912 Big Bore

[mr bill]

They are relatively simple to install, but two things to be careful with: piston cpmpression rings are thin and easy to break (I broke one), also be sure to use the cylinder head alignment tool or equivalent during reassembly.

[WWhunter]

Mr. Bill,
I am getting the kit with the pistons already install so I wouldn't think I have to worry about breaking a ring but I definitely appreciate the heads up. I am oblivious to what the cylinder head alignment tool is. Since I don't know what it is I was in the dark that I needed one.
Is this easily available? Hate to say it, but I wasn't ready for any additional expenditure right now. Heck, I have been saving to buy the kit since it was announced. Haven't told the wife I ordered the kit yet, so if you hear of an unexplained/mysterious death in northern MN, you'll have a clue to the suspect.
I have rebuilt/restored many old engines but they are all of the automotive/racing type variety and this is my first attempt into the Rotax engine.

[mr bill]

The cylinder alignment tool is a flat plate lightly bolted to the cylinder heads across the intake manifold ports, while torqueing the heads to the crankcase. This is done to ensure a good seal later, when attaching the intake manifolds. This Rotax tool costs over a hundred bucks. I loaned mine to Tommyg in NY. If you will pay the postage, I'm sure he would send it to you. I think using the intake manifold itself would work, Just be sure not to tighten the bolts so tight that the heads can't move during torqueing.

[HighWing]

For this old retired guy, I think I would try to make my own alignment plate and save a couple of bucks. Blue Collar Supply - local scrap and metal salvage store - has lots of thick aluminum plate scrap. I'd drill the four holes as accurately as possible and then make steel bushings that could be epoxied in the holes for perfect bolt alignment. I would think that the critical part would be to ensure that the faces of the manifold mating surfaces of the heads are exactly on the same plane with the secondary benefit of providing accurate bolt alignment. Half a days work and I could spend the other $95 on a tool that I could use more than once.

Keeping in mind this would have to be done using the existing cylinders and heads immediately after removing the intake manifolds as the alignment fixture.

[Slyfox]

I would think that using the intake manifold would work out real nice sense you will be aligning to the intake that is being used.

with that I would save the whole 100dollars and have extra time to go fly

[mr bill]

The holes in the alignment plate were oversize, to allow the head locations to move as required during torqueing.

[WWhunter]

Mr. bill,
I will take you up on that offer!!! I haven't heard back from Jay yet on the availability of the kits and when mine will be shipped...of course he may have told me on the phone and I forgot. He did mention that if there weren't any available it may be 6 weeks til they get more sets in.
I will let you know when I hear back on a delivery date. That way I would not be holding up anyone else's progress.
Keith

[BigJohn]

In Washington at my Sons place, Hal flew in this weekend and we installed a new lower end with a modified Cam, Cams design is for the 1622 BigBore to increase the valve opening by approx 40 thousanths and approx 6 more degrees overlap. Innitial tests today showed a much smoother idling, at one point we saw smooth at 1100 RPM not that you would want to idel there due to gear box. To early to report pro or con on the flight testing yet, Plan on significant testing the next couple of days.

[cap01]

big john , since you are in wa , are you going to make it to arlington?

[KitfoxJ]

Thought this might be a good time for you interested in the 1484 ZIPPER KITS to see the easy plug and play installation instructions.
Jay