Topic: forged TRW 64mm piston to wall specs?

[754]

 When you go really big on sleeves, its easy to get sealing /leaking problems.
  some things you can do;
 Rough out the bores in the cylinder , then weld any holes apearing, I think MEC showed this being done. Then finish bore the somewhat sealed cylinders.

 Rough bore, clean, then goop it up with epoxy, then finish bore.,

 That may help, another thing that may have gone wrong is.. if ANY sleeves got switched after finish boring & honing..

[paulages]

When you go really big on sleeves, its easy to get sealing /leaking problems.
  some things you can do;
 Rough out the bores in the cylinder , then weld any holes apearing, I think MEC showed this being done. Then finish bore the somewhat sealed cylinders.

 Rough bore, clean, then goop it up with epoxy, then finish bore.,

 That may help, another thing that may have gone wrong is.. if ANY sleeves got switched after finish boring & honing..

these sleeves can't be mixed up, as the flanges overlap the stud and oil holes and had to be milled around them. i numbered them anyway.

i'll report back on the impregnation sealing when the engine is back together, but they only charged me $75 (including shipping i believe) to run the thing through the process twice. In my opinion, it's well worth the money to go this route rather than welding, etc. i will still be gooping the bottom "o-ring" area, as i didn't end up having o-ring lands machined after all. guess i'll have to trust the goop and the impregnation sealing.

in good news, Soos has saved the day with some 64.75mm pistons which are in the mail already. he believes they will be close to a direct drop in, so hopefully i'll be back on track next week.

if the bore will now be 736cc, what do i call this thing to not confuse it with a stock bore cb750? 

[754]

 a straight up 750..

 BIG Bore 500...

[Terry in Australia]

if the bore will now be 736cc, what do i call this thing to not confuse it with a stock bore cb750? 

How about "Hand Grenade"? Ha ha, just kidding Paul, how thin are those sleeves going to be if you bore them another 3/4 of 1mm? My 750 sleeves after boring to 65mm for an 836cc kit were only 2.5mm thick, are yours still the same OD, or were they thinned externally as well as machining the cylinder block? Cheers, Terry.  

[paulages]

if the bore will now be 736cc, what do i call this thing to not confuse it with a stock bore cb750? 

How about "Hand Grenade"? Ha ha, just kidding Paul, how thin are those sleeves going to be if you bore them another 3/4 of 1mm? My 750 sleeves after boring to 65mm for an 836cc kit were only 2.5mm thick, are yours still the same OD, or were they thinned externally as well as machining the cylinder block? Cheers, Terry.  

no, the O.D. wasn't changed, except that the tapered part at the bottom was brought up to the right spot for the 650 block. if your 65mm pistons left the sleeves 2.5mm thick, i reckon my 64.75mm pistons will leave the sleeves 2.75mm thick. 

[Terry in Australia]

No worries, that should be fine Paul. Cheers, Terry.

[scottly]

[quote author=paulages link=topic=70922.msg791283#msg791283 date=1274580941

no, the O.D. wasn't changed, except that the tapered part at the bottom was brought up to the right spot for the 650 block. if your 65mm pistons left the sleeves 2.5mm thick, i reckon my 64.75mm pistons will leave the sleeves 2.75mm thick. 
[/quote]

Slight miss-calculation there paul; if the bore is .25mm less, then that will mean .125mm more sleeve thickness: 2.625mm.

[paulages]

[quote author=paulages link=topic=70922.msg791283#msg791283 date=1274580941

no, the O.D. wasn't changed, except that the tapered part at the bottom was brought up to the right spot for the 650 block. if your 65mm pistons left the sleeves 2.5mm thick, i reckon my 64.75mm pistons will leave the sleeves 2.75mm thick. 

Slight miss-calculation there paul; if the bore is .25mm less, then that will mean .125mm more sleeve thickness: 2.625mm.
[/quote]

Yes, true.

[paulages]

this worked out great... Soos and i are trading pistons, his 64.75mm for my 64mm. the new pistons are at the machine shop and the boring should be done tomorrow. setting them up at .0012" P/W clearance. one more part of the saga complete...

[Big Jay]

this worked out great... Soos and i are trading pistons, his 64.75mm for my 64mm. the new pistons are at the machine shop and the boring should be done tomorrow. setting them up at .0012" P/W clearance. one more part of the saga complete...

Sounds right to me.  Did you call and talk to Pat?

[paulages]

this worked out great... Soos and i are trading pistons, his 64.75mm for my 64mm. the new pistons are at the machine shop and the boring should be done tomorrow. setting them up at .0012" P/W clearance. one more part of the saga complete...

Sounds right to me.  Did you call and talk to Pat?

yes. thanks for the advice!