You'd be surprised just how far into the throttle opening that the progression circuit can cause problems on small engines.

If you raise the revs slowly do you get this problem? if so it doesn't really seem like the accelerator pump is causing it anymore.

have you put the original large jets back in?
do you have the choke connected? if so when you are felling the loss of power try pulling the choke on a little, if it seems to cure the problem you are running lean for some reason.

Do you have vacuum advance hooked up? if so check that the points earth is properly connected. You may find that there is a bad connection whilst the points base plate is going through the advance phase.

Make sure all the jet holders are tightend firmly, but not over tightened.

Still sounds like the progression circuit to me though.

MLS thanks heaps for your help so far much apriciated.

Yesterday I went and bought some drill bits and made some dodgy solder jets 120 size (was 110) and the difference was amazing the car was actually driveable with only a little flat spot so I made the jets into 125's the flat spot has gone away a bit more but it was now running slightly rich so I changed the emulsion tubes from 7772.6 to 7772.8 and now it dosnt have hardly any flat spot but its still there.

I checked the progression drillings I think someone said there should be 2 or 3 holes mine has 5 holes they dont look damaged and it dosent look like someone has put extra holes in So I dont know if thats the norm !

I think the pump jets might be causing the little flat spot.


I will check the things you posted today MLS

Thanks everyone

Hi

Check this site for a jetting program

Dave`s Homepage

OK things are better now, I have reasearched my ass off and found out so much info its not funny.

MLS u were right about the progression being too lean so the idol jets are now 65's
The idol air correctors cant be changed on my particular carb but you can alter the amount of air by putting sleeves in the air bleed holes (1.2mm hole = 7850.? forgot will edit soon)(not yet done hence the 65 idol jets) CSC done this for me but did it wrong the holes are too big so i got to re do it (maybe I should send it back?).

So anyway runs allot better still needs bigger pump jets and maybe main jets just have to wait and see.

The new problem now is I cant get full throttle I spent a whole day trying to but could only get a little more throw on the linkage kit, probably now the throttle opens only 66 degrees (guestimate). I want full throttle!
It seem as if the accelerator dosent have enough throw to open the butterfly the full 90 degrees, I have shortened the outer casing of the cable moved the position on the swing arm and lengthened the rod as far as i can

what else is there to do put a hole in the floor so i can put my foot down further! lol no I wont do that please help

thanks

Sounds like your lever lengths are not suited to the accelerator pedal of the datsun.

If you can shorten the distance between where the throttle arm on the carby bolts to the carby and that of where the throttle linkage bolts you will solve your problem.

This means that the arc distance required to get to full throttle is less.

Is you look at the top of your accelerator pedal when you push it to the floor you will see that where the cable connects is only moving about 50mm (more or less), that means that you only have a 50mm arc length available to you at the carby.

using the calculation (pi)D=C to find the circumference of a circle you can work out the maximum throttle arm length to use on your carby.

We know that you need to rotate the arm approx 90 degress to get full throttle and we have 50mm arc length available for that.

so that means arm length = ((50*4)/(pi))/2 = about 31mm, make sure you actually have 50mm travel at the top of the pedal, if not just insert the actual measurement into the equation.

sorry about the long post but this sort of fiddly stuff is always tricky to explain.

hope all this makes sense to you and let us know how you go.

731200, did you get a chance to fix your throttle linkage problems today?

I broke the swivel cable bolt thing that goes on the linkage arm I got to get one from the fastner shop then I can try again. I did 2unit maths so I fully under stand that very well explained solution.
Thanks once again.