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Author Topic: having a heart attack  (Read 1849 times)

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Offline Rootcellar

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having a heart attack
« on: September 19, 2016, 10:15:53 AM »
I was moving some stuff around in the shop and noticed that i have a little chip at the bottom of one my cylinder walls. about 1/8" high by a little less than a 1/4" long...

Please tell me that I am not screwed.... 
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Offline BomberMann650

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Re: having a heart attack
« Reply #1 on: September 19, 2016, 10:23:23 AM »
This post has no context
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Offline Rootcellar

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Re: having a heart attack
« Reply #2 on: September 19, 2016, 10:25:24 AM »
no context?
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Offline flybox1

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Re: having a heart attack
« Reply #3 on: September 19, 2016, 10:26:02 AM »
that part of the cyl wall is not in contact with the piston or rings.

Post a picture of it.
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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Offline Rootcellar

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Re: having a heart attack
« Reply #4 on: September 19, 2016, 10:28:13 AM »
I don't have a pic at the moment, but it should be fine? it's right at the bottom of cylinder 4...sorry, I saw it and ran to the computer panicking...
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Offline flybox1

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Re: having a heart attack
« Reply #5 on: September 19, 2016, 10:31:08 AM »
go take a picture
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline Rootcellar

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Re: having a heart attack
« Reply #6 on: September 19, 2016, 10:31:46 AM »
here is a pic
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Offline flybox1

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Re: having a heart attack
« Reply #7 on: September 19, 2016, 10:46:24 AM »
Bummer.  Bigger than I thought.
If you are in the US, cheap cyls can be had on ebay.
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline 70CB750

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Re: having a heart attack
« Reply #8 on: September 19, 2016, 11:06:11 AM »
I would at least check how far the piston goes, it could still be ok.
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Offline flybox1

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Re: having a heart attack
« Reply #9 on: September 19, 2016, 11:12:04 AM »
My only concern would it might be really hard to get a ring past that without damaging it.
If you're going to punch it out, get a different head and save the worry  :-\
$50
http://www.ebay.com/itm/Honda-CB750f-Cylinder-sohc-1976-/172322303659?hash=item281f35aeab:g:eXAAAOSwFdtXw5cw&vxp=mtr

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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline Rootcellar

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Re: having a heart attack
« Reply #10 on: September 19, 2016, 11:57:33 AM »
I have the original block for the bike...this one was already bored out...that's why I'm peaved....
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Online PeWe

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Re: having a heart attack
« Reply #11 on: September 19, 2016, 12:06:20 PM »
More worries about where that piece has landed?
Inside engine and runned after that, or just in the garage?
Must be a problem when piston with rings going in.

CB750? Look like 836 thin sleeves
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Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
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CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline Rootcellar

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Re: having a heart attack
« Reply #12 on: September 19, 2016, 12:24:10 PM »
Luckily the engine is completely apart as I am rebuilding it ....the chip is on the floor somewhere...i checked the piston vs the crack and it seems like it would be okay as I am just barely seeing the wristpin at it's lowest point...my biggest fear is as calj737 suggests, that the heat and daily use will just make it worse ...think i am just going to resleeve, or just send my original block to be bored out...it'll prolly cost the same either way...thanks for the help guys...
« Last Edit: September 19, 2016, 04:32:26 PM by Rootcellar »
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Offline Rootcellar

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Re: having a heart attack
« Reply #13 on: September 19, 2016, 12:53:14 PM »
Quote from: PeWe on September 19, 2016, 12:06:20 PM

CB750? Look like 836 thin sleeves

Yeah PeWe they are 849
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Offline 754

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Re: having a heart attack
« Reply #14 on: September 19, 2016, 09:30:58 PM »
So the easiest way..ask on here for a pooched 836 sleeve.. Install it, check deck..then bore that one to fit your piston..
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