Topic: piston ring groove measurements

[hymodyne]

Howdy all,

Back from France and trying to attack this oil consumption issue and get on with it...

Ed at Total Seal needs bore size, ring groove width and depth for henry abe 60mm pistons as supplied in the 605 overbore kit that classicycle in OH sold on ebay  a while ago ( they still have the 555cc version of this kit). I'm going to take a piston to a local machine shop and have the measurements taken, but I'd thought I'd check if anyone who, like me had to get replacement rings for these kits and their supplier who won't break full kits to replace rings, etc., has the measurements available. BryanJ suggests that the 750 K 1st and 2nd rings will work (I've got one top ring in place on my #4 piston); I'm hopeful that I can use 750 rings for the top two and just have get the oil rings from total seal.

hym

[bwaller]

Hym,

When you bought these pistons were they advertized as 60mm at the skirt? I have a set of Henry Abe that are 61, the same size as standard 750 pistons and the top two std. 750 rings fit perfectly. Unfortunately they are installed so I can't give you that measurement you need.

As I mentioned before the oil ring groove width can be machined slightly wider (I think it is 0.011") to be able to use a three piece 750 oil ring also.  Maybe it's less dough just to get oil rings from Total Seal but it's safe to say Hondas rings are top quality.

[hymodyne]

In light of the adaptability of the 750K standard rings, can a 750 person give me the depth and width of the top two 750 piston ring gaps

many thanks,

hym

[bryanj]

I do have both a 605 kit and 750 pistons but niether are here and i cant find my vernier, given time (we are talking weeks here not days) i may be able to gat all in the same place at the same time and help you out---just not right now or quickly

[hymodyne]

Many thanks BryanJ

Just let me know.

hym

[TwoTired]

Many years ago I bought a piston kit, sleeves and all.  I believe I was told it was a Henry Abe 605.  I never installed it.
It has the one piece oil ring.  The ring box is stamped  HA-61 STD

I measured these dimensions:
60.95 mm -Piston skirt diameter
60.55 mm -Piston skirt diameter at pin bosses.

2.55 mm  - oil ring groove width
1.59 mm  - 2nd groove width
1.59 mm  - top groove width

3.09 mm  - oil ring groove depth
3.03 mm  - 2nd ring groove depth
3.02 mm  - top ring groove depth

2.44 mm  - oil ring width
1.45 mm  - 2nd width
1.45 mm  - top width

Hope this helps,

[hymodyne]

Many thanks, Lloyd.

I'll forward this information to Ed at Total Seal.

BTW, You wouldn't be interested in selling that old, clunky, and totally unattractive 605 kit you mentioned having hmmm??

hym

[bwaller]

I have a new std. 750 piston and can post those measurements tomorrow if you like.

[hymodyne]

That would be great Bwaller, I can compare your measurements to those TT provided.

hym

[hymodyne]

Ed from Total Seal got ahold of me. I sent him TT's measurements from his 605 kit.

He said they didn't have any rings in those dimensions in stock.
Suggested Hastings.


The supplier I bought this kit from has a phone # that is no longer in service and a website that has been taken down.

I'm hopeful that bwaller's measurements on stock 750 rings will be better news... If top two rings from the 750 will work properly, then I'll only have dig deep for the custom oil rings to be made.

hym

[FunJimmy]

Great info

Hopfully Bwaller will find those 750 measurements.

[bwaller]

Sorry for the delay, here's the poop for a standard CB750 piston.

61mm      piston skirt diameter
60.4mm               "               at pin boss

2.82mm    oil ring groove width
1.52mm    second ring width
1.52mm    top ring groove width

3.3mm     oil ring groove depth
3.3mm     second ring groove depth
3.2mm     top ring groove depth (I imagine this is likely the same as the other two @3.3)

2.78mm   oil ring width (this is an old one piece ring)
1.5mm     second ring width
1.5mm     top ring width

2.88mm   oil ring depth itself
2.8mm     second ring depth itself     
2.8mm     top ring depth itself

The Henry Abe pistons I used have identical top two ring groove widths as the standard 750 piston. If you use 750 compression rings on the piston TT measured, tolerance (1.59mm-1.5mm=0.09mm) is within Hondas serviceable limit of 0.18mm top and 0.15mm for the second groove.

I had my machinist pal widen the oil ring grooves to 2.82mm to match the 750 pistons and then could use the full set of STD.750 rings.

Good luck Hym.

[hymodyne]

This is great. I'm going to see if hastings or wiseco will make an oil ring to match with the 750 replacements.Is the machining for the oil ring a common task how much to have 4 pistons turned?

hym

[bwaller]

I can't tell you what machining costs would be as I traded something he needed in exchange for the work. I know the setup was the most time consuming part of the job, as usual.

I'm not sure I follow you though. If you are able to modify the HA pistons, then you won't need Hastings, but can use genuine Honda rings.

[hymodyne]

Wiseco will only make rings for their pistons. hastings is closed for the Holiday

hym

[hymodyne]

Would stock 750 K rings 1 over(.25mm) work in this application too?

hym

[bryanj]

No too big for the bore

[hymodyne]

"I had my machinist pal widen the oil ring grooves to 2.82mm to match the 750 pistons and then could use the full set of STD.750 rings."

This was Bwaller's quote. I need to find someone who would be willing to turn my piston's lower ring groove this same way so I can run stock 750 rings on this engine.

I'll box them up and ship them to wherever, Just as long as I can get them back in a reletively short amount of time.

PM me if interested or know of a machinist that is able to do this. I'd really like to start enjoying this bike instead of looking over my shoulder all the time to see how much oil I'm pushing...

Help a brother out,

hym

[StrongPerf]

Sorry for the delay, here's the poop for a standard CB750 piston.

61mm      piston skirt diameter
60.4mm               "               at pin boss

2.82mm    oil ring groove width
1.52mm    second ring width
1.52mm    top ring groove width

3.3mm     oil ring groove depth
3.3mm     second ring groove depth
3.2mm     top ring groove depth (I imagine this is likely the same as the other two @3.3)

2.78mm   oil ring width (this is an old one piece ring)
1.5mm     second ring width
1.5mm     top ring width

2.88mm   oil ring depth itself
2.8mm     second ring depth itself     
2.8mm     top ring depth itself

What years is this for? I think I read somewhere that the 750 rings got thinner around 78 or so. Can anyone confirm?  Thanks

[bwaller]

These numbers are for the "300" piston. The later rings for the 410 pistons and at least some of the 392's?? were thinner.

How did you make out with your engine Hymodyne?

[hymodyne]

I decided to take it out, bwaller, and replace it with a 550 engine I had in my shop.
I'm installing .25 over pistons and rings in this one, and using the Rieke'd stage two head from my 605 engine.

It'll be a winter time project I can finish in my basement. I'm also looking at a box muffler, like those used on snowmobiles that I can fit under the frame, instead of a side pipe and canister.


hym

[Soos]

I dunno if they would work, but I'll measure my cb650 pistons rings.
The cb650 pistons are 59.8mm. not sure if you would even be interested as they are smaller than what you need.
(although DSS sells rings for the 650 in .25 and .5mm over for the 650)


l8r