New motor is fantastic

I just built a 2004 XR 650 L from the ground up.

10.25:1 Wiseco piston STD bore

Hotcam

Mikuni TM 38 flatslide

Yoshimura exhaust

Uni filter

Smog removed

Airbox opened up

Bridgestone ED-77,78 Gritty tires

15-45 gearing

IMS 4.0 gallon tank

Acerbis DHH headlight

Superbrace

XR's only skidplate

Well the list goes on and on but I must say that the bike works awsome.

The motor has alot more power from down low to the top end. It pulls alot harder than a stocker and has a ton of throttle response. I am going to break the motor in a little and then have it dynoed. :ride:

I think it has to be jetted. It has a TINY backfire when i shut the bike off. Also a little flatspot when the throttle is wicked.

Any ideas for jetting? Right now i have a 270 main and 27.5 pilot. I was thinking about a different air bleed.

Any help?

You might want to do a search & seek out goblin127 here on TT. He's runnin' a Mikuni flat slide on his L.

A little pop could mean a rich pilot circuit. Higher compression = higher octane. Try different brands of fuel as well. Just that slight change might make enough of a difference... :ride:

Hey goblin127 are you here man????

I have a 270 main and 27.5 pilot with a 2.0 air bleed in.

I will try a search and try new jets.

Thanks

Got any pictures? She sounds like a beast.

Hey goblin127 are you here man????

I have a 270 main and 27.5 pilot with a 2.0 air bleed in.

I will try a search and try new jets.

Thanks

Are you sure that's not a 170 main? Unless mikuni changed their jet numbers, I'm still running the same 160 that came with the 41mm mikuni performance kit to replace the stock cv carb. I keep the needle in the bottom groove.

I may have to try a 170, hmm, it's easy enough to change! Is the tm38 a pumper?

Are you sure that's not a 170 main? Unless mikuni changed their jet numbers, I'm still running the same 160 that came with the 41mm mikuni performance kit to replace the stock cv carb. I keep the needle in the bottom groove.

I may have to try a 170, hmm, it's easy enough to change! Is the tm38 a pumper?

Nope not a pumper. It has 270 stamped on it..... :ride:

I tried a 22.5 pilot and a 260 main also I removed the 2.0 air screw and it made a big difference in throttle response. The bike hauled alot harder on the first drive. Im Not sure if Mikuni changed numbers or not. These mains have a symbol plus the number. I have 240 - 280 mains and 17.5 - 30 pilot jets.

Sorry Man, I was completely out to lunch on the jet numbers. The 41mm mikuni I have came with a 260 main, I go to 250 for Moab @ 4K and up. A 250 main won't pull Imogene without blubbering, so 8k and up I use the 240.

Enjoy your new engine, mines ate about 10k of my buddy's dust at about the same state of tune as your's. My bike doesn't roll on wheelie like it used to in 3rd so it's probably time to freshen things up again. :applause:

Well now I have a 260 main and 22.5 pilot. There is NO air bleed. Seems to work good. Still backfires when I shut it off. Still a small flat spot or load up also.

My bike will roll on wheelie in 3rd everytime. It will flip over if ya don't lift.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now