Topic: Engine break-in... Agree or disagree

[Dennis]

Good theory Raul.. Now add to that, the parts on gas pressure that say its related to the diameter of the opening it is forced through, plus recall the taper in the cylinder (which plays a key role in lubricating the cylinder and sealing the chamber) .............

 ......................  Second, consider the stroke as it moves the piston down then up again.  In the combustion chamber the pressure is rapidly decreasing (after the exhaust ports open).  However, behind the ring, this is not so.  That means that as the piston travels down, the ring expands with the cylinder taper, sealing the chamber.  That ring expansion and subsequent contraction on the upswing, ...........

 


Cylinder taper??

What is that? Please explain!

[andy750]

For me...I followed the engine builders advice (Mikes) and its the same as Ive used on previous engine builds all with success in the long run...pour oil through tappet cover on #1 and allow to settle then fire bike up...let idle for a few minutes and then hit the road, hitting high 6000rpm in short blasts and basically riding it through the rpm range...spending short times at higher rpms. Following this 50 -100 mile period, ride it as normal (i.e. fast and hard) and then change oil at 500 miles with another oil change at 1500miles.

For your engine Art Id do as someone else already mentioned - follow Mikes advice and this way if any problems hes the guy to blame  ....if you deviate from the advice then only yourself to blame. Not that there should be anything wrong in this case!

Good luck and keep us posted!
cheers
Andy

[Tower]

Cylinder taper, also sometimes referred to as counter-taper is when an expandable split lap is used  for honing. This hone design gives an adjustable capability required to impart a slight taper to the bore. If the cylinder is lapped with the top of the cylinder towards the chucking piece, it ends up with that picture perfect taper about TDC to give that extra compression that race engines so love, but, becomes slowly more loose towards BDC. This lowers bottom end friction and aids in lubricating the cylinder.  Arguably, taper also puts more twist into the rings, and so it can be argued that this disadvantage outways the good.  Maybe so - I'm neutral on this issue.

Hone RA (roughness average, and other grit measures such as RK - core roughness, RPK - peak height and RVK - valley depth, must be matched to ring material. e.g chrome, moly, steel all require different honing values.   But counter-taper must be matched to engine specifications as it depends on the engine/cylinder material. Most manufacturers will give the maximum wear taper for their engines.  Taper honing should be no more than 50% of this value.  i.e counter-taper should be around .002" to .003" (wider at the bottom than the top of course) for an engine that tolerates 0.005" wear taper.

If your machine shop is not taper boring/honing then you're just not at the peak of perfection on that rebuild 

[Jim F]

Always lube everything from the valve stems up with a good Assembly lube (Molly coat is good)
Until the oil pressure gets the slippery stuff up there
very important

[clarkjh]

When I had mine done, I just used oil when I put it together.  I also hit to high an RPM to soon, less then 30 miles on the rebuild, and caught a skirt.  A little over 3000 miles now and tight as a drum and the harder you thrash her the better she runs.  Changed the oil at 500, 1500, and she's just about due again.

James

[Dennis]

Cylinder taper, also sometimes referred to as counter-taper is when an expandable split lap is used  for honing. ...........

...............

If your machine shop is not taper boring/honing then you're just not at the peak of perfection on that rebuild 

 

WOW! Am I the only one here who has never heard of this?

I don't want to tell how many years it has been since I've rebuilt a 4 stroke engine ...... maybe I've been spending too much time on the 2 smokers!! LOL

Anyone care to comment?

[Jim F]

Both of my bikes (the K750/836 and my Suzuki GS 750/840)
I built my self and the piston to cylinder wall clearance was so close
that I had to push the pistons in with the back side of a dead blow hammer
and this is using no oil in  the cylinders.

Although I did pull the plugs and turn the motor threw with the starter to get the top
end oiled up good.

Then started the motors and went to 6000 RMP for 30 seconds.
Shut the engine off and let it cool completely, then go out and do some pulls for a while


after that Its been holding 175-178 PSI cranking pressure with a less than 1% leakdown
that was over 10 years ago and both bikes are still very strong runners

This is how I break in my engines

But its not for the faint hearted

Jim

I build them dry (except for a wipe of WD40 to prevent rust). With forged pistons I think about .018....possibly .017 with good skirt coatings is about as tight as you want to go.

isn't that suppose to be .0018 to .0017?
not sure you would want to run that much clearance

Just checking mike
Jim

[MRieck]

Both of my bikes (the K750/836 and my Suzuki GS 750/840)
I built my self and the piston to cylinder wall clearance was so close
that I had to push the pistons in with the back side of a dead blow hammer
and this is using no oil in  the cylinders.

Although I did pull the plugs and turn the motor threw with the starter to get the top
end oiled up good.

Then started the motors and went to 6000 RMP for 30 seconds.
Shut the engine off and let it cool completely, then go out and do some pulls for a while


after that Its been holding 175-178 PSI cranking pressure with a less than 1% leakdown
that was over 10 years ago and both bikes are still very strong runners

This is how I break in my engines

But its not for the faint hearted

Jim

I build them dry (except for a wipe of WD40 to prevent rust). With forged pistons I think about .018....possibly .017 with good skirt coatings is about as tight as you want to go.

isn't that suppose to be .0018 to .0017?
not sure you would want to run that much clearance

Just checking mike
Jim

Yes Jim....you are right. I'll blame it on late night responses. I hope I did it late at night.

[MRieck]

Both of my bikes (the K750/836 and my Suzuki GS 750/840)
I built my self and the piston to cylinder wall clearance was so close
that I had to push the pistons in with the back side of a dead blow hammer
and this is using no oil in  the cylinders.

Although I did pull the plugs and turn the motor threw with the starter to get the top
end oiled up good.

Then started the motors and went to 6000 RMP for 30 seconds.
Shut the engine off and let it cool completely, then go out and do some pulls for a while


after that Its been holding 175-178 PSI cranking pressure with a less than 1% leakdown
that was over 10 years ago and both bikes are still very strong runners

This is how I break in my engines

But its not for the faint hearted

Jim

I build them dry (except for a wipe of WD40 to prevent rust). With forged pistons I think about .018....possibly .017 with good skirt coatings is about as tight as you want to go.

isn't that suppose to be .0018 to .0017?
not sure you would want to run that much clearance

Just checking mike
Jim

Yes Jim....you are right. I'll blame it on late night responses. I hope I did it late at night.

Damn I didn't....no excuse.....I'm retarded.

[sparty]

Both of my bikes (the K750/836 and my Suzuki GS 750/840)
I built my self and the piston to cylinder wall clearance was so close
that I had to push the pistons in with the back side of a dead blow hammer
and this is using no oil in  the cylinders.

Although I did pull the plugs and turn the motor threw with the starter to get the top
end oiled up good.

Then started the motors and went to 6000 RMP for 30 seconds.
Shut the engine off and let it cool completely, then go out and do some pulls for a while


after that Its been holding 175-178 PSI cranking pressure with a less than 1% leakdown
that was over 10 years ago and both bikes are still very strong runners

This is how I break in my engines

But its not for the faint hearted

Jim

I build them dry (except for a wipe of WD40 to prevent rust). With forged pistons I think about .018....possibly .017 with good skirt coatings is about as tight as you want to go.

isn't that suppose to be .0018 to .0017?
not sure you would want to run that much clearance

Just checking mike
Jim

Yes Jim....you are right. I'll blame it on late night responses. I hope I did it late at night.

Damn I didn't....no excuse.....I'm retarded.

Maybe you had too much Chimay.  I hope you set the clearance correct after all that beer.  BTW, You don't look retarded to me, but what do I know I am retarded as my wife.

[Sam Green Racing]

Ya can't have to much Chimay