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Discussion Starter #1
Okay I'm doing my first valve adjustment on the 900 and I found something very strange. I'm doing the rear cylinder first and I've got it set at TDC. I can't even fit my .0015 in there! The spec for intake is .010 to .015 so something is definitely not right. Have any of you had this problem? I didn't expect it to be perfect, but THAT worries me.

One of 3 things are wrong:

1.) For some reason I have to do the front cylinder first.
2.) The picture in the manual is wrong where it shows TDC for the rear (top of the "T" on the "TR" marking).
3.) It really is that far out of spec.

Engine experts, I need some guidance.
 

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How far out is it? What feeler can you get in?
 

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You might be one crank rotation away from Top Dead Center on the compression stroke. Cam rotates one half turn for each crank rotation. Try turning the crank exactly one turn. You should be turning counter clockwise.

Also, on my bike, there's a scribe line across the cam sprocket that, when horizontal to the plane of the head, is TDC. If yours has the scribe lines, and it's below the sprocket center, you're TDC between exhaust stroke and intake stroke, rather than TDC between compression stroke and power stroke.

Once you confirm you're at the proper TDC, if valve is still tight, then I'd reshim to spec lash, and see if it runs okay. If fuel economy is still in mid 40's then you're valves are okay, but I would check that valve's clearance in a thousand miles, or so.
 

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Discussion Starter #5
So fuel economy is linked to valve clearance? When I first got the bike, my mpg was in the upper 40's to low 50's. Now at 15,500 miles I'm down to about an even 40 mpg. I've wondered why in the world I could have lost 10 mpg, maybe it's my valves!? I will be checking TDC again as several of you have suggested. If it is at TDC where I think it is, then I'm gonna re-shim and check my economy on a tank of gas. I really hope my valves are what has caused my dramatic loss in mpg. That has really been bothering me!

You might be one crank rotation away from Top Dead Center on the compression stroke. Cam rotates one half turn for each crank rotation. Try turning the crank exactly one turn. You should be turning counter clockwise.

Also, on my bike, there's a scribe line across the cam sprocket that, when horizontal to the plane of the head, is TDC. If yours has the scribe lines, and it's below the sprocket center, you're TDC between exhaust stroke and intake stroke, rather than TDC between compression stroke and power stroke.

Once you confirm you're at the proper TDC, if valve is still tight, then I'd reshim to spec lash, and see if it runs okay. If fuel economy is still in mid 40's then you're valves are okay, but I would check that valve's clearance in a thousand miles, or so.
 

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Probably the twist of the wrist that lost the mpg.The more you get used to a bike the more you rev it,at least for me.I get about 42mpg expressway.Now if I ride with my Dad I can get in the 50's he does the speed limit @ most
 

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Discussion Starter #8
I'm still finishing up this 15K service. I just finished my valves yesterday ... I think! I was confused by the TDC markings on the crankcase: TF and TR. For adjusting the front cylinder, I set the mark to the top of the "T" in TF. For adjusting the rear cylinder, I set the mark at the top of the "T" in TR. I also assumed that the inlet valves are the 4 valves in the middle (surrounding the air box). Am I right?

I'll tell you why I'm suspicious, every single one of them needed an adjustment. Additionally when I set the crankcase to "TR" and attempt to do the inlet valves on the rear cylinder, I can't even move the rocker arms to get the shims out because they are pressing down too tight.
 

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It seems to me that you're not at TDC when you think you are. Remove the plugs so you can stick a drinking straw or something in there and tell when your piston is at the top of its stroke. Watch the intake valve and when it closes, keep turning the crank until the piston is at the top of its stroke. Now check your valve clearance.

hth,

rick
 
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