Author Topic: Swapping con rods  (Read 483 times)

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Offline timtune

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Swapping con rods
« on: January 08, 2021, 01:40:33 pm »
While taking a 78 F motor apart I managed to partially drive one of the bronze bushings out of the small end of one rod. I'm pulling a second engine from another bike and I'm wondering how best to proceed.

Can I just swap another con rod and make sure the gap is good with PlastiGage? If so can it be one from any cylinder?

Should I be trying to keep the rod mated to the crank and replace the small end bushing?

Thanks all.

Offline gschuld

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Re: Swapping con rods
« Reply #1 on: January 08, 2021, 02:42:04 pm »
Please post a picture of the rods in question. Factory steel rods did not have a bronze bushing installed.  So if they are factory, they were modified to some extent.  RC Engineering and others years ago installed bronze bushings in their improved factory rods, usually along with oversized rod bolts installed, shot peening, etc

George

Offline 754

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Re: Swapping con rods
« Reply #2 on: January 08, 2021, 06:32:58 pm »
Can you not fix the  rod.. new bushing maybe  ?
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Offline dragracer

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Re: Swapping con rods
« Reply #3 on: January 09, 2021, 07:53:04 am »
Can you not fix the  rod.. new bushing maybe  ?

I was thinking the same thing Frank. Any competent automotive machine shop should be able to replace that bushing. At least he'd still have have a matched set and for less than $40 i bet.

Offline Alan F.

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Re: Swapping con rods
« Reply #4 on: January 09, 2021, 08:44:52 am »
Can you not fix the  rod.. new bushing maybe  ?

I was wondering if the existing bushing could be pushed back into place? Too thin and easily damaged maybe?

2 wood blocks and a c-clamp?  (G-clamp even)
« Last Edit: January 09, 2021, 08:46:34 am by Alan F. »

Offline 754

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Re: Swapping con rods
« Reply #5 on: January 09, 2021, 09:34:47 am »
Use or make a stepped bushing driver ... if you end up buckling it, you are making one needlessly.
 If it goes in too easy , then that has to be considered. . Wonder why it  moved ?
« Last Edit: January 11, 2021, 07:53:05 pm by 754 »
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline MRieck

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Re: Swapping con rods
« Reply #6 on: January 09, 2021, 11:23:19 am »
Use or make a step led bushing driver ... if you end up buckling it, you are making one needlessly.
 If it goes in too easy , then that has to be considered. . Wonder why it  moved ?
I have seen them spin in the bore Frank blocking the oil holes.
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Offline 754

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Re: Swapping con rods
« Reply #7 on: January 09, 2021, 11:52:25 am »
Too loose then. If you machine a shallow groove  around bushing od it may get oil... yeah i kniw they are thin..
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline timtune

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Re: Swapping con rods
« Reply #8 on: January 11, 2021, 05:23:47 pm »
Thanks all. Now I'll be popping a few motors apart to check the con rods.

I think I got sloppy trying to knock out the wrist pin and started driving on the bushing.

Offline kmb69

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Re: Swapping con rods
« Reply #9 on: January 11, 2021, 07:00:34 pm »
Thanks all. Now I'll be popping a few motors apart to check the con rods.

I think I got sloppy trying to knock out the wrist pin and started driving on the bushing.

The pins are designed to "float" in Hondas. Must have been some other issue if you were having to pound them out.

Offline kmb69

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Re: Swapping con rods
« Reply #10 on: January 11, 2021, 07:15:09 pm »
Can you not fix the  rod.. new bushing maybe  ?

I was thinking the same thing Frank. Any competent automotive machine shop should be able to replace that bushing. At least he'd still have have a matched set and for less than $40 i bet.

"Competent" is the key word.
Proper rod bushing installation involves "burnishing" the bushing to the rod, to bond the bushing to the rod, prior to final machining/honing.
This is more or less a standard procedure used by most rod builders/re-builders.

Offline timtune

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Re: Swapping con rods
« Reply #11 on: January 12, 2021, 12:31:29 pm »
Thanks all. Now I'll be popping a few motors apart to check the con rods.

I think I got sloppy trying to knock out the wrist pin and started driving on the bushing.

The pins are designed to "float" in Hondas. Must have been some other issue if you were having to pound them out.

Was probably tapping them out when my drift caught the bushing giving the impression of it needing a good solid whack. Then another and another. And of course then onto a bigger hammer when that didn't work.