timing belt adjustment.


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John Verburg
Posts: 8
Joined: Thu Aug 04, 2016 3:19 pm
Location: Olympia, WA
Motorcycle: 1975 GL1000, 1976 GL1000

timing belt adjustment.

Post by John Verburg » Tue Jan 01, 2019 1:12 pm



I am a bit perplexed and hope someone knows the answer. When I changed my timing belts I set both sides, I thought, as directed, but noticed that the right side has moved about on tooth to the left (retarded). I moved the engine by hand a full turn and all went well so I thought I would do a compression check to see what that did. My compression was about 23 pounds lower than my records showed. So I new it was wrong and went to correct it. This time I over corrected a bit and went one tooth to the right (advanced). But again I turned it my hand and no interference so cranked it again and got a compression reading that was about 10 pound higher than my what my records indicated. How odd. Anyway I changed it again and as said the third time was the charm. All timing marks lined up perfectly. And sure enough my compression dropped back down 10 pounds to my recorded settings. What I can't figure out is why my compression would go up if I advanced the valve timing. I did not try setting the left bank ahead one tooth as well and then trying to run the bike, but wondered if anyone out there knows what is up?



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Fred Camper
Posts: 1337
Joined: Sun Aug 16, 2009 9:15 pm
Location: Metro Detroit, MI
Motorcycle: 1977 GL1000, 1976 LTD GL1000

Re: timing belt adjustment.

Post by Fred Camper » Sat Jan 05, 2019 10:44 am

Valve timing is a compromise. You will note most advanced automotive engines now have variable valve drive to improve efficiency. Maximum compression pressure is different at different valve advance and engine rpm. You are checking it at very low rpm (150 rpm) and honda did not want to maximize compression at that speed as say 1500 rpm is way more common of operation. If you advance it one tooth it improves at 150 rpm, but likely degrades at more relevant speeds.

User avatar
John Verburg
Posts: 8
Joined: Thu Aug 04, 2016 3:19 pm
Location: Olympia, WA
Motorcycle: 1975 GL1000, 1976 GL1000

Re: timing belt adjustment.

Post by John Verburg » Sat Jan 05, 2019 12:41 pm

Thanks for your reply. That makes sense. Perhaps the next time I change belts I will test out that theory further just for fun. Curiosity has always been a problem for me.

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