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Discussion Starter #1
how important is it to space ring gaps 120 degrees apart?

also, with a freshly built ca160 honda, before even installing it in the frame, should it have some sort of compression with the plugs in it or does it need to seat everything first?

i helped a friend over the phone and forgot to mention a couple things....[8D]
 

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I try to space the gaps 120 degrees whenever I build a 175...but...often by the time I get the little pistons in those little bores at the same time so you can slide the cylinders down...well, they aren't exactly 120 apart anymore. Typically I'm more concerne with keeping the gaps away from the thrust sides of the piston and the wrist pin holes.

Typically my engines definately have compression on the bench after a rebuild and plenty of it. Yes you will pick up some sealing as thing seat in, but you should have noticable compression turning the engine with a wrench. Two basic methods I use...the old thumb over the plug hole while you turn it over, and the other is I wet my palm and put it over the intake port as I turn it over. If it doesn't pull my palm in and hold suction for 5-10 seconds I usually feel the intake isn't seating as well as it should.
JohnnyB
 

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JohnnyB is right.
Ken
 

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Discussion Starter #4
he said he isn't getting much compression. Has anyone done a ca160 here before?

he put the pistons at tdc, and then cam was positioned so that all valves would be closed. the dowel pin for the advancer on the end of the cam shaft was facing straight down at this position but he couldn't find any marks to make sure it was in the correct position before he put the chain back on the sprocket. there was no valve to piston contact.
is there a manual for this motor specifically? I'm going to look at the engine this evening and see what i can tell.

the two things i want to verify is cam timing, and whether it has compression or not. i'll try the wet palm trick...for testing the compression too! zing!
 

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There is a mark on the alternator rotor, and there is a mark on the cam sprocket. The cam sprocket has a small "0" that should face straight up. The rotor usually has a "T" mark. "T" mark should usually be facing the timing indicator on the left engine cover.

These engines only have a 41mm stroke, you won't feel much compression till the piston gets close to TDC. My valve springs are so stiff I have use the thumb on the spark plug hole because compression stroke or lifting valves feels about the same :)

Make sure the cylinder is not completely dry, a few drops of oil on the thrust faces (probably too late in this case), will help seal the rings for testing. Plus...you won't feel much compression turning it over real slow. Not like these are big singles.

And yeah there is a manual...they only sold about a million of those bikes. You can find reprints of the original Honda manual here:
http://www.helminc.com

JohnnyB
 

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Discussion Starter #6
he found the T on the alternator, but nothing on the cam or sprocket at all. is that manual available for download anywhere? or does anyone know of a site with obscure honda service manuals for download?
 

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The mark is there on the camshaft...just very faint. It's right out towards the teeth. On the side facing the points. IF it doesn't have the "0" mark, then there are a series of lines etched across the sprocket, you line it up so that the line is parallel with the surface of the head.

You might be able to find a manual to download at:
ftp://ftp.manuals.homeftp.net

Don't make me give a speech about people digging into an engine without a manual. I'd say something like....any problems they have serves them right for not spending $30 on a manual :).
JohnnyB
 
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