Engine Tuning Pt III (Cut it off and Match it up)

At the bottom of the barrels at the entrance to the boost port are two lugs. If you look at a set of TZ barrels these lugs have been cut back. So get the Dremel out and cut them back. Does this do anything? The answer is I don't know but they do it on the TZ so it must be good? See below for latest thoughts before cutting. All these can be carried out using a Dremel and a cutter as shown. To aid cutting use a lubricant, this stops the cutter clogging and gives a better finish ( I use a squirt of WD40 every couple of minutes).

I have seen a number of barrels over the years with different mods to the rear lugs see piccies below. In the past I have just cut them down with out really thinking why - following fashion. Then something Shaun up at R&S said made me think. His comment was that it wasn't how much gas you sucked it was where you put it. I took this to mean that rather than suck just into the crankcase direct the flow towards the ports so that when the piston comes down it just carries on pushing gas in the direction it has already started to move? Also if you cut the piston down to much some of the skirt area becomes exposed - maybe the piston can tip further? So on the latest barrels I have not cut down the Lugs as far and have shaped it so it pushes gas towards the transfers.

The next thing to do to your barrels while you are working in this area is shape the edge of the barrel knife edge the partition. Shaping the edge of the barrel is meant to promote flow into the transfers, it also provides a little more volume in the area around the transfer. This is the area that it is easiest for gas to get pushed into the transfers. The knife edging is mainly to promote flow. See piccies below.

You should also match the barrels to the crankcases. This usually means taking a bit of metal off the barrels. To check the what needs to be done put a standard gasket onto the crankcases. The match is usually quite good (Crankcases are diecast so tolerance is good). Then put the gasket onto a barrel and check the match again (Barrels are sandcast and are all over the shop). I have found on most barrels that they need a little bit taking off to match the crankcase.

Next page Previous Page

Return to KR1-S Tuning Index Return to Main Index

This document maintained by mark@teamsparrow.fsnet.co.uk.
Material Copyright © 2000 Mark Jordan