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[Tomshayes]

[Bullet Whisperer]

Hi Tom - A '19' pilot jet?, I would think a 25 to be nearer the mark. Did you take a look at the needle for tiny letters / numbers at the top, to check what type you have?
Regards, Paul.

[Tomshayes]

It's a Mk1 Premium Concentric... Standard is 17...no numbers they're identified by the number of grooves.. The pilot jet identification... You count the rings on the jet.. 1 = 15, 2=17, 3=19, 4=21 & 5=23... Whipped mine out and its a 17 Amal fit Premier pilot jet size 17 as standard.It is suggested where there is difficulty starting or an erratic tick-over a 19 pilot jet is used. So I'm going for a richer 19

[Tomshayes]

Already ordered the 19 so I'll give that a try...

[Tomshayes]

17 Premium is equivalent to 25.... 19 is a 30.

[Tomshayes]

Hi Paul... Been thinking about the cam timing Std cams.. Inlet opens 30 BTDC.. Closes 60 ATDC.. Ex opens 75 BBDC and closes 35 ATDC

Hitchcocks cams. Inlet opens 45 BTDC closes 55 ATDC.. Ex Opens 65 BBDC and closes 50 ATDC

No I've got the performance cams.. Obviously there is 15 degrees difference in the open g times of the inlets which is more or less in line with the 18 degrees difference that one notch makes... Do you reckon its just too much for the performance camto allow enough fuel in?..

Tom

[Bullet Whisperer]

Hi Tom, the inlet timing can play a big part in how an engine will start and run, but usually retarding it is the safer and more productive option to advancing it. I have seen cases where an engine can be ticking over for perhaps 10 or 15 seconds, before a tiny spit back through the carb stops it. Retarding the inlet timing fixed that problem and I believe the cause was the incoming charge was, on occasion, being lit by the residual exhaust charge from the last firing stroke or some sort of 'hot spot', which once the inlet timing was retarded, stopped occurring because there was a little more time for things to cool down before the next incoming charge started entering the cylinder. A later inlet timing also reduces cylinder pressures, which can help high compression engines in many ways, including better power at high engine speeds and less chance of pinking. The timings you quote for your performance cams seem a bit short - I would have expected a later closing figure of around 70 deg. 75 / 35 looks ok for the exhaust, though. I see you have a 3 way pinion, so perhaps you could aim for around 35 / 65 for the inlet timing? Regards, Paul.

[Tomshayes]

Hi Paul

The figures are as supplied with the cams I assume when set up on standard timing... marks...I will try setting as you suggest once I've got carb and ign timing set.

Cheers

Tom

[Tomshayes]

Just done dynamic ignition timing.. It was way out according to strobe... Advanced it up a fair way... Tick over perked right up and no spitting through carb.... Now the timing was initially set statically exactly as per the Pazon instruction sheet... I might now have half a chance of sorting the jetting out and the cam retardation might even work...

Tom

[Bullet Whisperer]

Good news, then, Tom. It will probably run fine with the inlet cam retarded by 1 tooth in this case. Regards, Paul.