Cylinder re-lining

[chrisx1]

Does anyone know the cost of cylinder re-lining for an A65
Also cost of having the head and barrel drilled and tapped from 5/16 to 3/8"

[Allan G]

I think the last barrel I had line was about £250. This was at cotterall engineering in clay cross, nr chesterfield. They have done a couple for me and always done a great job!

[DAVE BRADY]

Hi,

It is worth considering tying to find an alternative piston.  The cylinders on my wife's A10 are on +0.80 with I think a Triumph piston.  This was supplied by SRM and meant that the barrels could still be lined at a later date.  It was also cheaper as the cylinder would have to bored several times to take the liner and then the liner bored to standard.
Pistons would be needed any way.
I think that SRM offer a kit to enable the larger studs to be used.  "3/8 UNC TAPS & Drill kit for convert base studs to 3/8 UNC" at about £16

Dave.

[DAVE BRADY]

Hi,

You may get an extra bit of life from your A65 cylinders by boring them to take T140 pistons.  STD T140 are 76mm with A65 being 75mm.  So the T140 at STD is roughly A65 + 80 thou.  The Triumph piston is 8.6:1 but as the crown height is shorter by about 2mm the piston sits a bit lower in the bore so the compression is less but CCs a bit more.

Dave

[Mike Farmer]

 

I would have thought that the difference between 75mm and 76mm is only 040". Perfectly happy to be corrected.

Mike

[DAVE BRADY]

Hi,

Yes! 40 thou.  I am thinking of the +80 thou for A10 which I think uses a T120 piston at +40.

Dave.

[chrisx1]

So would a Triumph +.020" at 76.5mm be what I want for a 60 thou rebore?
What is the advantage of using the Triumph piston over a +.060" A65 piston?
Also the current pistons are flat topped, not domed.

[chrisx1]

The lining is damaged at the bottom. Is this likely to cause an issue?

[Mike Farmer]

 

That  chip certainly wouldnt bother me too much. A lot of the old singles (and new ) had a larger piece than that cut out purposely for the conrod to clear the liner.

Just make sure that there is no extended crack from the space,

Mike

[DAVE BRADY]

Hi,

If you need +60 then use A65 pistons and as Mike says check for extended crack.  At the very end of the crack drill a small hole.  This should stop the crack from spreading.  I think the flat topped pistons are about 7.5:1.

Dave.

[chrisx1]

If I'm currently running 7.5:1 pistons, what power increase will I achieve with 9:1 which I believe is what my engine should be.

[DAVE BRADY]

Hi,

The 7.5:1s were offered as an option and I ran an A65 for many thousands of miles with this ratio.  The engine was quite soft and smooth to ride.  On switching to 9:1 I did notice an better throttle response and the engine was more crisp in its performance but there was an increase in vibration.  This may been down to the 9:1 pistons being a bit heavier than the 7.5:1s.
If your engine has bee balanced then weigh the 7.5:1s and then if replacement 9:1s are heavier reduce the weight to match by removing material from the skirt of the piston.

Dave.