Tuning my 1969 750 S fitted with VHB30's.

[Tippie]

But first check your timing marks against correct top dead centre.

 

[Paul Marx]

Simon,

You can play a bit with the points gap to adjust the timing.. Nothing is going to blow up.
Whip the points plate off and enlarge the slots.

Paul

 

[Dellortoman]

is there any other way or retarding the timing slightly?

You don't want to retard the timing, you want to advance it. 2-3? ATDC is already way retarded. Are you sure you have your BTDC and ATDC the right way around? It's easy to get confused sometimes.

 

[piranha-bro2]

Hope you're not getting bamboozled by all the replies. The crank rotates fwd, the points cam backward (when sitting on the bike!). It's quite common for the oil pump drive to be one tooth out either way when it's been reassembled, but the simplest way to get it right is to just widen the slots a tad (for 2 deg that would only be 1 deg on the backing plate!). Be aware that you obviously adjust the points on the main plate first, then the smaller plate fitted onto that for the other cyl). And once you've adjusted the smaller plate, recheck the points gap, because play in the plate can easily affect points gap).

As Paul said, a tad wider or narrower on the points will have no negative effects on engine running.

For triple heads, don't be alarmed by the timing figures - it is correct to set static timing at 0 deg - ie, TDC.

But no doubt, your problems are carb (includes all air-fuel functions, such as inlet stub sealing) related. As an almost universal rule, I've found with later 36mm PHFs, you will generally get the best pickup off idle with the idle mixture screws about turned 1/8 to 1/4 further out than where smoothest idle occurs - ie a smidge richer.

 

[Dellortoman]

I've found with later 36mm PHFs, you will generally get the best pickup off idle with the idle mixture screws about turned 1/8 to 1/4 further out than where smoothest idle occurs - ie a smidge richer.

I've found the same on most Dellorto equipped bikes. My Jota was like that (when it had Dells). My Ducati has 40mm Dells and they're the same. Gotta have it a bit rich on the idle setting for smooth pick-up.

 

[Simon Yates]

Thank you all for the advice.  Back to basics I think.
Firstly, satisfy myself that TDC co-incides with the P/M timing mark.
TDC should equate to the point where the 'saw-cut' mark, P/M and the crank centreline are in a straight line.
If this is all OK, then it is likely that the oil pump drive may be one tooth out of position.
This would explain why the ignition timing screws are at the limit of movement permitted by the slots.
Then either reset the oil pump gears or extend the slots a smidgen.

 

[phil37]

  If you want to do a quick check on the oil pump cog timimg - set motor at TDC and remove the A/R unit - then the bolt and washer holding the A/R carrier to the shaft - the slot for the woodruff key should at 12 o'clock. - regards - Phil

 

[Simon Yates]

Thanks Phil, the keyway was indeed at 12:00.  Slots extended and timing done.
Time for another carb check.