Rotax 582 hydro damper on 717 pto?

[truck240]

I posted this same question on another site but have got no response. I am looking for a winter project and thought I might try this.

Following a series of ultralight crashes it was determined that the Rotax 582 crankshafts were prone to early failure from vibration induced stress. Bombardier introduced a fluid-bearing damper and was required on all 582 engines after 1991.

The part was designed to be able to retrofit existing engines. From what I've read due to the lack of a counter balance shaft the 717 suffered similar crank stress at high rpms. Some ingenious racer's in the PWC community started using the 582 damper on 717 engines to prolong crank life and reduce vibration.

If I understand correctly the 717 PTO has to be lathed to remove the extra mass & protruding lip. Perhaps a 580 PTO would be easier to lathe to a smaller circumference. The PTO then has three mounting holes drilled and tapped. The Rotax 582 damper mounts to the smaller, drilled 717 PTO. The result is significantly reduced vibration and longer crank bearing life.

The Rotax 582 dampers are fairly inexpensive to buy. It is also recommended to replace OEM Mag flywheel with a lightweight design. Had anyone done this before? Can somebody provide me with more information?

 

[glsmohio]

this is very interesting to me, i hope that someone post on this. call me crazy but somethings i think it would be fun to do up a 580 or 657 for the fun of it

 

[Matt Braley]

You are on to a good thing. A few different companies made dampeners for the 717 and 787 motors but they came and went in the mid 90's.

You will never wear out a 587 or 657 from hrs. The problem was with the 717. The 65&X had a shorter stroke but still needed the big heavy pto because the crank bearings got to hot. The 717 had the same problem but they would(will) wear the inner crank bearings and they could not push things further without a counter balancer.

Where the issue came to a head was when racers made stroker motors out of 717's by placing a plate under the jugs and using longer rods. These pre-RAVE motors made big power but would not last without fluid balancers.

I would be a customer of yours if you put some together and offered them up for sale. I do believe they would smooth the ride out and extend engine life.

 

[Mbogardus]

I just stumbled onto this post with by a Google search, after looking at groopks list for there kits they list a fluid balancer for the 720... I was wondering is this what they are doing or are the remaking a true damper for the 720? And how do I get one under $400

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[Matt Braley]

I think those GroupK writings are from the mid to late 90's. I doubt there is a source for 717 dampeners today but please post it if you find one.

 

[Mbogardus]

Aah, got ya... Does anyone have any of the fluid balancer part number that they we here using...

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[Mbogardus]

Matt you mention about the lower ends getting hot, in the later prodution di, and rfi 787 and 951s they had a water cooled lower end. I was wondering if anyone messed with water cooling the lower end of the 720?

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[Minnetonka4me]

Post pictures if you find one.

 

[Matt Braley]

No I've never seen water cooling the case on a 720. Some of us performance geeks use RFI cases when we build personal 787's because they have that case cooler. The intake ports are a little smoother on RFI's also. I built my XPL engine with RXX cases because they are the only carbed engines to use the case cooler.

 

[Mbogardus]

I wonder if running some 3/16 tubing on the bottom of the case would help... I am a 720 guy with my gs... I just happen to have a full roll of 3/16 nickle copper iron line sitting

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[Mbogardus]

They started that around the 2002 2003 era, with the case cooling... Great idea but I guess the 720 was out by then for any upgrades

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[1of500]

The case cooler was to help prevent detonation from heat build up in the crank/lower end of the cases I have an article on it some where

 

[Mbogardus]

I found these 582 ballencers on line kinda cheap too.. Are these the style people where using? If so that maybe fairly easy to create a 720 pto, may even be able to use a wsm pto and bolt it to will little to non latheing...

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