XS1B Engine Teardown

Pistons cleaned up nicely... and measure good.

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The cam chain guide is in remarkably good condition. So much so that I considered putting it back in the motor. The rubber is intact and I couldn't seem to get it to peel loose at any point.

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At the end of the day I couldn't bring myself to reuse it, even though I'm fairly confident it would hold up just fine. So much so that if I was building this engine for me, I'da reused it. But... I have a rule of thumb when it comes to bits like engines, "If you have to pull the engine to replace it, replace it while the engine's pulled." So...

The guide for this early motor is a bit different. Not quiet as beefy as the newer ones and perfectly flat instead of curved.

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I made a fixture to hold the guide while I took the rubber off and clean it up for modding. Hat tip to @5twins for the idea.

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Used the belt sander to remove the rubber. That confirmed my suspicions that the rubber was still firmly attached. Too late to turn back now... :cautious:



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I case y'all ain't figured it out, I'm doing the frankenguide mod. Switched it up slightly this time and bonded the SR500 guide with J B Weld along with the Hi-loks... kind of a belt-n-suspenders approach.

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Standard rings are on order from Cruzinimage. We'll get there...
 
Cleaned up the head. Checked the deck with a straight edge... nice and flat. Went ahead and dressed it down a bit just 'cause... :rolleyes:
Best way I've found to check the guides is to measure the guide ID and valve OD. Unfortunately my ball gauges seemed to have rolled their way outta town. :cautious:
Next best way is with a runout gauge. Mine only reads out to 3 digits, so these numbers are best estimate. But all 4 are well within limits, so close enough.
Valve guides:
LEFT​
RIGHT​
LIMITS​
​
INTAKE........................... <.0010"​
INTAKE.............................<.0010"
.00079 - 00173"​
EXHAUST.......................... .0015"EXHAUST.........................<.0015"
.00138 - 00232"​

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Prior to measuring the guides, I noticed what looks like a small crack in the face of one of the exhaust valves. Can't say for certain it's a crack, might just be a gouge. I had a good replacement, so this one'll go on the shelf 'till I get around to regrinding and see if it'll clean up. Problem solved.

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The broke off spark plug was a real bugger to remove. I tried every trick known to man me. PB Blaster, torch... various different easy outs.... wasn't budging. Finally had to resort to the drill. And we all know what happens then... :doh:
Yep... I cut into the threads slightly.

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Took a plug and cut slits in it to clean up the threads.

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That did a fair job cleaning 'em up and the plug actually feels pretty good threading in. Having said all that, I'm gonna put a helicoil in it anyway. Kit should be here Sat.

Removed all 4 exhaust studs. Of the 4, only one was kosher. One was bent, one was completely stripped inside the head and one was a huge SAE bugger some idiot half assed in place. I've got a helicoil for the stripped one. For the huge bastard, I managed to find a stud that's 10mm on one side and the correct 8mm on the other. But the threads they cut look rather ragged, so I've got a 10mm bottoming tap on the way just to chase it out a bit.

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Was gonna lap the valves and install 'em... but my lapping compound left with my ball gauges and it's too late to go buy some. :cautious:

Are we there yet? :er:
 
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Probably unacceptably costly for 1 valve, but maybe you can have it magnetic particle inspected? Like I said though, might not be worth it if the cost of the test is higher than the cost of a new valve.

All that aside, that just looks like a gouge to me.
 
I was taught to "ring" a grinding wheel before installing it on a bench grinder. Tap it with a wrench gently, if she (the grinding wheel) sings she's good. If she thuds she's a dud (has a crack and needs to be thrown away immediately).

Could the same possibly work on a valve? Dangle it up gently by the stem between 2 fingers, just enough pressure to keep it from falling, and tap it with a small 6mm wrench or something.

Just thinking what I'd do in the situation. 🤔 🔧
 
Jan_P said:
Any signs inside motor why it was parked ..?
Click to expand...
I'd guess the mushroomed valve caused him to park it. Most likely bad heat treatment at the factory? Anyway, the engine got noisy, the PO either tried or had someone try and adjust the valves and saw the mushroomed stem, decided to park it until he could get the engine fixed.... and there it sat until I found it.
 
Jim said:
I'd guess the mushroomed valve caused him to park it. Most likely bad heat treatment at the factory? Anyway, the engine got noisy, the PO either tried or had someone try and adjust the valves and saw the mushroomed stem, decided to park it until he could get the engine fixed.... and there it sat until I found it.
Click to expand...
As good a theory as any.
Everything indicates that this is an extremely low mileage engine -- almost no stretch on the cam chain or wear on the guide, pistons and cylinders still within specs, etc. Yet, within the brief operating life of this engine the owner managed to screw up 3 of the 4 exhaust studs. And who knows how he broke that spark plug, or lost the tachometer drive shaft. If the owner managed to do all of that in such a short time, then maybe he was also able to find a way to mushroom a perfectly good, properly heat treated valve.

Jim, you are going above and beyond at every turn on this rebuild. The thread subtitle should be "the uncompromising build."
 
DogBunny said:
As good a theory as any.
Everything indicates that this is an extremely low mileage engine -- almost no stretch on the cam chain or wear on the guide, pistons and cylinders still within specs, etc. Yet, within the brief operating life of this engine the owner managed to screw up 3 of the 4 exhaust studs. And who knows how he broke that spark plug, or lost the tachometer drive shaft. If the owner managed to do all of that in such a short time, then maybe he was also able to find a way to mushroom a perfectly good, properly heat treated valve.
Click to expand...
Thanks William.

Sue has an excellent memory. According to her (she went with me to pick it up) the odo only showed 4000 and change and the son claimed it was accurate. So yeah, other than being locked up, broke plug, bits loose in the right cover and a mushroomed valve... she was jus' barely broke in. 😜
 
Jim said:
I'd guess the mushroomed valve caused him to park it. Most likely bad heat treatment at the factory? Anyway, the engine got noisy, the PO either tried or had someone try and adjust the valves and saw the mushroomed stem, decided to park it until he could get the engine fixed.... and there it sat until I found it.
Click to expand...
Theory ??
New machines have tight valve guide play ..
?? Maybe a cold start redlining over rev from the start .. Not much oil present .. Wroa aaaa aaaa mmm valve stem a bit stuck in guide
friction --- bigger forces
Smashing the end of valve ?
 
Jan_P said:
Theory ??
New machines have tight valve guide play ..
?? Maybe a cold start redlining over rev from the start .. Not much oil present .. Wroa aaaa aaaa mmm valve stem a bit stuck in guide
friction --- bigger forces
Smashing the end of valve ?
Click to expand...
Looks like a classic case of running with too much valve lash. I'm gonna guess that someone tried adjusting the valves but didn't get the engine on the correct TDC when they did it. They added lash to a partially open valve which means WAY too much lash when it gets back to the base circle. Unless, of course, you found a loose lock nut on that tappet. Then it's pretty self explanatory.
 
mrriggs said:
Looks like a classic case of running with too much valve lash. I'm gonna guess that someone tried adjusting the valves but didn't get the engine on the correct TDC when they did it. They added lash to a partially open valve which means WAY too much lash when it gets back to the base circle. Unless, of course, you found a loose lock nut on that tappet. Then it's pretty self explanatory.
Click to expand...
I would assume getting the adjustment wrong One would hear it on a new Machine.
But the loose lock nut Maybe --- I heard about one many years ago out riding and the rattling ..came .Did not tow it
Kept on Riding Home and caused damage . ( Not sure what problem )
This case perhaps Coming loose and then tightening at home But to late.
 
gggGary said:
PS: Jim what are your intentions for this motor?? :umm::pimp::whistle:
Click to expand...
Jim said:
It's spoken for. I'm currently not at liberty to say beyond that. :whistle:
Click to expand...
It was never really a secret, but props to Jim for keeping me anonymous when I hadn't explicitly said that it was okay to name me.
How this engine became headed my way was a bit serendipitous. Jim wasn't really looking to rebuild it, and I wasn't really looking to buy an engine. It just sort of happened.
 

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