First of all, thanks to all on the forum who share their experiences and ideas. Took my first ride on a Superhawk yesterday. Wow. Couple of minor issues to work out, but all in all I was quite satisfied. Like to get some of your thoughs on this one.
The top end was noisier than it should be given all the new parts I put in it. Bike ran well, idled, etc, just made a strange noise that sounded halfway between a valve tick and a blown head gasket. Seemed to vary with throttle position too - a little louder at rpm with the throttle closed. Checked the valves again this morning and they were right on at .004". Then I grabbed the left intake rocker with the crank at TDC, felt the .004 slop and rotated the crank. The rocker tightened up about halfway through the exhaust stroke at about 270-degrees past TDC. So the mystery sound was likely exhaust hissing back through the intake valve. I set the clearance to .003 at the 270 point and it opened up to .009 at TDC. Left exhaust tightened up to zero at about 90-degrees past TDC, way before it should start to open. Set it to .003 at the 90-deg point and it opened up to .007 at TDC. Similar story on right side.
Started it up and the mysterious noise was replaced by valve ticks which I can live with because at least I know what it is. Didn't seem to be much difference in performance. Still a blast to ride! I may try to tighten them down to zero clearance at the tightest point since I think the clearance probably opens up as the head warms up.
Anybody else ever check their valve clearances at other points besides TDC? I would chalk this up to the cam being worn there for some reason or bent? I put in new bearings, sprocket and cam chain but reused the camshafts. I didn't see any unusual wear marks on the cams, but I didn't measure them either. Everything went together as it should with no particular problems.
Thoughts or comments?
Top end noise - interesting cam issue
Re: Top end noise - interesting cam issueYa don't mention if the new parts are tappet adjusters or cam followers or what they are.
I suspect ya may have the idea that the engine is a normal firing 2 cylinder. It is actually a 180 crank and it fires Right, left, exhaust right, exhaust left. Set the clearance at .004 for both sides at "T" and "LT" and be sure the points are set correctly and unless ya have something warn/broken the engine should be OK. Ya may want to look at the FAQ in the yellow area on the left and look at How I tune my engine if ya think that would help. ...........lm
Thanks for the replies. I get all that, I rebuilt the engine myself (not my first one, but my first 305) As I said, the new parts were cam bearings, cam sprocket, and cam chain. My point is that the clearance doesn't stay .004" for any of the valves as I rotate off the point where I set them. The rockers should stay .004 wiggly until its time for the valve to open. Mine don't. Ever check the clearance anywhere else besides "T" and "LT" on any of your engines???
Thanks!
Set the .004 clearance at "T" then "LT" and leave things as there are.
Ya have done all that's necessary. .......lm
48,
Think about it. If the cam were worn, the rockers would stay loose for more of the closed duration than less of it. The lead on each side of the open position just assures the smoothest landing of the rocker arm on the cam. Help avoid beating the daylights out of the two mating parts. Otherwise cams would be polygons instead of curves and inclines. regards, Rob
Hi,
A cam has a shape of a ground circle with a lob on it. If this camlob would start abrupt, the whole mechanism would wear out quickly, plus jumping valves, because you would need more "spring force" to keep the valve in place. There's only one place where to measure the valve - follower clearance, and that place is described in the Honda manuals and the tuning recipe written by Ed. However, if you wiggle the rotor a bit, and put it back on "T" and "LT", and measure different clearance, (and the valve seats are clean), I advice you to look around for some rockers and rocker pins, and tappet screws, in the meantime that you ride the bike. Jensen assembly of Japanese motorcycles requires great peace of mind (Pirsig)
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