Cam timing

[Dave450]

Eldert, Nigel - many thanks for your replies. I also thought the timing was out when I looked at it but I wanted to hear from you guys as to how significant this was and what, if anything, I might do. I will let you know how I get on!

Dave

[Bevel bob]

This has got me checking cam timings, spent a couple of hours with a single expert who tells me i have a full race cam in my roadrider NC mark 3. No wonder it was happiest at megga revs. Now on the lookout for a green white,or grey white/red.Also looking to swap the 29SSi for a 27.Much more sensible for those impromptu off road excursions into the greenery. the readings i got make little sense to me ,in 70--90,ex 75--72, valve clearance 7 thou both,checked to point lash caps stick.Does anyone recognise this cam from the figures?.

[DewCatTea-Bob]

[quote= Bevel bob ...
"spent a couple of hours with a single expert who tells me i have a full race cam in my roadrider NC mark 3. "

____ So exactly what is your experts explanation of what a "full race cam" actually is ? _ Some aftermarket regrind-affair, or what ?
Can you please post a picture of your odd cam ?



" the readings i got make little sense to me ,in 70--90,ex 75--72, valve clearance 7 thou both,checked to point lash caps stick. "

____ Why did you choose to take your readings with .007" lash valve-clearance ?
If your unknown cam has clearance-ramps, then your set lash is probably including that part of the cam-lobe as well, (which doesn't count).
Eldert or someone may recognize the results of readings taken with 1mm-lash/gap.


" Does anyone recognise this cam from the figures?. "

____ Those figures aren't the exact-same as any stock-cam but come close to that of a Green&White F1-camshaft. _ (With a .3 or .4mm offset-key, your cam could then be advanced enough to bring it's figures in-line with that of the 250F1-cam's official-specs.
You should try taking your readings again, with a tad little more set lash/clearance.



" Now on the lookout for a green white,or grey white/red. "

____ With fair confidence, I can say that you don't want either of the G&W.cams, but a Gray-cam or a Red-cam or even a w-c.White-cam may suit your needs quite well enough.


Duke-Cheers,
-Bob

[Bevel bob]

Hi Bob, As i dont have alternative shim caps setting up different clearances was not an easy option. From what you say it appears that you are of the same opinion as my pal. As my bike was built from the remains of a racer its likely that the cam was re-used . Some years ago I thought the cam might be a Greenwhite and checked the lift which was well less than would be expected for a GW. We are thinking now that its possibly a well worn race grind thats been tidied up.I am getting carb blowback at medium revs which is making it difficult to get the bike to run cleanly.Going to try a different exhaust next.

[DewCatTea-Bob]

[quote= Bevel bob ...
" Some years ago I thought the cam might be a Greenwhite and checked the lift which was well less than would be expected for a GW. "

____ The lift of the two G&W.cam-models is close to the same... near 10mm for the intake and near 8.5mm for the exhaust.
__ What did you find your lifts to be ?


Duke-Cheers,
-Bob

[LaceyDucati]

Bob (Bevel!)
Unless you use the Factory checking clearances specified the figures will be quite a way out against the factory figures.

I could believe that cam could be a Ducati road cam even a G/W. Incorrect clearances and things like slack bevels or couplings can give figures a long way off. Also the cam may be out either advanced or retarded, my guess is yours is possibly retarded. Most Genuine Ducati cams are easily identified out of the bike by simple measurement.

Those timing figures are a long way short of most "race" cams for duration. Race cams are usually not quoted at initial lift and therefore the figures are not comparable to factory figures. If it's got less lift than a G/W then It's unlikely to be a "race" cam.

If you fill the gaps with feeler gauges (zero clearance) and give me 1mm lift figures and either lift at the valve or as measured at the cam, I may be able to shed some light on it. Otherwise you will need to get some smaller shims to set the factory clearances for checking to give comparison. If you use small shims to give the widest factory checking clearances, you can then "frig" the clearance using feeler gauges to provide the equivalent other factory clearances. That way you can check for all the factory cams with there correct checking clearances.

Regards Nigel

[Bevel bob]

Hi Nigel, I think i will try it your way,(with zero clearance) , thanks for your kind offer,My pal has a tool that locks into the crank notch,mounts a disc, and gives a large hexagon to turn the motor accurately with the case on. Also a good piston stop . No backlash on my gears!!.

[Dave450]

2nd update on 450 cam timing:

I had a chance to give the 450 a road test after altering the cam timing as suggested above. This is a 'seat of the pants' impression rather than scientific, because access to a dyno here is not easy. Ignition timing and carburation were not altered from their previous settings and no other changes were made. Acceleration does seem crisper. The mid-range was good anyway but it now feels better. I haven't yet been able to do some full throttle, 5th gear runs but it accelerates nicely through the gears. My initial impression is that, yes, it was a worthwhile exercise. I'd like to see how it performs on a track day with a race pipe and the altered cam timing, since the Conti replica silencer takes the edge off the top end and fattens the mid-range. This is good, though, because a flexible motor with a bit of an edge to it is what I want for the road.

Nigel, Eldert - I appreciate your advice, thanks!

Dave