Kawasaki ATV Forum banner

1 - 19 of 19 Posts

·
Registered
Joined
·
26 Posts
Discussion Starter #1
looking for some help on my 04 prairie 700 installed hmf slip on exhaust
no power gain feels like i lost power so i installed jets from hmf 142jet in front carb 148in rear carb now when you give it the gas it pops and pops back through the carb so i installed a148in front carb 152 in rear carb made it a little bit better but now it i think it is getting to much gas like it is loading
up at low speed i have adjusted the air but still doing the same thing so i put the smaller jets back in re adjusted the air no better any help would be nice i am doing all my adjustments with air filter & lid installed
 

·
Registered
Joined
·
26 Posts
Discussion Starter #3
they are a little on the black side but not to bad do i need bigger or smaller jets or what
 

·
Registered
Joined
·
178 Posts
I would try 1 size smaller. Or get it tuned with a O2.
 

·
Super Moderator
Joined
·
9,446 Posts
Jetting without a dyno or a/f meter is all about trial and error. The slip-on isn't going to be a significant improvement in performance and I'd be surprised if your jetting is more than 1 or 2 sizes bigger with just the slip-on. Have you already done the airbox mods (like Twin Air or K&N filter and 12 one-inch holes in the lid)? If not, do those first and then try to jet it.

If I were you, I'd add 1 shim to each needle and go back to the 142/145 or something like that.

Good luck and happy trails...:)
 

·
Registered
Joined
·
26 Posts
Discussion Starter #6
mikeyboy i have not done anything with the air box where do i cut the hole in the lid
i am running uni air filter hmf said to run the 142/145 jets but it runs better with the bigger jets i have the 142/145 in it now have the air set about 3 turns out runs good till about half throttle then it starts to pop back through the carbs and never seems to reach full throttle
 

·
Super Moderator
Joined
·
9,446 Posts
Did you add a shim under each needle yet? If not, start there first before you go any bigger on the main jets.

The 12 hole mod is popular on this forum. If you do a search, I'm thinking you'll find some pics or instructions. Basically, you take a 1 inch hole saw bit and drill out 12 holes on the lid. I don't think it matters exactly where you place them so long as they are spread out evenly so a good amount of airflow will enter the airbox and go towards both venturi stacks below the air filter.

Good luck with that.

Happy trails...:)
 

·
Registered
Joined
·
711 Posts
looking for some help on my 04 prairie 700 installed hmf slip on exhaust
no power gain feels like i lost power so i installed jets from hmf 142jet in front carb 148in rear carb now when you give it the gas it pops and pops back through the carb so i installed a148in front carb 152 in rear carb made it a little bit better but now it i think it is getting to much gas like it is loading
up at low speed i have adjusted the air but still doing the same thing so i put the smaller jets back in re adjusted the air no better any help would be nice i am doing all my adjustments with air filter & lid installed
Popping out the carb off of an idle is a lean low speed condition. To fix this you can go up on the low speed jets or do what most jet kits do.What they do is put in a lighter spring above the diaphram.You can buy a jet kit or just cut the spring shorter one ring at a time until you get it to run right.Then once you get the popping to stop you can play with the main jets to fix the high speed lean condition that will also be there.This will be done by upping the jet size and playing with shims under the needle.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #9
i ran it this morning to check the plugs pulled them out and they were black
going to try to shim the needles and see what happens then do i need to cut a ring off the springs or wait and see if the shim fix it thanks for all the help from everyone
 

·
Registered
Joined
·
26 Posts
Discussion Starter #10
ok guys here is the deal now i put a shim under each needle cut one ring off each spring
runs a lot better now but still has a little bog when you rev it up on the low side but sounds a lot better now thanks for all the help gonna go for a ride and see if it better or not will let yall know later
 

·
Registered
Joined
·
26 Posts
Discussion Starter #11
went for a ride does great up to about 40mph then it seems to stop pulling no more popping out the carbs but now it don't seem to have the power it had before all this was done now it has 142f 145r jets 1shim under each needle 1 ring cut off each spring & 12 hole mod to air box cranks very easy idles great takes off great but no top end power what do i need to try now? this is a great site and i thank everyone for there help
 

·
Registered
Joined
·
26 Posts
Discussion Starter #12
now it runs fine up to 3/4 throttle then it starts to bust up like it is running out of gas do i need to put another shim under the needle or install a larger jet
 

·
Registered
Joined
·
29 Posts
I have the same problem except that I have a few more mods. I reach about 45mph and almost feels like the belt is slipping.
 

·
Super Moderator
Joined
·
9,446 Posts
As I recall, the needle adjustments (adding shims) only effects the quad from just off idle to about 1/4 throttle. Above 1/4 throttle is mostly controlled by the main jets. If I were you, I'd try to go up or down on the main jets and see how it runs. You might try blocking off a few holes in the lid first (as suggested by painterx) and that may tell you which way you need to go with the main jets (leaner or richer).

Good luck and happy trails...:)
 

·
Registered
Joined
·
1,274 Posts
Pilot Jet - Pilot Screw: Controls the fuel/air mixture between Idle and 1/4 throttle. Turning the screw IN makes the fuel/air mixture leaner. Turning the screw OUT makes the fuel/air mixture richer. Lean means less gas, rich means more gas.
Every jet is identified by a number and that number relates directly to the size of the opening inside the jet. Again smaller is leaner, larger is richer. When jetting your carb if you find that you need to turn the pilot jet all the way in to improve response then you likely need to switch to a smaller number of screw.
If on the other hand you need to turn it more than 2.5 turns out you likely need a larger numbered screw. When your engine bogs down at the smallest increase in throttle position your pilot jetting is likely too rich.

Needle Jets: Controls the fuel/air mixture from the 1/8th throttle position all the way up to the 3/4 throttle position. The needle within the needle jet is a long tapered pin. As you increase the throttle position the pin pulls out of its jet allowing the fuel/air mixture to become richer. There are several different shapes and diameter of needles/needle jets but the needle jet is often left alone during tuning as it doesn’t affect idle or top end performance. The same rich/lean characteristics apply as with the pilot screw.

Main Jet controls the fuel/air mixture from the 3/4 throttle position up to wide open throttle. Again the main jet is numbered and a larger number indicates a larger hole and a richer mixture. A stock engine will perform well with a stock main jet but once engine performance parts are added its likely that you will need to revisit at least the main jet of your carburetor. Different performance part combinations will create different demands from your carburetor. Anything that increases horsepower will also increase fuel demand.
 

·
Registered
Joined
·
4,802 Posts
tape up some holes... to see if you regain some top end.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #19
ok here is what i did today pull carb and installed 145f 148r jets runs better installed 2shims under needles has great throttle response now but still no top end. it was stronger with the factory set up going to try to tape up some holes to see what happens any more ideas will be great thanks guys
 
1 - 19 of 19 Posts
Top