Friday, April 6, 2012

Rebuild time!

I love rebuilds.

First time I pulled apart an engine I was 12 or 13.  Sure it was just a simple 2 stroke top end job but it stirred inside of me an urge to see what makes things work.  I think I was 16 when I did my first 4-stroke, and thanks to many years of a "2-stroke only" mentality, that was also the last one I did until now.

Nothing fancy this go around.  Bunch of stuff was at its service limit but I figure if it lasted 16 years, is aftermarket even an upgrade?  Sure I could have bored it out to a 440, or tossed in a high compression piston, but that really undermines what I consider this bike's best selling point: uncanny reliability.

There's a dozen similar sized bikes that go faster than the XR, but very few bikes that are as bullet-proof.  Jump around on the forums a bit and you'll see rider after rider trying to get more power out of their XR's.  End result is they make a bike that has more power than stock, but still falls short to most 450cc bikes.  In exchange, they've tragically altered the longevity and reliability these bikes are so well known for.  Honda engineers weren't dumb when they made this bike, they just didn't design it to eek every possible horsepower out of the engine.  Instead they made something that would take you wherever you wanted to go and last 16 years between rebuilds...

 Anyway I kept things pretty close to stock.  I didn't really have money to burn on this build so I replaced anything that was anywhere near it's service limit and I only went aftermarket when it was so close to the price of OEM that I felt silly not to.  Did add some Kibblewhite valves/springs/retainers.  All and all I'm really happy with what I found inside and I now feel completely confident to stray far from civilization on this bike.

And finally because paint is cheap and I figure I improved my cooling by removing all that crud off the fins, I decided to paint the engine.  Unfortunately it's looking like the side covers are going to really stand out like a couple of bandaged toes.  So I'll take care of those when I change the oil after this tank.

Everything went back together easy enough, except for some issues with the most stubborn broken bolt I've ever come across.  Started up on the 2nd kick and seems to be quieter and making more power - although I'm still doing the break in so hard to say at this point.

There's a lot of hubbub about how you do your break-in.  Some people say you should ride it like you stole it from day one, others say that's crazy and you should baby it for the 1st tank.  I've always bought into a mixture of both.  Essentially I do 4 break in cycles and then a full tank of varying the throttle and not really pushing it for too long.  For anyone who's curious:

#1.  Make sure you've got dino oil in the bike.  Last thing you want is synthetic on a new top end.  Start the bike and let it idle up to operating temperature.  Shut it down and allow it to cool to ambient (by the way each cool down to ambient can take several hours).

#2.  Start the bike and allow a brief warm up, then ride it easy in the lower-mid rpm range with as little load on the engine as you can manage.  Avoid fast acceleration and whatever you do, don't lug it.  Stay out of top gear and don't keep the rpms the same for more than a few seconds.  Residential streets are pretty much ideal for this step.  Ride for 10-15 minutes like this and then park it again and let it cool off to ambient.

#3.  Another 10-15 minute ride while varying the throttle.  Again, no top gear and avoid lugging it at all costs.   This time you'll want light-medium power and mix in a short burst of acceleration every 30-60 seconds or so.  I generally will hit WOT on the last 4 or 5 power bursts.  Park it and while the bike is still warm, change the oil and filter.  Again, stick with dino oil.

#4.  Fill the tank and repeat this step until it's empty.  Only ride for 15-20 minute sessions, and keep varying the RPM.  You'll want some WOT but don't make the engine work too hard for too long.  Whatever you do, don't lug it.  The idea is to make the engine work at maximum output, but not overheat.  Allow ample cooling time between fast WOT moments.  Let the engine cool to ambient after each ride.  After the tank is empty you need to change the oil and filter again and once again I'd suggest staying away from synthetic.  Really I like to have at least 1000 miles on a piston before I even consider syn. 

So for 200 miles I get to be the most annoying person in the world to follow.  Gotta keep the rpm varied so gonna be 50>55>50>55>50.  Please don't ram me if you happen to be the poor soul stuck in my rearview.

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