Unusual chrome bore question

[Petrus Rocks]

I have a '74 Rickman 125 with a Zundapp two stroke motor.  The piston bore is chrome, no peeling, looks great. 
It had low compression so I installed a new piston and rings, new main bearing seals. 
Ring gap is correct but still low compression. 
Does anyone know methods for seating rings in a chrome bore?  Someone told me about using Bon Ami household cleanser in the cylinder (disassembled) Old drag racing tip.  manually use the cleanser in a  paste with the piston and rings

[oldbike54]

 I've heard the Bon Ami trick , always figured it might be a bit of a myth . I have used 00 steel wool to clean up a cylinder after honing , not sure about employing that method on a chrome bore . Where is Triple Jim ?

 Dusty

[Triple Jim]

Right here, Dusty, wondering how you seat new rings on a chrome bore. 

[Chuck in Indiana]

With airplane engines, you just run the snot out of them..

[Aaron D.]

What is the compression? And is the throttle wide open?

These are very tough engines and if the air filter was in place it should go a long time. I assume the main bearing seals are crank seals?

[Triple Jim]

With airplane engines, you just run the snot out of them..

There you go, Dusty.  You put in something called "snot" and run the engine until the snot is used up.  Must be some sort of abrasive aircraft ring-seating product.

[Muzz]

There was a "honer" which used (Ithink) boron balls on the end of flexible wires that were spun around inside the bore. Can't remember if it was for chrome or Nikasil bores though.

[oldbike54]

There was a "honer" which used (Ithink) boron balls on the end of flexible wires that were spun around inside the bore. Can't remember if it was for chrome or Nikasil bores though.

 Nikasil .

There you go, Dusty.  You put in something called "snot" and run the engine until the snot is used up.  Must be some sort of abrasive aircraft ring-seating product.

 Then you give the engine a good dose of mucus relief ?

  Dusty

[Curtis Harper]

Better wait for Gilardoni to make a kit for it.

[Petrus Rocks]

 
Ah well, 
I'm trying to avoid spending more $$ on this thing-I can get it Nikasiled for a few hundred bucks. 
So far it has new piston and rings, main seals and a new Kokusan ignition. 
Oh, and a pretty British racing green paint job on trade.
Too many projects, not enough cash.

[acogoff]

    First make sure the rings are not chromed. A spring hone for about 25 strokes. Then run the crap out of it, but not so that it gets overly hot. Works out about 75% of the time on the Lycomings. The ones that don't work out usually have a slight non round (bulge) area below the bottom plug for some reason and just have to get that one nu-chromed or similar rechrome process with the grit imbedded for ring break in. But then that is a different kind of bear, but the basics are the same.

[CalVin2007]

  Should be plain cast rings in a chrome bore, and usually they will seat decently IF the bore is still round. I would pull the head and measure to see if this is the case...the cylinder may be out of round. If so, there's machine work in the future....

   Terry

[Petrus Rocks]

Thanks- I'll check the bore, see what I've got.

[leafman60]

A judicious Bon Ami dose and revving is well-known among engine builders of days gone by.

[Zoom Zoom]

Please excuse the stupid question, but just in case, you did make sure that the gaps in the rings do not line up with one another, right?

ZZ

edit: Thanks Jim. Never messed much with two stroke except model airplane engines. Makes sense though.

[Triple Jim]

2-strokes have the rings pinned to they can't rotate and have the ring ends snag a port.  I should say every 2-stroke I've worked on. 

[Trogladyte]

This is probably useless as not chrome bore. But when my boy was racing Aprilia RS125s we changed the piston after every race meeting. The compression was always poor to start with. We'd run it up to temperature twice on the stand, then send him out for a couple of laps at 5000rpm, come in, cool off while we checked fasteners, and torqued the head bolts, then out on the track beyond flat out for a 20 minute session. Then we were good to go.Except for the times it seized.   

[Sasquatch Jim]

  Zunnis are high quality stuff, use high quality snot and run it out of them.
 Then flog the shite outnof them, they develope their own shite so don't add any.

[lucky phil]

There was a "honer" which used (Ithink) boron balls on the end of flexible wires that were spun around inside the bore. Can't remember if it was for chrome or Nikasil bores though.

Flex hone, its called. If there is still a cross hatch on the bore you should be good. A few passes with the flex hone wont hurt and wont remove any material worth mentioning and will break any glaze on the bore. Just go to your nearest re borer and he should do it for a few bucks while you wait. Its done after every normal re bore just to remove the sharp edges off the cross hatch marks anyway, usually with a hand drill.
Ciao

[myway]

This is probably useless as not chrome bore. But when my boy was racing Aprilia RS125s we changed the piston after every race meeting. The compression was always poor to start with. We'd run it up to temperature twice on the stand, then send him out for a couple of laps at 5000rpm, come in, cool off while we checked fasteners, and torqued the head bolts, then out on the track beyond flat out for a 20 minute session. Then we were good to go.Except for the times it seized.

My 74 yz had the same recomended treatment. An if I remember correctly it was a crome bore with one ring. Rings where cheap an easy to change. If it did not seat I would get a new one an try again. Dan