Drilling a jet question

BBQJOE

BBQJOE

Member
#1
#1
I had a dead throttle after about half open.
Mikuni jets start at 85mm and g oto 500 in increments of 5's.
I'm certainly not going to buy 100 jets to figure out which one is best for me.

I decided to drill my own a little bit at a time.
The improvement keeps coming.

I'm just about to attack it with a 1/16th inch bit.

Anyone venture to guess what metric equivalent that might be?

As always,

Thanks!
 
125ccCrazy

125ccCrazy

Well-Known Member
#3
#3
I would buy a set of micro bits and a hand held bit holder, find a bit that just fits the jet in the set and go to the next bigger jet..it doesn't take much difference in jet size to make a big difference in performance..
 
BBQJOE

BBQJOE

Member
#5
#5
125ccCrazy said:
I would buy a set of micro bits and a hand held bit holder, find a bit that just fits the jet in the set and go to the next bigger jet..it doesn't take much difference in jet size to make a big difference in performance..
Click to expand...
Good idea! I've been doing it the hard way, with just a hammer and cold chisel. :D
 
BBQJOE

BBQJOE

Member
#8
#8
Well I believe I found the top of the curve, and started heading down the other direction.
This morning I heated the jet and melted a little solder into the orifice. I then cleaned it up, and re-drilled a little smaller.

For now, I think this is about as good as I'm going to get.

I think my real problem is that I live @3500 ft. I operate my bike anywhere from 1900ft to 5700ft, and I'm beginning to doubt that there is a main jet than can cover them all. But oddly, it starts and idles fine on either end of the spectrum.
 
minibikegi

minibikegi

New Member
#9
#9
I might get this mixed-up but..mikuni is sized by flow not decimal equal, Khein jets are by actual hole size? Obviousley there both flowing fluid. just how there measured. like pipe vs. tube sizes?
 
M

metal man

New Member
#11
#11
Yes get wire drills so nice and kinda cheep widget supply has both mm and inch got a set of them not bad for light use may not last forever but cheap to replace
 
FirePowerMinis

FirePowerMinis

Active Member
#12
#12
minibikegi said:
There was a mikuni POWER Jet? it was a conversion that would pull from the bowl when needed. Dennis-Kirk might be a place to look?
Click to expand...
Power Jet is mostly for 2 strokes that lean out on the top end. Maybe the Dial-A-Jet?
https://thunderproducts.com/shop/dial-a-jet-karts/

Benzie County? We owned the house just below the lookout in Elberta. Still have a cousin at M22 and Cox headed out of Frankfort and a blueberry farm in Honor. I miss "home".
 
minibikegi

minibikegi

New Member
#15
#15
Sorry, but the power jet kit is for both 2/4 cycles. I personally only used it once, I normally use the micro drills. I would never charge for this type of work either. theirs usually a cause for the problem? EPA is always a starting point. but not gonna play jets with 250hp Yamaha on a customers bass boat!
 
BBQJOE

BBQJOE

Member
#16
#16
The whole concept of drilling my jets was a waste of time, being as I had a hidden crack in my intake manifold.
I'll be starting all over when I rework the engine.
 
minibikegi

minibikegi

New Member
#17
#17
Kool ya found the cause, that's what I tried to say. I look at why did this motor change its performance, what did the owner Do before he brought it in/gave up? But yes, the EPA makes the manufactures really LEAN out there engines. Its always fun to do battle with a motor an come-back to see the simple problem. If I was only smart enough to keep a personal journal...
 
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