Rotax Rebuild

[JPXman]

hey karl is this that engine that i picked up cheap? if so i wonder if it really came off a lazair after all...

[flyalaz]

Hi Guys,

Shannon- By normal sized bearings and seals do you mean that both ends are big (.983"), or little (.788")? As far as sealed bearings go, I am thinking that any leaks around the seals are greatly reduced by having a sealed bearing, but with only an oil inlet, how well are the bearings actually lubed? I am sure that I could have run this engine longer, but this rebuild seemed a prudent thing to do after the other failed. Visual inspection of the bearings revealed no defects, and they both spun well. As I said before, this motor ran very well, with more juice than the other!

Tyler- Nope, the cylinder and head from that motor is on the one I just finished, the crank was bent and is unuseable, and the crankcase halves I mated with another cylinder, waiting for a crank to fall into it! I have a bunch of other motor bits and pieces and I don't remember what or where I put parts to and from, but I think that's what I did. I know I had a failure with one crank, (white hair #1000 to 1500),but I have 4 useless cranks on hand, and where they all came from....

[Shannon]

Yes, I should have stated .78". This is the size you would normally expect to find.

Shannon

[flyalaz]

I have re-ordered all the bushings and seals, (I'll keep the others I have for spares), so while I'm waiting, I am going to install a new spinner on the completed engine. The book shows a gap of 1/8" gap between motor and spinner flange. The new ones I have (made from original mould), sit at close to 3/4" !

Question: when the Lazair first came out, did the spinners sit that high? I know the manual says to push down hard with 1/8" spacers in place and drill, and that after making the cut-outs, the spinner will stretch out and close the gap, but this will make the spinner out of round. Is this normal?
I have the original spinner back plate, no cracks or defects.

Karl

[lazairiii]

Karl,

1/8"...

George

[flyalaz]

Hi George,

Is that how it fit on- loose with no pressure? Or did you have to force it some?
I compared the old and new, and the dimensions are the same. However, the open sides on the old one are splayed out a little, showing that it was forced down.
This is what I have. First the old, just layed on top

[flyalaz]

And here is the new one.
I attached the prop and screwed down the old one and used tape to outline the new contour for the P-Tip, now all I have to do is make a template to cut the new spinner and find out then how it will fit. Don't have much of a choice, but from what I see, if it was done on the old one, I can probably make it happen on the new.
Thanks for the pic, and your motor looks great.

[lazairiii]

Karl,

My spinners are the spinners I got from John Nagy a while ago. The backing plates were made by Dave Curtis a while ago too. BUT, your spinners should just lay on there and shoudn't require any forcing at all to go down to the 1/8" clearance.

This is about the only shot I have of the spinner backing plates, and it just happens to be in this pic I took of the routing of the choke/decomp line. Click on the pic to get a better view!

George

[flyalaz]

Hi George,

That backing plate looks quite a bit more substantial than the stock ones I have. My spinners are also from John, and anyway I look at it, I am going to have to make those cutouts in the spinner eventually, so I might as well start and see what it gives me. If it doesn't go down far enough on the backplate after cutting and without forcing it, I guess I'll have to either look for, or make some new ones.
My other goodies should be in at Wildfire tomorrow or Friday, so I also need to move on cleaning the cases and cylinder bits, and prep it all for final assembly. Hope I can squeeze in the time to make it all happen.

Thanks again,

Karl

[flyalaz]