Author Topic: Henry Abe 900cc big bore pain in the ass  (Read 4363 times)

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Offline Rio83

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Henry Abe 900cc big bore pain in the ass
« on: August 23, 2018, 04:05:00 AM »
Hi all:)
I got a cb750-75 engine with Haindst pistons marked with 0.50 on the top. Guess these are .50 oversized? All looks very good, but what do I have to replace? Does all come down to clearences and such?

Offline BPellerine

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #1 on: August 23, 2018, 04:33:56 AM »
what is wrong with it at present?it will come down to clearance and bore and ring wear,I have never seen a .50 set of henry abes,they are usually 67mm.bill
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Offline ekpent

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #2 on: August 23, 2018, 07:26:55 AM »
 Do the piston tops have a dome and cut-outs for the valves or are they flat top. Picture would be good when you get enough posts.

Offline Rio83

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #3 on: August 23, 2018, 07:35:02 AM »
Nothing wrong, but recently bought it and wanted to check cylinders and such. Glad I did, cause I had no clue it was a big bore And the cam chain tensioner wheel was a little bit messed up. Picture on its way


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Offline Rio83

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #4 on: August 23, 2018, 07:42:30 AM »



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Offline Rio83

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #5 on: August 23, 2018, 08:04:50 AM »
Can see the 0.50 barely on the first pic.


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Offline 754

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #6 on: August 23, 2018, 08:40:58 AM »
That looks like it may be stock size with overbore.l
 And stock compression. It's only the last few years you could get big bore pistons with stock  compression, unless you custom ordered.
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Offline Rio83

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #7 on: August 23, 2018, 08:55:46 AM »
That looks like it may be stock size with overbore.l
 And stock compression. It's only the last few years you could get big bore pistons with stock  compression, unless you custom ordered.

Im a noob and norwegian, so my understanding isnt the best. What does this actually mean? When was this kit made you think? And could I get some piston rings and stuff for it without custom order it from totalseal for 270$?



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Offline Rio83

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #8 on: August 23, 2018, 09:03:01 AM »
Cycle X just stated that these pistons are really old


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Offline 754

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #9 on: August 23, 2018, 09:08:48 AM »
 If those  are 61mm. You could go big bore  low compression, cruising image kit for 130.00 ish. But expect a big price for boring.
Rings for 61mm should be under 100 bux.

 So measure the piston with a ruler or tape, widest part of skirt, at the bottom.
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 Rio83

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #10 on: August 23, 2018, 09:11:04 AM »
As you see in the topic these are for 900cc, so they are 67,12mm.


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Offline PeWe

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #11 on: August 23, 2018, 09:26:19 AM »
I have  same pistons. 67.5 mm bores, 901.7cc or 900cc which is the normal saying and written inside the pistons.
When those bores are worn, not possible to bore a little bit more for next size since the sleeves are of the type that will fit case without machining (or just a little grinding).
You need to measure at the skirt 1/2" up from bottom under wrist pins. Not top where all pistons are slimmer.
« Last Edit: August 23, 2018, 09:33:11 AM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
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 Rio83

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Henry Abe 900cc big bore pain in the ass
« Reply #12 on: August 23, 2018, 09:32:20 AM »
I have  same pistons. 67.5 mm bores, 901.7cc or 900cc which is the normal saying and written inside the pistons.
When those bores are worn, not possible to bore a little bit more for next size since the sleeves are of the type that will fit case without machining (or just a little grinding).
You need to measure at the skirt 1/2" up from bottom under wrist pins. Not top where all pistons are slimmer.

But its not the same top as mine. Does yours say 0.50 PeWe? What about the clearances?


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Offline PeWe

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #13 on: August 23, 2018, 09:42:36 AM »
Have you measured at the skirt?
I saw your photo with 900 inside the piston.  My pistons are dirty and somewhere in the garage.
My photos are a few years old.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
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 Rio83

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #14 on: August 23, 2018, 10:04:19 AM »
Depends on how I measure. Both the sleeve and piston seem to be a little oval.




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Offline PeWe

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #15 on: August 23, 2018, 10:20:01 AM »
Yes, pistons are oval, your top pic show the correct place to measure. Your measurement verify 67.5mm and 900cc as printed inside pistons.
Bore diameter - piston diameter at the skirt is the clearance. Cast pistons have usually smaller clearance than forged.

CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
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 Rio83

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Henry Abe 900cc big bore pain in the ass
« Reply #16 on: August 23, 2018, 10:27:08 AM »
Yes, pistons are oval, your top pic show the correct place to measure. Your measurement verify 67.5mm and 900cc as printed inside pistons.
Bore diameter - piston diameter at the skirt is the clearance. Cast pistons have usually smaller clearance than forged.

Thanks PeWe
And how much should the clearance be? What about the clearance gap on the rings
Need to verify that all is good before I put it together.

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Offline PeWe

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #17 on: August 23, 2018, 10:44:54 AM »
Attached Henry Abe installation instruction.
Clearance is huge compared with other pistons. Henry Abe Pistons might expand a lot when warm?
Even bigger than my forged 1000cc pistons with 0.0025" clearance.

ring gap..compare with dynomans forged pistons.
http://www.dynoman.net/engine/pistons/piston-install/67mmSOHC.pdf
top ring min 0.25mm, 2:nd min 0.3mm

oil ring usually 0.25 as min.

Also note how the ends will be placed.
Note that I have mixed mm and inch
« Last Edit: August 23, 2018, 10:59:21 AM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
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 Rio83

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #18 on: August 23, 2018, 10:55:26 AM »
Perfect


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Offline BPellerine

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #19 on: August 23, 2018, 12:35:17 PM »
thought dynoman had pistons to clean up a 890 kit?
1978 CB 750K ard and webers
another anfob

Offline PeWe

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #20 on: August 23, 2018, 01:44:51 PM »
890cc is 67mm pistons (888cc).  900cc 67.5mm
Next step is 68mm 915cc. Bigger sleeves needed. Yes, Dynoman has that
My Henry Abe 900 pistons and cylinder to them had very thin sleeves. Not possible to go bigger without taking out sleeves, bore and press in bigger sleeves. case need to be bored too.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
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 Jerry Rxman Griffin aka MuthaF'er

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #21 on: August 23, 2018, 02:10:01 PM »
Hey PeWe, you're saying that going from my 67 HA to 68mm is not going to be possible without re-sleeving? I may need to do this as 1 of 4 liners is showing vertical scratching above and beyond normal break-in wear.  >:(
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline Rio83

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #22 on: August 23, 2018, 02:24:59 PM »
Hey PeWe, you're saying that going from my 67 HA to 68mm is not going to be possible without re-sleeving? I may need to do this as 1 of 4 liners is showing vertical scratching above and beyond normal break-in wear.  >:(
Do you got pictures of the scrathing?


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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #23 on: August 23, 2018, 03:16:31 PM »
Yeah. Heads still on and the pic is not so great with the cheap bore scope. Of course it's on my laptop and it's packed away for Bonneville tomorrow. Maybe I can figure out 1. how to locate it on my laptop 2. post it if I can find it next day or so once settled in at The Salt. 

Won't wonders ever cease LOL  ;) Fresh cross hatch 135 miles.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline Rio83

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Re: Henry Abe 900cc big bore pain in the ass
« Reply #24 on: August 23, 2018, 03:34:38 PM »
That didnt look all that good, but Im sure its fixable Have a good time at Bonneville


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