Author Topic: CB750 mystery part found (Read 4533 times)

saltysultz · « **on:** February 06, 2018, 12:16:41 PM »

Hello,

I am rebuilding my 1977 cb750 motor and when i dropped the oil pan i found a mystery part seen in the picture. I figured i would crack the case and match it up to the cog or whatever it was missing from... no luck. Doesnt match any transmission or crank cogs. So my question is, does anyone know where this piece came from? It looks asymmetrical and almost like the last 1/2 inch of a claw from a hammer that broke off. Thanks for all the help!

ekpent · « **Reply #1 on:** February 06, 2018, 01:09:32 PM »

These threads are always fun. Is it steel/magnetic ? Looks porous.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #2 on:** February 06, 2018, 01:43:33 PM »

Shift fork?

mrbreeze · « **Reply #3 on:** February 06, 2018, 01:48:18 PM »

Kinda looks like half of a woodruff key.

Swoop · « **Reply #4 on:** February 06, 2018, 01:50:42 PM »

It looks like it expired in Nonember 😎

Stev-o · « **Reply #5 on:** February 06, 2018, 02:26:29 PM »

Quote from: ekpent on February 06, 2018, 01:09:32 PM

These threads are always fun.

For everyone except the thread starter!

dave500 · « **Reply #6 on:** February 06, 2018, 02:51:16 PM »

tang end from kickstart mechanism?

FuZZie · « **Reply #7 on:** February 06, 2018, 03:15:08 PM »

Quote from: mrbreeze on February 06, 2018, 01:48:18 PM

Kinda looks like half of a woodruff key.

I had the exact thought until I enlarged the image.

saltysultz · « **Reply #8 on:** February 06, 2018, 03:25:23 PM »

Woodruff keys aren't curved on both sides, correct? This one is curved on both sides. It looks too skinny and shiny to be a shift fork. going to take a look at the kickstart mechanism. it is attracted to magnets.

my name is nobody · « **Reply #9 on:** February 06, 2018, 03:46:11 PM »

Quote from: Jerry Rxman Griffin aka MuthaF'er on February 06, 2018, 01:43:33 PM

Shift fork?

x2..

przjohn · « **Reply #10 on:** February 06, 2018, 03:56:43 PM »

It looks to be anodized the same color as some Motion Pro brand tools, maybe a broken piece of a tool, gear holder?

saltysultz · « **Reply #11 on:** February 06, 2018, 04:08:03 PM »

figured it out guys. my girlfriend who knows nothing about bikes or engines comes in and takes a look at the broken part and says "it looks like its from a wrench." It is an exact match to a 10mm open end wrench. I didn't break one but it has to be what it is. Thanks for all the help guys, sorry it wasn't a better answer.

spotty · « **Reply #12 on:** February 06, 2018, 04:11:16 PM »

Quote from: mrbreeze on February 06, 2018, 01:48:18 PM

Kinda looks like half of a woodruff key.

on vespas the flywheel is held in place by a woodruff key and so one day a friend of mine is trying to start his indian copy vespa when i noticed as he was kicking the flywheel wasn't turning in response to his ever more aggrieved efforts, pulled the flywheel and splinters of wood fell out of the woodruff keyway...ah those indians, environmentally conscious even back in the early 80s

setdog · « **Reply #13 on:** February 06, 2018, 05:16:10 PM »

my girlfriend who knows nothing about bikes or engines comes in and takes a look at the broken part and says "it looks like its from a wrench."

ahem (cough) thats exactly what i was gonna say (cough)

dave500 · « **Reply #14 on:** February 06, 2018, 05:37:51 PM »

hope you've eaten that bread its expired!

scottly · « **Reply #15 on:** February 06, 2018, 05:57:16 PM »

Quote from: dsultz on February 06, 2018, 03:25:23 PM

Woodruff keys aren't curved on both sides, correct? This one is curved on both sides. It looks too skinny and shiny to be a shift fork.

Wrench jaws aren't curved on both sides. How thick is it? Your picture angle makes it hard to get any sense of scale.

ekpent · « **Reply #16 on:** February 06, 2018, 08:11:47 PM »

If indeed it was a 10mm open end wrench tip it may have broken off while somebody was really reefing down hard on a cam sprocket bolt and it fell down the tunnel. Was there evidence that the engine had been opened up before ?

saltysultz · « **Reply #17 on:** February 07, 2018, 10:09:47 AM »

upon looking closer at it, it starts to curve at the end (broken end), same spot where the wrench jaw curves to go to the other side. The engine looks like it was taken apart before; looks like someone was messing with the valve train a bit and the cam sprocket, but didnt dig deeper. 10mm bolts are super common on it and i just bought the bike, so i'm just going to just pray that it's from a wrench. My girlfriend, who is way smarter than me apparently, pointed out it looks shinier than anything else in the engine and it does took like stainless steel.

slikwilli420 · « **Reply #18 on:** February 07, 2018, 10:30:09 AM »

Wrenches aren't stainless steel.

DaveBarbier · « **Reply #19 on:** February 07, 2018, 12:40:13 PM »

Quote from: slikwilli420 on February 07, 2018, 10:30:09 AM

Wrenches aren't stainless steel.

+1

Looks chrome or satin chrome. But it does look in good shape meaning it wasn't thrown around by the chains or transmission.

Allow me to hypothesize. I wouldn't think I'd be able to break off a 10mm wrench on a small bolt that easily. I am weak though. Perhaps it was a cheap crow's foot on an extension? Doesn't really help to make up a story but it's fun and I'm off work today.

przjohn · « **Reply #20 on:** February 07, 2018, 03:31:47 PM »

Is it just my picture or computer because it sure looks Blue to me?

MoMo · « **Reply #21 on:** February 07, 2018, 03:42:19 PM »

Quote from: przjohn on February 07, 2018, 03:31:47 PM

Is it just my picture or computer because it sure looks Blue to me?

Most likely be the sky reflection

madmtnmotors · « **Reply #22 on:** February 07, 2018, 03:48:07 PM »

My first impression was a piece of an open end wrench as well. A couple of bolts that might snap a 10mm wrench could be the cam sprocket bolts or maybe the rocker arm adjuster lock nut.

Yamahawk · « **Reply #23 on:** February 07, 2018, 03:53:09 PM »

Quote from: madmtnmotors on February 07, 2018, 03:48:07 PM

My first impression was a piece of an open end wrench as well. A couple of bolts that might snap a 10mm wrench could be the cam sprocket bolts or maybe the rocker arm adjuster lock nut.

You can see the grain structure of the metal, that is a fracture of a poorly heat treated piece of steel for sure. It may be a cheap wrench, as I have had one or two break while hammering... er... adjusting them with a 24oz micrometer...
Charlie

DaveBarbier · « **Reply #24 on:** February 07, 2018, 04:36:08 PM »

Yeah, not blue. In shadows digital cameras tend to cool the entire image down.

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Author Topic: CB750 mystery part found (Read 4533 times)