XR650R Mikuni TM40 or Edelbrock?

DerViking,

your high idle revs - is most likely too tight cables. Adjust a bit more free play in them and it should be fine.
And, at 7000ft you just may try a 137.5 main, especially so when some riding fields are even higher?


Smoothride,

3/4 of a turn is too little - change the airjet from a 1.1 (which I bet you have in) to a 1.2? Mine is set up precisely that way, and I'm close to 1.5 turns.


Tannerc,

3 turns out - surely you mean 3 half turns, so 1.5 full turn?
And your thinking - no offense pls - is a bit skewed. This carb's screw doses an emulsion of fuel&air sort-of, hence both jets must be correct. A 27.5 fuel + a 1.2 air works well, so try this - with a 1.5 turn or thereabouts?

Ok, I recently broke down and installed a bung for an o2 sensor, I found I am running lean using the popular jetting setup i have read on here. The info on the fuel emulsion screw was helpful thanks.
I am going to have to order some new jets and air screw. Curious what you are running for main jet and what your elevation is?

I run a bit different needle & jet (numbers at home), and my main is a good 'seat-pants' size - but I have to dyno this lot still.
The idling circuit is fine though, and won't even change when the dyno will tell me different. No sizes/numbers offhand for the main, I think I remember 145 or 142? Altitude is 1500m, temp 30C. Opened sidepanel, UNI filter, XRsOnly SS headers & PC T4 pipe, plus a homemade Batwing. Runs fine as is, as said I need to get the lot measured.

I'm 27.5, either 1.1 or 1.2, 3rd clip needle, and 140 main.

My spark plug after 6000 km was looking much darker then I would have wanted.

Keep in mind, elevation in a whole was much higher then our normal riding. Often 8000-10000 feet on the CDT.

Our riding here is 4000-7000 ft and where I originally jetted it. It's not bang on, but once again my elevation and temp is never consistent.

Shibs,

got an opened side panel? If so, maybe re-jet for a next such trip high up, but tape-shut the panel & jet accordingly, smaller (duh). Yeah, a bit less tops but this way you ride to the high bits - where you take off the tape, opening the panel. Beats farking around with jets, maybe an idea.

My Mikuni floods all the time. My XR is still out in the wood where it left me, stranded for the millionth time, I walked home...
It runs awesome on the street and on fire trails but when you try and ride in the woods and you go over steep mounds, or god forbid you tip over the top heavy elephant, it floods and shuts off then will not start back up until it has fully cooled down. I put a new iridium NGK plug and it worked good for a few months now back to being stranded.
What gives?!

I got it fired off on the first kick... I also put the fuel screw at 2 turns open (3.5 before). Much better throttle response. You gotta let the pumpers do the work. Or else they will flood you out.

Also pull the carb and double check the float settings.

Changing the plug is usually only dealing with the sympton not root cause.
Plugs will last a veritable eternity if all else is in order.
Re flooding - does it drip fuel out the breathers when on the side stand?
if so, suggest revisiting float level or needle and seat (float valve) before moving on to anything else.
Neither Mikuni or OEM carby was designed to run on its side, clearing the old girl so it starts easy is not a major issue when set up correctly (unless you drown them in a river - don't ask)
Theres enough details here to get you in the ball park.
My TM is certainly not set up exactly right but generally runs well and dowsn't cause me issues.
Start with the basics and work through methodically.
Good fuel,
Spark in the right place (you can't change that)
Compression etc and all should be good
If not post you're findings and we will try and help
JM

Hey!

I have a good deal on a FCR39. Is it ok for a stock piggy?? It's off a 2002 KTM exc 450

I have two r's and have been messing around with the carbs, forever! I hate the deceleration pop with my edelbrock and went back to stock. I am now excited to try a different model. Are there fit issues with the FCR?

yup, you need to clearance the tank.

And if you are just buying a ebay FCR (meaning not the sudco XR650R FCR kit) you'll need cables, airboot / intake manifold adapters.

I missed this bit when I read it the first time, or maybe I had a polite moment.
Erm.... I do ask now?

Photos would help, just a pushy hint

Also, carefully inspect the needle seat for wear, even slight wear will cause the fuel to continually flow.

Time to come clean.
For quite a while I've been advising to use the 27.5 idle jet instead of the 25, for reason to keep the engine cooler at low revs/pace. Oh, airjet 1.2, altitude 1100-1700m HASL, temp ~30C.
Well, it doesn't, or not enough, on my last trip it boiled over again, in an area even where I'd have thought the wind/speed was enough.
So, I'm going back to the 25: better idling (perfect doesn't exist but it's close), and getting as hot & as quick (maybe a tiny notch quicker) as with the 27.5 it seems.

What jets are included in the new set from power barn ?

No idea, never bought from them

Thanx for the valuable information everyone