XR440 kit

mtngoat, Gary Hazel at Thumper and I had a long talk about all this stuff. Also a local guy here has dropped over $2k on an XR250 motor trying different hop-ups. What I am about to say is from the experience of others, not me, but seems to be of some help here.

Gary said that the higher lift, longer duration cams cause all kinds of problems. Rockers get eaten up and seat life is shortened due to the slamming closed of the the valves in comparison to the stock cam. Even with hardened rockers the problem just moves around due to the increased stress caused by the cam. Longivity the XRs are famous for goes out the window.

The other guy has finally settled back to a 290 bore (very thin liner but he already bored it out), stock cam, stock carb, ported head, and the adjustable cam drive gear. The adjustable gear lets you compensate for cam chain wear plus move the power around some by changing the cam timing. He was never happy with the pumper carb's throttle response, even though the extra flow did help out when he had the hot cam in it.

Now, I must confess, even though I planned on keeping this a secret. I did a XR250 big bore a few weeks ago. Went with the 10.3:1 (stock ratio) 277cc JB piston from White Bros. Cost on the kit was $95, the base gasket was $7, and it cost me $60 to get the cylinder bored, honed, and chamfered. Another $20 for rush shipping and my labor, so for under $200 I have an XR280. Other mods are just the usual pipe grind/baffle extraction/snorkel removal/jetting.

I flat love this bike, let me tell ya. New springs are in order as it packs down in the whoops at race speed, but overall the bike is awesome. Never would I have imagined that the little XR would be so fun. The 277cc piston represents about an 11% increase in displacement. Quite frankly I question the XR400's 415cc mod - just 4% increase in displacement? Seems like alot of work to me.

Having owned the WR400, now the XR280, and ridden about everything that burns petroleum, I have a hard time understanding why someone would drop a bunch of coin in the XR400. It does not have that light feel the 250 does, and its 400 class competition is SO good in stock form. Not to say the 400 is a bad bike, it is not, but perhaps is the one that should most be left alone and appreciated for its attributes.

The under $200 big bore kit for the 250 is a no-brainer and best I can tell does nothing to effect durability. The cool thing is the non-Nikasil barrel makes this possible. Beyond that though, I'd say look for a different bike like a DRZ.

At one time alot of this work may have made sense, but maybe not so much sense now that the WRs, DRZs, and KTMs are available. I picked the XR because I wanted no radiators since I do trips in Mexico and did not want dropping it on a rock to end my ride and leave me 1,000 mi from no-where. It only takes 15 hp to go 75 MPH, so the 280 making 24 or so ponies will pull me and my gear fine on those rare pavement sections at 60-70 MPH. The 280 does not roost, but it does reward and promote a smooth riding style.

Good luck on picking the right mods for your XR Traylrider42 and let us know how it comes out.

The adjustable gear lets you compensate for cam chain wear plus move the power around some by changing the cam timing.

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Not much - valve to valve and valve to piston clearance are tight on all the XR's. I'm not saying cam timing can't be changed, it's just not something that should be tackled by the average joe in his garage - unless you're willing to clay the top of the piston to check tolerances.

As far as cam chain wear goes, I assume you're talking about stretch - the change is negligible, so adjusting for stretch is typically not necissary - if the cam chain is stretched enough to change cam timing - it's time for a new chain.

I did a XR250 big bore a few weeks ago. Went with the 10.3:1 (stock ratio) 277cc JB piston from White Bros

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Excellent kit! really makes a difference in torque especially. 10.3:1 is still higher comp than stock, but not so high as to cause any detonation problems for most. I assume you mean JE piston - I'm not aware of the JB brand.

$60 to get the cylinder bored, honed, and chamfered

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No chamfer on a four stroke - hope you didn't pay for it :)

. Quite frankly I question the XR400's 415cc mod - just 4% increase in displacement? Seems like alot of work to me.

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The reason it seems to work so well is that it utilizes the stock porting and camshaft so much better than the stock displacement - the stock head/cam configuration actually flows better than the 400cc requires. The 415cc just kinda optimizes everything. Admittedly, the 440cc will add more, but is more expensive and for lighter riders doesn't gain much over the 415cc kit - I was just offering a cheaper option which many people aren't aware of.

Having owned the WR400, now the XR280, and ridden about everything that burns petroleum, I have a hard time understanding why someone would drop a bunch of coin in the XR400.

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For the same reasons you chose the 250 over your WR400. Bullet proof, long-proven technology. Smooth trail-friendly power. No hi-tech radiators to deal with.

Why do modifications? For the same reason you did the 277cc kit. You weren't looking for a different bike, just more of what the XR already has to offer!

Yea, JE piston not JB. JB was to fix that nasty hole left by the con rod ;).

On the cam chain wear and adjustments, just relaying what someone with experience told me. Technically it is not stretch, it is wear, and the wear shows up as lengthening the chain. The metal does not stretch. XRsonly touts the merits of the adjustable gear on their web site. Must just be marketing BS then?

Chamfering - yes the xr250 has a chamfer on the bottom of the barrel. Taking out the material from the bore job squares the taper on the base of the cylinder. The chamfer makes it easier to get the piston in upon reassembly. The work was done by the guy who did Colin Edwards' race bikes prior to him being picked up by Yoshimura, so I assume it was done right. If you still disagree maybe you can supply some type of write-up and I'll make sure he sees it.

Compression ratio - per honda's web site:
"SPECIFICATIONS

Model: 2002 XR250R
Suggested Retail Price: $4,699
Engine Type: 249cc air-cooled dry-sump single-cylinder four-stroke
Bore and Stroke: 73.0mm x 59.5mm
Compression Ratio: 10.2:1 "

10.2 vs. 10.3 - as far as I'm concerned they are the same.

If you would not mind expounding a bit more on some of your statements dualsportr it might be of some interest here. Example:

"The reason it seems to work so well is that it utilizes the stock porting and camshaft so much better than the stock displacement - the stock head/cam configuration actually flows better than the 400cc requires. "

Any supporting info would be appreciated. Thump provided a nice head flow chart, stock vs. modified, on another Yamaha-related thread.

Thanks for the feedback Tex. Kinda figures (especially with the cam) that Honda struck the right balance of performance/longevity and attempts to improve the former, can overly compromise the latter. Forgive me if I get even more ethereal, but it seems like the fundamental enjoyment of riding (not racing) can fall prey to performance obsessions too.

Funny thing happened a few weeks ago. My bro-in-law crashed and broke his clutch lever. We switched bikes and I rode his "stock" (excluding airbox, exhaust) 01 Xr4 out of the woods (eventually I rigged the compression release as a clutch lever). Now my 96 Xr440 was purchased used with a lot of goodies, upon which I piled on a fork brace, stabilizer, header, etc. What's ironic is I really enjoyed riding the stock bike. It felt lighter, snappier; just fun. Now I know my motor is a little tired and the stabilizer makes the steering a little heavy, but setting all the rationalizations aside, I really had fun riding that stock bike :confused:

Anyway, I really like to see others learn from my mistakes and when my bro-in-law asked me about mods, I steered him towards stuff that would make the bike more enjoyable for him (triple clamp, pro-tapers; he's a big guy starting to stand up more on the bike) rather than "velocity" mods.

Sorry if I digressed. There seems to lots of "end-use" feedback that the "bore-mod" maintains that longevity/performance balance. My advice is to also consider enjoyment (depending on where and how you like to ride) in the decision process.

'goat, no apology necessary. I like your digression as you called it.

The 250/280 really opened my eyes to what you are saying. Man was it fun, just a great companion. Since I was riding alone quite a bit, max velocity was not the objective for my rides. Max fun with a high degree of safety was. The XR really shined. Once I got the jetting right I put 3 tanks (big tanks, clarke 3.8) thru it with just lubing the chain and an occasional bath. The thing was always ready to go. It would putt like a trials bike while I cruised and watched the sun set over the mountains or would scream WFO up any hill out there. Traction was the limiting factor, not HP, with the 280 at 9000 feet.

I hope this does not jynx me, but man was I glad I did not have my 300EXC with me as originally planned. With the #6 slide (now in the mail to Enduro Eng to be cut to a #7) jetting would have been a bitch.

Taking out the material from the bore job squares the taper on the base of the cylinder.

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Typically done with a deburring tool - about a 10 second job - which is why this is the first time I'd heard it mentioned in the four stroke context. I guess I took it as a given that a good shop does this as part of the deal. I agree it's very helpful when re-installing parts.

You're really lucky to have such an excellent shop near you. Most people have to resort to the local OEM dealership (some of which are good - others ??). Having someone with that level of expertise do your work is awesome, you know they go the extra mile and make sure everything is right.

Any supporting info would be appreciated. Thump provided a nice head flow chart, stock vs. modified, on another Yamaha-related thread.

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I will try to dredge it up. We've closed our head room at work - so the flow charts have been boxed up, but I believe they're in a box I can get to pretty easily. The thing is, what I may come up with is the chart from the TRX, and not the XR. The tests I'm referring to were done back when the XR400 was new. That means I'll have to dredge through literally thousands of flow charts to find the first few on the XR400 (which would be the one with the cc comparison and cam specs). The TRX numbers came out almost the same, but I wouldn't expect you guys to take my word for it.

Yes, I know it's something I should have handy - but I don't. I'm working out a new system and entering stuff into the computer, but I haven't even started on the flow charts yet. Heck, I'm only up to dyno data from 1977 right now, and I've been at it off and on for about 3 months!

Thanks, Rich. Sounds like the "no replacement for displacement" idea.

I was hoping for some specifics on the XR400 that would substantiate the efforts of the overbore with only a 4% increase in displacement.

Dualsportr, my apologies for not knowing your background. A quick look at your profile tells it all. My opening remarks about talking with Gary and a local guy were an attempt to say I am no expert on this stuff, just relaying some comments. Thanks for participating.

No problem Tex - Actually Gary and I are friends. I spend quite a bit of time on the phone with him. He's always trying to get me to come down and do some Texas-style riding. I'm gonna have to take him up on it sometime.

Rich - as always - your knowledge stupifys me. I'm frustrated that I don't have the technical learning you do, and wish I'd started in this business earlier.

I sometimes also wish my boss would not be so anti-computer. His input on this forum would be interesting - I'd love to see the fireworks! Rich and Pete together out-tech-ing each other. Oh man! Talk about brain overload. Holy toledo!

I am still on a steep learning curve - but I have a tendency to just catalog the knowledge I want or that is interesting to me. Because of this, I remember the effects of a process, rather than the cause.

And you'll all have to forgive me - numbers have NEVER been my friend. So when asked to quote chapter and verse, you'll have to wait awhile - I'll need to go look it up!

Summary, 1st cut

This thread achieves my "print & file" threshold. Thanks for all the responses. Now, for us "end-users" who need an exec summary, here's my glean:

Bore -- Most available bore kits provide expected benefits of higher displacement/compression, but on the XR4/6, they also realize higher, more desireable port velocity, even with smaller bore kits. Caution is warranted with bore kits leaving thin cylinder walls.

Cam -- Higher lift and/or longer duration cams may provide benefits, however, longer duration cams "synergize" with larger bores further exploiting related port velocity improvements. High lift cams stress valve train components and compromise longevity. Longer duration cams stress less, if at all.
Cam choice is stock (little or no "con", other than price) or aftermarket comprising: hard-weld/re-grind (wear/rockers need consideration) or re-grind/without added material (better wear, but hard rockers still recommended).

Re: Summary, 1st cut

Originally posted by mtngoat
This thread achieves my "print & file" threshold. Thanks for all the responses. Now, for us "end-users" who need an exec summary, here's my glean:

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:) :) Thank you :) :)

I just got an e-mail from xrs-only about the 430 kit. I hope I don't step on anybody's toes by posting this:

....The 88mm piston or 430 kit is cutting it close on the cylinder wall being
too thin. To be on the safe side I would put a BIG BORE sleeve.
Thanks
Kamell

That's kinda funny. I met Kammel last month, he handles inbound calls, counter service and e-mail. The discussion I related above (verbatim) was with Kammel's boss, the GM. Appears we've flushed a little inconsistency. Maybe they're watching this thread. ;)

Anyway, thanks to all again. This has been the most substantive and informative thread on XR4 cam and bore mods I've enjoyed so far.

Printed & Saved

Hey Guys,

This has been a very informative post. I have learned a lot about my bike.
You see it was my bike that Trailryder42 rode and started this whole post.:p
I have to say that I really enjoy the bike, more than I thought that I would. It is a really a blast to ride. The power feels nothing like a stock XR400. If you like low to mid range power do the 440 kit. This bike produces tons of torque. It is so much fun because you can pick up so much speed with so little RPM's. I can usually ride it a gear higher than maybe I should. It will pull hard right of idle and has a really strong mid range. The top end is not that great but, in the mountains of Colorado, I don't ever need it. It also seems to rev a lot quicker than the stock bike. As far as mods go the only other engine mods the bike has is a an E-Series pipe with the large diameter headpipes, lightened flywheel and the floats have adjusted so they don't move up and down too much in the woops. The compression ratio is close to stock and the cam is stock. Most people can't believe that an XR can go that fast. I just need to get in better shape so I can hold on better. Basically, the limiting factor is my ability and not the bikes. All in all I have a tremendous amount of fun with the bike and it will do anything that I want it to do or am able to do at this point.

Whoa, cool thread! It's amazing the kind of info you come across here at DRN.

This is a great thread if you like XR400's or are planning on doing some mod's to your XR400.
I am running a 415cc JE 10.5 piston, an HRC cam , heavier valve prings, stainless intake valves, slightly ported head, stock carb(62 pilot,168 main A16A needle), W.B. air filter, W.B. E- series exhaust with headers.
This engine excelerates very hard and you can still rev it. With very broad power this bike is easy to ride with minimal clutch work.
We tried the 406 kit first but the 415 is quite a bit better. It's hard to imagine such a little increase in displacement can make such an improvment.
I also had a 96 XR250 with a 280 kit, a great investment for this bike realy wakes it up. I traded that bike for an 00 XR650r, I like power, I like heavy bikes, I guess that makes me nutts?
As for dumping money into an XR400, I'm probably the worst guy on the DRN as far as that goes.

Kevin

Hey CUZ,

Glad to see you pokin your ugly mug around here for a change!

Get in touch, we'll get together and I'll slow ya down on a ride sometime soon!

Rod

Hey Rod,

I am allways pokin around here. I am just usually the quiet type, lurking in the shadows and absorbing information.;)
What are you doing Wednesday? I think I might hit Rampart with whoever else wants to go. Or there is always the weekend. Let me know.
I will try and not hit any trees, or break anymore fenders or fall down for no reason like I did last week.:o

Cuz

Hye Cuz,

Wish I had paid better attention to your location and riding areas. I just got back from 3 weeks near Woodland Park (Crystola Canyon) and had my XR with me. Ride the Divide trail system about 8 times, mostly alone. Did RR one weekend while a friend was in town.

I'll be back up there in a few weeks but just will have the KLR with me - left it behind. It can do the forest roads and lots of 717 without a problem, just not at speed.

Tex,

Look us up!

We're usually good for a ride. If you don't mind waitin' for a boat anchor like me!

Love riding Divide, it's geting a bit whooped out.

Sorry to let this thread go on this tangent

Rod

Yea, a few whoops and 4 wheeler ruts to deal with for sure. I went way West the last time I was there over past Signal Butte and found the trails to be better. The right map and a compass sure help navigate that place.
That Signal Butte single track was a blast, as is 717 over parallel to CR 33.

Do you know of a better map than the Thunder Trail map?

Nope I use the Tundertrail map exclusively. THat and the map between my ears.

Rod

THat and the map between my ears.

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Mine's defective - does anyone know where to get a replacement that actually knows which way is North??