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Old 03-17-2011, 09:44 AM   #31
sporthog93
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I had an '01 with 285 kit, hot cams, full exhaust system, ( i forget what brand) and ohlins forks, The bore kit was the single best mod, if i had it to do over again I would probably not do the hot cams, i don't think they really did that much for me, although to be fair I did not upgrade carb or stiff valve springs. There are weld on adapters that widen the footpegs that helped me keep my toes up.
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Old 03-20-2011, 07:30 PM   #32
Moto Beak
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I didn't do anything to the suspension. The last time I raced the bike I broke my hip, going too fast for the suspension. I was stupid for not knowing better. After healing up I switched back to two strokes. I would expect you could get good results with the stock components (with revalving and springs), but upgrading the suspension would be a good idea. That is a whole different project in itself.
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Old 04-22-2011, 09:31 PM   #33
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Breathing Part 2

One of the biggest disadvantages of the older 4 strokes vs newer is throttle response. Newer bikes have carbs with accelerator pumps, and once jetted correctly, the extra snap helps immensely with obstacles, breaking the rear wheel loose, etc. My whole plan for this bike was to have it be nimble and snappy, and I knew I needed to ditch the stock carb to accomplish this.

I was planning on getting an FCR, and Sudco listed a kit for a 35mm. But I starting running into a lot of BS about using it. Several people said it was too much carb, though they never tried it. One person who has built several XR250s, and knows his stuff, said he tried it and flat out insisted it would not fit. But Sudco had a kit, so I dug a little deeper, and finally found pics on an Italian site of a 250 with an FCR35 on it. I also never found a single person who actually tried it. So I ordered it up from Sudco.







Side by side with the stocker:



Side note: while ordering from Sudco, I found out that they have an FCR33mm carb that will fit also. It has a slightly longer fuel-side bell and shorter air-side bell, so it sits about 1 cm farther back. This would be better for cable fitting, but put it closer to the frame rails. Since I was going to increase displacement, I stuck with the 35.

More....

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Old 04-22-2011, 09:45 PM   #34
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Test Fitting

First thing to do was to test fit the carb, so I could get some scope of the project. I did not have the correct intake boot yet, but wanted to see how it fit, how cables routed, etc. It was a bit of a hassle to get into place, but once in, fit fine:







More....

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Old 04-22-2011, 10:02 PM   #35
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Parts needed:

A few parts are needed to fit it. First, the throttle cables come off the stock carb on the left side, on the FCR they are on the right. Additionally, they are really close to the upper motor mount:


I called Ed Willis at Motion Pro, a super smart applications guy. He set me up with cables that have 45 degree elbows. They fit, and will work acceptably, but not as nice as stock. I had to be really careful so they did not contact the cylinder head and melt the housing. Additionally, the bracket is threaded, so I had to spin the cables into the bracket before putting the carb on, otherwise.....not enough room to spin the cables into the threaded bracket ( know, confusing). I ended up carefully drilling out the threads on this bracket:



Note that I covered the openings up with plastic, and cleaned the bejeezus out of things afterward. Once I got this done, it was much easier to fit, position, and adjust the cables.

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Old 04-22-2011, 10:11 PM   #36
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The airbox side OD is bigger, so an XR400 boot is needed:





One thing that is different, and still unresolved, is the crankcase venting. My bike is a California model, and had a more extensive crankcase recirc system. The 250 boot has a boss to attach the hoses to, that the 400 boot does not have.



Also, I noticed that the stock intake manifold had hardened considerably, so I took no chances and replaced it.

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Old 04-22-2011, 10:39 PM   #37
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AP Timing

The biggest part (hassle) of the carb install was figuring out how to time the accelerator pump.

Several people let me know that I had to 1. time the squirt to start a little late, and 2. limit the duration of he squirt to 1.5 secs, to not bog the motor.

The newer FCR-MX pumpers have a leak jet, which can be changed out to control the squirt. A larger jet bleeds feul out of the circuit instead of pumping it into the motor. It is quantitative and works well. But, the older FCR slant body carbs like the 35 do not have leak jets. There is an accessory from Boyesen that duplicates the bleed-off, so I got one to try:





and mounted it up:



I started testing the squirt off the bike, with odd results. The pump would hesitate, then squirt for what seemed like forever, definitely not 1.5 seconds. No amount of adjusting was helping, and I was getting confused.

By now I had burned a load of time and money ordering parts, and was getting kinda pissed. I try to be patient, and do homework before assembling, but I was at my limit. I finally decided to just send the carb to Eddie Sisneros ("Burned" on Thumpertalk) and have him set it up.

I put the thng back to stock and didn't really describe the spitting, because I just thought I was clueless. After a few days , Eddie calls me and says - get this - THE SQUIRT PASSAGEWAY WAS NOT FULLY OR PROPERLY DRILLED FROM KEIHIN. W.T.F!!!! He describes it and says "yeah, the thing would hesitate and spit, and then squirt forever. I drilled the hole, wired the AC pump linkage, and now it is fine." My lack of experience, I would have never spotted this, and would have chased the squirt timing forever.

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Old 04-23-2011, 07:55 AM   #38
hanksmybuddy
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Verbage, more verbage, some more friggin verbage, pics, more pics, blah blah blah. When in the hell do I get to flog the shit out of that thing, break something, so you can work on it some more.
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Old 05-26-2011, 05:33 PM   #39
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Any updates. I am in a similiar position myself. I have a dr650 that I modded with rmz forks, cogent shock, fcr carb, gsxr exhaust and a long list of farkles. It does great for dual sport rides where we may cover half the state in one day on dirt roads, railroad beds and trails. The tougher atv trails in this area tend to be mud, rocks and roots, not as much fun on a big bike. I keep thinking about adding a smaller bike for the tight stuff.
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Old 05-26-2011, 11:04 PM   #40
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Yes, lots of updates. Did two good rides, some jetting circuits are way off. Power was very good, should be even better now, as I put the 280 kit in and ported the head. But for now, the edited version.

I started with the following jetting specs:

Slow air screw 1.25 turns
Pilot 42
Fuel Screw 2.5
Needle CEMT #2 position from top
Main 140
Boyesen 1.5 turns out


I did some short runs around the neighborhood, and these settings were close. So, about 6 weeks ago I went for a shakedown ride at Cline Buttes, nearby here. It is mostly flat desert singletrack, kinda loose, and whooped out in places.


First, the bike starts like it has been sitting three years. Kick about a 10 times,, sputter, kick x10, sputter longer, kick 10x, sputter longer again, eventually it ran. Once it got warm, it would run well when it got up onto the main jet. But the pilot circuit, needle, AP pump, are all still off a bit.


Power was better than I thought. It is not fast, but it makes consistent, steady power. On singletrack it is quite efficient. Stock, it would just fall off, now it moves you forward right up to CDI cutout. Even with the sloppy jetting - I had to slip the clutch out of turns to get past a flat spot - it worked well. Once I get it dialed it will be better.


Steering took a bit to get used to. It is much, much quicker steering than my 650L, but also felt more quick than some 250Fs. But in an odd way. It did not feel light, and you can't stuff the front into a turn as well as a 250F. It almost felt like a mountain bike, where you work the bars more and use body english less. I kinda liked it.


Few things I did not like. I did not touch the forks yet, but they were not bad. The back though....sucked. It bounced and deflected off every rock, and I generally tacked back and forth down the trails all fricking day. I don't know if it is acclimation, or tuning, or whatever, but I need to corect it.


Another thing that is a real problem: the footpegs are too low. I was paying attention, and skimmed rocks several times. I have been told this by others, but it is a real problem. If you are not careful, it is dangerous.


Basically, I think I am 90% of where I wanted to be with it. However, in different ways. I thought the power would be disappointing and the handling would be dialed. Instead, it is the other way around....power is adequate and easy to use, and I adapted to it right away. But the chassis requires bigger changes in riding style than I thought, and needs to be dialed in. It was actually decent in whoops but skipped around a bunch in the rocks. Plus the jetting is way off.

I grew up in NE, and rode in Maine once or twice. On those cruel jokes you guys call trails, low to medium speed stuff, it would be great. Takes less effort than just about anything else. XR400 would be great also. So easy to ride.

They sorta remind me of FJ40s.

Hope that helps.

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Old 05-27-2011, 06:48 AM   #41
CodyY
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Old 05-27-2011, 07:33 AM   #42
hanksmybuddy
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Way too much technical jargon bullshit here. Just ride it somewhere cool and give us friggin pictures. We don't need all the other bullshit!

Call me when you want me to school that thing with the KDX!
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Old 05-27-2011, 08:19 PM   #43
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Quote:
Originally Posted by hanksmybuddy View Post
Way too much technical jargon bullshit here. Just ride it somewhere cool and give us friggin pictures. We don't need all the other bullshit!

Call me when you want me to school that thing with the KDX!
Did you know they make a CRF 250X? You could probably pick one up for about the same price as half your mods JK I spent way too much on my 125 so I know what it's like
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Old 05-27-2011, 08:35 PM   #44
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Perhaps. But I wanted the shorter wheelbase and simplicity of this. The motor actually works really well.

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Brtp4 screwed with this post 02-14-2012 at 07:01 AM
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Old 05-27-2011, 08:45 PM   #45
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Fair enough...
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