To hone...or not to hone

I'm in the process of restoring my '74 MkIIA that I bought with 26K original miles. Yesterday, I miked the bore with a very expensive and calibrated bore micrometer accurate to .0001" that I borrowed from work. All the manuals say that any wear .005" over the nominal 3.032" bore diameter requires a rebore and oversize pistons. Well, my bores showed only .0005" of wear; in other words, almost no wear after 26K miles.

So my question is, should I simply reinstall the pistons using the same rings, or should I hone the bores and seat new rings? I'm leaning to the "if it ain't broke..." mentality and just put the pistons back in with the same rings, but perhaps someone with more experience can chime in. BTW, the bike didn't burn any oil before I started tearing into it, and the rest of the engine--pinions, chains, clutch assembly, etc.--shows almost no evidence of wear. Thanks for any input.

Check your pistons for wear in the ring grooves. Still running the original bore here after 34,000 miles but new standard pistons. The ring grooves take a beating. To hone or not to hone - very controversial. (I did.)

Hi:
That is very low mileage.Just check the piston grooves and deglaze.I did a 750 combat with original bores last year.Even the piston grooves were fine.I deglazes,new rings ,and after 2000 miles everything is fine. The commando bores are tough,no need to waste them.The 71 commando I bought new had new rings after 28,000 miles and new pistons after 60,000 miles. I deglazes both times and the bores still showed no wear.I only hope the mother f--- who stole it has it blow up when he is wearing shorts and sneakers.
Bruce

Hi,

I'm in the same boat - the bores are worn less than a thou, but the rings are pretty worn. The speedo is showing 11k, and I think it's genuine, based on the condition of the rest of the engine (except the cam and rocker spindles...).

I've decided to just put new rings in it, but I haven't cleaned the pistons to check the ring clearances yet.
I won't be honing mine: I regard honing as the final operation in the boring process to remove the radial boring tool marks, which would not be very beneficial to the piston rings if left alone. I'm unconvinced of its positive effects with regard to new rings only (with the possible exception of chrome-faced rings), and it will increase the piston clearance to some extent.
I've been told that it's better to hone out the lip at the top of the barrel, but I'm inclined to think that if the lip is bad enough it definitely needs a rebore, and if the lip isn't significant it isn't going to damage anything...trying to hone it away may compromise the parallelism of the bores further down as the stones respond to the high spot at the top.

Just my opinion....Then again, I am Mr. non-intervention himself

Replaced rings early this year after 18000 miles on new barrels and pistons (stupidly broke the oil rings trying to install without compressor). No honing and ran these in hard from new (lots of 4-5000 rpm blasts). 2500 mile snow with no oil usage, hardly any blowby and substantial mileage improvement. Ran in for 700 miles on straight 40, now back on 20/50 Amsoil synthetic. Wish I'd discovered this running in method years ago as it does seem to work. I wouldn't try it on brand new bores though IMO.

Keith1069 said:

Replaced rings early this year after 18000 miles on new barrels and pistons (stupidly broke the oil rings trying to install without compressor). No honing and ran these in hard from new (lots of 4-5000 rpm blasts). 2500 mile snow with no oil usage, hardly any blowby and substantial mileage improvement. Ran in for 700 miles on straight 40, now back on 20/50 Amsoil synthetic. Wish I'd discovered this running in method years ago as it does seem to work. I wouldn't try it on brand new bores though IMO.

Click to expand...

I made a very simple pair of ring compressors

I took two, 4" hose clamps and two 1" strips of aluminum sheet, about 10" long. I wrapped the aluminum around the rings, trimmed for about 1" overlap, held them in place and compressed them with the hose clamps, and installed the cylinders. Once the rings were in their bores, I unscrewed the hose clamps and removed the strips. Not as pretty as those quick-release ring compressors, but I can use them on just about anything.

I made a very simple pair of ring compressors

Click to expand...

I have a pair but one broke so I went for the hand assembly approach (pistons on rods & lower barrel) and paid for it. Needless to say the new rings were more carefully installed, pistons in barrels first then lowered onto rods and pins inserted.

Hi all, I think that whenever you service your cylinders, pistons, and rings that one of the steps to complete the job is to hone the cylinder liners. This process will remove the shine/glaze where the rings do the work and allow the new rings to wear in/seat correctly. I think it would be standard procedure on any professional engine rebuild. Not to be confused with boring which is done to reduce the inside diameter of a worn/damaged cylinder.
Doxford

Here i would read this. http://home.clara.net/captain.norton/cn ... tml#3.14.2

I tried posting a question regarding the information in this and got nowhere....

mighty fine article GavinJuice I must pass this along to a few hard nose mechanic's. Excellent reading thanks.
Doxford

GavinJuice, thanks for that interesting article, which pretty much helped me decide to just reinstall the pistons back into my shiny, unworn bores and get on with the rest of the rebuild.

Ring grooves OK I take it?

Yes, ring grooves and pistons are fine. Really, it's surprising how there's almost no wear in all of the engine internals. The bike evidently had previous owners who cared.

I wish I had read that article before deglazing my cast iron barrells.They definitly did not smoke before they were honed athough one could use it to brush his hair
Now nobody followed me anymore or they would sufficade themselves...
And I even bought the tool for it because emery paper was not good enough
Well that gave me another reason to change the barrel to a Maney one
The tool is free to anyone who wants to ruin their own barrels

Interesting parallel discussion on the ADVRider board. I posted the link to the above article - isn't getting a whole lot of credibility over there. Dunno who's right or wrong but FWIW.

haha....see what i mean. i posted this on the britbike forum i believe and it didn't get any replies. this was right after a lengthy post about proper cylinder preparation, honing, rings etc...

Here's a link to another article that's a bit more in depth. It's written by the same guy who wrote the controversial article in the link given above by GavinJuice.

http://www.snowvalley.20m.com/bikes/dnthone.htm

Pete Snidal happens to be a very respected member of the Royal Enfield community, and he's written a complete service manual for the Royal Enfield Bullet, which I also own. Kind of hard to argue with Pete's logic. My mind's made up. I'm going to leave my shiny bores alone.

Good Post Huffer, awesome Information!

I wish he would have covered these too, we'll see what the net provides...
# lapping valves (after refacing seats and valve faces by grinding)
# removing cylinder ridges

Lapping properly refaced seats and valves is a total waste of time and if the cylinder has a ridge that needs to be removed it's rooted any way.