Topic: HA Pistons and Rings

[Mark K]

Hi everyone. I know this topic has come up before but was not able to find the answers to my particular problem, as the forum posts were a couple years old. Attempting complete tear down of '73 CB750K3. Removed the pistons and found "HAINDST 900cc" stamped inside. Figured out what that meant after an internet search. Currently have 2 pistons that have stuck rings soaking in PB Blaster. Anyone know where can I obtain new rings? Am going to attempt to use existing pistons (after I have a knowledgeable machinist look at the cylinder bores, pistons, head, etc.) Any help would be greatly appreciated.

Thanks,
Mark

[PeWe]

Measure bore to ensure dimension.
I think 67.5mm
There are also 67mm version, 890cc.

[Tim2005]

Try this thread for some info.... http://forums.sohc4.net/index.php/topic,149234.msg1702388.html#msg1702388

[Mark K]

Thanks, I'll do both of those things.

[Jerry Rxman Griffin aka MuthaF'er]

I probably have a set of the 1 piece original oil rings at home should the need arise. Downside is I will be 3000 miles away until May. Maybe even a HA head gasket too. Not sure about that. 3 spare slightly used pistons and 1 FUBAR piston.

[PeWe]

If the pistons are like mine in that old thread, no meaning to use them if a hotter cam is in mind. No pockets for higher lifting cams.

Old used pistons have often worn grooves for rings. Rings should not have much play up- down, maybe 0.05mm (as In valve lash)
If bores are 67.5mm and worn, not possible to bore more. HA sleeves are very thin where enter the case.

Outer diameter wider than CycleX stepped sleeves of 74.2mm. My old HA sleeves where around 74.25mm. Maybe too loose fit for CycleX sleeves

That cylinder can be bored wider to use CyxleX next sleeve for 70mm pistons.

Dynoman has too but cost more. They can make sleeves that fits. Their pistons are very fine. Same type of sleeves and 67 mm pistons leave thicker sleeve.
 
My HA 900 cylinders too worn, pistons too after consideration of the very limited use.

A friend of mine has a similar set with HA 67mm pistons. He bought my not much used forged Wiseco 67.5mm pistons after he found out no higher lifting cam possible with the too old and limited HA pistons. He also see the need of better rods at 900cc. I told him

Other option for good use.
Another good cylinder, bore to 64mm ( 811cc kit Dynoman has) which leave restore posibility to 65mm 836cc to be used with hotter cam.

If no hotter cam is needed and important to keep budget low. Bore a cylinder to fit Cruzinimage 836cc pistons. Complete set with gasket $120 US
https://www.cruzinimage.net/2017/08/25/69-76-honda-cb750k-836cc-65mm-bigbore-pistons-kit-w-head-gasket/

[Mark K]

Thanks for the additional suggestions, budget is a concern as funds are limited. Attempting to re-use anything and everything if possible.

Planning on using the cam that was in the engine, haven't measured it yet, don't know if it's a hotter cam.

I dropped off the 2 pistons (with stuck rings) to my local cycle service shop, he's going to agitate them overnite, said he's had success with that method. I tried applying heat and WD-40 last night (as seen in a YouTube video), no luck. Also had the shop remove the lower shock bushings from the swingarm today, he had to burn/cut them out. I broke my vice trying to remove said bushings a few weeks ago.

I'll take some measurements tomorrow after I get the pistons back, although I think they're 67mm, as I mic'ed them the other day, just neglected to write it down. I did not measure the bore, think I need a dial guage to do that?

I will need to purchase a complete set of rings for all 4 pistons, if the piston tolerances are correct and they're reuseable.

[Mark K]

Got the two pistons back, all rings removed except a piece about an inch long, will have to work on that some more. Mechanic says the pistons are useable. I emailed Total Seal to check on rings. This is what I receive back,

"Thanks for contacting us. We do not have those exact ring sizes in stock. We could make a custom set, but the minimum order size for the top ring would be more than 4 cylinders worth."

I emailed back this evening asking what the minimum order would be and how much $$.

Anyone have any additional suggestions on where to get a set of piston rings?

[Jerry Rxman Griffin aka MuthaF'er]

Anyone know the sizes of the CB450T pistons and rings?

I can cover you for the 1 piece original HA oil rings. If you become interested PM me.

[Bodi]

"Anyone know the sizes of the CB450T pistons and rings?"

75mm bore

[Mark K]

Anyone know the sizes of the CB450T pistons and rings?

I can cover you for the 1 piece original HA oil rings. If you become interested PM me.

I appreciate the offer, but after speaking at length with a Tech Rep at Total Seal, I think I'm going to take PeWe's advice and have it rebored (if possible) and use an oversize piston or go with new sleeves, pistons, etc.

Can anyone suggest a good cycle machinist near southeast Alabama?

[Mark K]

Update on my HA Piston issue - local machinist and Honda expert recommended different cylinder, as whoever put in the HA big bore kit did not change anything else out. Head is damaged and would cost more to fix (weld to build up broken off exhaust header mount hole and redrill, remove a heli-coil and also to remove broken off spark plug). So I'm going with a different 750 Honda cylinder and head, machinist is going to overbore .50 over, once I receive the pistons kit. Also going to replace the intake valves, exhaust valves judged to be ok. Piston kit ordered along with oil seal kit since we're tearing engine completely apart. Waiting on a couple special tools to continue teardown.

[Jerry Rxman Griffin aka MuthaF'er]

Anyone know the sizes of the CB450T pistons and rings?

I can cover you for the 1 piece original HA oil rings. If you become interested PM me.

I appreciate the offer, but after speaking at length with a Tech Rep at Total Seal, I think I'm going to take PeWe's advice and have it rebored (if possible) and use an oversize piston or go with new sleeves, pistons, etc.

Can anyone suggest a good cycle machinist near southeast Alabama?

Larry Hayes in Dothan. Old drag racer with bad ass big block turbo injected 750

[PeWe]

If you go for the Cruzinimage +0.50mm pistons, make sure that total clearance of piston vs bore is max 0.025mm.
I do not know the min limit. I guess 0.020 is OK too.

[Mark K]

Can anyone suggest a good cycle machinist near southeast Alabama?
[/quote]

Larry Hayes in Dothan. Old drag racer with bad ass big block turbo injected 750
[/quote]

Thanks! I've been in contact with him. He was working on his drag bike yesterday. He's selling me a head and cylinder and is boring it. Dropped off new pistons (.50) to him yesterday so he can check clearances. Another guy (Scott) is working head, dropped off new intake valves to him yesterday.