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Old 05-29-2012, 08:02 PM   #1
Maliwal OP
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Joined: Feb 2012
Location: Southern California, USA.
Oddometer: 78
Yamaha 'XJ 650' Maxim Rebuild Thread!

Hey folks, I've got a certified bad-ass looking Maxim sitting in my garage now, belonging to my buddy Mike. He picked it up for $300 and the work begins!

It's got so much power! Approximately 1 Man-Power!
At least we got it up the driveway.
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So we tinkered and whatnot, investigated this strange shaft-drive thingy it's got, played with the seized rear brake (the drum decided it was going to be fused to the pads, whether we liked it or not) but got it worked out eventually.

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So first note: It's missing #1 cylinder's spark plug. Hard to see, but take a look anyhow.

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Off come the carbs for their later cleaning.

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Getting the head off was a lot more involved than either of us anticipated. Timing chain have to be broken, and for lack of the proper tool, we used a punch and hammer to pop a link apart. New timing chain is in order. Joy.

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Minus one cam...

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And a gap arises!

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We quickly discovered that the piston was seized solid from a disgusting amount of rust.

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There are solutions for rusted things...

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And the result of some hammering:

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So a couple hours, a wire brush or two, and one anal probe later...

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We have a freshly cleaned piston and cylinder. Unfortunately the cylinder is pitted pretty badly, and the piston rings are gone. A new sleeve and rings are in order, pending discovery of shop to preform said work cheaply.

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On to the next project: The carbs. We tore all four apart in record time, cleaned them, inspected every nook and cranny we could find, and slapped 'em back together. The diaphragms looked surprisingly good.

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Three of them looked good, but #1 was nasty.

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And something tells me an intake isn't supposed to look like this...

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But through it all, our mascots remained as energetic as we were.

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So next weekend we see about cracking the crank-case and taking a peek into the belly of the beast.

Stay tuned

- Maliwal
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Old 05-31-2012, 04:34 AM   #2
gunnabuild1
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Any questions that come up can be answered here http://xjbikes.com/Forums.html
Good luck with it,Xj's are great bikes! well worth the effort.
Course I'm biased.
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Old 05-31-2012, 11:25 AM   #3
zap2504
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Location: Middletown, PA
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FYI an engine from an XJ750 will directly fit a XJ650.

+100 on the XJ Bikes site. Go to the Modifications section to see all sorts of custom projects.

The hard part of the carbs (for 1st timers) is the idle circuit due to the really tiny interior passages (starting with the pressed-in jet at the base of the float bowl).
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Old 12-13-2012, 02:41 PM   #4
bman2440
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Question?

I am also rebuilding an 81 XJ 650 and my cylinder bolts look similar to yours in the fact the sleeves are cracked and not all there. I was wondering what the purpose of the sleeves are and what are you guys going to do. The answers I have received so far are that they are for alignment. In order to have the sleeves you've got to buy the whole bolt at $20 a piece.
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Old 12-13-2012, 06:37 PM   #5
Tosh Togo
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Quote:
Originally Posted by bman2440 View Post
I am also rebuilding an 81 XJ 650 and my cylinder bolts look similar to yours in the fact the sleeves are cracked and not all there. I was wondering what the purpose of the sleeves are and what are you guys going to do. The answers I have received so far are that they are for alignment. In order to have the sleeves you've got to buy the whole bolt at $20 a piece.
The "sleeves" are there to damp vibration and reduce noise coming out of the top end. The ones at the rear of the engine that are dedicated oil paths to the head don't have them. You don't need the sleeves, so don't worry about it.

The OP needs to get a copy of the XJ CDs.
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Old 12-13-2012, 07:22 PM   #6
Maliwal OP
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Very unfortunately we hit a few obstacles with the XJ

First off, funds dried up [i.e. Mike bought an XR600, lol]. Then we investigated a little more and it turns out we can't find a cylinder sleeve for that rusted one; it's pretty well shot and needs to be replaced. No such luck. He's just about given up on the thing since his funds have been directed towards other things (Jeep, XR, DR, my KZ440, etc). Alas, it's likely going to be sold.
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