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Shiny's adventure with dirtbikes

30K views 571 replies 33 participants last post by  shinyribs 
#1 ·
So,I dig the KLR, but it didn't quite fill the bill in the offroad department. Who da thunkit? So I bought this '98 XR400R. Street title, partially installed Baja Designs dual sport kit. The engine was supposedly rebuilt, but who really knows without digging in? Looking the bike over I could easily see fresh gaskets where the cases had been split, and the seller had a clean looking shop...so I took the risk. His claim: new piston/pin, new rod bearings, new cam chain. Fingers crossed.


As I got it. Dingy, but looked solid. Hardware looking healthy, no crushed frame tubes, but a pretty badly bent rear rim. Started easily and felt strong, but I have no experience with these bikes to judge against. Talked him down to $1,200 and loaded her up. Baja Design kits are $500 and the street title has to be worth something. I figure if the engine dies I'm not in it too badly anyway.



As always, my new bike needed fork seals. But at least I finally own a bike that won't be needing a fork swap right off the bat! This is a first for me. Never had a cartridge fork apart before, but it wasn't a bad job. Turned up a fork seal driver and cleaned up a couple dings on the legs. Good to go.



Took her out for a ride and it had a pretty loud valve tick. Checked the lash, it was good. Did some research and found out the auto decompression system is known for going wonky on these bikes. When you press off the auto decomp it leaves oiling passages exposed. Typical approach is to put a sleeve over the passages and call it good, but there were a couple pressed in pins that I didn't like the look of. So I made a sleeve that would capture them as well.

Stock set up.



Exposed passages and pins.



Fixed.



Cam chain was supposed to be new, but it wasn't. Cam chain tensioner was just about at the end of it's travel. Found out that a CRF450 cam chain swaps right on, is a few bucks cheaper and is two plates wider, so stronger. Win-win. :thumbsup: Motor seemed clean inside. Cam lobes and rocker faces look nice.



Took her back out, tick was gone. :) With the auto decomp gone it was easier to start and a low speed stumble I was having was gone. Altogether just ran better. 2nd and 3rd gear power wheelies at will. The auto decomp was intermittently opening an exhaust valve. Motor was nice and quiet now. Went to change the oil and it was filthy. Black and speckly. :doh: Ran a couple gallons of gasoline through the motor, frame, oil lines and cooler. Figured the PO didn't clean things as well as he should've. The lie about the cam chain isn't giving me much hope about the engine in general. Didn't find anything alarming in any of the oil screens, though.

With the engine running strong, the clutch started slipping in higher gears. Pulled her open and found glazed steels. Springs and frictions are well within specs. Scuffed up the steels, back together....4th gear power wheelies if I hit it right, 5th gear clutch wheelies are easy. This thing is a horse. :shocker:

But....clutch started slipping again after a few rides. Tore back in to the clutch. Steels are completely polished smooth already :wtf: Took another look at the frictions plates and they're hard. Almost feel like ceramic. Dropped the oil to have a look....black and speckly....fook. Maybe the frictions have gone hard somehow ( baked? overheated?) and are grinding up the steels to make this dirty oil? Engine runs too strong/quiet to take a chance, so it's time to dig in.
 
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#2 ·
Re: XR400R

Present day....

Now that the wife's Jeep is healthy, I tossed the XR on the table.

Currently cleaning up the extra plastics the bike came with to doll her up a bit. Half tempted to order fresh plastics, but the Jeep ate up those funds. :(

Sorry for the ultra closeups. Kinda cramped in the shop.



Beautiful... does nobody take care of their bikes??




Oh, I took a bad landing of short cliff and finished off the rear rim, so this will be getting replaced, too. Bought a replacement off a guy for $25.



Three bolts pulls the subframe off.



Two more pulls the rear suspension off.



^^^ I'd read horror stories about swingarm pivots freezing up and guys ruining frames trying to pound them out. The rebuilt engine theory was giving me confidence that the PO had the pivot out when I was buying the bike, but I was nervous about it tonight. Slipped right out, though :) Happy.

This will need a proper rivet-on. Clip-on link and offroad chain guides don't jive.



Knocked loose all the cables, wiring harness and plumbing.


Sat the cables, controls and the whole wiring harness off to the side with the bars.



I was impressed with the header design. Very beefy. Unbelievably light, too. Can't say the same about the muffler though. It's a brick.



Not much left at this point.

 
#3 ·
Re: XR400R

Removed the starter. No battery box, cables, neutral safety, solenoids, etc...:thumbsup:



Popped the head off and was happy with what I found. He actually did replace the piston! Bore looks clean, too. Hasn't broke through the crosshatch yet.



Skirt looks 10x worse in the pic than it does in real life. Kinda shocked how bad this pic looked. Rings don't show a scratch on 'em. So still wondering where all the metal is coming from at this point.




Happy to see it's a quality piston in there.




Not happy to find a scored pin and little rod end. :( Still not enough to explain the oil contamination. But probably a result of it, though.




Dug in a little deeper and found the rod is loose on the crank. Needs a rod and big end bearing. Problem is, I'm not really set up to press the crank apart to do it. Checked some prices and a new rod & bearings is around $100. It cost $200 to have the crank professionally rebuilt. Easy decision. It'll get sent off to MrCrankshaft one day this week. Meanwhile, I gotta find a 20..x 1.50 bolt to press the flywheel off so I can get the durn crank outta the case. Luckily, every case bearing is healthy. There's a lout of 'em, so I'm glad about that. Everything in the transmission looks like new. The clutch basket needs some attention.




Notice the empty poles on the stator. The two thick looking poles at 11 and 12 o'clock are the ignition windings. The other 4 poles are the lighting coils. To run a proper headlight I'll need to strip those off and wind the remaining 6 poles that were never used. Should take my lighting output from 55 watts up to around 150 or so. I do plan to plate this bike.



One thing I was happy to find, there's not a damaged bolt or thread anywhere on the whole bike. At least there is that.


But for now, we wait. :(

 
#8 ·
Re: XR400R

The cushion springs in the clutch basket are a little weak. I checked in to aftermarket baskets, but they all just reuse the stock cushion plate. Replacement springs are not available, and apparently guys just don't worry about it. I didn't like the idea of things slamming around, though. I could turn the springs with my fingertips.



Drilled out the rivets. Pretty neat setup. There's a Belleville washer to soak up lateral slack and the rivets don't see any drive forces. They only retain the springs. You can see the oval holes that allow it all to work. The rivets drilled out easily. They weren't very hard. Some 10.2 bolts will be stronger than what it was built with initially.



Mock up the primary drive to make sure there's enough room for my idea. Looks like tons of space to put bolts back in place of the rivets.



Went ahead and drilled and tapped the old rivet holes. The rivets were 6mm, the news bolts will be 8mm.



Measuring the difference between free length and coil bind. Unfortunately, not as much room available as I wanted.



I wanted to run a button on each end of each spring, but I've only got enough room to fit a button on one end. I'm not comfortable making the buttons thinner. Guys make preload spacers for worn fork springs, figured I could get away with it here.

Turned up some buttons.



Installed a couple to make sure I'd be able to squash them back in their pockets. Not easy, but doable. Compress a spring and button in the vice, then slip the primary gear over it. Kinda nerve-racking, but so far no projectiles.




Looks like it's gonna work, but I need to pick up some different hardware, so called it a night on that. I'll harden the buttons tomorrow before I assemble the basket back together.


Spent the rest of the time dressing up the basket fingers. The dents weren't severe, but might as well flatten them out while I'm in there. Oughta make neutral easier to find now. The clutch was pretty grabby. This always smoothed out the clutches my old CB's.


Like factory :thumbsup:



Swung by Hardware Mecca on the way home.



But they didn't have a 20-1.5mm bolt, so I had to order a legitimate flywheel removal "tool" to get the job done. More waiting. It oughta be a crime to sell a bolt for $12 just because Motion Pro labeled it a tool. :(

Gasket kit and new clutch steels and fibers on the way, too.
 
#13 ·
Re: XR400R

After waiting forever, the tool finally came in to press the flywheel off the crank. I'll try to get that sent out this weekend.



While I've been waiting I laced the replacement rim up on the rear. Bad things happen to spokes when the rim twists up.


Turns out the bike has stainless aftermarket spokes, so they straightened out easily. I wonder if they're Buchanan spokes since there's a "B" embossed on the ends, but whatever they are , they use a big nipple that requires redrilling the rim. I like em.

Trued up and back in business.





Clutch basket all back together. Just gotta get this crank sent out, but I won't have time to fool with it until after holidays. Maybe I'll just sit on the whole thing for a couple weeks.

 
#16 ·
Re: XR400R

Dropped the crank in the mail Wednesday. I got a phonecall from Vince ( MrCrankshaft) confirming everything Friday, and another phone call today letting me know it's on its way back home. Dude doesn't mess around. Nice to get a phonecall vs a bunch of emails,too.
 
#18 ·
Re: XR400R

Welcome home you little beauty. I was impressed in the packing. Heavy, oiled paper wrapped then in plastic.



I'll go ahead and say I'll highly recommend MrCrankshaft. Top notch communication, super nice packaging and a very fair price. mrcrank@vincescycle.com - www.MrCrankshaft.com - (270) 205-3222. He's in Benton, Kentucky.

Anywho, stuck the transmission and crank in the lower cases and stuck the bottom end back in the frame. The rear engine mount is the swingarm pivot, so it's nice having her on her feet again. Also nice being able to hold your engine with one had while the other is free to stick the bolts in their places. :D Will assemble the rest tomorrow.




Cleaned and lubed all the suspension pivots. Saw something about the upper shock mount that I think is cheesy, so I'll fiddle with that before the subframe goes back on.
 
#19 ·
Re: XR400R

My shop is in dire need of spring cleaning. Bottom ends all together. Dumb me forgot to pick up a wrist pin, so now I'm twiddling my thumbs instead of finishing up. Gonna give the brakes a good once over while I impatiently wait...



I don't know how I lived without a lift table before.
 
#21 ·
Re: XR400R

I've seen quite a few online that were sumo'd up. I thought they looked really good. I wouldn't mind having a 600 or 65O sumo'd, not sure I'd spend the effort on the 400 unless I never rode outside of town.

Spent three hours and 2qts of fluid trying to bleed the front brake yesterday. Never lever, no pressure, no air bubbles- nothing. Weird. Decided to give the ziptie trick a go, so headed out in a few to see if that performed any miracles while I slept.
 
#22 ·
Re: XR400R

What is the zip tie trick supposed to do? Force fluid into dry spaces?


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#23 ·
Re: XR400R

Supposed to let any trapped air float to the top by leaving the mc open. I have used a few times when I had a soft lever and it worked pretty good.


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#24 ·
Re: XR400R

I've never tried it myself but i knew there were tons of people that do it, i just didnt know the reason why it worked or what itwas doing exactly


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#25 ·
Re: XR400R

Yep, air floats up is the idea I heard. Makes sense, I guess, but no luck here.

It's odd. I can open the bleeder and pump solid streams of fluid all day, but zero pressure. The pistons in the caliper move when I pump and you can see the brake line pulse, but nothing. I don't get it. I know there's air in there. The system was bone dry and zero air came out. First time I've ever had problems with this, but it's also the first time I've owned a tiny 10mm bore MC,too. It doesn't move much fluid.

Gonna ride the trusty Kawi over to HF and check out their vacuum dealios. I've heard good things about them.
 
#27 ·
Re: XR400R

Zip tie trick is to compress the air bubbles in the system to a smaller size and allow them through the connections in the system. When not under pressure they can be large enough to fit the entire diameter of the hose and then be under capillary forces as well as surface tension forces with not enough buoyancy to lift the bubble from the hose. The decrease in size can squeeze it to smaller than the diameter of the hose and remove the capillary forces and allow the buoyancy to overcome any surface tension forces.

Think of a shake with a large strawberry in the straw and the suction required to pull it through versus a small strawberry in the straw, the large one has more resistance due to the walls of the straw acting upon it.
 
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