EKN needle results


All three points were considered when I went to the larger bore. I hate domed pistons and prefer flat topped pistons, if I remember correctly this piston was a flat top but I may have missed a slight dome, getting old memeoy is fading. I still believe the deck height was set in the ball park by Eric Gorr and since my head was previously modified for better flow which in itself decreased the stock compression a tad leds me to believe that there may or may not be a squish area problem. I will not know unless I disassemble the top end stick some clay in there reassemble crank her over disassemble and measure what I end up with and then consult my favorite enging builder and go from there.

Again this bike has excellent low to mid range and is perfect for trail riding the only thing thats a issue is not getting to the ELEVATED rev limiter of my Vortex ignition. I was trying to build a torque trail motor and this is what I have.

I will work some with jetting the MAJ and mains etc. and do the best I can for top end.

I will not go back into this motor unless I break something that requires fixing. As it stands now it starts easily runs strong and signs off a little earlier than the stock 400 motor but it a vastly better trail and hill climb bike than the stocker more torque is addicting.



there is no way i'm trying to teach you to suck eggs here ok?

if you do your own squish, go get some plastacine, get some 1mm solder, some engine oil.

put a ball/pellet of plastacine over EACH END of the gudgeon pin part of the piston face. get 20mm of solder & turn it into spagghetti.

plop onto the plastacine like plopping a strawberry on thick cream the solder.

smear oil on top of the lot.

place in oven for an hour & cook until golden brow.... ooops! there i go i forgot where i was for a moment.

ahem, yes, errrr, where was i? ahh yes!

turn engine over & pull head off.

measure the spagghetti with micrometer.i.e. where the middle of the number '8' is. get me?

i hope you know what i mean & good luck (one day!).


Originally posted by Hick:

I don’t know the source of the pumper carb for sure, I just assumed it was from XRs Only. I just sent an email to my friend to find out, plus I will be in Phoenix this wknd so maybe I’ll get to talk him then.


FWIW, the carb on my friend’s XR was from Sudco. But he did not do the installation, did not know what other parts were needed for the swap, and could not remember if it was a 40 or 41 mm.

He’s a heck of a rider but has never really liked working on his bike and isn’t all that mechanically inclined like you (and me :) ). Hard to relate, I know.

He plans on running iron man in the 500, so his state of tune upstairs leaves something to be desired also. Call Sudco and see what they say.


I do believe I see some humor posted by you!! :)

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