Topics

Cylinder hone


Mick O'Connor
 

My engine like many other 2200s suffers from tight pistons after a 2 minute run-up.
My cylinders measure 97.63mm after a light gone.
Manual says max cylinder dia is 97.67mm.
Is it worth honing out to max ? would the extra 0.04mm (1.5 thou) make much difference ?
My new ring gaps are 25/28 thou in all cylinders

Mick


Jay Scheevel
 

Don't have an answer for you Mick, but I do have the same question. Maybe
someone with a lot of engine repair experience can chime in??

Jay

-----Original Message-----
From: main@JabCamit.groups.io <main@JabCamit.groups.io> On Behalf Of Mick
O'Connor via groups.io
Sent: Sunday, February 07, 2021 9:58 AM
To: JabCamit <main@jabcamit.groups.io>
Subject: [JabCamit] Cylinder hone

My engine like many other 2200s suffers from tight pistons after a 2 minute
run-up.
My cylinders measure 97.63mm after a light gone.
Manual says max cylinder dia is 97.67mm.
Is it worth honing out to max ? would the extra 0.04mm (1.5 thou) make much
difference ?
My new ring gaps are 25/28 thou in all cylinders

Mick


Mick O'Connor
 

FWIW, honing our the extra 0.04mm will increase circumference by 0.12566mm (4 thou), so ring gap still well within max limit
I think my maths is correct !

Mick

On 7 Feb 2021, at 17:27, Jay Scheevel <jay@scheevel.com> wrote:

Don't have an answer for you Mick, but I do have the same question. Maybe
someone with a lot of engine repair experience can chime in??

Jay

-----Original Message-----
From: main@JabCamit.groups.io <main@JabCamit.groups.io> On Behalf Of Mick
O'Connor via groups.io
Sent: Sunday, February 07, 2021 9:58 AM
To: JabCamit <main@jabcamit.groups.io>
Subject: [JabCamit] Cylinder hone

My engine like many other 2200s suffers from tight pistons after a 2 minute
run-up.
My cylinders measure 97.63mm after a light gone.
Manual says max cylinder dia is 97.67mm.
Is it worth honing out to max ? would the extra 0.04mm (1.5 thou) make much
difference ?
My new ring gaps are 25/28 thou in all cylinders

Mick











Marc Bourget
 

I'd verify cylinder temps, particularly on the bottom, before exploring the "oversize"  option. 


From: main@JabCamit.groups.io <main@JabCamit.groups.io> on behalf of Mick O'Connor via groups.io <mickoconnor909@...>
Sent: Sunday, February 7, 2021 8:58 AM
To: JabCamit <main@jabcamit.groups.io>
Subject: [JabCamit] Cylinder hone
 
My engine like many other 2200s suffers from tight pistons after a 2 minute run-up.
My cylinders measure 97.63mm after a light gone.
Manual says max cylinder dia is 97.67mm.
Is it worth honing out to max ? would the extra 0.04mm (1.5 thou) make much difference ?
My new ring gaps are 25/28 thou in all cylinders

Mick






Mick O'Connor
 

Hmm, don’t think I’ll be completing the overhaul, refitting engine and then run it to see cylinder temps !
Anyway, It’s not an ‘oversize’, it’s increasing to max limit.
Mick


On 7 Feb 2021, at 17:50, Marc Bourget <marcbourget@...> wrote:

I'd verify cylinder temps, particularly on the bottom, before exploring the "oversize"  option. 


From: main@JabCamit.groups.io <main@JabCamit.groups.io> on behalf of Mick O'Connor via groups.io <mickoconnor909@...>
Sent: Sunday, February 7, 2021 8:58 AM
To: JabCamit <main@jabcamit.groups.io>
Subject: [JabCamit] Cylinder hone
 
My engine like many other 2200s suffers from tight pistons after a 2 minute run-up.
My cylinders measure 97.63mm after a light gone.
Manual says max cylinder dia is 97.67mm.
Is it worth honing out to max ? would the extra 0.04mm (1.5 thou) make much difference ?
My new ring gaps are 25/28 thou in all cylinders

Mick






David Amsler
 

I think Sosthene (in Switzerland) did that to his engine with Ian's input when rebuilding to put in solid lifters.  Perhaps he still has info on the specs he used for that.  Hope he is still lurking out there.   He did end up with a looser engine that he was happy with.  I do recall that when lightly honing mine a tad larger, that Ian strongly suggested reversing the piston orientation in larger bores. (The pin offset, arrow facing opposite direction.) when doing so. 

David A.

On Sun, Feb 7, 2021 at 12:54 PM Mick O'Connor via groups.io <mickoconnor909=btinternet.com@groups.io> wrote:
Hmm, don’t think I’ll be completing the overhaul, refitting engine and then run it to see cylinder temps !
Anyway, It’s not an ‘oversize’, it’s increasing to max limit.
Mick


On 7 Feb 2021, at 17:50, Marc Bourget <marcbourget@...> wrote:

I'd verify cylinder temps, particularly on the bottom, before exploring the "oversize"  option. 


From: main@JabCamit.groups.io <main@JabCamit.groups.io> on behalf of Mick O'Connor via groups.io <mickoconnor909@...>
Sent: Sunday, February 7, 2021 8:58 AM
To: JabCamit <main@jabcamit.groups.io>
Subject: [JabCamit] Cylinder hone
 
My engine like many other 2200s suffers from tight pistons after a 2 minute run-up.
My cylinders measure 97.63mm after a light gone.
Manual says max cylinder dia is 97.67mm.
Is it worth honing out to max ? would the extra 0.04mm (1.5 thou) make much difference ?
My new ring gaps are 25/28 thou in all cylinders

Mick






Marc Bourget
 

No argument here,  I didn't think that deep.   I have a 2200 early and 2d gen and a 3300 and all the cylinders I've inspected showed scoring on the "bottom" of the cylinders from 4-8:00 o clock. 

Call me prejudiced :^)  hahahahahaha


From: main@JabCamit.groups.io <main@JabCamit.groups.io> on behalf of Mick O'Connor via groups.io <mickoconnor909@...>
Sent: Sunday, February 7, 2021 9:54 AM
To: main@jabcamit.groups.io <main@jabcamit.groups.io>
Subject: Re: [JabCamit] Cylinder hone
 
Hmm, don’t think I’ll be completing the overhaul, refitting engine and then run it to see cylinder temps !
Anyway, It’s not an ‘oversize’, it’s increasing to max limit.
Mick


On 7 Feb 2021, at 17:50, Marc Bourget <marcbourget@...> wrote:

I'd verify cylinder temps, particularly on the bottom, before exploring the "oversize"  option. 


From: main@JabCamit.groups.io <main@JabCamit.groups.io> on behalf of Mick O'Connor via groups.io <mickoconnor909@...>
Sent: Sunday, February 7, 2021 8:58 AM
To: JabCamit <main@jabcamit.groups.io>
Subject: [JabCamit] Cylinder hone
 
My engine like many other 2200s suffers from tight pistons after a 2 minute run-up.
My cylinders measure 97.63mm after a light gone.
Manual says max cylinder dia is 97.67mm.
Is it worth honing out to max ? would the extra 0.04mm (1.5 thou) make much difference ?
My new ring gaps are 25/28 thou in all cylinders

Mick






Mick O'Connor
 

Mark,
Just checked my cylinders in the area you mentioned. No scoring, just slightly shiny areas about the size of a very small bird’s egg. Can’t feel it with finger nail. I guess this is the area the piston skirt touches ?
Mick

On 7 Feb 2021, at 19:51, Marc Bourget <marcbourget@...> wrote:

No argument here,  I didn't think that deep.   I have a 2200 early and 2d gen and a 3300 and all the cylinders I've inspected showed scoring on the "bottom" of the cylinders from 4-8:00 o clock. 

Call me prejudiced :^)  hahahahahaha


From: main@JabCamit.groups.io <main@JabCamit.groups.io> on behalf of Mick O'Connor via groups.io <mickoconnor909@...>
Sent: Sunday, February 7, 2021 9:54 AM
To: main@jabcamit.groups.io <main@jabcamit.groups.io>
Subject: Re: [JabCamit] Cylinder hone
 
Hmm, don’t think I’ll be completing the overhaul, refitting engine and then run it to see cylinder temps !
Anyway, It’s not an ‘oversize’, it’s increasing to max limit.
Mick


On 7 Feb 2021, at 17:50, Marc Bourget <marcbourget@...> wrote:

I'd verify cylinder temps, particularly on the bottom, before exploring the "oversize"  option. 


From: main@JabCamit.groups.io <main@JabCamit.groups.io> on behalf of Mick O'Connor via groups.io <mickoconnor909@...>
Sent: Sunday, February 7, 2021 8:58 AM
To: JabCamit <main@jabcamit.groups.io>
Subject: [JabCamit] Cylinder hone
 
My engine like many other 2200s suffers from tight pistons after a 2 minute run-up.
My cylinders measure 97.63mm after a light gone.
Manual says max cylinder dia is 97.67mm.
Is it worth honing out to max ? would the extra 0.04mm (1.5 thou) make much difference ?
My new ring gaps are 25/28 thou in all cylinders

Mick






jabcamit@...
 

If you hone the bores to max and have a subsequent scoring  event (any reason) you are stuffed (new cylinder if you can get one)

If your engine has run for hundreds of hours without seizing, and its obviously looser than when new, so seizure is unlikely.

I'd just (wet and dry paper and finger) make diagonal honing marks on JUST the polished area of the cylinder.

As previously posted a number of times  Racing motorcyle engine builders used to test run their engines and then
relieve  any  areas on the piston that were polished. I can send you  a book extract on exactly how to do this  if you want. 

For the Jabiru engine you can easily get new pistons so better to risk writing off a piston than the cylinder.

My tuning racing bike engines book also makes the point that too much piston clearance  increases the risk of  piston failure. The piston rocks and this  causes the rings to wear to a  "barrel"  shape inceasing blowby.  Also the piston land above the top ring is  more exposed combustion temperatures.  

Roger Lewis  reported that hot engine friction can be reduced by  heating the barrels before torquing them down. I guess the same effect could be obtained by having a fixture to distort the barrel in the same way during  torquing.

Just Ideas (its what I would do).

BobP


Rob Turk
 

Here's another idea. The cylinder wall are thin enough as they are, it would be good to keep as much material there as possible.

ather than widening the cylinders, how about a smaller piston? I have not done the math on how much extra clearance it would provide, but to my understanding, the pistons are Holden 0.040 oversize type. As the engine is in pieces now anyway, would it be crazy to consider finding better quality 0.030 oversize pistons and get the rings to do the seal? Or would this be too loose a fit?

Any alternative piston would need to be machined to accept the gudgeon pin retainer clips.

Rob

On 2/11/2021 7:25 PM, jabcamit@... wrote:
If you hone the bores to max and have a subsequent scoring  event (any reason) you are stuffed (new cylinder if you can get one)

If your engine has run for hundreds of hours without seizing, and its obviously looser than when new, so seizure is unlikely.

I'd just (wet and dry paper and finger) make diagonal honing marks on JUST the polished area of the cylinder.

As previously posted a number of times  Racing motorcyle engine builders used to test run their engines and then
relieve  any  areas on the piston that were polished. I can send you  a book extract on exactly how to do this  if you want. 

For the Jabiru engine you can easily get new pistons so better to risk writing off a piston than the cylinder.

My tuning racing bike engines book also makes the point that too much piston clearance  increases the risk of  piston failure. The piston rocks and this  causes the rings to wear to a  "barrel"  shape inceasing blowby.  Also the piston land above the top ring is  more exposed combustion temperatures.  

Roger Lewis  reported that hot engine friction can be reduced by  heating the barrels before torquing them down. I guess the same effect could be obtained by having a fixture to distort the barrel in the same way during  torquing.

Just Ideas (its what I would do).

BobP