Topic: Cylinder Rust Removal

[69cb750]

Piston is 2.4005", bore is 2.402", clearance is .0015"
.0015", .002", .003" is good, .004" is ok, service limit is .009" (worn out).
Measure piston at base of skirt with micrometer.
You can measure bore with od micrometer or expanding gauge, I prefer inserting piston with feeler gauges

[Maltboy]

Is this from a 750K?  It may be way cheaper just to get a good used block and pistons.  I bought a nice used cylinder block, including pistons for $40.  It was a standard bore, and the pistons had almost no wear.  Heck, some of the parts hoarders preservationists on this forum might have one they could part with.  I can send you a standard one with a few chipped fins for what it costs to ship, but that might be kinda spendy from Texas to Canada.

[bryanj]

Idealy you should have pistons in hand before boreing BUT back in the 70's when i did this a lot i never found a genuine Honda piston, no matter what size or model to be anything other than spot on size.

[Darren Jakal]

Again, thanks for all the help everyone!

I'm looking for a good used one (for a 550), but I have to say that all the ones I saw did not appear that great. So, buying another used one may put me right back into the same place, but now with 2 jugs that need work. Love to find good jugs and pistons in one go, but I'm not feeling confident in that happening. I'm tramming the mill today and will do some practicing with the boring head just to see what is involved.

I'll keep cleaning these ones up, measure them and the decide what to do.

cheers, dj

[754]

Your average used one, will clean up to 1st oversize.. not like yours..
 

[Darren Jakal]

Hey 754, thanks for your help, but doesn't that still put me in the position to bore? I would rather use this jug and go up to the next size than spend more money and take a chance with another one.

later, dj

[bryanj]

You can put 500 ones on, no great power loss

[754]

Well here is one consideration , 1 oversize can be bored and honed,  or just honed.. the latter should be cheaper.
 But that will likely not be as easy on yours. .  Its all four holes are bad or just a couple ?   
 Yo got nothing to lose by boring a bit of yours out.

[Darren Jakal]

The worst one is the one I posted pictures of. Two are pretty good really and the last one is in between.

I might just give a bore a try eventually. Again I’m in no rush and will look to the best alternative (and that may be doing nothing at all as this in an non essential project and more of a something to do project).

I have friend who is the real deal mechanic/machinist and I’ll try to get his opinion (he is a very busy person).

Thanks again Bryan, Maltboy, 69 and any one else I missed (you too Frank!).

Cheers, dj

Edit to add: not that I doubt you guys are also the real deal, but seeing something in real life and potentially having a solution available at that time (hone, boring tool, measurements etc) is what I’m thinking.

[PeWe]

Fresh bores and new pistons must not be very expensive.
Tight clearance needed
https://www.cruzinimage.net/category/item/itemgenre/motorcycle/honda/pistons-honda/page/4/

[bryanj]

Its the machining that costs most, 2 years ago was quoted £65gbp per hole so i resurected my old Van Norman boring bar but it will only do 500 and up

[trigger]

Its the machining that costs most, 2 years ago was quoted £65gbp per hole so i resurected my old Van Norman boring bar but it will only do 500 and up

I must be too cheap as, i only charge £40 per liner 

[PeWe]

I paid around $200US to bore my CB750 cyl block, all 4 bores.
New pistons with shipping another 140.

[dave500]

id just rebore it anyway,itll be nice n square then,get the pistons first and have the guy bore n hone for each piston,go 2nd over.

[Darren Jakal]

Thanks again for the interest in this.

Pistons are reasonably priced and not the issue here.

The quote of $130 per hole or $520 CDN for the bore job is not going to happen for a side project. This is from the one machine shop that i know specializes in motorcycles. I'll look around for more quotes, but if I know this town no one is going to be interested in a project like this for much less.

I'm also not interested in buying a jug off the web unless I can see it in person (there are not a lot of local options for used 550 parts here).

I've been working with the mill and bore head and will eventually try to bore it myself.

Again, this is a side project (low budget) and I'm in no rush.

Cheers again for the help, darren

[754]

Okay so if you bore the worst one , no more than 15 thou over stock, you should be safe. Enough left over to hone. For 2nd oversize.. .50 mm. At that point  you will see if it cleans up or not.

[Darren Jakal]

Thanks 754,

So, in metric if the standard bore is 58.5mm then 15 thousand over stock would be 58.538mm, correct?

Cheers, dj

Edit: 58.881 is more likely

[754]

1st post of this page ...bore is 2.402 plus 15 makes 2.417..
 I have to sit to think in metric or calculate..
 But whatever your micrometer is.. go with that..

[Darren Jakal]

Yea, I have metric micrometer and the DRO is both decimal inch or metric to 3 decimal place (machinist is off today and still hasn't remembered to bring in the bore gauge, so not sure what that one will read).

If things are made metric I feel more comfortable using mm. Translation has #$%*ed me up before.

Cheers, dj

[69cb750]

So, in metric if the standard bore is 58.5mm then 15 thousand over stock would be 58.538mm, correct?

std bore = 2.402" = 61.0108 mm
2.402" + .015" = 2.417" = 61.3918 mm

[bryanj]

61 is a 750 the post is a 550

[Darren Jakal]

Measure twice, cut once, right?

Thanks guys, dj

[754]

61 mm  is the 750 bore.
 If yours don't clean up, look into fitting 750 pistons and be a big bore.. get nice used 750 pistons, and bore to fit them..

[Darren Jakal]

Sounds good Frank!

[bryanj]

750 pistons make the liner too thin to be safe but you can get a 605 kit that comes with liners