A Heart Transplant for the old '81 XT500!

[Crazy Uncle Larry]

Well, it finally happened after 28 years, 15,000 plus miles, 6-7 years of neglectful storage, and a short span of Dual Sport riding from last February (Laramie Lap) through June 09. On Mother's Day weekend in May, she popped smoke on me for the first time at start-up. This soon settled down but oil consumption became very noticeable during moderate use. I eventually resigned myself to the fact that I would need to constantly keep it checked and filled until I could find a shop who could get it in for a rebuild. Three weekends ago on a Saturday morning, I decided to give the bike a once over before spending the rest of the day mowing grass. I gave her one kick-nothing (she had been sitting for over a month). Then, as I started the second kick, N O T H I N G ! No compression! "Nada! Zip! That's all she wrote! I rolled her back into the garage to await further consultation with various specialists.

Number Two/Aaron continued to encourage me to find an answer to the question of when we could get her in for a complete work-up as he wanted to get together for some more rides. Nothing shaking until after Sturgis! He called and said to bring her on down when we came to see them and he would give it a go. It pays to have a son who rides who is finishing his Masters in Mechanical Engineering! Anyhow, he has the XT and we will post photos and update the report as work progresses. Hope to have things done and zipped up in time for the Fall Rally. Still have one grandson on the way up in Farmington, MN, so I hope that doesn't throw too much of a wrinkle in the mix. We've talked it over and plan to address the piston, rings, hone the cylinder (only as much as is needed to clean it up, i.e. .10 or.20 over), take care of the valves and valve train, add an additional oil line hook-up to the mix so the intake and exhaust rockers are lubed, put new sprockets and an o-ring chain on, new drum brakes, and maybe if the well hasn't run dry by then and the fates smile down on us, we might even do a little something with the suspension-front and rear. Otherwise, if we win the lottery between now and then, we'll send her off for a total balance and blue-printing and get ourselves two new WR250Rs to ride in the meantime!!!

Have a great remainder of the summer, take care riding around during Sturgis, and we are looking forward to seeing you guys at the Fall Rally! More to come...

[Number Two]

Alright, this afternoon, I got a start on the teardown.  Mostly I want to get these pictures up so that Crazy Uncle Larry knows what he's dealing with.  I also look forward to any advice or suggestions from those who've done this before.  This is my first attempt at a top-end rebuild.  Notice how I'm doing it to someone else's bike, right?

I rounded up my help and dug in.



Trace of an exhaust leak.  I'm thinking a little permatex ultra copper ought to seal that up on the rebuild.

[Number Two]

Here's what I have under the stator cover.  Hope the germans can hook you up with the 12V goodness.



After a few hours of wrestling, I got it out.

[Number Two]

Lining up TDC so I can find it later.



I pull off the head, and am stricken with horror at the sight of .... TROGDOR the BURNINATOR!!!

[Number Two]

Sure enough, the lack of compression is due to the exhaust valve not sealing.  It's toasted. 



Anyone have thoughts on what typically causes this?  The plug was a dull sooty brown, so I don't believe it was over-lean.  I initially figured the white smoke event was a valve guide seal biting the dust, but would excess oil cause the exhaust valve to shell like this?   

[Number Two]

There's still quite a bit of carnage left in the cylinder.



The piston skirt has a bit of scoring, but nothing major.

[Number Two]

The cylinder was bright an shiny much to my surprise.  The crosshatching was gone on top, but still visible toward the bottom.

[Number Two]

This is how she sits for now.  I need to get some tools from work so I can actually check the specs on the piston and cylinder, and pull the valves out for a proper look.

Jug with blue towels.  Note bungy to the rafters.



Not a whole lot left to it.  Thumpers are great because they're simple.  Old thumpers anyway...

[Number Two]

oh right... the big valve (the toasty one) is the intake not the exhaust. 

[Number Two]

While I was in the garage, I was doing a little preventive maintenance on the mighTTy 600.  This is how you know when it's time for a new sprocket, I guess.



All of the teeth are busted off, and it was just starting to slip the chain on the rough stuff.  I feel like I should own a KLR.

[Number Two]

I do like this method of sprocket attachment much better than the bolt on type of the XT.  I can change the sprocket fairly quickly, so I got a new 14t(stock) and a new 16t for more top speed.  I'm not sure if the chain will fit both or not.  I put the 16t on last night, and cut my fancy new chain down to 114 links instead of the stock 112.  We'll see what it looks like fully adjusted.

[Hank]

Need one those little popcorn icons like they have on advrider.    Keep it up, good stuff!

[loingrader]

that sprocket is impressive.  must be the original.  i've never seen one that bad before.  props!

[Number Two]

Time for some forward progress here.  I got the head and cylinder back from the machine shop.  They bored and honed the cylinder, decked the cylinder and head, installed new valves, guides, and seals along with a new valve grind, cleaned everything, and supplied me with a new gasket set, and a Wiseco 10:1, .020 over piston.  I ordered up a new cam chain, tensioner, and guides this evening, so perhaps the XT will breathe by the weekend?  We shall see.  For now, here's some shots of the fresh parts.

[Number Two]

Masked for paint.  Masking is one of those things where "Hard work may pay off over time, but laziness always pays off now."  Here's my 2 1/2 hour tape job.  I hope it works, I'm not a painter.  Might try the paint tomorrow night.