High Altitude Jetting

[rdalley]

I tried searching the Jetting forum but most of it wasnt for an RMZ. I know I need to lean out the carb all the way across the board from Pilot to Main. What are you guys running at altitudes around 5000ft? My bike is a stock 05 RMZ450 and it runs good but the plug is black and wet every time I look at it so I know I can tune it and get a little better mixture.

[Wayward Son]

you shouldnt need to lean the pilot jet.

160 main jet

clip 3

go here to set up your pilot circuit.

https://www.thumpertalk.com/forum/showthread.php?t=327405

[Joffter]

We live at 5000ft+ and run the 05 RMZ450 on a 165 main, needle on the 3rd clip. The pilot we have found some bikes run well with a 38 pilot, yet others, don't like it and run a 40 pilot. My first two 05 RMZ's ran well with the 38 pilot, yet the 3rd one worked better with a 40 pilot. We have also changed the leak jet from the stock 35 to a 40 for a little leaner on that circuit. Remember the leak jet works opposite to a normal jetting system. The bigger number means more fuel bypasses the circuit and less fuel goes into the engine, which means leaner.

[rdalley]

Thanks guys. I tried the pilot jet method and found no change when I turend the fuel screw all the way in. I will try one leaner on the pilot and use the 160 main and let you know.

[rdalley]

Can anyone confirm the stock jetting for my 05? The manual says 170 main is stock but I just pulled it and it had a 165. I havent looked at the pilot yet. What is stock?

[Joffter]

The stock jetting on the European and rest of the world models is a 170 main and a 42 pilot. I know the US Model comes with a 165 main as stock, and think a 42 pilot is the stock pilot jet. As far as I know the only difference is the main.

[swchopper]

is the '06 the same stock jetting? I also live 1 mile high!

[rdalley]

I went with the 160 main and stock pilot with the needle in 3rd position from top. The bike runs awesome with quick response from idle to WOT. The plug is a nice tan color so I think it is right on but since I rejetted it the bike has started puking coolant. It isnt a lot but it is enough to notice. Is this a lean condition causing it to run hot? Should I go with a 162 main? It has cooled off since I rejetted it and yesterday it was in the low 70's. Maybe that caused it to be too lean?

[Joffter]

In my opinion, it is spewing coolant because it is running hot because it is too lean. I would richen it up by one or two main jet sizes. Being a little on the rich side on the main, is not a problem on a 450. As long as the pilot system is spot on, the bike will pull nicely like that. You can also try getting a stiffer 1.6 bar radiator cap, and also running Engine ice or similar. That will keep it running cooler as well as stop the unnecessary overflow from the radiators.

[paulhonda]

i have 06 rmz450 stock main jet was a 170 the bike runs great but it is lean plug is white changed to a 175 main same problem runs great doesnt over heat but plug is white does any one have any ideas

[rdalley]

How many hours do you have on the bike between each jet change? I have found it takes a couple good rides, 4-5 hours total, for the plug to burn in and give a good reading on being rich or lean.

[rdalley]

After rejetting to a 162 and moving up one on the clip the bike runs great. But now I have to use the hot start to start it. When it was stock i never used the hot start and could easily start it in gear. Now it wont start without the hot start, but wehen I do use the hot start it fires very easily, i barely have to kick it. Why the change with only a main jet and needle clip change?

[marc177u]

Another you guys might think about is what your running for exhaust. On my '05 I use an FMF Powerbomb system with a Titanium 4 silencer. When I ride moto-x I just run it open as it's meant to be. But when I run Hare Scrambles or woods ride I need to put in a FMF spark arrestor and FMF quiet insert which of course changes the backpressure. Then the whole carb. needs to be leaned way out.