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I'll repeat... check the valve clearances. Too-tight valves can drop compression numbers by 2/3. The XS valves get tighter (not looser) as they wear and this is a common problem on neglected motors.
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Fast, Cheap, Reliable... Pick any two
'78E original owner - resto project
'78E ???? owner - Modder project FJ forks, 4-piston calipers F/R, 160/80-16 rear tire
'82 XJ rebuild project
'80SG restified, red SOLD
'79F parts...
'81H more parts...
Other current bikes:
'93 XL1200 Anniversary Sportster 85RWHP
'86 XL883/1200 Chopper
'82 XL1000 w/1450cc Buell, Baker 6-speed, in-progress project
Cage: '13 Mustang GT/CS with a few 'custom' touches
Yep, can't leave nuthin' alone... -
And by that, you are talking about shim-to-lobe measurement getting tighter right? As that measurement gets tighter the actual valve gets looser (opens bigger).Originally posted by crazy steve View PostSkids (Sid Hansen)
Down to one 1978 E. Stock air box with K&N filter, 81H pipes and carbs, 8500 feet elevation.Comment
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Yes. I've personally seen tight valves reduce compression numbers by as much as 100 lbs, lesser reductions are very common. Once valve clearances get below about .003", the valve 'closed' duration gets shorter. So before you go off on a tangent with leakdown tests and pulling the head, this should be the first thing you look at if you get low numbers...
Fast, Cheap, Reliable... Pick any two
'78E original owner - resto project
'78E ???? owner - Modder project FJ forks, 4-piston calipers F/R, 160/80-16 rear tire
'82 XJ rebuild project
'80SG restified, red SOLD
'79F parts...
'81H more parts...
Other current bikes:
'93 XL1200 Anniversary Sportster 85RWHP
'86 XL883/1200 Chopper
'82 XL1000 w/1450cc Buell, Baker 6-speed, in-progress project
Cage: '13 Mustang GT/CS with a few 'custom' touches
Yep, can't leave nuthin' alone...Comment
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OK, so I checked the other bike and I got similar numbers.
I'll check the valve clearances and see what I can figure out.
How do I do that again?
1980 XS1100G - Coming together
1979 XS1100 Midnight Special - Still in one rusted pieceComment
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Ah, I found the section in the service manual on how to do this.
Where can I get the shims without getting dealer gouged?1980 XS1100G - Coming together
1979 XS1100 Midnight Special - Still in one rusted pieceComment
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2H7 (79) owned since '89
3H3 owned since '06
"If it ain't broke, modify it"
☮Comment
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There is also supposed to be a valve shim library on this site, but as I have heard nothing about it lately I do not know who runs it or if it even exists now. Many members like myself will swap shims if we have what you need. Often it is just a matter of posting the values you need and see who has them.2-79 XS1100 SF
2-78 XS1100 E Best bike Ever
80 XS 1100 SG Big bore kit but not fully running yet.
Couple of more parts bikes of which 2 more will live!Comment
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Hmmm, ok. I googled around and found these and other resources. I was hoping there'd be some secret stash somewhere, haha.
I'll post again when I know more about my clearances.1980 XS1100G - Coming together
1979 XS1100 Midnight Special - Still in one rusted pieceComment
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I know I have at least 20 shims lying around here. Problem is some are the same size value so it ends up being 10 different shim sizes I have available for swap. Once you know what you need post it up and others will help if they can.2-79 XS1100 SF
2-78 XS1100 E Best bike Ever
80 XS 1100 SG Big bore kit but not fully running yet.
Couple of more parts bikes of which 2 more will live!Comment
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I figured out what I have and what I need. I don't have the paper on me, but I figured it out using the manual. Crazy Steve was right, things got tighter!
Anyway, I also came across this if anyone is interested:
http://www.bikebandit.com/1980-yamah...093?m=8241&f=3
They're more expensive than the other place, but it's another resource.1980 XS1100G - Coming together
1979 XS1100 Midnight Special - Still in one rusted pieceComment
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