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Author Topic: Rod weight, one rod 2 grams lighter than the rest.  (Read 863 times)

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Offline KayOne

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Rod weight, one rod 2 grams lighter than the rest.
« on: October 31, 2013, 07:35:00 PM »
Starting on the engine build on the K1. Removed the rods to check the bearings and weighed them. Three rods 281 grams, one 279 grams. Should I lighten up three rods to match the lightest or just leave them alone?
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CB750 K1 restored
1979 CB750Fz - original except for exhaust, 14000km
1984 VF45F Interceptor - all original, 12000 km
1968 S90 - all original, 2100 miles
1973 H2a, Restored
1973 H1D, next project
CB750K1 (sold)
1976 KZ900 (sold)
1981 CB900F (under restoration)
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Offline Don R

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Re: Rod weight, one rod 2 grams lighter than the rest.
« Reply #1 on: October 31, 2013, 07:50:19 PM »
You took the time to measure, I'd lighten 3.
  I didn't do that to an engine 30 years ago, it still bugs me that I didn't take the time, although it runs strong as ever.
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Offline calj737

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Re: Rod weight, one rod 2 grams lighter than the rest.
« Reply #2 on: October 31, 2013, 08:32:27 PM »
While individual rod weight is an important factor, remembered pistons all bear not he balance of the engine.

Mark each rod with its weight, then weight he pistons too. Mark them. Then find the total weight you seek and carefully grind those not in spec.

You should also weigh both ends of a rod, not just the total weight. FWIW-
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Offline Dream750

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Re: Rod weight, one rod 2 grams lighter than the rest.
« Reply #3 on: November 01, 2013, 06:53:33 PM »
Quote from: KayOne on October 31, 2013, 07:35:00 PM
Starting on the engine build on the K1. Removed the rods to check the bearings and weighed them. Three rods 281 grams, one 279 grams. Should I lighten up three rods to match the lightest or just leave them alone?

Looks like you are within weight specifications according to this Honda service bulletin:

http://manuals.sohc4.net/CB750SB/750_31.pdf

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Offline KayOne

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Re: Rod weight, one rod 2 grams lighter than the rest.
« Reply #4 on: November 01, 2013, 09:07:17 PM »
Very interesting reading Dream! I don't think I will worry about it after seeing this article. It's not like I don't have enough work to do already.
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CB750 K1 restored
1979 CB750Fz - original except for exhaust, 14000km
1984 VF45F Interceptor - all original, 12000 km
1968 S90 - all original, 2100 miles
1973 H2a, Restored
1973 H1D, next project
CB750K1 (sold)
1976 KZ900 (sold)
1981 CB900F (under restoration)
2015 Yamaha FJ09, my appliance rider
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