#6

[RMS eng]

the beast was running cool on the dyno

top of the radiator was 60-70 deg and the bottom around 40 deg

head was around 40-45 deg and the cylinder was up to 70 deg sometimes

any 100cc two stroke making more than 22HP will lose power if it is air cooled,a while back i spent two days at Mt wellington helping some one with a TS100 motor i built for them,with water cooled head and no pump, after 10 laps head would 70-75 deg but cylinder would be 100-110 deg,but with head and cylinder water cooled and a pump motor would run at 65-70 deg,late 70s air cooled MX bikes could lose up to 20% in power after 15mins running from getting to hot.
chris p

[speedpro]

The old totally air cooled motor definitely lost it's edge after a couple of laps.

Last time at the track with the new motor, watercooled head, I couldn't feel any difference after any number of laps, and that was with the RG50 radiator. It was only peaking at about 25hp but even so. The temp was about 70 as it read "Hi" when I stopped the motor but immediately dropped to 70, 69.9, 69.8 and so on.

I do agree that ideally the head and cylinder both need to be watercooled but just doing the head supposedly gives you 80% of the benefits of water cooling. The requirement for a pump I disagree with for a motor that has the cylinder sloped forward. The water circulates at a reasonable rate once warmed up as witnessed with clear hoses and a bit of dirt in the water.

[jasonu]

The old totally air cooled motor definitely lost it's edge after a couple of laps.

Last time at the track with the new motor, watercooled head, I couldn't feel any difference after any number of laps, and that was with the RG50 radiator. It was only peaking at about 25hp but even so. The temp was about 70 as it read "Hi" when I stopped the motor but immediately dropped to 70, 69.9, 69.8 and so on.

I do agree that ideally the head and cylinder both need to be watercooled but just doing the head supposedly gives you 80% of the benefits of water cooling. The requirement for a pump I disagree with for a motor that has the cylinder sloped forward. The water circulates at a reasonable rate once warmed up as witnessed with clear hoses and a bit of dirt in the water.

You use dirty water???

[Buckets4Me]

You use dirty water???

only after missing a corner or 2

[F5 Dave]

He's using creek water 'cause that's the coldest.

[jasonu]

He's using creek water 'cause that's the coldest.

I used to piss in mine...

[speedpro]

I used to piss all "over" yours

[jasonu]

I used to piss all "over" yours

only when mine blew up...

[Buckets4Me]

only when mine blew up...

or you were not around

[bucketracer]

Is someone is taking the Piss.........

[speedpro]

I'm pretty sure Nigel used heavy water in his. Could be why it keeps melting down, Chernobyl and all that.

[speedpro]

Well, was at ESE at 6am today. We finished off adjustments, jets timing and air correction. The end result was 29.5hp(DIN). The graph shows the first and last runs and the increase we got. There's one more test with a slight mod to the pipe which I've seen make a nice increase but apart from that 30hp isn't going to happen with this engine I don't think.

Thanks to ESE for letting me fill their workshop up with 2-stroke smoke and especially to Rob for being so keen and helping do the tuning.

[speedpro]

Done a couple of meetings and a few laps of Taupo. Figured I should have a look inside just to check. It looks sweet with either fine crosshatch marks or a nicely polished surface. The piston has been used and has just the faintest marks on either side at the back. The photos are after Avalon had done a few quieter laps at Mt Welly. Interesting how the chamber is cleaned off a bit where the boost port is aimed.

[TZ350]

To my untrained eye, that looks a very good even patten on the piston.

With the boost port striking so close to the edge of the combustion chamber, does that mean its upward angle is set to high or is that where its supposed to be?

Hopefully Wobbly will describe what he sees in the pattens.

[jasonu]

To my untrained eye, that looks a very good even patten on the piston.

With the boost port striking so close to the edge of the combustion chamber, does that mean its upward angle is set to high or is that where its supposed to be?

Hopefully Wobbly will describe what he sees in the pattens.

After a full race meeting on my 1991 RS125 the pattern on the top of the piston looked like a map of Australia. The deposit was a lighter color than that in your pix. Might be due to the fuel I was using which was Av+castrol A747