EZT251 Running Very Cool

[stuart-glos]

I'm running an ETZ251 engine in a 301 frame (all OK) - it has a Bing carb.

It starts easily and runs well but seems to run very cool. I have to keep it on choke for a few miles before it warms up and even then on a run it never gets hot. You can't leave your hand on the cooling fins (so it is warm) but no where near as hot as I would expect from an air cooled engine.

My Guzzi engine gets so hot you can't touch it and I'm sure that was the same when I ran Suzulki and Yamaha 2-strokes years ago.

My ideas?

thanks

stuart

[arry_b]

There's a lot more cooling fins on a 251 than there are on a Guzzi or a Jap stroker.

What plug are you running?

[djsbriscoe]

Maybe the mixture is a bit too rich. But that is better than being too lean as this will cause overheating. Remove your plug and look at the colour. There will be a guide somewhere on the interweb explaining how to read plug colour.


David.

[breakwellmz]

Galaxy chocolate colour

If it needs the choke on for that long i don`t think it will be running rich.

[mr_luke]

The massive cooling fins do mean they are cooled very effectively. The exhaust gets very hot on mine, but the rest of the barrel and head stay pretty cool really. And that's pulling a sidecar around! As mentioned, having to keep the choke on would suggest it's running a bit lean, if anything, which will actually tend to make it run hotter!

[mr_luke]

As an aside, though, it would be worth checking your ignition timing is correct.