first venture into jetting 14 bing

Hello all ! Just hoping i can think aloud here and make sure im doing the right things !

some info first

1971 Puch 14mm bing stock airbox stock exhaust 30 mph uk model . carb has a 68 jet bike runs well and often edges over 30 .

Just brought a big bag of jets 62 all the way to 86 from puch shop just fitted a bi turbo pipe and a spare stock but trimmed larger hole airbox.

68 jet = bike lumpy power delivery bike edges over 30 depending on the road condition.

70 jet = pulls way smoother but 30mph is like hitting a spluttery wall patches of 4 stroking.

my next thought is to go back to 68 and drop the needle to the bottom.

(just a note even though the jets are new the 68 in the new looks bigger than the old 68 i have ?!?)

any thoughts guidence or advice ? first time playing with this .

Re: first venture into jetting 14 bing

air filter will make a huge difference, if you've already got a 68 in there you are probably good with the pipe

where the airbox goes into the frame , you can cut that all open into a big hole, then it should run well with a 70 and gain some speed. it might still be good with the 68, that is a awfully huge jet for a stock puch.

also be sure to check your points and timing, you can increase point gap to the large side of the spec (gap closes as the points wear out) and you might see some performance gain.

and ditch your stock head gasket, if you haven't already, just clean both surfaces and re-torque with no gasket in there.

those mods should get you to a solid 35, you can tweak clutch, gearing, etc from there.

Re: first venture into jetting 14 bing

supermoto lew /

perfect thanks Graham some good things to do there.

so my modified airbox i did exactly that cut the frame part off to make 1 big hole put the 70 in and did the test smoother but not perfect mid throttle but full throttle was slower and started to 4 stroke. then the 68 jet test. results in OP

as soon as i find the right carb settings ill scrap that head gasket . (or should i do that first?) (edited)

Re: first venture into jetting 14 bing

do that first.

if it wants a 68 give it a 68. they almost always run 68 unless you have no filter then they are 72.

Re: first venture into jetting 14 bing

Probably Fred /

You probably have a 212A atomizer/needle jet which can be too rich sometimes.

You got to pitch the stock airbox its no good on piston port cylinders except to go slow, run mesh filter or no filter and try 222 atomizer/needle jet around 72 jet

Re: first venture into jetting 14 bing

ken and i will forever disagree on the stock airbox, ha ha. its never kept me out of the 40's on stock maxis plus i like that it is quiet and doesn't fall apart or let in rain.

my 47 mph stock cylinder puch was running a stock pinto airbox, also didn't seem to slow me down too much either.

Re: first venture into jetting 14 bing

supermoto lew /

Righty thanks for the input all ! . I'm getting somwhere 68 back in and I looked at the needle it was up top leanest setting . Thought to hell with it put it on the bottom . What a diffrence rips from 20 to 35 mph and tops out there on the flat.

Very slight bog now on the first few mm of throttle at lowest revs . Might raise it 1 notch and re test ?

Re: first venture into jetting 14 bing

> supermoto lew Wrote:

> -------------------------------------------------------

> Righty thanks for the input all ! . I'm getting somwhere 68 back in and

> I looked at the needle it was up top leanest setting . Thought to hell

> with it put it on the bottom . What a diffrence rips from 20 to 35 mph

> and tops out there on the flat.

>

> Very slight bog now on the first few mm of throttle at lowest revs .

> Might raise it 1 notch and re test ?

Try it and report .

Not the same set up , but one notch definitely makes a difference on my FA50 .

Re: first venture into jetting 14 bing

Charles Cole (OFMC) /

An easy & cheap way to get the head & top barrel surfaces really flat, is to find a piece of glass, thicker the better, and tape some fine wet n dry sandpaper to it, facing up. My glass is 1/4" X 16" X 16" & got it free, for the asking, at the local glass shop. They usually have a pile outback that usually makes it way to the dumpster. I start with 400 just to see which way I need to go & find the drit that takes it down to flat quickly. Then go finer, in stages, till 800 with some WD or light oil. Press in figure 8 pattern & turn the part every 10-15 strokes so it's even pressure. When flat bolt those puppys together & blast away. No leaky! (edited)

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