Dirt Rider . Net Text Version Home
Pages: 1
How to jet additional "power jet kit"
(Click here to view the original thread with full colors/images)
Posted by: thunderkiller---------------------
I will install power jet kit to my 83 kx125's mikuni VM34s. I hope to improve low&mid-range power. So the question is;
-the standart main jet is 152,5. what should be the new main jet and power jet kit jet sizes.
Posted by: whenfoxforks-ruled---------------------
You have never jetted a bike before? Do you have a link to this power jet kit? Have you never heard of JD jetting? Vintage Bob
Posted by: thunderkiller---------------------
I did jetting before. I am talking about mikuni power jet kit, link below;
http://www.mikunioz.com/power_jet_kits.htm
As I know I have to reduce the size of the main jet to 70-80%.
My question was that, what should be the ratio. for example;
standart main jet is 152,5.
when I install power jet kit (it has 82,5 jet on it), so I will replace the 152,5 main jet (152,5x0,75=115) with 115 main jet.
Is it correct or not?
Posted by: Chili---------------------
Unless your bike is pouring oil out the silencer going from a 152.5 to a 115 will likely end up in a seizure.
There is no magic formula you will need to work through each jetting circuit making small incremental changes and then riding the bike to do plug chops and check the throttle response.
Posted by: 2strokerfun---------------------
Keihin had some carbs in the mid 70s with a power jet. Yes, the main was about 70-80 percent of the main jet on the standard Keihin, but the power jet kicked in when carb was off the needle, making up the difference. The honda MR250 used one of these carbs. While nice in theory, it made the bikes horribly difficult to jet. Serious enduro riders tossed the carbs and put on the CR250 carb which had a standard main jet and no power jet.
Looking up my old manuals, the MRs came with a 110 mainjet, vs about a 148 on the CR. But the powerjet on the MR pushed it to 140 when past the needle. With a 115 main, the total was 150 when past the needle, according to the manual charts.
But that was a Keihin that was made 34 years ago, so I have no idea about the Mikunis.
Posted by: whenfoxforks-ruled---------------------
Who knows with that power jet set up? Most all newer carbs have power jets in them, not like that though! I would start rich and see? Good Luck! Vintage Bob
Posted by: thunderkiller---------------------
I had it rejetted. It is running greatr now with #30 pilot jet, #130 main jet & 85 power jet. 1,2,3,4 wheelies, I love this old bike
Posted by: whenfoxforks-ruled---------------------
Very nice indeed! How difficult was the machining? I have to assume there is a blank hole? Vintage Bob
Posted by: thunderkiller---------------------
I drilled the carburator body with dremmel first and then resized the holes with driller. Then opened the screw teeth with.
All the installation and jetting work took 3 hours.
Text Version Home
vBulletin Copyright ©2000 - 2009,
Jelsoft Enterprises Limited.
vB Easy Archive Final ©2000 - 2009
- Created by Stefan "Xenon" Kaeser
