Rust and pitting on GL1000 cylinder wall

[LLRelease]

That's a gorgeous '79.

I'm more than a little impressed by the work you did to the motor!

Thanks! I am not going to lie, splitting the cases the first time was scary. However, it was not as difficult as I imagined. The Honda shop manual and Haynes manuals were invaluable, and the community helped out when I had questions.

[gltriker]

The intake and exhaust valve clearances are both set at .006” per a recommendation on this forum.

Was thinking that's why you witnessed those very favorable compression testing results.
Well Done

[rcmatt007]

sweet looking ride!

[LLRelease]

Thanks! I will post more pictures as I source and install missing cosmetic bits like the radiator shrouds and the front emblem.

Is there a trade-off when setting the valve clearances at .006 inch?

[gltriker]

Is there a trade-off when setting the valve clearances at .006 inch?

I had to think about your question and eventually recalled this 'conversation' I engaged in with Mike Nixon.
My concern was if the additional 0.002" lash clearance would accelerate valve seat and valve face wear.
I took a screenshot of his answer.
My '75 GL1000's engine responded very favorably to a seemingly slight increase of its Dynamic Compression Ratio number.
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Screenshot 2025-05-28 195835.png

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You may have already seen this one of his many tech articles?
https://www.ngwclub.com/forum/viewtopic.php?t=63468
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screenshot taken from page 1
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Screenshot 2025-05-28 214245.png

[redglbx]

My .02,,,,, I’ve done a lot of this with my Hotrod engines and is something I wanted to check before I lost dyno access. So with that said, opening the valve clearances up ,002in reduce the h-power some , should be a small amount but it will reduce it some,,,, BUT, it should also increase the torque some (increased compression) all because you’ve reduced the cam lift and the cam duration. The added clearance should also increase the wear between the valve tip and rocker a very small amount so you’ll probably see that wear show up after several hundred k miles,,, nothing to really worry about ! Changing your timing belts is probably a bigger priority than the extra .002in of clearance in your valves.

Increasing/decreasing valve clearances are common tuning tools in hi performance engines with increasing clearances to reduce duration in extreme cams which as I said will improve the torque. A cam with a lot of duration requires more rpm to extract the most performance from it, most engines never are able to reach their optimum cam rpm which is why a lot of people will advance the cams in their engines, usually 2 to 6 degrees.

I did have new keyways EDM’d into my cam pulley’s which made a big difference. On my bike on the dyno it was clear that at the 8500rpm redline the power graph was still increasing so it wasn’t reaching it’s peak power, the early 75-77 GL’s had fairly aggressive cams in them. Advancing the cams 4deg allowed that to happen with the hp power peak now occurring at around 8k rpm now.

Now with that said it did drop 2hp off the peak but the important thing is that it increased the torque a fair amount with a much flatter power curve with it now providing peak torque within 2 ft/lb from 2200rpm through 6800rpm ,, a very flat power curve now.


So after a long winded, complicated explanation opening the valve clearances the extra .002in basically does the same thing to some degree. I should add that production tolerances and stack-ups have an effect on all this and is why some motors respond differently than others.

[LLRelease]

Thanks for the explanations. It makes perfect sense.