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I want to machine a step in the lower fork tube (on an old XL250R) to accept a custom clamp to mount a brake caliper so I can update from the front drum brake and keep the OE speedo drive mechanisms

the question is how well would it need to be clamped to the tube?

thats the first step anyway..

untill I find out what size forks are on the NX250 I think the only other option is finding a late model XL125R front end (late 80s) from a bike that was never imported...

thnx

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By the time you pay a machine shop to modify a set of forks that were never designed to accept a disk, plus buy a disk, a hub, a caliper, a custom caliper mount, a master cylinder/brake line, brake line guides and clamps, and re-lace your original wheel.... it might be cheaper to just buy a modern (1990 and newer) XR250L and get disk brakes on both ends... unless you're snowed in and looking for a big project :cry: :cry:

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I thought about adding a side note to tell folks not to suggest getting another bike since thats what you get everytime you ask about an older one.

obviously you think this is my only bike and I dont have the spare parts or the machinary needed. sure, your advise may help to somone but its useless to me. did you even see the question?

a "Big Project" HAhaha!

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Whatever. If your gonna give smartass replys to an honest attempt to help...

1) If you're in love with the awesome power and amazing handing of an old XL250R go ahead and put as much $$$ and time into it as you want.

2) If you actually own the machinery needed to do these modifications you should be making enough money by using them to actually pay for a real motorcycle.

3) Your "question" was how well the caliper mount would have to be clamped to the fork tube... it needs to be clamped really well. Satisfied? I suggest you look at all the major manufacturers that clamp the caliper to the fork tubes and copy what they do.

4) If you don't have the skills to hang on to the power and handling of a new bike (and by new, I mean one that has been manufactured in the last 20 years) the stock drum brake is probably fine for your abilities.

You really should try riding a modern dualsport motorcycle. You will be amazed at how much the bikes have improved since the 80's.

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I want to machine a step in the lower fork tube (on an old XL250R) to accept a custom clamp to mount a brake caliper so I can update from the front drum brake and keep the OE speedo drive mechanisms

the question is how well would it need to be clamped to the tube?

thats the first step anyway..

untill I find out what size forks are on the NX250 I think the only other option is finding a late model XL125R front end (late 80s) from a bike that was never imported...

thnx

After you build the clamp and mount it make sure it works like you want then tig weld it on.

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I had a 1986 XL250R, as well as a 1993 XR250L. To be honest, the drum brake on the 86 worked pretty well for the speeds that the machine was designed for, the one on my 93 wasn't any stronger, but on a long downhill, the drum would fade a little, but the difference wasn't night & day.

There would be a LOT of work trying to add a disk brake where the drum was. It will take a whole front wheel, calipers, master cylinder, hoses, etc, etc. The fork tubes are different diameter between the two, but I wonder if the whole front end assembly might be interchangable at the steering head. The suspension on my 86 wasn't nearly good enough for aggressive riding (the rear actually wasn't all that terrible for not being adjustable, but the forks were wimpy, the forks on the 93 were a HUGE improvement). Anyway, if you could get a whole front end, triple clamps & all (if it would fit) I think that would be the better way to go. Whenever you start cutting down, welding & clamping on fork tubes you risk making them out-of-round at the least, and weak to the point of failure at the worst. For what it would cost, I just can't see how it would be worth it.

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mxbob, the only "smartass" entries I see here are yours, I refuse to waste any more of my time replying to them.

>> After you build the clamp and mount it make sure it works like you want then tig weld it on.<<

Ive thought about that but I would need to pre heat the tube so Im concerned about distortion there. I cant imagine there would be a whole lot of rotational force at the clamp anyway but thats why I ask.

>> I had a 1986 XL250R, as well as a 1993 XR250L. To be honest, the drum brake on the 86 worked pretty well for the speeds that the machine was designed for, the one on my 93 wasn't any stronger, but on a long downhill, the drum would fade a little, but the difference wasn't night & day.<<

I have a '92 250L aswell that I bought just for the suspension, 1800mi and runs/looks like new. the '85 has 5mph more and gets to it in half the time the '92 does.. (Honda took "detuning" to an extream on the 250 thumpers after the dual-carbed fire-breathers.) what I discovered attempting to swap the front suspensions on these two was that the later bike uses ball head bearings and the earlier has needle bearings so a simple swap job it isnt. the rear end of the newer has an offset shock so nothing will swap including engines eitherway because of the dualcarb set on the XL. I dont have a problem with the drums stopping power, its just that Im on my 3rd drum because they get warped somehow so the get a tight spot which can be hazardous when threshold braking on pavement. time for a disc. this conversion is really not that big of a deal for me either. Ive allready installed a same year 350R front onto it by swaping the stems but the extra wieght and higher handlebar position was not acceptable to me. Im also trying to keep the extra pounds to a minimum (it is a 250)

I keep the XR250L for friends to ride but its aneamic compared to the XL250R, yup the suspension is night and day off the road but it cant make up for the gutless engine and since I cant fit the dual carb set-up on it I dont care to "help" it.

I could do this alot of different ways but what limits me is trying to retain the OE clamps (for the steering lock) and the OE speedo (aprearance)

>>For what it would cost, I just can't see how it would be worth it.<<

It wouldnt be for most but half the enjoyment I get from this bike is improving it.

a grey market XL125R front end would be the best solution but so far I cant find one. still looking into the NX250 parts option but those aint exactly plentyfull either.

next is an XR100R f.disc brake "kit" which is sure to be of more intrest to the masses. sombodys making them now but they are WAY to proud of them.

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>> After you build the clamp and mount it make sure it works like you want then tig weld it on.<<

Ive thought about that but I would need to pre heat the tube so Im concerned about distortion there. I cant imagine there would be a whole lot of rotational force at the clamp anyway but thats why I ask.

There will be a significant rotational force. I don't see how you could get sufficient clamping force to prevent the caliper from trying to spin around the fork leg without welding. The other option would be to machine a lip or step of some kind but I doubt you have enough material to start with.

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I'm with starmoto.

Any of you guys build or modify something just because you can?

If not you have no idea how much fun you are missing.

I gave my neighbor kid my wretched 04 CRF250X. He has just finished putting a 1999 CR250 engine in it. Everybody told him he was crazy but 2 months later he has the most sano conversion I have ever seen. He did all of his own aluminum welding (learned in shop class) and machined parts in his uncles garage.

Now the kid is in the process of trying to figure out how to put the electric start system from the X motor into the CR motor.

I would have said, if anybody asked me, that the whole idea was a waste of time and not worth it. Well the kid has a relatively new bike with a much stronger engine than the X engine and so far has less than $500.00 in it (free bike and engine helped).

I rode this thing in the woods and it really rips.

By the way the kid is 15 years old. Most of us probably couldn't have done it at that age.

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I think it will see minimal forces that could rotate it myself because the rotor itself would make it hold that angle but cant be certain myself w/out making it I guess...

I would have put the dual carbed air cooled 250R engine in that 250X. if they were streetable here I would have allready. I buzzed the crap out of a stock dual carbed 250R for 27,000 miles it finally started some really odd smoking symptoms that didnt effect performance, when I got in there I discovered that the top two ring gaps had lined up, I could have put it all back together and got atleast another 10k on it.. (from the dual carbed "grenade" everyone said was not "reliable")

Honda really droped the ball bigtime here.. these CRFs are useless for real world use (occasional street service)

while looking into the older ('88) Honda NX stuff I found that the NX250 was a watercooled thumper, the NX 125 and 650 were air cooled. I didnt know that Honda had a LC250 before the CRFs. these were electric start aswell. Im sure they had to be more reliable than new CRF but probably gutless.. Id like to find one of those and find out now..

how long before you had problems with your 250X, was it the valves or other?

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What about modifying the head tube to accept the bearings from the later set-up? I assume you have a lathe, could you turn some adaptors/spacers or maybe even make some new cups all together to accept the later style needle bearings? Cut out the old ones and weld in the new ones, the run the whole new front end from the '92.

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>>What about modifying the head tube to accept the bearings from the later set-up? <<

yeah, but I prefer the needle bearings and lighter front end. and that is alot more work than I really want to get into with it. potential geometry changes if not perfectly accurate allthough a little less rake might be good if I were to go there. it would be do-able.

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The bike burned oil from day one. Honda replaced 2 sets of rings then replaced the piston, rings and cylinder. It still burned oil so they decided it must be the head and replaced it. Still smoked like crazy. Honda, of course, said it was my fault. I was dealing with idiots.

I may ride over 100 miles in a day and there was no way this bike could go that far withiout running out of oil. I've owned Hondas for over 30 years and this will be the last. Chrysler did the same thing to me. It took a while but I've finally figured out that brand loyalty is pointless. Most large manufacturers seem to care less about you.

After riding my 02 400exc for over 10k miles and my CRFX experience I bought an 04 400exc, a very smart decision. I've put a little over 2k miles on it.

Unfortunately I made the mistake of riding a Husky TE450. Oh well, it's only money.:cry:

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OK, NOW I get it.

At first I thought you were trying to shadetree something, trying to make the XL into something it was never meant to be. Now that I see you are doing it as more of a 'project' than going the easiest/cheapest route it makes more sense. I have done my own share of making my own, rather than just buying something someone else made. There is a certain amount of pride in building it yourself.

I sure am glad someone else echoed my thoughts. I went from my 86 XL250R (the 85+ years were the best engines, and IMO, the 86 seemed tuned the best. I bought my 86 new after I graduated High School, and it ALWAYS was the fastest, best running 250cc 4 stroke in the group I rode with). Well, to make a long story short, I sold it because of the suspension shortcomings(probably a mistake, I had the thing 10 years, the engine was absolutely 100% trouble-free, and still ran as strong as it ever did, didn't use any oil, and had no rattles/clatter). The worst thing I could say about it was the suspension, especially the forks, just weren't up to par. Constantly bottoming out. If I added a spring spacer, they 'bounced' (not enough rebound for the stronger springs) so I went back to stock springs, and tried raising the oil and playing with the air. I ride about 80% off-road, and am not that aggressive, but when I ran enough oil to keep from bottoming hard in the front all the time, I would blow fork seals at least once a year. I became very frustrated with the forks because of that. Rather than spend the money to get the forks re-valved, I sold it, after 10 years of ownership, for $100 more than I paid for it new (at the time I thought I had a sucker on the line, but now I wonder...) Reason: I rode around on a buddies 'new' XR250L, and fell in love with the suspension action. His wasn't broken in, so I was taking it very easy on the engine, but I could tell how improved the suspension was. Bought a '93 XR250L in '96 for about $200 more than I got for the old XL, thinking I had a bargain. It wasn't until I got it home, and rode it around some that I realized how WIMPY the engine was. All this time I thought I had somehow gotten a 'lemon' but maybe that is just the way they were. To top it off, this bike never started worth a darn (ran just as good, once started, except for lack of power, especially at speed). The last straw was when it started developing engine problems, in half the miles as my old XL, given the same care (got rid of it, and got a KLX300, but that is a different story). Your post brings back fond memories of that XL250R. Mine had the wildest powerband of any bike I have ever owned. Torquey off idle, it pulled good, revved up to a 'dead spot' to where you didn't know if to short shift, or let it rev out more, and then WHAM! it would take off. Yea, I know, a 250cc thumper isn't an arm stretcher by any means, but it sure was to an 18-yr old skinny kid.

Getting back to your original question:

Maybe it would be easier to machine the clamp to fit the fork tube diameter, and cut a slot or boss or whatever you would call it into the clamp, to prevent the caliper bracket/clamp from rotating. This boss could engage the boss already on the leg where the stock brake plate or whatever you call it locked into the fork leg. There will be quite a bit of rotational force on the clamp, trying to twist it on the fork leg. I would be scared to just use clamping force to hold it, as I would be afraid that in order to get it tight enough to hold without slipping, you could slightly 'crush' the diameter of the fork tube, and get a sticky spot in your suspension action, or worse yet some form of internal damage. I definately wouldn't rely on the brake disk to hold the caliper from rotating, as either the disk or caliper has to be 'floating' and that would put a binding action where it most needs to be free. I could see a worst-case scenario, where the disk got bent, and the caliper skewed, locking the front tire solid.

I also think the front end could be converted from needle to roller bearings, as well, or the other way around, if need be. Might take some machine work to make adapters, but if you have access to a lathe, it should be easier than modifying the shock leg, and fitting will likely be less critical, as the stem is threaded so you should have more than enough adjustment there to make it work, unless the stem is either too big to fit your frame, or too short.

FWIW, I have never had brake/drum problems on my 86 XL250R, as far as needing to replace any parts on it. However, the drum brake had one disturbing quirk, now that I think of it. Whenever the brake material got damp, it would get EXTREMELY grabby after it dried off. After a couple stops to 'glaze' it over, it worked normally. I learned that after the bike hit ANY water, rain, or even sat more than a couple days (even a DEW would make it do this) I very gently would drag the brake to glaze things over some. The first time it happened, I was on a gravel road, going about 15-20MPH, and wanted to stop. Hit the brakes like you normally would, when you wanted to come to a halt in gravel, and the front locked up, washed out, and caused one of the 3 times I had that bike laid over in 10 years. I was a new rider, with maybe 40 miles experience at the time. After I learned about the quirk in the brake (the rear, strangely, never did that) I wished it had a front disk, like the XR-R series. After a couple hundred miles experience, I figured I could live with the brakes, and wanted the XR suspension (especially the fork!).

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with y'alls help Im starting to understand how the rotational force would be more than I thought. I was planning on only removing enough material on the tube to make the surface smooth/round. I had thought about the crushing effect of a clamp either because I was assuming it wouldnt need that much.

I'll have to find an NX250 before I decide exactly what to do to it. another reason I didnt want to modify the st. head is that I just re-painted the frame ("flash-red" epoxy) after welding on XR250R oil cooler mounts. before I tore it apart (it was still running great but smoking only when idleling, hot or cold) I collected some speed equipment for it since I was going into it anyway.

now Im running a +.040" wiseco, headwork by a competent Indy/Nascar specialist with stock size seat diameters, the one year only XR350R secondary carb w/ XL350R primary, a Cobra pipe on a jet hotted the OE exhaust header (which is much larger on the se early RFVC w/duals) and added w/02 sensor port for the digital mixture indicator (I made) used to safely start/break-in/tune the fresh engine & 350 carbs since I had no baseline whatsoever to go by. this is a must, the early DC RFVC heads can crack between the sparkpkug hole and exhaust valve seat if combustion temps ever skyrocket even once and thats where the bad reputation came in, incompetent tuners trying to fiddle with a dual carb per cylinder arrangment and leaning the engines out.

the oil cooler also took some effort to make it appear absolutely stock exactly as on the XR250R. the XRs side cover wouldnt fit the frame so I had to modify the XL cover, I definately run the oil-temp dipstick on it that too.

this engine was the best AC 250 Thumper ever made by Honda or anyone else. that is my opinion of course but the only other I am aware of is Yamaha with the IT and XT from the same era. were talking dual inlet ports, one for each intake valve. a design that makes it possible for truely race prepped engines to retain ridability while putting thru towns so not to attract attention.

I would love to see this design come back on something! I would make it Liquid cooled and use a 4 stage digital injection induction system, using 100oct w/2.7% O2 base and H2O and NO2 on auto-fly!

farmr123, your suggestion to make the clamp fit the tube as-is sounds like a plan, Ill have to look into that. I think I can get these forks to comply to motard specs OK which is mostly what Im after since I hate to get this one all muddy anymore. you would love a ride on this bike man, it has it for sure! Ive got one of the last XL600Rs too! same engine design but w/fdisc, its too heavy for most of my fun though. they both look the part as original.

anyone know of an NX250 for sale? Honda was selling street motards (supermoto) in the US over ten years ago with these, I gotta find one!

I also thought about not mentioning this bike but Im sure everyones first question would then be..

"Stay Tuned and Safe Motoring" -SM

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