, (which is not supposed to be allowed anyhow).
But even with my previous hinting posted here, I now see that we have still picked-up a new post by one of us who seems openly willing to allow getting the ball rolling towards that undesired direction. _ So whereas before I was commenting on the issue as merely a fellow-member, I now feel that as 'moderator', I ought to more obviously make it clear that we all are expected to reasonably avoid getting off topic with posting any posts (solely) on nonDUCATI-Single related subject-mater !
Hopefully, this added-word will now put the brakes on, ADEQUATELY.
__ If anyone-else cares so much to give praise for the posted non-DUCATI, then PLEASE use our PM-system to do so, (and perhaps learn of whatever w.site the H.305 might be better covered at, if there's any real need to make such praise public).
____ Now to help this-post to be more worthy of posting, I'd like to bring-up that it was the relative success of Honda's '305' series of models that I've heard was the motive for Ducati to produce a 300cc motor of it's own (for the 1964 model-year).
While I've only ever heard of this (certainly likely true) tale from Italian sources, I'd still like to know if anyone-else has ever learned of any evidence for that (quite sensible) intended engine size !?


Dukaddy-DUKEs,
Bob H.