Can you believe this... XR600R

I thought I'd post this to see what you people thought.

Last year, we re-built a '96 XR600R, making it a 629, valve job with new valves & bigger springs, and we removed the auto-decompresser from the cam.

This year, the spark plug got accidentally cross-threaded, so we took off the head to heli-coil the spark plug hole. While it was apart, my cousin decides to port & polish the head. He did it himself, and did a great job. Also, he fadricated a stock WR450 muffler to fit on the XR600. Again, I can't believe how good it looks.

So anyways, we put the bike back together and fire it up with the same jetting as it had before. I'm not sure of the pilot, but the main was a 170. With a little throttle, the headers started to glow, almost instantly. Figuring it's too lean, we try up jetting it.

172 - Headers still glowing.

175 - Still glowing.

178 - still glowing, but not near as quick.

180 - still glowing, but again, not near as quickly as before.

Keep in mind we live in CO, and our base elevation is 5200 ft. It just seems crazy to me that we opened up that engine so much, it needs this much fuel at a high elevation. We didn't have any bigger jets, so we quit for the night. Can you guys believe that this bike wants a 182 or 185 main jet?

I was wondering if anyone else has done similar mods? Does it seem right to have that much of a gain in fuel needs?

The other possibility we thought of is that the stock headers are too small for the ported head & new exhaust. How many people think this bike needs bigger headers?

If it was a true "stock" WR muffler they are quite restrictive ...can you swap back to the original one you were using and see what happens??..

if its glowing so much you might want to consider an oil cooler, ive neever ported an xr but i know when you port any motor the fuel needs jump trmendously just tinker with it until you get it right

few questions....

What year WR muffler is it? UNLESS you rip out the 3 baffles welded inside the can, its VERY restrictive. There's one baffle up front and two behind it and they are very restrictive. I"ll get you a link.

Glowing headers isn't necessarily an indication of bad jetting. My 06 WR450 as all are known for, commonly will glow the header bright cherry red with no airflow. That's is NOT an indication of any jetting problem.

I also have a 93 XR, same elevation....I"m using a 150 mj on a fairly stock 600. Were you idling the bike? Why are you changing Main jets when its the pilot jet circuit that is only affected at idle?

Just some data points to look at.

You should go back to the pipe you had on it in the first place. Porting and polishing should have not even caused your problem at all. As you can see from my sigiture mine is the same thing. Mine is an Al Baker 630cc with hot cam stage 1 and Kibble white springs, with a port polish job from Al Baker. I'm running a 62 pilot with a 155 main with the stock carb. K&N filter and an Al Bakers head pipe and a FMF mega max muffler.

One thing you may wish to consider, just my 2 cents, ported polished head = better air flow, stock wr silencer terribly restrictive, due to the restriction in the silencer it is not allowing the heat to escape, therefore the glowing red hot header. You went to all the trouble to make a better performing engine then you stuck a cork on the exhaust:excuseme: Also as a previous member posted the fact that the header glows does not indicate a lean condition, I am willing to bet that if you put a free flowing silencer on and go back to a 160-165 main jet, possibly a larger pilot, things will be fine. what does your spark plug look like? This is a much better way to read fuel mixture adjustments. Have you ridden the bike with these settings? I am just above sea level and I am running a 165 main and 58 pilot on my uncorked L model, have slightly brown spark plug. All of my bikes will glow the header if sitting still and revving the motor. Did you say the header was glowing just idling? Seems unlikely. :bonk:

These guys are right on. But the STOCK header? Not Good. Upsize all exhaust, and get back to some reasonable jetting. I was at the cyclefest the first year, and I had to but some seriously small jets to keep the thing from bogging. (White Bros Stainless Header and E-Series Pipe)

my xr400 did that, i started it up one night after jetting and it glowed when i revved it up a bit, but as soon as i started moving just a little bit it died down. you don't notice it unless you have it idling high, your not moving and its dark. at least thats what happens to me

Ok, it was an '04 WR450 Exhaust without the bolt-it baffle. Just looking at the two mufflers side-by-side, the WR muffler seems much less restrictive.

Before the port & polish, the bike was a 629, otherwise stock. The stock muffler had the baffle removed. It also has a Uni air filter without any back-fire screen. It ran perfectly with a 170 main jet & 58 pilot jet.

With the new mods, the muffler glows only at 50% throttle or higher. Idle, and initial throttle seems perfect. After a test ride with the 180 main jet, the spark plug & the exhaust residue look lean, with a light gray color. We last stopped at a 180 main jet, and still the 58 pilot.

The other mod, I forgot to mention was holes cut in the air box. My cousin did that after seeing my success with cutting out my side panel on my 650R.

I'm sure the bike needs more fuel, and we'll be working on it today, I'm sure.

I just wonder if we're trying to cram too much exhaust through the small stock headers.

The oil cooler might be a good idea. All I really know at this point, is the more gas we give it, the better it responds. I was having to work to keep the front wheel down on the ground. I'm worried it might be able to take my 650R, once we get it running right.

Hey, I just thought of this... How much richer will raising the needle 1 notch make? Is it more or less than 1 main jet size?

Wow, You state the muffler glows red? this should never happen! There are still internal baffles in the WR silencer, Try looking in with a flashlight or probing, you still have way too much restriction for a modded motor, and yes header, possibly xrs only or FMF powerbomb header with a straight through design silencer. I refer to the power bomb because it helps with scavenging, and from your posts it sounds like you need all the scavenging you can get.

Try raising the needle, or shimming, also you may try a larger pilot. But I cant believe its jetted that rich and still wants more fuel, especially at elevation. Are you certain the carb has no blockage, have you cleaned it to be sure? The way your going you will be lucky to get 15mpg when its done!

pilot is to small you need a 68s I beleve

pilot is to small you need a 68s I beleve

i agree i have a 58 in my xr400 so I think you need a bigger pilot.

Are you sure the timimg is right?

Timing is great. We haven't messed with it on account of cold temps outside.

I think the needle has to go up. I think the needle is restricting the amount of fuel, and the main jets aren't making much of a difference.

It's possible the pilot needs changed, but we richened the adjustment screw and the first 25% of the throttle, including idling & starting, seems perfect. A 68S is for the 650R, which I ride. But I'm talking the older 600R. It has a smaller carb than the 650R, and always wanted a leaner size pilot. If anything, it needs a 60 pilot jet.

That muffler is causing the pipe to glow because it can't get the hot gases out. Get rid of it.

For the record, I have a '93 XR600R and I am running the 68S pilot. My bike does run a little rich, but otherwise, it is a BEAST with that pilot. So that blows your theory that the 68S won't work in a 600. I can tell you for certain that my bike starts much easier with the larger pilot. Do I think it is optimum? No. But I do think it is a good place to start if you want the bike to run a little cooler, and start easier.

And depending on what year "old school" 600 you are talking about, some-like mine-came with 62 pilots from the factory which are very lean to begin with.

Jumping to the 68 will insure that you are not lean from off-idle up to 1/2 throttle which is where I suspect most non-race bikes spent the majority of their time. Since I know the 68S is actually a little too rich, I am planning on going back down to probably a 65 just to see how the bike responds. If it loses any performance, or the temp comes up at all, I will immediately switch back to the 68S.

OK, I thought I'd update this with the results.

With the '04 WR450 muffler (baffle removed) I promise it is much more free flowing than the stock 600 muffler (baffle removed). I'd agree with you it it was an '05-'07 WR muffler, but '04 was the year Yamaha made it wide open, and got flak from the noise the bike made.

This bike used to be all bottom-end power. Now it has a much better balance of bottom, mid, and top-end power.

The glowing headers issue was easily solved by installing the 170 main back in as a baseline, and raising the needle one notch. (I'm not sure which notch it is/was).

It's perfect now. 170 main, 58 pilot, and like I said, a richer needle adjustment. This bike has POWER!!! WOW!!! A 629 with ported & polished head & cut open air-box.

I've been working on XR600's for years (I used to work for SRC). The correct jetting from sea level to about 5000 ft with a medium flow exhaust is 3rd groove, 2.5 turns out, 65 pilot and a 155-158 main.

Motopsycho650, you are way to lean on your pilot. and too rich on your main.

1st, my elevation starts at 5000 ft and goes to 10000+ ft.

If the pilot was too lean, you could never get the bike to start. Plus, you'd get a lean backfire on decel, and bogging on initial throttle. If it were as lean as you suggest, we would have a racing idle problem too. We don't have any of those symptoms. In fact, the bike starts with one kick warm, and 1-3 kicks cold. It has perfect response in low range, and you have to work to keep the ft. wheel down.

If the main was too rich, we'd have a black spark plug, and bad mid to top range. The plug is perfect. Not white, and not black. It's perfect toasty marshmallow color.

Not sure why there is so much of a difference between what you say, and what works for my uncle's bike. I've been active in the mods of this bike for 10 years. I've never seen it run better.

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