Barrels

[250 drummie]

How do you tell the difference between the KR1 and KR1S barrels and I presume the KR1S barrels are a bit better. I have a spare motor for bits and as my motor is a bit tired I am going to get the spare barrels recoated.
And while on the subject as this is my track bike how much work is involved in getting a few more HP

[Charles]

How do you tell the difference between the KR1 and KR1S barrels

KR1 barrels got 2 transfer ports (one under the other) opposite the exhaust.

Charles

[KR-1R]

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later KR-1S doesnt have the mystery lower boost port (so 8 ports in bore instead of 9)


http://kr-1s.co.uk/forum/viewtopic.php?t=6201

[Luders]

Blimey, that's old school. I very nearly bought one of those TZR's back in the day!

[250 drummie]

Perfect thanks for that, looks like I have KR1 barrels then

[TwoStroke Institute]

And while on the subject as this is my track bike how much work is involved in getting a few more HP

The KR-1 cylinder is pretty good as is, the exhaust port can do with some help, but the igniton and pipes will transform the engine.

[Luders]

Gains from the top and bottom end seem quite even and I'll try to explain as best I can.

You'll need a long dremmel attachment to do the barrels.

If you put a power valve down the barrel in the open position, you will see in the casting of the barrel, it doesn't quite line up with the hole in the power valve. You just need to take that bit of meat off the port to ensure it's as wide as the power valve hole and lines up nicely.
Take care not to take off too much, otherwise it won't seal properly when closed.

The bottom end is easier to get at, but you'll need to take your cases apart to do the work.

There are some areas which need to be filled, where the oil feeds are, which I can't explain very well and will need a picture (anyone here got a pic handy?).
If you take a look at the inlet where the reed valves sit and have a feel around on the upper side of the casing, you should feel a sharp edge. This needs smoothing out and a radius putting on. Also a bit of filling and smoothing is required on the sides, to contour and flow it all nicely.

Make those changes and you should notice a significant power gain on your motor and it won't make it unreliable either.

Hope that helps and if there are no pictures kicking around, I can take some at the weekend.

[ScottaKR]

Matching the barrells to the cases with a die-grinder or dremel-style tool to remove the step, is about the easiest tuning mod you can do, and should give some good gains.
http://myweb.tiscali.co.uk/teamsparrow/kr1stune.htm
This is MJ's tuning work, and while you may not be able to do the port timing changes easily, the parts about matching the barrells to the cases, as well as flowing the cases arn't too difficult, and theres some pics to help explain. There has been some argument about filling the wells around the oil feeds, as well as matching the exhaust port exit to the pipe being good or bad, but you can't argue with the results MJ gets.
I'm pretty sure he's changed some of the tuning tweaks on his more recent engines, but I can't find any of the posts he's made that detail them.

[250 drummie]

Thanks for that lads. I need to get the barrels replated anyway so may as well have a play.

[Si7]

Sorry bit O/T, have you got the rest of that article KR-1R?

[ScottaKR]

Sorry bit O/T, have you got the rest of that article KR-1R?

viewtopic.php?t=6201
There's also a few other interesting old articles that have been scanned and posted up in the KR-Kive that are well worth a read.