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choke sizes on 1700 x/flow

Graham Howard

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I have just rebuilt my 1700 x flow, which apart from forged pistons with 10.5:1 cr is in in fairly standard spec.


The previous owner of this engine upgraded it from a 1600, but I have noticed that it still has 30 mm chokes fitted.


When it is run in I intend to go for a rolling road session to get it properly set up. All the information I have indicates I should be running 32 mm chokes.


In the period before the rr sesion I want to make sure I am running safe jetting.


The current set up is:

main jet 120

Air corrector 165

Emulsion Tube F16

Idle 50F9

Choke 30 mm


From Dave Andrews web site the indication is that I would need to go to 130 main jets.


Can anybody tell me what jetting they are running on their 1700 x-flow so that I can be in the right ball park if I fit 32 mm chokes.





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My Seven was a 1600 and was upgraded to 1700cc Supersprint spec (234 cam) prior to me buying it.

I had to change a shed load of bits to finish the job. 32mm chokes were on the list.

I am looking at the receipt for the rolling road session afterwards and it needed the following:


F16 Tubes

130 Mains

155 Airs

Idle 50F9


Hope this helps




www.Se7en-Up.co.uk id=limegreen>



Edited by - steve motts on 17 Feb 2002 21:38:52

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A Supersprint with forged pistons (I am assuming that this is what you now have, rather than a completely standard engine) will benefit from 34mm chokes.


Your current jetting is for a standard Supersprint, but you have chokes that are 30mm instead of 32mm. You are therefore likely to be running rich at the bottom end at the moment. Supersprints tend to be jetted too weak at higher revs, so you may find you are about right here.


Try this:-


Choke 34mm

Main 130

ET F16

Air 140

Idle 50F9

Pump 35


Bear in mind that the main jetting is determined more by choke size than engine type, so if you run a smaller choke, lots of other things will need to change from the above suggestions.


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