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What is effect of moving forks up or down in clamps? XR400 with USD's

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I've got a 2000 XR400R that I just put 2003 CRF450R forks on using stock CRF triple clamps and the All Balls bearing conversion kit.

I also have 17" Excel / Talon supermoto wheels on it with Maxxis Presa DOT SM tires. I just finished the fork install and mounted the wheels. Have driven a couple miles around town to make sure everything was working properly. I haven't had a chance to get it out on the road.

My buddy and I are taking a 300 mile road trip this weekend through the Sierra's. I'm wondering what effect raising or lowering the forks in the clamps has? I'd like it to be most stable at 40 to 60 mph on pavement for this trip. Right now I have the forks sticking out the top of the clamps maybe 3/4 of an inch. I think this is about as high as I can get them. My only adjustment would be to lower the forks in the clamps. Right now it seems to ride fine, but I haven't been at highway speeds yet.

Thanks.

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Lowering the forks has the effect of better stability at higher speeds. Raising the forks, as you have them now, makes for better/sharper turning for things like technical off road trails.

Try lowering them til they are flush with the top clamp.

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As stated by Trailryder to lower the forks will lengthen your wheelbase and provide the most high speed stability.

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Lowering the forks has the effect of better stability at higher speeds. Raising the forks, as you have them now, makes for better/sharper turning for things like technical off road trails.

Try lowering them til they are flush with the top clamp.

Thanks. I did that before I left, they are not flush, but maybe 1/4" out of the top of the clamp. It was rock solid until about 70 mph, then I'd get a little wobble. I think I got up to nearly 80 at one point and the wobble got to where it wanted to start tank slapping no matter how hard I tried to hold the bars so I backed out. We were mostly 30 to 50 average and it was perfect for those speeds.

That was my first trip out in supermoto trim, we got into some twisties heading east over sonora pass in the sierra's and that section of about 10 miles or so turned out to be the best time I've ever had on my motorcycle, dirt or street. We were carving corners and with a 320 mm rotor on the front, could come hot into corners and just absolutely stop on a dime. My buddy has a 2007 KTM 450 EXC-R street legal from the factory with supermoto wheels and Michelin Pilot tires and my old XR400 was able to keep right up with him.

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sounds like a great ride. i just recently put sumo trim on my xr400 and love it....(also have the USD forks).

i was thinking of doing a ride similar to this sometime soon. i was wondering how welll your Mikuni worked. did you have to re-jet at all b/c of the elevation. i'm at Sea Level in Santa Barbara and was wondering if i would have an issue with the jets i'm currently running. any info would be helpful.

btw...i have my USD forks sticking about 3/4 inch through the top tripple and don't have any speed wobble at all. it sounds kinda scary yours was almost tank slapping at 70mph. you might wanna check the front end and make sure everything is snug and tight. not sure if your front wheel is balanced but that might cause an issue at speed if it isn't.

where in CA are you? it's be fun to ride with another USD sumo'd xr400.

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are the USD forks than the stock 400 forks?

Longer is more stable in general BUT you are changing the steering geometry with longer forks.

Given what you experienced I'd try putting them back up above the clamps and try a high speed run to compare.

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lowering the forks in the clamps extends wheelbase AND rake. As mentioned before, steeper rake (higher in the clamps) will make the bike steer "quicker" but sacrifice high speed stability. If you have headshake at 50mph with them at the lowest setting, it's likely you'll increase headshake moving them higher in the clamps.

If you have consistent head shake on smooth road going straight, you've got something else happening here, time to inspect bearings, tires, balance, etc.

I know Sonora pass well, there's one turn that will bite you going east to west if you're not careful. Monitor pass is a blast as well. We used to make trips through there on 1000cc sportbikes. Always felt like it was way too much bike for the road. Sumo setup is perfect, especially with the gravel in the corners.

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are the USD forks than the stock 400 forks?

Longer is more stable in general BUT you are changing the steering geometry with longer forks.

Given what you experienced I'd try putting them back up above the clamps and try a high speed run to compare.

When i measured mine when i first did it i think the the cr's were just a little bit longer but not by much. the difference was the the axle center-line was little further forward than the xr axle position. So lowering the forks would actually bring the wheel back into the correct "position." I have mine basically flush it's really stable. I have had mine flat in 5th out on gravel roads and it only get's wobbly when i let off the throttle at high speed or if i am too far over the tank for conditions.

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sounds like a great ride. i just recently put sumo trim on my xr400 and love it....(also have the USD forks).

i was thinking of doing a ride similar to this sometime soon. i was wondering how welll your Mikuni worked. did you have to re-jet at all b/c of the elevation. i'm at Sea Level in Santa Barbara and was wondering if i would have an issue with the jets i'm currently running. any info would be helpful.

btw...i have my USD forks sticking about 3/4 inch through the top tripple and don't have any speed wobble at all. it sounds kinda scary yours was almost tank slapping at 70mph. you might wanna check the front end and make sure everything is snug and tight. not sure if your front wheel is balanced but that might cause an issue at speed if it isn't.

where in CA are you? it's be fun to ride with another USD sumo'd xr400.

You know, my steering headset was just a tad loose. We rode over the pass, then out to Bodie ghost town via 13 miles of nasty dirt road, (worst part of the trip). By the time we got back on the pavement, I think my bearing races seated completely and left me with them just a little loose. I could feel it going over rocky bumps kind of a klunk in the front end. I got home and sure enough, it was loose.

I'm hoping that's what the problem was with my instability. It wasn't tank slapping, but I couldn't hold the bars tight enough to keep them from wobbling back and forth. If I'd eased up on my grip, maybe it would've tank slapped.

But I put 15/40 gearing on it, got a 160/60-17 Maxxis Presa rain on the rear and a 120/70-17 Maxxis Presa rain on the front. Had my local bike shop mount the tires and balance them before I left.

We came out of Bodie heading back towards 395 and there was a long straight on a nice smooth road, so I opened it up to see if I could put any distance on my buddy behind me on his KTM 450. I was surprised at how much top speed I had with this new gearing, but it was nearly 80 and still had some to go and it started wobbling, so I got out of it.

Next time I will definitely rejet my Mikuni. It was fat the whole way, which was about 4000 ft up to 10,500 ft at Saddlebag campground on Tioga pass road. It was burbling every time I'd shift. When I was hammering the throttle it never stumbled, only if I let it coast a ways, or took my time between upshifts, it would load up and stumble getting back on the gas. I got the same mileage as my buddy on his 450 so that should tell you I was rich. I expected to fill up every other time he filled up, but we got nearly identical mileage. I live at sea level and my pumper is jetted for that. I will definitely take the extra 30 minutes or so it takes to rejet it for next time.

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where in CA are you? it's be fun to ride with another USD sumo'd xr400.

I'm in Modesto, CA. Central valley 70 miles south of Sacramento. My wife dropped us off in Mi-Wuk up 108. We rode over Sonora pass to 395, then out to Bodie near the CA/NV border, then south on 395 to Lee Vining. Next morning we rode Tioga Pass Road highway 120 through Yosemite to Groveland where my buddy's wife picked us up.

It was an awesome ride. About 240 miles or so total. Sonora pass was better riding with great scenery. Tioga pass wasn't as twisty and had tons more traffic, but it was absolutely gorgeous going thru the high country of Yosemite.

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...I know Sonora pass well, there's one turn that will bite you going east to west if you're not careful. Monitor pass is a blast as well. We used to make trips through there on 1000cc sportbikes. Always felt like it was way too much bike for the road. Sumo setup is perfect, especially with the gravel in the corners.

Sonora pass was awesome, we were going West to East and there's one downhill right hand 20 mph corner on the eastern downslope that we came into pretty hot and I really had to get on the brakes and my new 320 mm Braking front rotor just stopped me on a dime. I would've been real worried with my stock rotor, I don't think I could've slowed up quick enough to enter the corner.

That section over the top of the pass and heading down the eastern slope was the most fun I've ever had on any motorcycle. The money I spent on my sumo setup paid for itself in my mind in that 10 or 15 mile stretch. I had an ear to ear grin the whole way down through those twisties. I not only got a kick out of the handling, but the braking is just phenominal.

Yes, I've been over monitor and ebbets passes, which is where our next trip will take us. I did it on knobbies a few years ago. I can't wait to do it on my sumo setup.

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nice to hear you think you know what was causing the issue...hopefully it was just the lose steering stem.

what's the width of your rear rim? i was gonna get a 160 for mine but every thread i read on other sites said i shouldn't do it on a 4.25 rim cause it changes the geometry of the tire and will most likely chain rub. have you experienced any of this with your 160?

i grew up in Fresno (in SB now) and used to drive those roads to flyfish alot in the sierras. didn't ride then but, man i bet it's a blast up there on a sumo'd 400.

also thanks for the info on the carb. if i decided to head up that way i'll be bringing jets with me.

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nice to hear you think you know what was causing the issue...hopefully it was just the lose steering stem.

what's the width of your rear rim? i was gonna get a 160 for mine but every thread i read on other sites said i shouldn't do it on a 4.25 rim cause it changes the geometry of the tire and will most likely chain rub. have you experienced any of this with your 160?

i grew up in Fresno (in SB now) and used to drive those roads to flyfish alot in the sierras. didn't ride then but, man i bet it's a blast up there on a sumo'd 400.

also thanks for the info on the carb. if i decided to head up that way i'll be bringing jets with me.

I got these Maxxis rain tires on ebay from that dude that's selling them for $47 each including shipping. I got these tires for under $100 so I decided I had to give them a try. The 160 fits fine on the 4.25" rim. I changed to a non-oring chain to get some more clearance, but I have about 1/4" to 3/8" clearance from the sidewall.

The 160 on the 4.25 wheel though does make it really rounded over. There's no way I'll ever be able to use the sidewall on the rear tire cause I think I'd have to be dragging the bar to get to the sidewall.

No clearance issues though. My next set of tires will most likely be Continental SM's and a 150 on the rear to get a little flatter profile on the rear.

I just wish I had a little more power. When you're running 7000 feet plus up over the passes, heading uphill, my 400 gets a little winded. I'd absolutely love to have a plated uncorked XR650R with my sumo setup. Man to me that would be the ultimate.

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I don't mean the actual sidewall of the tire in the post above, but the farthest tread on the edge of the contact patch.

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thanks for the info on the tire. i'm running Pilot Powers and love em just so you know. not great when you hit the dirt, but if i know i'm gonna be riding dirty i just switch to dirt trim. i have friend that runs Distanzias on his DRZ and them seem to work well and hook up in dirt better too.

one of my riding buddies has a totally trick 650r sume. Ohlins front and rear sus, 680 kit...the thing is amazing....scary fun.

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one of my riding buddies has a totally trick 650r sume. Ohlins front and rear sus, 680 kit...the thing is amazing....scary fun.

That is the dual sport that i want. a plated 650r uncorked. would be sick. Probably wouldn't sumo it right was as i would want to use it as a desert bike too. lol

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I got these Maxxis rain tires on ebay from that dude that's selling them for $47 each including shipping. I got these tires for under $100 so I decided I had to give them a try. The 160 fits fine on the 4.25" rim. I changed to a non-oring chain to get some more clearance, but I have about 1/4" to 3/8" clearance from the sidewall.

The 160 on the 4.25 wheel though does make it really rounded over. There's no way I'll ever be able to use the sidewall on the rear tire cause I think I'd have to be dragging the bar to get to the sidewall.

No clearance issues though. My next set of tires will most likely be Continental SM's and a 150 on the rear to get a little flatter profile on the rear.

I just wish I had a little more power. When you're running 7000 feet plus up over the passes, heading uphill, my 400 gets a little winded. I'd absolutely love to have a plated uncorked XR650R with my sumo setup. Man to me that would be the ultimate.

WIth the extra power of the 650 I've read of quite a few transmission problems with the R's in street use. No cush hub and alot of power with real sticky tires. Wicked fast.

I had one and liked it a lot. But overkill for me.

I actually like the 400 better. :smirk:

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Bike looks sick!!! alot like mine (just commented on it in advrider)

curious why you call it the XRF400....is the "F" for FUN :smirk:

or just cause of the USD forks?

That is the dual sport that i want. a plated 650r uncorked. would be sick. Probably wouldn't sumo it right was as i would want to use it as a desert bike too. lol

best desert bike i have ever ridden? a close second is the 450x.

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Just got back from a 300 mile supermoto weekend from Murphy's CA to North Lake Tahoe and back. I properly adjusted my steering stem after our last trip so it wasn't loose anymore and I'm happy to say it was rock stable. I was cruising at 65 mph with one hand in some spots. No shimmy or shake whatsoever. Actually it seemed too stable so I'm going to raise the forks in the triples a little to see if I can get it to want to turn a little better now. But even if it stays like it is, it's very comfortable on the road.

It ran like a top and seems to keep up with my buddy's KTM 450 EXC supermoto pretty well. Up on the passes at 8000 to 10,000 feet it feels a little sluggish and his bike can pull away from me very easily, especially on uphill grades. But when we're back down to 2000 feet or so, mine really comes alive and he only pulls on me a bike length or 2 up to 50 mph or so under WOT acceleration, and of course, his 6th gear has it all over me in top speed, but we did pass a few cars in a passing lane today and got my XR up over 80 to get around some motor homes and I think it had even more. I was surprised it would go that fast. Great trip though, still loving the supermoto setup.

I'm still amazed at how versatile the XR400R is with a few adjustments to whatever riding conditions you throw at it. Street, desert, nasty rocky trails, fireroads, reliability. It just does it all pretty dang well with the right gearing and setup for the situation.

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