Jez,

I have found that the Norvels are actually NOT critical to fuel. I've used all manner of fuels in my LiteMachines heli with no problems. But I broke that engine in on a prop. The Norvels WERE set up very tight so that the abrasive, anodized liner would actually, kind of hone down the piston to a perfect running fit. The crucial part of starting and breaking in a Norvel Revlite engine, whether in the heli or with a prop, is to first heat up the cylinder as hot as you can get it with a heat gun. Then it turns over easily for a start. Then, as the engine wears in, the fit gets better and better.

But even after that, the other important element is to NOT overprime. We all have been accustomed to slobbering the prime to small engines because they would tolerate that kind of abuse and because, very often, that's the only way they would start by hand. Back then, micro starters were not available.

The issue is the anodized cylinder. Anodize is a form of aluminum oxide. Where have you heard of that? Well, aluminum oxide is used on SANDPAPER. Yep, it's very abrasive. BUT, the aluminum oxide layer has a honeycomb structure. As such, the pores actually hold oil, becomes slippery and makes the compression seal very good,, better than any other system, really.

The problem arises when you overprime. All that raw fuel tends to wash out the oil from the pores and now you have a cylinder that'll snag the piston UNLESS it's turned over very fast. BUT, when you do THAT, remember the overprime? Because of the good compression seal, and the extra fuel in the engine, you can too easily get hydraulic lock and applying even a micro starter, you can jam up the engine and bend a rod. Then, the piston bangs against the bottom cover and the rod eventually breaks. You can break cranks this way too.

And BTW, the latest batch of engines and piston/cylinders have eliminated the tight fit. They are now set quite loose so all the old problems have gone away.

Plus, LM is having a half price sale on both the 6 and the 7 engine.

And about fuel, I run Cool Power 25% in mine, for heli AND airplanes with no problems. Another issue is that if you use a fuelling bulb, the rubber compound dissolves in the fuel and fouls your glow plug. And the rubber in a plunger type fueller can also do the bad thing too. I've never used either and have never had a problem.