LCGB Forums

I have a rt195 barrel that I'm considering using with a 62 or 64mm crank.

If I do, this will mean the exhaust duration will be low if I get the transfers about right.

So I'm thinking that I should just take a couple of mm off the top of the exhaust port. Seems obvious.

But I'm concerned about chipping the coating as I've never touched this stuff before.

Are cheap diamond burrs in a dremel ok or do I need something special?

Or should I stop farting about and just stick with a 60/110 crank?

Check out Mark Broadhursts latest post on FB regarding doing the same. I've always used 6mm fine cutting burrs taking it steady working across the port to remove the flash coating inside then remove the alloy.I chamfer the port with diamond burrs after and never had a problem.

'Stroking' is IMHO an excellent modification as the capacity is enlarged & there is the greater opportunity to tailor the duration of the ports.

As for the risk involved in affecting the existing plated surface, I've tuned plated barrels, the last one quite extensively. I used one of my two die grinders for the 'easy' ports because it has variable speeds. I used low speeds as a caution & avoided TC cutters (& paraffin) with the finishing cuts. Sanding drums are what I used & I have sizes from Ø10 up to 30 mm. Spiraband type are the best. The final cuts I do dry (as I always do with sanding) to enable me to see what was going on, though you probably could use a cutting fluid with certain abrasive drums.

Transfers are obviously trickier, but the same principle applies, though if you have a Dremel (or equivalent) you will need a 90° head. The Chinese items will suffice & for less than a tenner, you can afford to modify them to gain greater clearance whilst working inside the bore. Although the shell is plastic, the gears inside are metal. As I needed to dismantle the one I bought to cut back the collet & tightening nut, I repacked it with a better grease. It works well enough for me. again, I used slow speeds with sanding drums from Lidl.

Aluminium alloy is so quick to machine, compared to cast iron, that I'm happy to go with lower speeds & hope it helps maintain control.

I managed to fully port the last barrel with no chips to the surface but should mention that when deburring/chamfering the port edges I only went outwards &/or sideways with the hand tools I used which were either stones or fine rifflers, though fine emery wrapped around a bar will work.

Ideally, we'd all have the disposable cash to tune then replate, because good platers will take the process around the port edges. Sod that! What if you then want to advance any port duration, or have asymmetric transfer timing?

Thanks gents. I think this is what I'll do. Really the question was just to give me a bit of confidence that I'm not going to have to get it replated before it's even been run!

The work won't be extensive, I'll just pack it to get the transfers where I want them so the only work will be to the inlet and exhaust ports which are obviously easy to get at.

Like I say, I won't be going mad as this will be a pootler for around the doors.