Hi guys,

So I've done a full strip down on the engine (Kohler 1AM, 220cc single) and replaced the deck...

sealed all the joints below the floor and around the new deck...

repainted and started to re-build.

I Used a new belt of the same type and size as the original, set it all up out of the hovercraft but when I tried to install the engine the top fan blade was about 1/4" too high, maybe more, and wouldn't go into the duct.

I'm sure that it popped out with no problem when I removed the engine, I don't recall bending any of the blades at all...I wouldn't have forced it as I'd not want to damage anything at that point, being a novice.

The annoying thing I can't see what I've got wrong here.

The engine frame drops into it's four mountings with no problem. The floor mountings haven't been moved and the two on the duct mouth can only fit in one hole each side.

The engine in the frame fits in it's slots OK and tensions up the belt. The top pulley will only go one way round, bolts into the four holes with a bit of movement to adjust the belt 'run'.

The belt seems to line up ok judged by eye, looking down from the top pulley to the bottom one.

So I removed the spacers from under the top pulley, one thin (approx 1.5mm) and one thick (approx 5mm), but now the belt edge nearest the engine is tight while the other edge is definately slack...I can see it bulge as I turn the engine by hand.

I tried putting the engine in place and then easing the spacers in, it works but the fan-tip at the top is only a couple of millimeters away from the duct while there's a much larger gap at the bottom fan tip.

I assume it'd not be good to run with one belt edge tight and the other looser?

Any ideas please?

The fan's a Multiwing Copenhagen, 17mm hub with five large white blades 22x8.5mm (at the root) and five black blades 17.5x8.5mm,

The overall fan size is 60mm.

Could I slightly twist the engine in its frame, forcing the outer edge of the pulley down by adding spacers to the lower engine bolts?

The old belt looks 'square' but I suppose it could have stretched one side to match with the other over time.

I'm pretty sure that I have the top spacers in the right place as I took photos at every stage of dis-assembly.

Does the fan have to be central in the duct or can it be out by 2 - 3 mm in any direction?