yerf dog suspension modifacation

[jetasen74]

thank you sir that what i have been using

[jetasen74]

do ya need to thake apart the drive unit(40 series) to lube it and what is the easy way of going about it.

[jetasen74]

well guys i have been jones'n to drive so removed the seat and took off the rails and made some brackets to get all the leg room i could. i will ride tomarrow but it feels alot better and it'll do until i make my buckets.

[x-bird]

Originally Posted by jetasen74

do ya need to thake apart the drive unit(40 series) to lube it and what is the easy way of going about it.

I'm not sure, the yerf is my first time messing with these things. Grew up on centrifugal clutches .... I'm pretty sure there's a highly detailed thread in one of the "mechanical" sections explaining how to lube & clean them.

[jetasen74]

maybe yous guys can help. i am still try'n to tune my 32mm mikuni carb. it runs great and the plug is just a hair on the rich side. my problem is when i am at a stand still and i try to take off fast it will cut out.

[metalstudman1]

Originally Posted by jetasen74

maybe yous guys can help. i am still try'n to tune my 32mm mikuni carb. it runs great and the plug is just a hair on the rich side. my problem is when i am at a stand still and i try to take off fast it will cut out.

In my short experience with these carbs-it sounds like an intake leak

[metalstudman1]

Originally Posted by jetasen74

do ya need to take apart the drive unit(40 series) to lube it and what is the easy way of going about it.

This is link is where I learned how to maintain them: http://www.*****************/comet.htm

[speedshopmike]

if it's a CV carb the diaphragm may have a pinhole in it and/or gotten stiff, slowing the slide rise.

[jetasen74]

its a round slide,no intake leak. maybe need more restricted filter?

[speedshopmike]

only thing a free-flow filter should do is require you to jet the carb correctly.
this doesnt mean just playing with the main jet, though.
your problem sounds like it's lean off-idle, which means you gotta go into the idle and low-speed circuits and fatten them up, **assuming** the existing internal parts are all 100% clear of varnish and other foreign matter.
check your carb and see what's in it now.
then go to your local motorcycle shop and ask what the mechanics have around left over from other customers' "jet kits" (the Dynojet brand is most popular) and scrounge some stuff to try out....you should only have to spend a few dollars to get what you need.

[jetasen74]

i think i have a 160 in now but i have a 175 and a 190 to try

[jetasen74]

i checked and i am runnin a 35 pilot jet and a 200 main.and the adjustable needle on the throttle is 2nd from the bottom.if i put it on top it drives like crap, havent tried it all the way down yet.

[jetasen74]

i drilled out an extra pilot jet and ran it with a 200 main and it ran good except at low speed it sputterd a bit but it would throw some serious dirt. it ran realy rich and carbon fouled the plug, i went down to a 100 main and still a black plug. gonna put the 35 pilot back in and try again.

[speedshopmike]

i'd drill the stock pilot out one size at a time, assuming you're using a full set of pindrills.
these circuits are so small that even one bit size is a large percentage change in fuel flow and the shape of the entry and exit of the jet matters also.
drill extremely carefully and slowly; don't push it though.
only make one change at a time and only on one circuit at a time.
if you've got a mechanic buddy ask if you can use his exhaust gas analyzer; it makes narrowing the tune down quickly much less of a chore.
or you could weld a 16x1.25 (iirc) nut on your headpipe, burn a hole, and screw a $10 universal oxygen sensor in it and read it w/ a dvom.

[jetasen74]

why does it run like a bat out of heck on top end with even a 200 but run like poo with a 100 but it still shows rich on the plug?

[speedshopmike]

1st, at this point please start with a new plug so you can see it well.
to answer, because the motor's always running on the pilot (where it won't clean out well) but isnt up on the main until higher speed/throttle opening.
(and/or could have weak spark)
if you have a good camera and light, post some pics of the plug if you like, but i'd start fresh first.
even the 100 could be too fat, btw; i'm not saying it isnt, or could be lean.
only discussing that dying off idle usually indicates it's lean there.
you could experiment by fattening the heck outta the idle mix with the small pilot in and see if it helps before you drill it.
the extra fuel from the idle circuit will *partially cover up the lean sag.
you can also raise the needle up a position at a time; that''ll bring in the enrichment sooner.
also, needles with different tapers are available.

[jetasen74]

thanks for the info, i will hit hard today and see what happens and will let you know.

[jetasen74]

ok, i ran it with a 35 pilot and 100 main it ran like crap and still rich. i have to order a smaller main. probly get a 80 and a 90 and if that doesnt work i will probly get rid of the mikuni.and it keeps fouling plugs

[jetasen74]

i found out the stock size is .88mm and it ran rich and like crap on a 100. would it make that big of a differance?and would a 90 be about right?

[speedshopmike]

yes it would.
if you do the math on surface area of the jet opening then compare them as a percentage of change you'll see why.
how did it run on the 88?

[jetasen74]

how did it run on the 88? dont remember. do ya think a 90 would do.

that 88 was on the stock carb and now i have a 32mm mikuni(it came with 30 pilot and 160 main) i got from affordable go kart supply i think and they told me it is ready to go the way it was.

[speedshopmike]

you lost me - what carb was the 88 in?

[jetasen74]

the 88 was in the stock carb. it seemed under powerd so i bought the mikuni.

[jetasen74]

i started a tread on this one

[jetasen74]

i checked da oil and low and beholed lots of gas in the oil. i also had to move the air filter cause it was getting realy muddy. and added a tool box.

[jetasen74]

took apart the driven (40 series) and cleaned it.glad i did cause it needed it.