Vento 350

[machten]

And I've used the same in bevel twins ... and to great effect too. The key's for twins are available in 2, 4 and 6 degrees. The cam timing from the factory for bevel twins was specified as being +/- 5 degrees. I have a 750 Sport that was -6 on the rear and +5 on the front. Fixing that timing transformed the performance (and sound) of the bike.

Kev

[DewCatTea-Bob]

" And I've used the same in bevel twins ...
The key's for twins are available in 2, 4 and 6 degrees. "

____ You didn't mention if they're the same size to also fit within Duke-single camshafts as well.
__ Since their designations are given in 'degrees' rather than spacial-offset, then the amount of 'degrees' altered, would vary depending on the shaft's circumference. _ So-therefore if the L-twin camshaft's shaft is larger in diameter (where the key is fitted), then if employed within a smaller Duke-Single camshaft, the exact amount of altered degrees would then become larger !


Dukaddy-DUKEs,
-Bob

[graeme]

Hello Bob,
A bevel twin cam has a 3mm key way.
A bevel twin cam (imola in this case, but the same dimensions as SS Darmah, etc) has a shaft diameter of 15mm. A single has a shaft diameter of 15mm also.
So lucky for you Muz, you should be able to obtain an offset key.
Woohoo!

Graeme

picture, top to bottom. single Desmo, twin bevel, Pantah type (later rear cam backwards type in this picture)

[Muzz350]

Thanks for your time and imput guys. Its all sounding easier to fix and I tracked down some offset keys for a single. Can I have a recomended number of degrees and confirm for my peace of mind which way the scrambler cam is going? Looking at the cam from the left hand end is retarding a few degrees moving the cam clockwise and advancing the cam anticlockwise?
I could refit the cam and degree wheel it if necessary.

Muz

[graeme]

I would fit a degree wheel and a piston stop to be sure of tdc.
Then note how many degrees the cam is out, either advance or retard, using a dial indicator.
Bob has given the timing for a scrambler cam, i think. If not I'm sure he will. (Deg btdc open, atdc close, etc)
That will give you the amount of degrees the key way (cam) is out in relation to the piston. Reading the degree wheel.
Then that is the offset key required.
Fit it one way to advance or the opposite way to retard.

(works in my head, anyway)

Graeme

[Muzz350]

Thanks Graeme.
I had already refitted the Vento cam so I could ride the bike so I'll look at where (as Bob mentioned) the overlap-center point is and then look at the scr cam and adjust to suit. I will also check the crankshaft timing marks bottom end. I don't remember there being 2 dots to choose from on the bevel gear but I'd better check that as well.
Muz

[DewCatTea-Bob]

Hello Bob,
A bevel twin cam has a 3mm key way.
A bevel twin cam
has a shaft diameter of 15mm. A single has a shaft diameter of 15mm also.

____ Thanks for the useful info Graeme !
__ So now we know that offset-key designations can be left in 'degrees' without any conversion required.

Stay-Tuned,
-Bob

[DewCatTea-Bob]

By: Muzz350...
" Can I have a recomended number of degrees and confirm for my peace of mind which way the scrambler cam is going? "

____ The number of degrees that your Scr.cam seems to be retarded from the crankshaft's (advanced) position is 17-degrees.
Thus the valve-timing you had (which allowed the piston to contact the ex.valve), should've been
intake = 10BT to 92AB & exhaust = 43BB to 49AT
which is way too far retarded.
__ So (as I've already indicated on the previous page), the Scr.cam must be rotated (about) 17-degrees forward (without the tower-shaft turning along-with),, so as to advance the camshaft with respect to the tower-shaft & crankshaft.



" Looking at the cam from the left hand end is retarding a few degrees moving the cam clockwise and advancing the cam anticlockwise? "

____ Yes, of-course,, but, to avoid confusion, you should always look at the camshaft from it's RIGHT-side end, because that's the same side where the clockwise-turning camshaft-gear is located.



" I could refit the cam and degree wheel it if necessary. "

____ I'm sure that that job won't be NECESSARY.



Hopeful-Cheers,
-Bob

[DewCatTea-Bob]

By: graeme...
" I would fit a degree wheel and a piston stop to be sure of tdc.
Then note how many degrees the cam is out, either advance or retard, using a dial indicator. "

____ This work should not be REQUIRED to be done, but it would be good for confirming the expected cam.model.



" Bob has given the timing for a scrambler cam, i think. "

____ Actually Muz-himself was the last to post the stock valve-timing figures for the Scr.cam,, and (also on THAT page), I had posted the resulting valve-timing if Muz were to chose to merely reset just the upper bevel-gearing.
So anyhow, Muz is thus already aware of the timing-specs expected for the Scr.cam.



" That will give you the amount of degrees the key way (cam) is out in relation to the piston. Reading the degree wheel. "

____ Yes, indeed that would but,, as I've already indicated, the tower-shaft is most-likely 1-tooth (of the crankshaft bevel-gear) out of (normal) time-sync with the crankshaft, and that single tooth advances the crankshaft 17-degrees !



" Then that is the offset key required. "

____ So-then the offset-key needs to be good for 8 or 9 degrees of cam-rotation. _ However I suspect that the offset designation actually rather references the crankshaft's rotation in degrees,, so then (as it seems), it's unlikely that a '17-degree' offset-key is available.
So that would thus-then leave us back where we were before the possible use of offset-keys was considered to completely resolve the issue.



" Fit it one way to advance or the opposite way to retard. "

____ Right but, in this case Muz would certainly not wish to 'retard' it any further, (as he wouldn't want to actually damage the valve-train, (not to mention the piston).


Hopeful-Cheers,
-Bob

[DewCatTea-Bob]

By: Muzz350...
" I had already refitted the Vento cam so I could ride the bike "

____ Too bad that you hadn't kept us constantly updated with your progression-steps before you jumped-ahead & reinstalled your Vento-cam,, cuz then/otherwise, you little-doubt would've already had the Scr.cam properly installed now, instead.
__ Since you have the Vento-cam back-in, you should take advantage of the opportunity to take & test-out it's power-characteristics by getting yourself better acquainted with it's capabilities against repeatable test-outs.
Such a good measure would best be to run your Vento against another well matched bike & rider. ...
Roll-on test-run comparisons should be carried-out not only at high-RPM (as most riders merely do), but also at mid-range -(about 5500-RPM), and low-end -(about 3000-RPM).
For "roll-on" testing, you simply pick a speed & gear which yields the chosen test-RPM, then you & your rider-opponent grab full-throttle and take-note of the speed reached when one pulls-away from the other.
That way, after you've finally installed the Scr.cam (and test-run again), you will then be able to much better determine the pros & cons of the two very-different cam.models' performance-variances !



" so I'll look at where
the overlap-center point is and then look at the scr cam and adjust to suit. "

____ That procedure really shouldn't be a necessary step, (as the bevel-timing correction which I've already well covered should provide the same result).
__ On a regular/std.camshaft, the overlap center-point is EXACTLY 180-degrees opposite from the keyway-slot !
So if all is I've expected, then the Vento-cam's k.slot should be located near 8.6-degrees (counterclockwise-around the shaft) from the REGULAR k.slot TDC.location (of a nonVento-camshaft) !
However, that's assuming that the Vento-camshaft bevel-gear is the very-same as any other standardly-marked cam.gear, and not with an altered timing-dot location (as the Vento crankshaft bevel-gear has).



" I will also check the crankshaft timing marks bottom end. I don't remember there being 2 dots to choose from on the bevel gear "

____ I'd expect that there would be only one timing-mark/dot on the crankshaft bevel-gear for a Vento-engine stock with a Vento-camshaft.
__ The timing-dot is normally located right at the 12-o'clock position, when at TDC, (for regular-type camshafts). _ But in the Vento's case, the t.dot would be located more towards 11-o'clock.


Hopeful-Cheers,
DCT-Bob