2 Strokes Down Under

Who's Using Mikuni Power Jets? Anyone?

I've been interested for some time but now the price seems to have plummeted.

vhttp://www.ebay.com.au/sch/i.html?_odkw=mikuni ... r&_sacat=0

They seem cheap enough. I've just bought 2 . $68 posted.

"Power Jet Kit

The Mikuni Power Jet kits are popular in 2 stroke engine applications because of their resulting improvement in mid-range throttle response and ability to add additional fuel to wide open throttle running conditions. These are easily installed on Mikuni VM and TM series carburetors and come with a full set of instructions. The general rule is to lower your main jet size by 25% and to then in the power jet kit install a jet of a size corresponding to the main jet drop. For example if you are running a size 300 (HEX) main jet you will reduce it by 25% =225 in which case as the hex jet is only available in increments of 10 over 200, you’d try a 220 or 230 main whilst at the same time installing a 75 power jet (available in increments of 2.5). Some experimenting may be required to achieve the perfect result but generally it’s as easy as following the fore mentioned formula. Use this formula to order your additional tuning jets when purchasing the Mikuni power jet kit, the kit itself comes with an 80, 100 and size 120 jet "

http://www.mikunioz.com/product-category/power-jet-kit/

$44 plus postage from Mikuni Australia.

OzzyElsie wrote:...in the power jet kit install a jet of a size corresponding to the main jet drop. For example if you are running a size 300 (HEX) main jet ...you’d try a 220 or 230 main whilst at the same time installing a 75 power jet...

That is interesting. I see they use the N102.221 small-round-type main jet as a power jet. As far as I knew, Mikuni hex-type main jets are rated according to flow, whereas round-types are rated according to inside diameter. If that is true, 230 hex plus 70 round will not necessarily equal 300 hex.

I've never done any experiments, but perhaps flow rate (ml per minute?) is nearer to hole size (mm x 100) at the lower end of the Mikuni jet scales. I'd be glad hear from anyone who can set the record straight on this.

Thanks & regards,
James

A few guys on the RDRZ500 forum tried something like this that was adjustable (automatically i think) and ISTR the results were that they were a good thing, but i cant find the thread(s) now... i think they called it something else tho and my memory is failing me on this :/

My only concern with these is that this is basically what the later RZ carbs do with jets in the bowl (fixed on 250, swappable on 350), and theyre generally a nightmare if youre tuning a bike thats had work done as its juts another jet to mess with. The aftermarket extra jet contraption might be better?

found this one thats externally adj: https://www.vitosperformance.com/atv_pa ... id=440&cat

and this http://www.davemooreracing.com/Super_Jets.html

Interesting point that the last link says they tend to really just cool the charge, as i found a few links where mikuni suggested their auto version was used to cool the engine down!

http://www.scooter-center.com/en/produc ... ERSATZTM28