Desertrunner's XR400 rebuild thread

[Desertrunner 0]

Be warned, this is a long thread.

First, a little background: picked the bike up in June for $2100. Owner claimed a recent top end rebuild. The bike didn't reveal any problems other than maintenance items, so it seemed like a good deal. I did notice what seemed to be low compression through the kickstart lever, but I figured the bike had a low compression engine. I had never kicked anything with a compression ratio less than 12:1. A few days after purchasing it though, I did this :

Yes, I did it on the bike <_</>. Riding in the dirt, a tree branch instantaneously sprung out of the ground and attacked my front brake lever. The bike fell on my boot in an awkward position. You'd be surprised how much damage can result from 10MPH. I wasn't capable of riding again until September/October, but mostly just short jaunts around town. After that noob ride in November, which was the most I had ridden the bike since I purchased it, I discovered the oil was low. It wasn't much, so I presumed it to be incorrect measurement given the bike's pain in the rear oil-check procedure. A couple days later, I'm sitting at a stoplight when I realize that I smell burning oil. I look over the engine but do not see a leak, so I give credit to the old, beat up civic next to me with painted rims and a fart can sticking out the back. However, through the next couple stoplights, I still smell oil and then notice excess engine heat. I limp the bike home and check the oil. It doesn't even register on the dipstick! I drain it and only find a quart, but it holds two quarts! It used a whole quart in 200 miles.

After pulling the top end apart, I discover an oil soaked piston coated in carbon crust. The cylinder was barrel shaped, the valves leaked oil past the seals, and none of them sealed against the valves seats. Additionally, all the components were original OEM components. I couldn't believe that it even ran in such a state. Some people (read previous owner and politicians) are very good at selling complete BS

I don't have pics of the mechanical catastrophe. You'll have to excuse my lack of patience with cameras. However, here is one of the old valves:

You can clearly see the rounded shape around the seating surface. The seats themselves were even worse. They had no angle at all, just a rounded edge. Besides the top end, the rest of the engine was in great condition. The crank was well within spec and the bottom end as a whole showed very little wear. So, with that in mind, it was time to get to work fixing somebody else's screw up. Seems to be a trending theme in this country

Meanwhile, I did some other modifications while the bike was down. I started with a stator rewind. In OEM trim, the stator could power the 55 watt headlight and 5w taillight, but as soon as I turned on a signal and stepped on the brake, the entire system would dim and flicker. I pulled off the cover and discovered an original XR stator with only four of the ten coils wrapped. This is not my photo, but it is exactly as mine was:

I had one little goof up in finding the magnet wire. I decided to use 16 AWG wire. I checked all over the county and no one carried it, so I went online and ordered a 1/4 lb. roll which was 32 feet of wire. Well, as I'm just finishing the winding, I discover the wire is about 45 wraps short out of the 300 I needed. I then ordered 1/4 lb. of 18 gauge, which transfers to 50 ft. This provided me enough wire and even gave me a bit of excess. Plus, it was easier to wrap, although it does have more resistance than the 16 gauge. The photo below shows the different gauges of wire. On the bottom is the stock 22 AWG, then 18, the 16. Take note, the wire has a thin coating of whatchamacallit that is easily scratched off the surface. You DON'T want this to happen as it will cause a short, so spare yourself the frustration of using pliers to pull the wire and then having to redo a half hour of winding coils. Ask me how I know this...

As for the epoxy, I used some stuff I found locally. It has a heat range up to 300 degrees and was resistant to oil, so it met my criteria. I ended up with this:

I'm happy to report that it works flawlessly now that the bike is running.

Next, I needed to repair the wiring that the previous owner did. The Baja Designs kit came with its own wiring harness. This harness needed to be spliced into the stock harness. Here is what I found after I unwrapped my present and removed the tank:

Look, exposed wires! Actually, the ground connection for the turn signals was held with electrical tape. It basically fell apart once I touched it. A real half-@$$ job, to say the least.

Additionally, there were hanging wires. This connection was from the stock regulator that was no longer needed since the Baja Designs kit came with its own.

It cleaned up nicely. Excuse the phone pics.

Next I installed a 12 volt power outlet. Now that the stator put out the extra juice I needed, I could charge my cell phone or GPS without inadvertently turning my headlight off.

I purchased the bikemaster outlet from this place:

My link

I got free shipping, but I can't remember if that was a holiday special. Here it is installed:

Don't forget to add an inline fuse. I got this water resistant fuse holder from Autozone.

Black is power and green is ground in case anyone is wondering. The outlet doesn't come with instructions, so know what you're doing before hacking into wires.

Next, I needed to install a new front wheel. My stock one was cracked at the weld and it was bent. Also, many of the spokes were corroded or the nipples were stripped, so it was impossible to true. I had enough with the incessant bump-bump-bump-bump and ordered a new pro wheel from RMATV. I also got a box of polished, stainless steel spokes from Moose.

Crack at weld

New wheel installed

It took me a little under three hours from the time of removing the old wheel to installing the new one. This includes a few minutes of truing it on the axle. It only needed a couple spokes adjusted to get it straight.

With that done, I worked on the front brake caliper. I'm not sure if this is a design flaw or I'm missing something, but I needed to install washers on the inside of the caliper mounting bolts. Without them, the mounting bracket would rub on the rotor on the inside of the wheel. See pictures for reference.

This is looking down at the caliper between the wheel and the rotor. Notice the gap between the rotor and the mounting bracket. You can even see a slight ridge on the edge of the bracket where the rotor rubber.

Here are the washers creating that gap. Notice the washer between the bracket and the mounting bolt.

Regardless, the mounting bracket doesn't cause trouble anymore and the front brake works properly now. I replaced the old brake fluid a few months prior and that made quite a difference in stopping power.

Next, I needed to replace the old turn signals and the rear fender. The fender was trashed and the turn signals were pathetic. They were Ebay model LEDs, half of which had burnt out. In daylight, it was hard to tell whether or not they were on. They definitely didn't meet CA's "must be visible from 300 feet in daylight" requirement.

Here is the old fender. Apparently some people don't know how to drill a mounting hole :unsure:/>/>/>/>/>/>

I don't have a pic of the old signals, but that's okay, just picture a useless piece of trash.

Anyways, I ordered a new acerbic fender and some Western Power Sports (WPS) turn signals from motorcycle superstore. $11 bucks with free holiday shipping; that's what I call a deal. They are of surprisingly good quality and include a flexible stalk as well. Plus, they function better than those useless pieces of junk.

I didn't like the typical method of mounting them to the plastic, which isn't sturdy, plus it angles the signals awkwardly. I drilled two holes through the plastic and mounted the signals to the subframe.

Next, I needed to work on the handlebars. The bike came with Renthal bars, but they were in cruddy condition, so I replaced them with a set of MSR handlebars I had laying around($20 bars). I dropped the bike one night as my dog got under my feet and the bars bent. That was disgraceful. I cleaned up the Renthal bars and then remounted them along with some new Pro Grip rally grips, at least, I think that's what they are called. Regardless, they are WONDERFUL. They dampen vibration nicely and conform to your palm. Oh, and I can't forget my timekeeper on the barpad. Probably one of the most useful things I added.

Finally, I added some homemade plastic renew to the front fender. Look, no more scratches!

Alright, back to the engine. I got the bored out cylinder and head back from my local shop. I put it back together and started her up. She ran great except for some smoke. I chocked it up to residual oil in the cylinder and pipe. I rode if for about 45 minutes before I got off and noticed that is was still smoking. However, it was smoking terribly now. Oil was actually accumulating at the exhaust tip (ok, disks for supertrapp) and starting to drip. A little ticked off, I pulled it back apart and found this on the piston.

Excuse the phone pic

It was burning more oil than before the rebuild! However, this time, the right exhaust valve was coated in oil and the pattern on the piston showed additional evidence. It was obviously a faulty guide seal. I took it back to my shop. I call them nearly a week later and they say it looks fine, nothing wrong that they can see :withstupid:/>/> So, I take it home and replace the seals myself. Additionally, I removed the piston again, cleaned the crud from it, installed new rings, a whole new gasket kit, and put it back together, about $100 extra that I wasn't planning to spend.

So, it's back together and I give it a kick. No start. I give it an extra 1000 kicks, and no start... :tired:/>/>. So I check compression, it's good. I check spark, it's good. I know it's getting fuel. I figure perhaps the timing is off. I take it apart. Nope, the timing is good. I check the valves, they are already in spec. Regardless, I try starting it again. This time, it starts and runs great. I let it heat up and burn off some excess oil. Then I turn it off. I come back an hour later for a short ride. I kick, and no start. This time, I know it runs, so I try jump starting it. No start. :thumbsdown_anim:/>/> :hmmph:/>/> :shiftyeyes_anim:/>/> Once again, I pull the tank off and check the spark. It has no spark. Interesting, intermittent spark. So, I check my connections and discovered the insulation on the ignition wire coming from the stator has been pulled down. The wire was shorting out. I put it back in place and :lmaosmiley:/>/> it starts. After playing with everything possible to get it to stall, I decided it was good.

Today, I took if for a 60 mile ride and it performed flawlessly. :dance2:/>/>/>/>/>/>

So, I'm now into my 400 around $3500. I still have to replace the fork seal covers, replace the fork oil, the chain slider, but other than that, it is good to go. It was depressing not having a bike to ride.

Here are final pics

[bikeslut 1]

Great write up! Now go get that thing dirty

[kkug 146]

Honda 400,s are great. I rebuilt mine twice when I had it. Best part is you can do it with all the tools in your toolbox. Only thing special is a flywheel puller.Fun to work on .

[PastaPilot 17]

Thanks for sharing your "journey" with the ol 400.

Looks ready for some dirt.

[Desertrunner 0]

I realized I forgot a couple things. I couldn't get two of the valve caps removed, and I couldn't seem to find a 24mm wrench. I did find this though:

It's a combination axle wrench from RMATV. It just so happens that the rear axle nut and the valve caps are the same size. It works great, although I wish it was a little longer for better leverage. I'm sure I can find a rock on the trail though. Good deal for 12 bucks.

Also, I switched to Rotella T:

It's about $14 a gallon and is JASO MA approved for motorcycles. I have read many good reviews from others using this stuff, so I will put it to the test. So far, it has worked well and has saved me about $50 in oil since the engine rebuild. Frankly, $10 a quart for Honda's oil is ridiculous considering I like to change my oil frequently.

[Bagstr 288]

Good Stuff

Always good to see a mechanic at work.