My list #4777-4 gives the factory setup for my 650DP as 67 / 73 - 6.5 PV - 28 squirters

In the search for 11's I went as far up as 74 /73, #31 squirters , 3.5 PV (which we found with help of NOS) but I ended up with black sooty looking plugs - and car generally ran and smelled rich

we always felt that earlier poor performance was really inadequate carb and not the actual sticking distributor advance which we ultimately fixed

so I tried to go back to near stock setup to see if car would react better on the plugs now

re jetted down to 68 / 74, 6.5 PV, 50 cc primary pump conversion gives me an off idle flat spot but then it revs cleaner after 2000 rpm than before -

I have even tried #37 squirter in front and left #31 behind

Still flat spots - where should I go from here back up to where it was - like maybe 73 / 74 jets

what do you think??
thanks for any help

Trevor

yeah,maybe even 72's all around also make sure your accelerator pump linkage is set up with .015 clearance at wot with the pump arm pushed all the way down,correct float level,and mixture set for highest vaccum(idle if you don't have a gauge)- about 1/8-1/4turn.

Thanks

Trevor

The 50cc pump is overkill - you don't need it. 30cc with the stock cams and squirters is where I would start.

Sounds like you have some awefull big squirters in there - you could have a rich stumble. I'd try a much smaller squirter like a number 28 or 31 and see what happens.

Thanks for the tips

I went with 73/74 jets - #37 front/#31 back squirter - back to 3.5 PV and put the 50cc pump on the secondary side -

the pump conversion was a take off from another DP - it came with the plastic arm - it was on the secondary side but I tried to put it on the primary side - but since I got the flat spot I took it off

are they interchageable?? - the arm seems to be capable of working either side

carb is working now quite strong in my view - no flatspots at all and revs cleaner

but I still feel a 72 / 73 jetting might be better overall !!

will keep you posted

Just run it at the track and watch your MPH when you change jets. If MPH goes up when you increase jet size keep going up - if MPH goes down try decreasing jet size until MPH stops climbing.

The factory jet sizes are usually pretty close unless the carb is oversized, undersized, or altitude is significantly > sea level. If there is something weird with the combo like restrictive exhaust, tall spacers, etc it will throw you off too.