Author Topic: Henry Abe 900cc big bore pain in the ass (Read 4135 times)

Rio83 · « **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?

BPellerine · « **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

ekpent · « **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.

Rio83 · « **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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Rio83 · « **Reply #4 on:** August 23, 2018, 07:42:30 AM »

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Rio83 · « **Reply #5 on:** August 23, 2018, 08:04:50 AM »

Can see the 0.50 barely on the first pic.

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754 · « **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.

Rio83 · « **Reply #7 on:** August 23, 2018, 08:55:46 AM »

Quote from: 754 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.

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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Rio83 · « **Reply #8 on:** August 23, 2018, 09:03:01 AM »

Cycle X just stated that these pistons are really old

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754 · « **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.

Rio83 · « **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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PeWe · « **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.

Rio83 · « **Reply #12 on:** August 23, 2018, 09:32:20 AM »

Quote from: PeWe 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.

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

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PeWe · « **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.

Rio83 · « **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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PeWe · « **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.

Rio83 · « **Reply #16 on:** August 23, 2018, 10:27:08 AM »

Quote from: PeWe 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.

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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PeWe · « **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

Rio83 · « **Reply #18 on:** August 23, 2018, 10:55:26 AM »

Perfect

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BPellerine · « **Reply #19 on:** August 23, 2018, 12:35:17 PM »

thought dynoman had pistons to clean up a 890 kit?

PeWe · « **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.

Jerry Rxman Griffin aka MuthaF'er · « **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.

Rio83 · « **Reply #22 on:** August 23, 2018, 02:24:59 PM »

Quote from: Jerry Rxman Griffin aka MuthaF'er 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.

Do you got pictures of the scrathing?

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Jerry Rxman Griffin aka MuthaF'er · « **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.

Rio83 · « **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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Author Topic: Henry Abe 900cc big bore pain in the ass (Read 4135 times)