Ducati Scrambler tappet adjustment

[djstedman]

So this is new to me, I'm used to having a threaded valve adjustment for adjusting tappet clearances. What is the proper way to adjust the tappet clearances? Additionally the clearances seem wrong. I was expecting to see .15mm/Intake and .20mm/Exhaust, but instead measured .25mm/Intake and .15mm/Exhaust. Not sure of state of tune, but the cam has the white dot so I expect it to be the standard Scrambler (66') cam.

thanks

Doug

[Jordan]

It's the same principle as with threaded adjusters (which some Ducati singles were fitted with), but to change clearances you use different thickness shims.
The shims are in the form of valve caps.
You need to pull out the rocker spindles to remove and change shims. A spoke or similar can be used for this, threaded into the end of the spindles.
A micrometer is used to find shim thickness, from which the needed size can be calculated.
Shims can be bought (8mm for our singles), although they can be modified by grinding down and lapping as well - not best practice but it usually works.
Have you checked out YouTube and other online resources?
Info on desmodromic type valve adjustment is similar, just ignore the closing shim part, if you don't have desmo.

[djstedman]

Jordan thanks for the speedy reply-

Scrambler motor.jpg

I did watch some videos and I assumed that the cover would have to come off first, so I tried to remove the cover 640/650 in picture. It did not want to come out, I can see that there is a extension that holds the bearing, do I need to remove the cam first? that would see impractical?? This is the part that is tripping me up, so any of the details of removing the rockers spindles would be appreciated.

thanks,

Doug

[Jordan]

Make sure both valves are closed.
Remove 4 screws on cam cover, then rotate the cover until part of it protrudes so you can tap it carefully out of the head.
Some singles have a hollow camshaft. On these you can use a rod through it to help push off the cover.

[DewCatTea-Bob]

____ Perhaps being too-late for Doug now, I then of-course certainly regret submitting my-own response-post at this untimely point,, but the actual fault for the delay was beyond my-own control, as I had (once again) lost internet-access (for about 76-hours, this time) due-to a BAD-weather related occurrence which had happened nearly 2.5-hours before Doug posted this thread !
__ Anyhow, I'll now rather springboard off-from Jordan's response-post.......



[quote= Jordan ...
" You need to pull out the rocker spindles to remove and change shims. "

____ That valve-shim replacement-method is certainly true, but only for DESMO-heads !
There's really no need to go to all that extra troublesome effort for simply changing the shim-caps in springer-heads...
All that normally needs to be done in order to drop the valve & shim-cap down & away from the rocker-arm far enough to create sufficient clearance so as to then be able to simply lift-out the cap (from between the valve-stem & rocker-tip),, is to use a fairly long screwdriver (which has a square-shank - [and not a std.type round-shaft] ),
by placing it's tip-end fully-underneath the ledge that's located directly under the rocker-spindle, and with the flat-side of it's square-shank flatly resting against the spring-tie -(# 160), then press the screwdriver-handle downward until you create the required space-gap (to fit the cap through).
For rather rare instances where the valve, keepers, & spring-tie aren't all inclined to stay rather stuck together,, then in the (sometimes possible) event that the spring-tie tilts & compresses either valve-spring considerably unevenly, then simply rather try levering the spring-tie downward on the other-side of the valve & cap.
__ And in the extra RARE-event that the same excessively uneven spring-compression still occurs also on the other-side as well,, then ya could rather use a pair of screw-drivers, (one on each side), so as to then better control more evenly level spring-compressing.
And if this (USUALLY unnecessary !) method is used, THEN it doesn't matter so much as to what the particular shape of the shank/shafts are (of the chosen pair of screwdrivers).
And also,, if ya happen to have large-boned fingers, then you'll possibly require needle-nose pliers to grab the shim-cap out from between the screwdriver-shafts.
__ For additional details directly associated with this specific topic, see the (old/long-time established) related thread which the following link leads to... viewtopic.php?f=3&t=319&p=2009&#p2009


Hopeful-Cheers,
-Bob

[graeme]

Bob, I have learnt something today so it wasn't a wasted day.....
After only working on Desmos I never even considered your obvious opening shim removal for the non Desmo models. Thanks.
It's like when my battery drill with a screw driver attachment went flat at work and I had to wait for the battery to recharge before I could continue. Then I remembered I used to use screw drivers to undo screws!!!
Terrible how I got sucked in to doing something simple one particular way.

Graeme

[DewCatTea-Bob]

[quote= graeme ...
" I have learnt something today "

____ Perhaps many-others would also do likewise, if they'd bother themselves to read-through some/more of the older/long-established threads !?



" After only working on Desmos I never even considered your obvious opening shim removal for the non Desmo models. "

____ While I self-taught myself the method all on my-own as a teenager, I'm quite sure it was then already long established, (well before the std.DESMO-models were produced) !
__ Try it out, and see if you don't agree that it's a far easier & FASTER and also fairly safe method to much prefer.


Funner-Cheers,
-Bob

[Jordan]

[quote= Jordan ...
" You need to pull out the rocker spindles to remove and change shims. "

____ That valve-shim replacement-method is certainly true, but only for DESMO-heads !
There's really no need to go to all that extra troublesome effort for simply changing the shim-caps in springer-heads...
All that normally needs to be done in order to drop the valve & shim-cap down & away from the rocker-arm far enough to create sufficient clearance so as to then be able to simply lift-out the cap

I guess that would be a quicker way on a non-desmo.