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Discussion Starter · #1 ·
Does anyone know how to improve the response of the Fuji XCR 440 engine? With my XC700 I've been able to install a boost bottle, vforce reeds, gearing and clutching, but with the fuji 440 its not a case reed engine, and there is no port on the carb boots for a boost bottle. I've noticed that on the bottom end of the throttle the engine is very boggy and feels very rich, it does open up to some amazing power on top, but I would like to get a little more crispness on the bottom. Has anyone had success clutching their 440 engines? As of right now the 440 is running the factory carb settins which are a 240 main with the needle in the #3 position. Any info would help. Thanks.
 

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I'll be interested to see where this goes because I've owned two '97 XC 440's and both were turds, with that terrible low end bog.
 

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I have a 97 xc440 that I am rebuilding. What are you doing for clutching? I have not got into the carbs yet. Doing things that need to get done, track. Skis, seat, etc.
 

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Discussion Starter · #4 ·
rich1374670x said:
I have a 97 xc440 that I am rebuilding. What are you doing for clutching? I have not got into the carbs yet. Doing things that need to get done, track. Skis, seat, etc.
I have upgraded the driven clutch to a polaris R-11 helix with a silver spring, in the #2 preload slot. I'm currently researching what to put into the primary clutch for a spring and weights. I've been told that you have to ride this sled like it stolen to get the most performance, so i may increase the primary spring weight to see if i can push up the engagement RPM. This sled goes like a madman, but suffer greatly on the bottom end.
 

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From my research that is what I have heard about this sled. Goes great except for bottom end. Post some pics. Do you still have the remote adjuster? I had my rear shocks rebuilt and my fronts are being done know.
 

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rich, how well does that remote adjuster work? I installed that front shock system on my sled and have yet gotten to test it out. You have to turn the knob in for a stiffer shock, right?
 

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I bought the sled last spring and have been doing a little here and their. I was told it acts like a limiter strap. Screw one way and the sled has less transfer, screw the other way and more transfer.
 

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I had a '96 XCR440 SP. If I remember right, I had it engage at around either 5000 or 5500 RPM. I'd leave 600's standing still for about 1500' and then they'd slowly pass me. I had about 14 lbs of backpressure on the secondary to help with back shifting because I raced it. I'll try to find what weights/springs I had in it.

Because mine was an "SP", it had the remote adjuster as well. The purpose of it is to adjust your ski pressure on the fly. If you line up on a lake and want to drag, turn the knob counter clockwise, this will put more track on the ground and less pressure on the skis. When you get back to the trails, crank it back up.

You can make these sleds very quick. As with any sled, it's all in the clutching. I'll try to find my notes.
 

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From what I've seen its all about clutching, I'm still trying to figure it out myself so I'll see where this goes, but there is some about clutching in the XCR 440 thread on here, the problem is you have to dig through 134 pages to get to it. The only other thing I think you can really do to these sleds is put a T-flow in them to take the jetting factor out somewhat.
And if they are bogging on low end why not just swap in a smaller pilot jet? Out of curiosity my '95 XCR 440 had #40 pilots stock and I bumped it up to #42.5, do you guys know what your running for pilots?
 

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Discussion Starter · #10 ·
rich1374670x said:
From my research that is what I have heard about this sled. Goes great except for bottom end. Post some pics. Do you still have the remote adjuster? I had my rear shocks rebuilt and my fronts are being done know.
My 97 xc440 is also a project sled. I traded it for a mountain bike, and unfortunately someone took the fox shocks off and replaced them with the nonrebuildable black shocks. The hood is basically held together with tiewraps and the seat has 5 tears/rips. I've upgraded the skis to SLP ultra lites, and replaced all the crappy shocks with fox shocks, although i don't have the remote adjuster for the front track shock. Once i nail down the clutching and performance, I will refinish an old hood i have laying around. I plan on creating another 92' xcr440, kinda like the old 98 xc700 i have. Do you have pictures of your old iron?
 

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I will take some pics. When I got the sled it was rough. Things I bought new for it are new c/a pro trail skis, 1.25 predator track, new factory seat cover, all new bogies, slides, shocks rebuilt in rear. Drive shaft bearings. It has the factory decals but the hood is red. I also have a 03 pro x seat that I will eventually be installing with an edge tank. I want to get it back together soon. I will take some pics on Friday.
 

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Discussion Starter · #12 ·
Well here's the setup i ran today. (100 miles of trail testing)

I put an EPI Red spring in the primary clutch. Its a 145/300 i believe, which pushes the engagement rpms to around 5300. Polaris stock dark blue is 125/310. I also put a polaris silver/blue spring with a polaris R/11 helix on the secondary clutch. With the spring in the #2 position. The red spring puts the engagement right where the horsepower is. The sled came with polaris 10/M weights which are 49.5g. I noticed today that i could rev to over 8500 rpms, and the polaris spec says 8250 is the max rpm, so i am going to install polaris 10 weights which are 51.5g. Polaris 10 weights are stock spec. This should bring my max rev to somewhere around 8200 unless this engine decides to pull harder:)

But enough of the technical crap. This little 440 engine has some serious power issues. With this clutch setup, it feels the the 440 thinks its an 800! I have no studs on the standard 121" .875 track and i could not keep it from spinning. I could almost power slide every corner i was in today. As fun as no traction is, I'm going to have to find a way to get that track to hookup. I can't even imagine what it will be like if i can actually put the HP to the trail. I replaced the stock R8 helix with an old R11 which is not all that aggressive, but more so than the R8. If you really want to push the envelope you could try a more aggressive helix like a 48/36 or a 50/36. I have a 50/36 in my xc700. If i get some time i may drop it in the 440 to see what happens. By the way a 50/36 progressive helix on a xc700 is an extremely enjoyable experience, just remember to hold on to the handlebars.

On a side note, still no luck cleaning up the boggy low end of the carbs. As long as you stay above 4500 rpms there are no power issues:) If anyone has any tips on that please let me know.

Thanks,

XJ88Laredo said:
From what I've seen its all about clutching, I'm still trying to figure it out myself so I'll see where this goes, but there is some about clutching in the XCR 440 thread on here, the problem is you have to dig through 134 pages to get to it. The only other thing I think you can really do to these sleds is put a T-flow in them to take the jetting factor out somewhat.
And if they are bogging on low end why not just swap in a smaller pilot jet? Out of curiosity my '95 XCR 440 had #40 pilots stock and I bumped it up to #42.5, do you guys know what your running for pilots?
How does a smaller pilot jet affect wide open performance? I don't have enough experience with the resizing the pilot to know how it will affect the wide open throttle mixture. That's what would worry me. Can anyone comment on that? The stock pilot on the 97 xc440 is a #50 and the main jet is a #240.
 

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This should be a sticky or in the FAQ section.
You are the man for taking the time to test with the Fuji. Not many people would take the time on this motor and you would be saving many people time and money.
 

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[/quote]

How does a smaller pilot jet affect wide open performance? I don't have enough experience with the resizing the pilot to know how it will affect the wide open throttle mixture. That's what would worry me. Can anyone comment on that? The stock pilot on the 97 xc440 is a #50 and the main jet is a #240.
[/quote]

The pilot won't affect the wide open performance at all. Idle/low end = pilot jet. Mid range = Needle. The needle rests in the main jet. As you open the throttle, the needle starts to leave the main jet (there's your mid-range). Wide open you're just on the main jet (the needle is all the way out of the main).

Glad to hear you're having success. My '96 was very fast and had NO low end issues at all. You'll love it once you get some studs in her. I would leave the pilot alone. And would also leave the needle setting stock (a real quick way to melt a piston is to change the needle setting). You can safely drop one main jet size from stock under normal winter temperatures.
 

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Discussion Starter · #15 ·
How does a smaller pilot jet affect wide open performance? I don't have enough experience with the resizing the pilot to know how it will affect the wide open throttle mixture. That's what would worry me. Can anyone comment on that? The stock pilot on the 97 xc440 is a #50 and the main jet is a #240.
[/quote]

The pilot won't affect the wide open performance at all. Idle/low end = pilot jet. Mid range = Needle. The needle rests in the main jet. As you open the throttle, the needle starts to leave the main jet (there's your mid-range). Wide open you're just on the main jet (the needle is all the way out of the main).

Glad to hear you're having success. My '96 was very fast and had NO low end issues at all. You'll love it once you get some studs in her. I would leave the pilot alone. And would also leave the needle setting stock (a real quick way to melt a piston is to change the needle setting). You can safely drop one main jet size from stock under normal winter temperatures.

[/quote]

Thanks for the info. I've been studying the Mikuni carb handbook, and it shows the fuel flow diagram during the various throttle positions. I did notice that, like you said, under full throttle all fuel flows through the main, and doesn't scavenge any fuel through the pilot. THat was my main concern, if i were to change the pilot size or settings. So right now i have all stock settings with the stock 34mm mikunis. It has no stumble or bumble on the upper end of the throttle, tons of power, but on the lower end she feels very fat. It feels like the mixture is too rich. Would i be correct in thinking that i can adjust the air screw to lean out the low/mid throttle mixture? I want to make sure its still reliable, as in no meltdowns. My other idea was to fit up a pair of 38mm mikunis like those found on the 99 xc500. I've heard they are easier to tune. Did you have a sluggish low end on your 96 xcr? What carb settings did you use on it? In 97 polaris put 240mains in the xc440. I think in 96 polaris had 260 mains in the carbs.
 

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Unfortunately, I can't find any notes from the days when I raced my '96. It may matter that my '96 was an "SP", meaning special - the racer model of the year. So what the book says for the '96 may be different than the '96 SP. This means that it's likely that it was close to the '97 consumer model. In short, 90% of any sled's performance is in the clutching. I would not look at the carbs as the issue. As I said before, stock settings, other than the main jet (because Polaris didn't want any melt down issues), I say for most purposes leave the pilot, needle, needle setting, needle tube, and air screw to stock settings.

I also say, do not put on 38's. A lot of people think "more air + more fuel = more power". There are some instances on SOME motors, where this is true. On this motor, I don't think this is the case. There's only so much fuel and air you can throw at a cylinder. And the XC440 motors were designed to take what the 34's can give it. If you swap, you'll be starting all over trying to find the perfect jetting and may end up burning down a piston or two figuring it out.

Your problem may be a less than perfect belt. Even though a belt should be a belt, the measurements from the factory may be a little off. If it's an 1/8 of an inch to narrow, wide, or a 1/4" too long, this could affect a lot. I used to take a cloth measuring tape when I went to buy belts to make sure the belt I was buying was within the specs of what I spent hours clutching to.

In short, your carbs are probably good. Especially if you want a reliable trail sled. I'm not sure what else to tell you. Once your studs are in, you may find yourself thinking everything is different at well. I think your next step should be studs and then work on clutching since it sounds like you're pretty close.

Change one thing at a time and take NOTES! I always thought I'd remember stuff, but I didn't.

Good luck!
 

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Discussion Starter · #17 · (Edited)
Ok, so I now have another 150 miles of trail time with the 97 xc440 (440 Fuji Twin). Here is the current setup I have, and it works well for me at 240 lbs. in full gear:

Polaris Light Blue Primary Spring 300/120
Polaris 10/MB (47.5g) primary bushed weights
Polaris Silver/Blue Secondary Spring (in notch 2)
Polaris R-11 Secondary Helix
Set idle to 2200 rpm
Chaincase Gearing at 19/39
Stock 240 jets
No airbox mods
Stock exhaust

With this setup there is no bottom end bog. I know the high idle does not seem like a good solution, but it works. I was able to hit 100 mph on the lake and on the trails I could reach 85 mph in a hurry. I was contemplating selling this little rocket, earlier this winter, but now I'd rather ride this than my xc 700.

I trail rode with a 2002 xc700 and a 2003 Rev 700 Race sled. They completely put me to shame in the straights, but they could not touch me in the twisties. In fact when I was leading, they had a hard time catching me. In SE Minnesota we have a lot of farm land trails that travel through waterways, which I like to consider my own personal cross-country track. The beauty with this sled, due to its extremely low stance and its smooth power (also no studs), is that for most corners I didn't let off the throttle. I could simply blip the handlebars in the direction I wanted to go, the ass end would slide to follow the skis, and away I would go. When I'd look back at the 700's, I'd see a handful of brake and then a handful of throttle, with ski's in the air.

I'm no racer, but this little 440 makes me feel like one. Keep your Rev and your Rush, I'll take a 440 wedgie any day. (preferably with xtra-10)
 
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