Do any of ya'll do your own overhauls? I have a 447 that last ran about four years ago. I'm hoping to start an Airbike project in the spring and use this engine. My problem is I don't know any local shops that work on Rotax 2 strokes. I figure my options are:

A. Ship it to a shop. (Any recommendations?)

B. Learn to overhaul it myself. (Tempting, but is it doable?)

C. New engine.

Any advice is appreciated.

I hate to be a wet blanket but...

When you say "learn" I infer that you don't have much experience with engines. The Rotax two-strokes are simple to work on, but use a workshop manual.

The used contact-breaker 503 fitted to my UK spec 1600R in 2004 failed after a few tens of hours - the owner said he had descended at high speed with light throttle from a high altitude. New piston and "rebore". Some hours later the other cylinder seized. Piston and "rebore" again.

I put 'rebore' in quotes because when I had the engine serviced this year, they found that there was no trace of honing in the bores, very probably due to them not having been honed after boring. As a result there was some weird wear on the pistons and the clearances were very far out of spec. Risk of lower part of a piston skirt departing a piston apparently.

My point is, I suppose, that you need the tools to do the measuring and the experience to recognise other things that aren't right.

If you use an engineering outfit make sure that they *do* know what they are doing. Look out for sport hovercraft companies, they often use and service Rotax two strokes.

Sorry for being a bit preachy and possibly telling you nothing new.

I rebuild my own engines.

I take them apart and send the crank to rotax rick in florida for inspection if needed.
If the cylinders are worn I take them to a local powersports shop for oversizing and fitting of new pistons / rings. when I get my parts back i reassemble the whole thing with new seals.

rotax 447s are dirt simple, you will need a few specialty tools though.
3 jaw puller and propane torch to remove flywheel
gear puller to remove pinion gear
dial indicator and stand for setting ignition timing during reassembly.

helpful tips
mind the cageless needle bearings at the rod/piston pin. they will fall apart when you pull the pin. easiest way to reassemble them is using a piece of cut off piston pin placed in the center of the rod to hold the bearing together. when you install the piston the new pin will push the old segment out leaving a perfectly assembled bearing.
Use the intake and exhaust manifolds to align the cylinders before torquing head bolts.

get your hands on a 447 service manual (downloadable from rotax) and it will give you the basic steps as well as all the bolt torques.

Chris

I sent my 447 to Rotax Rick  last year. Great service, good support, engine runs well. I  have worked on two strokes before but never a Rotax. I did not want to invest in the special tools ( a few of which Rotax does not sell any more). Much easier to have it gone through by some one who knows what they are doing, has the alignment fixtures, and has the experience not to screw it up.
Joe

I was Rotax trained (on 2 strokes) about 30 years ago! I had all the specialist tools but sold them years ago when I bought a Taylorcraft, thinking I'd never need them again.... then I bought my Minimax 3 years ago!

Folk have covered much here. What I would say, is that not having experience (Catch 22 of course) means you may miss the specific Rotax signs. They are simple engines, like most 2 strokes, no valve gear, cam timing etc. to worry about. However, 2 strokes fail generally due to overheating. This can be a gradual thing and this is where experience will tell you what might need replacing - discolored gudgeon (wrist) pins, and rollers for example. A sure sign of high EGTs. If the pin/rollers are brown or worse still blue, there's no way they should be put back! In any case, if you are going that far, replace the rollers anyway.

You should measure the bores for wear both diametrically and for ovality at least at 3 points along the bore. Mild scoring from minute debris is common and generally can be sorted out with a glaze buster. Piston ring grooves need cleaning thoroughly and ring gaps measured. A Rotax manual will tell you what the limits are.

You can't do much with the crank other than change the crank seals. Important! If you see dirty colored oil deposits between the gearbox/crank face, its a sure sign of the seal breaking down; likewise behind the flywheel. A damaged seal will play havoc with the mixture and that'll lead to overheating and the inevitable!

If you are more adventurous you could change the two main bearings if you make up a puller, but you are getting into specialist territory!

Bottom line; cleanliness, the right tools (metric) a torque wrench, a manual and PATIENCE!

Lockwood Aviation (FL) also another good source for a rebuild location

https://lockwood.aero/

Heaven Bound Aviation as well (OH)

https://heavenboundaviation.com/

Great advice from everyone. Thank you. I think I will reach out to Rotax Rick and see what they tell me. If that doesn't work out, then I guess I will do it myself. I really wish there was a step by step video/manual to walk a person through a rebuild. Every 300 hours seems a bit much to be sending the engine off for overhaul.

Got this video off the net.Gives the general idea.I think the Rotax crankshaft needs renewal of bearings at 300 hours.The piston/cylinder cant be done at home anyhow but that might not be needed.https://youtu.be/xXVmRZdjVqA

I can recommend Heavenbound. $1500 for my 277. New piston, all gaskets and seals and gearbox overhaul.  If I get 300 hours that's only $5 an hour.

BTW:
If anyone needs Bing carburetor parts, the western hemisphere Bing support center is in Council Grove, KS.
Joe

Waiting on a response from Rotax Rick. I'll check with Heaven Bound also. Looking into it a little more, I'm feeling I could probably handle maintenance. The honing of cylinders and measuring for ovality is not something I'm familiar with. Depending on the price of the overhaul with shipping, a new engine might also be an option.

Good to know about the Bing support center. Thanks.

Rotax Rick says "The 447 is $1550 to overhaul.  I do a complete overhaul except for the crankshaft. I only replace the outer 3 main bearings & true it to .001 or less.  I do not replace the lower rod bearings. If the crankshaft is passed it's limits I will have to look for  good core crankshaft.
Go onto my website Rotaxrick & look up shipping. I give you a 2 year warranty & the engine will look like new."

I'll check shipping rates then compare the total to a new engine. (Maybe Hirth)

Rick responded in less than a day, and on Christmas week!