RE: Break-in a rebuilt engine?
 

My first ST3000 engine had a heavy cross hatch in the cylinder walls.:D As did my MDS 148[:'(] and the MDS 2.18[:'(]

But, I never took them apart to see if they still had the cross hatch in after break in. Both of the 148 engines had carb leaks that I was unaware of and they met an early demise. Broke the jug right off both of them when they hit the dirt. I sold the 2.18 when it leaned out. I managed to deadstick--but it went away fast after that. Had I known it was just a simple air leak that was curable--I'd have kept the 2.18. I was scared after that 3rd engine quit on me though. Live and learn.:eek:

The ST3000 got pretty slick inside after about 5 gallons. Very heavy cross hatch to start out. I took it apart after 15 gallons and it was mirror smooth. Should NEVER have sold that one.[:-] < DUMMY!!

I do concur that some engines are factoy cross hatched. But I still wouldn't touch one with a stone hone for a rebuild. Big ole chicken. BRRRAWWWWCK BRAWWCKKK!!!!:D

Interesting thread. Rebuilding engines is like making a pot of witches brew.[sm=bananahead.gif]

RE: Break-in a rebuilt engine?
 

I just put a new piston and ring in a Saito 91 with a chromed AAC cylinder. I just cleaned the cylinder real well. After 32 oz of fuel the ring was seated well.

I put bearings in a OS 52 and I must have moved the ring?? for it wasn't seated well after I was done. I've run almost a gollon of fuel through it to get it to feeling well. I have some old fuel to get rid of. I don't trust it flying. I just bench run engines with it.

I do have an assortment of brake cylinder hones. The finer grits are better for model engines.

Enjoy,

Jim

RE: Break-in a rebuilt engine?
 

WELL,WELL:
I guess I really started something here. I never took a second thought to honing, or in any way shape or form put scratches, cross hatching, or any other type of grinding on the sleeve of my 2-Stroke OS 1.08 FSR.
I may just take it apart and clean the sleeve with some alchohol to remove the previously mentioned castor residue. Thanks for your help.
I'll find out soon enough if there's a significant loss of power (compression).


Tom

RE: Break-in a rebuilt engine?
 

Tom,


This thread is indeed interesting, but as per your 1.08, just break the glaze on the sleeve with Scotch Brite, or Wet-O-Dry sand paper, clean it out with warm water, reassemble and break it in.

From what I sense in this thread, high loads will do the break-in better than light loads.

RE: Break-in a rebuilt engine?
 

Tom....

....I'm gonna run this past you one more time. Take a close look at this
picture. This is a new K&B .61 cylinder. It is a chromed liner. See the scratches
in the cylinder wall ? They are small, but they are there. If this was a steel
or a cast iron liner, the scratches would be deeper and easier to see.

This is how a new cylinder looks when it is assembled. The scratches are there
for a reason. This is how your cylinder should look when you put it back
together....like brand new. (or almost)

There is a reason for this. It is because this is how engines are prepared by
any decent engine rebuilder.

There is a reason for this. It is because that man wants the engine to perform
just like new....not OK, or good enough....just like new.

If you are re-ringing an engine, you must prepare the cylinder wall surface
to a "like new" finish....to accept the new ring, and have them mate (seat)

....just like new.

Now....I'm not a software engineer, and I don't have any degrees. But I was
trained at the Factory Yamaha School, and did this very procedure thousands
of times....for twenty years....full time, not to mention my two cycle engine
racing adventures.....on ringed two cycle racing engines. And not to mention
over 30 years rebuilding these aero-model engines.

Now, I used to be an Expert, professional full time two cycle (and four) engine
rebuilder and racer....now I just build hot rod engines and hot rods.

I hope you engine comes out OK....mine always did. ;)

FBD. :D

RE: Break-in a rebuilt engine?
 

RC, I have 4 MDS 1,48s and 3 MDS 2.18s and they all have mirror smooth bores as does my .78, no leaky carbs though, I guess the leaky carbs only came with the crosshatch models.;)

RE: Break-in a rebuilt engine?
 

Last year I rebuilt a OS 160 Fx that had been run lean on full synthetic more than once. (was not my engine) The cylinder was scored along with the piston skirt and the ring was toast. I cleaned up the piston skirt and ring land, used a well worn brake hone in the cylinder to knock off any protruding metal in the bore and discoloration. After this the liner was washed and a new ring installed.

The engine now runs great after a short break-in, even with slight scoring in the liner.