Power Valve Blade keeps coming loose or off the stud

Russ Kemple

My Rotax Max power valve blade keeps coming loose and off of the stud for the power valve. What causes this? How can I prevent it? When I go to clean it, the blade is in the cylinder and the power valve is not connected. Ever happen to any one else?

Nick Weil · Posted: Sun Mar 04, 2012 7:56 pm Post subject:

You are supposed to use a drop of Loc-tite to secure the blade to the stud. Be careful not to use too much though. Additionally, because of the heat and vibration, it will probably loosen up every 2-3 weekends unless you really use some good Loc-Tite (not Blue).
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Nicholas Cook · Joined: 18 Oct 2007 Posts: 36 Location: South Africa, KZN,

Loctite 603 works great, it's a retaining compound, and is resistant to heat and oil. Be careful not to glue your PV open or closed.
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Chad Hartzell · Posted: Wed Mar 07, 2012 3:10 pm Post subject:

I've always used plumber tape as oposed to loctite. Just clean it off and replace it after every cleaning...
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Chad Hartzell

Oscar Aguilera · Joined: 18 Jul 2001 Posts: 1614

i always viewed that problem as stemming from another problem. the spring that holds the rubber cup and/or the rubber cup itself as being too stretched?

if both the rubber cup is on tight with a good spring and the bottom part is clean with a tight fit....the rubber with the spring will not let the plastic part spin.

imo it might be time to replace the rubber cup and/or spring. the power valve operation is an extremely important tuning part of the rotax motor,,,,so if it does not have a good seal....it will not function correctly and it will spin loose when it needs attention.

if it is building up with oil...you might have the p valve closed too long or running the motor too rich on the jetting. if you like your jetting and p valve setting it might be fine. but you run your kart real slow at times (like a cool down lap...i am not implying you are a slow driver) and or race at a track there might have some slow corners and this will also happen. so you need to clean it our more often and extremely well.

also when taking it off to service it....always take the cup loose from the plastic part by rolling the spring down...then loosen the plastic part from the valve. if you spin it off with the rubber part connected...it seems to smooth off the rubber part and makes it easier to spin off.

just my opinion

Jean Stafford · Posted: Mon Mar 12, 2012 8:38 am Post subject:

LocTite 648 is recommended by the factory for this application.

Blue and red won't stand the heat.

There's no reason to turn the power valve after it's lined up. If it's still coming loose, I'd take it to the builder. The threaded opening in the aluminum may be worn or stripped, and need replacement.

The stud should be bottomed out in the aluminum, and LocTite 648 used to retain it in place.

To keep the engine performing well, you're going to remove the valve for cleaning often. It's important to check for tightness, but don't break the loctite seal.
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Greg Gabriel · Joined: 03 Apr 2003 Posts: 13

buy a new blade and stud problem solved

Nick Weil · Posted: Wed Apr 18, 2012 12:54 pm Post subject:

Brian Degulis · Posted: Sun Sep 16, 2012 3:37 pm Post subject:

I've been setting up a new to me DD2. It's a 2011 with 5 hours on it. I got the jetting squared away but I was having a problem with the PV. I couldn't get it to operate smoothly and consistantly get it to open @ 7500 RPM. So I took it apart and found the bellows had taken a set and was not in it's relaxed shape when removed. So I cleaned everything up and replaced the bellows and compression spring. That solved the problem and now it opens seamlessly @ 7500 RPM every time.

It would seem to me that it is a good idea to remove the black cap and compression spring when the kart is put away. I think without doing that the bellows and spring will take a set and not work properly? I'm new to this and maybe this is SOP? If not food for thought.

Brian

Nick Weil · Posted: Mon Sep 17, 2012 12:56 pm Post subject:

If the parts are properly cleaned before storing, this should not happen. We have stored customers karts for 5 or more months without a problem. The other thing is, this is exactly why the compression spring is adjustable. To accommodate for stiffer/softer bellows, stronger/weaker exhaust gas pressures, and varying compression spring tension.

Keep it clean, and keep a spare Power Valve completely assembled in your toolbox, this will go a long way to prevent a frustrating day at the track filled with hesitations and bogging.
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Nick Weil
Authorized Rotax Service Center and Dealer since 2002
2004 Team USA Rotax Worlds Finals DD-2 Driver

Want to save money AND grow the economy? www.fairtax.org

Joe Ricard · Posted: Wed Sep 19, 2012 4:57 am Post subject:

More Power valve questions. Started messing with mine on my new to me Rotax MAX.
Pulled it apart and cleaned it up, re-installed and wiggled around to get the best free movement of the assembly up and down. It doesn't seem to want to pop up all the way like I seen on one of the help videos.

Also I pulled the pipe back and reached up and felt the blade still sticking down into the exhaust port by 1/16" or so. That can't be right. Now my question is what the heck is the O-ring for? it seems to just sit there around the stud and up against the recessed hole in the valve body.
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Matt Clark · Posted: Wed Sep 19, 2012 5:59 am Post subject:

I've always had to play with the blade to get it to not stick after cleaning by turning in small increments one way or the other. As far as it sticking down in the port still, I'd imagine this means it is not screwed in as far as it should?

Joe Ricard · Posted: Wed Sep 19, 2012 7:47 am Post subject:

Ah, never thought of that. Whoo Hoo get to take it apart again tonight. Oh and getting real tired of putting the spring on the bellows. Is that spiffy tool worth the 95 bucks?
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Arrow AX-8/ Rotax Sr.

Keith Buffo · Posted: Wed Sep 19, 2012 10:56 am Post subject:

$95 bucks?! I didn't know they made them in solid gold. The $25 plastic one should do the trick:
http://www.fastech-racing.com/prospeed-rotax-power-valve-spring-tool.html

FWIW... if you can put the big spring on by hand, you probably need a new one. You also need the little one that attaches the bellows to the metal assembly (can't see why it would be any less important given that it seals the same space.) That little spring is easy to to over extend.

I do not leave the cover and tension spring on so as not to crease the bellows... but still replace the bellows regularly. I do clean out the oil from the inside daily (or more if needed.) I don't 100% understand the exact workings, but logically it seems to function by filling up with exhaust... thus if it is loaded with oil, I'm assuming that might effect the timing.

The manual indicates a specific length of the blade for proper operation when fully assembled. Depending upon the wear of the plastic threads in the piston (black plastic part), that length isn't necessarily what you get when the blade is screwed in, so LocTite isn't a bad idea.
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Matt Clark · Posted: Wed Sep 19, 2012 11:49 am Post subject:

I use a modified zip tie method which is VERY easy. Tie two zip ties around the spring, leaving holes big enough for your fingers. Stretch the spring over the widest point where the black plastic and green bellow meets, so the spring will be sitting around bellows, on the engine side. Now, grab both zip ties and start the spring in its groove at the top or bottom, and work each zip tie around opposite sides, lining up the spring in its groove. once you've reached the top or bottom and both zip ties meet, you should simply be able to cut the zip ties and slide them from underneath the spring.

I've seen this done but the person puts the spring on the opposite way, starting closer to their body than to the engine, this way seems much easier though.