Author Topic: Cylinder Rust Removal (Read 3150 times)

Darren Jakal · « **on:** November 16, 2020, 06:08:55 PM »

Hey Everyone,

I've got this roller bottom-end that I have decided to take on as a longer term project as my main project should be finished this spring (in time for the summer season).

Anyway, I'm cleaning up the barrel as I want to measure it to see what I have, as I want to make a plan for this build.

Can this rust (it is all proud of the surface) be cleaned off some how without damaging anything? I've been looking into honing and boring, but want to know how to proceed at this point. (this was a good read http://forums.sohc4.net/index.php/topic,126776.0.html)

Thanks for your time and help!
dj

754 · « **Reply #1 on:** November 16, 2020, 07:32:27 PM »

There is a high chance that the lumpy areas when cleaned will reveal pitting...
Which would mean boring.. and then itsa matter of will 1st over clean it up or not.

Darren Jakal · « **Reply #2 on:** November 16, 2020, 07:35:52 PM »

Yea, I just want to know what I’m dealing with, so do I try to hone it out first or just right to getting it bored?

Thanks Frank!

bryanj · « **Reply #3 on:** November 16, 2020, 08:01:53 PM »

Get a Flexihone but it will definately need reboring and may not even clean at max oversize, i just did a 550 that looked like that and it just cleaned at 1mm o s

trigger · « **Reply #4 on:** November 17, 2020, 12:46:13 AM »

They may never clean up with a rebore. Better and cheaper to look for another set of barrels to rebore

And then you must find a good machine shop to bore to Honda spec

Darren Jakal · « **Reply #5 on:** November 17, 2020, 07:08:12 AM »

Ok, thanks for all your input !

I have use of a Bridgeport clone milling machine with DRO and a Narex Boring Head.

If this jug is not worth saving would it be worth experimenting with and trying to learn how to bore a sohc/4 jug for future use, or is this best left to the experts.

(these are budget builds with as much DIY as possible, but I still want to do it right or not bother)

I use the mill all the time, but I'm no machinist, however I work with a machinist who is a great help to me. I'll also do some more searching on how best to proceed.

Thanks for your time and comments, Darren

69cb750 · « **Reply #6 on:** November 17, 2020, 07:15:03 AM »

Hone first to remove rust, you may have pits, need to get of rust first.

69cb750 · « **Reply #7 on:** November 17, 2020, 07:17:47 AM »

69cb750 · « **Reply #8 on:** November 17, 2020, 07:18:44 AM »

754 · « **Reply #9 on:** November 17, 2020, 08:24:14 AM »

DARREN , you could actually bore them at least part way. If you are good at clocking in with a dial test indicator.
Not much to lose on this set .How many bores are that bad ?
Clamp cylinder to a spacer or parallel , so sleeve is above table.
Check top of sleeve so you are square to bore. Use a used insert, come in close to bore size gently to avoid tearing rust out in chunks.
You want to leave a few thou for finishing, that is if the surface finish is not to rough.
That's what I would try in smaller cuts... to see how deep rust is.
Big mess that Kawi cylinder.. oh man..

Darren Jakal · « **Reply #10 on:** November 17, 2020, 08:57:21 AM »

Ok, Thanks Frank and 69,

If I did try to hone, would a flex (ball) hone work, or does this require a rigid hone?

I may try your suggestion Frank, but I'll go at it slow and easy as to not screw up something that may actually be usable. I have been cleaning up the worst cylinder with very fine steel wool just to try and see what's below the rust, but I ran out of wool, so it will be later.

Cheers, dj

69cb750 · « **Reply #11 on:** November 17, 2020, 10:09:53 AM »

Straight hone, ball hone, glass bead, they all work.
Sometimes surface rust, sometimes pits, depends on how much water and how many years.

PeWe · « **Reply #12 on:** November 17, 2020, 10:49:42 AM »

I had a stock CB750 cylinder with similar rust on 2-3. Thought that 61.5mm pistons should fix it. +0.5mm pistons.
The shop did not like the remaining very small pits and colorations.
I fixed 2 OK sleeves for replacement to be bored.
That cylinder sit today on my K2.

That was cruzinimage K7 pistons. They have +1.0 mm too.

Photos before bore. I brushed the rust away with flexhone brush after photos were taken. But some pits remained after bore, almost 0.25mm on each side.

754 · « **Reply #13 on:** November 17, 2020, 12:00:23 PM »

I think it will chip the he'll out if a rigid hone. Grind or bore it off first, sleeve can be changed.
If you find a block on eBay with major fin damage might be reasonable, then swap sleeves..
Or try Old Bike Shoppe..

Darren Jakal · « **Reply #14 on:** November 17, 2020, 03:15:59 PM »

Hey thanks for all the help ! Some pretty #$%*ty looking cylinders here.

Here is the same cylinder (the worst one) after I went at at with some 600 wet/dry and oil. Maybe this will hone out, I don't know.

I'll need to get a hone and the machinist had his bore gauge at home so hopefully tomorrow he will remember to bring it in and I can get some idea of what I have.

Cheers, dj

bryanj · « **Reply #15 on:** November 17, 2020, 03:17:34 PM »

That wont hone but should bore

Darren Jakal · « **Reply #16 on:** November 17, 2020, 03:18:57 PM »

wow fast Bryan, thanks for the input, I appreciate it !

dj

754 · « **Reply #17 on:** November 17, 2020, 04:44:01 PM »

At this point if the pits are cleaned out , he can say something like 10 over won't clean it but 20 or 30 might..
If the pits are 5 or 6 thou deep , that 2 thickness of a hair per side, then 10 won't clean it up.
1 oversize is approx 10 thou , just under.,

Darren Jakal · « **Reply #18 on:** November 17, 2020, 04:50:15 PM »

So I talked with the local motorcycle machine shop and was quoted $130.00 a hole. Now even with Canukistani dollars this is no longer a budget build.

Good thing I don’t need this engine right away. Maybe it’s time to figure out how to bore a cylinder and keep my eye out for a decent used jug as well.

Thanks again everyone, dj

754 · « **Reply #19 on:** November 17, 2020, 05:08:38 PM »

Wrong place , wrong price.. greedy fux .. geez do they think it was big bore and bigger sleeves ?
Try a few other places , tell em it's 20 or 30 thou coming out.
Check what a used one costs l

69cb750 · « **Reply #20 on:** November 17, 2020, 05:09:50 PM »

Quote

Now even with Canukistani dollars this is no longer a budget build.

Are you Canadian ? Please explain why istani has been added to your dollar.

It is usually cheaper to buy cylinders on ebay then have cylinders bored - https://www.ebay.com/itm/HONDA-CB750-SOHC-CB-750-K-HM308B-ENGINE-CYLINDER-JUG-TOP-END-BARREL/291561206121?hash=item43e266f169:g:x7wAAOSw0JpV6Jgx

Darren Jakal · « **Reply #21 on:** November 17, 2020, 05:54:30 PM »

Quote from: 69cb750 on November 17, 2020, 05:09:50 PM

Quote
Now even with Canukistani dollars this is no longer a budget build.
Are you Canadian ? Please explain why istani has been added to your dollar.

It is usually cheaper to buy cylinders on ebay then have cylinders bored - https://www.ebay.com/itm/HONDA-CB750-SOHC-CB-750-K-HM308B-ENGINE-CYLINDER-JUG-TOP-END-BARREL/291561206121?hash=item43e266f169:g:x7wAAOSw0JpV6Jgx

It’s a joke. Canadians are known to make fun of themselves (Canada was once called Canuckistan by some US news pundit and I thought it was #$%*ing funny).

Actually it was Pat Buchanan https://www.urbandictionary.com/define.php?term=Soviet%20Canuckistan

Yea, I’m looking for a used one, good thing I got time on my hands,

Cheers, dj

PeWe · « **Reply #22 on:** November 18, 2020, 03:03:10 AM »

Piston - bore clearance also a factor to avoid a smoker.

69cb750 · « **Reply #23 on:** November 18, 2020, 04:46:14 AM »

Quote

I got time on my hands,

Here is your assignment - Remove all the rust with #240 wet dry, clean cylinder, run straight hone with oil for three minutes, clean cylinder, inspect cylinder for hone marks, hone marks everywhere good, hone marks not everywhere you have low spots.
Sunnen hones can straighten cylinders, best to measure piston and cylinder bore before Sunnen hone to determine what clearance will be after Sunnen hone.

Darren Jakal · « **Reply #24 on:** November 18, 2020, 07:19:41 AM »

Thanks guys for your replies !

This is just what I was going to ask about - piston bore clearance.

It seems best to have the pistons on hand to bore/hone to size, but if I don't know how much material I need to remove I won't know what pistons to buy. Any advise on this?

So, I will get on what 69 has to say and see how things go. Taking it slow as this is a completely unessential project and I really need to use my budget for the runner coming out next season.

Cheers and thanks again! dj

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Author Topic: Cylinder Rust Removal (Read 3150 times)