Motorcycles

 

Tuono Flywheel Removal

 

One thing engineers do to smooth out vibrations in an engine and make it less prone to stalling is adding a heavy flywheel. The downside of that is slower engine response and acceleration. No surprise that many riders install a lighter flywheel. Aprilia added a heavy weight to the flywheel in the Tuono's 990 Rotax engine, but it is bolted on. So rather than having to purchase and replace the entire stock flywheel, it is possible (and relatively easy) to unbolt the extra weight. Here's how.


What you'll need:
Allen wrench
Torque wrench
Green Locktite #648
Grease
Propane torch
Aprilia flywheel-puller tool
Aprilia TDC locking tool
8x1.25 nuts (quantity: 6)
Hose clamp
Generator cover gasket


Is there a noticeable benefit to removing the flywheel weight?  I cannot say for certain.  It is a fair bit of weight which, in theory at least, can only slow things down.  You'll have to decide for yourself if it's worth the trouble and potential risks. Check out the discussions on the Aprilia Forum to hear from more knowledgeable folks than I.

 

What are the risks?  Completely destroying your engine, for one.  Stripping the threads out in the end of the crankshaft, which would prevent you from refitting the flywheel/generator. Or overheating the flywheel and ruining its magnetic properties.  Consider all this before proceeding.

 

Since you will be pulling the side cover off the left side of the bike, you'll want to drain all the engine oil out of the bike first. Therefore, you might consider performing this mod at your next scheduled oil change.

 

Aprilia Tuono flywheel removal

Drain all engine oil. To gain easy access to the engine side cover, I removed the oil tank.  This meant removing the hose clamp from one of the oil lines.  The ones the factory uses are not easily re-used.  Instead, replace it with a high-quality adjustable replacement when you're done with the entire job. 

 

Remove the 12 bolts holding the generator cover in place.

 


Aprilia Tuono flywheel removal
Carefully pull the cover off. There will be resistance due to the magnets inside. The cover will still be held on by the generator wiring so it is easiest just to swing the cover out of the way and suspend it with zipties or bungee cords. If your bike is relatively new, the green gasket may be reusable. Inspect it carefully and replace if necessary before bolting everything back up.

 

Aprilia Tuono flywheel removal

Before you remove the flywheel retainer bolt, use your small allen wrench to loosen up the 6 bolts inside the flywheel.  These bolts hold the flywheel weight to the flywheel itself.


Aprilia Tuono flywheel removal

Now use a 14mm hex to remove the flywheel bolt. There are two issues with doing that though.  1.) This bolt has been loctited on from the factory, so it won't come out easily. To help break the Loctite free you'll need to heat it up.  You'll need a torch for this.  Get anything flammable out of the area (and of course keep a fire extinguisher handy just in case) and apply it to the bolt and the center of the flywheel.  You'll need to heat it up for a good 5-10 minutes.  2.) The engine will simply turn with the bolt, getting you nowhere. You'll need to prevent the engine from turning.  Aprilia's TDC lockscrew is made just for this job. You'll need to remove an 8mm hex-head bolt from the clutch cover on the opposite side of the engine.  The bolt is located underneath, around 4 o'clock and the bolt must be inserted with the engine at TDC.  Be careful not to overtighten the lockscrew.

 

Now that you've softened up the Loctite and prevented the engine from turning, you'll need to apply a fair bit of force to break the flywheel retaining bolt free.  Be certain that the bike is stable as you do this.  Using an impact gun will come in handy here but it's easy to strip the threads.  You'll be a lot safer doing it by hand. 

Aprilia Tuono flywheel removal
Once the bolt is out, you'll need to start heating the flywheel. It too is held on by some green loctite so heat the center of the flywheel again. 

Aprilia Tuono flywheel removal
When the flywheel is hot, grease up the flywheel removal tool and screw it into the flywheel.

Aprilia Tuono flywheel removal
Only after heating the very hub of the flywheel for 5-10 minutes (with a torch, not a heat gun, not a hair dryer!), screw the bolt all the way in.  This should cause the flywheel to pop off the end of the crankshaft.  If it doesn't, back the removal tool back out a few turns, heat the flywheel some more before tightening the removal tool once again.  Repeat until the flywheel breaks free.  When it does, you're going to need to grab it. Be ready with heat-resistent gloves.

Aprilia Tuono flywheel removal
Here is the flywheel with the weight and primary drive gear. Slide the gear out and set it aside. Finish removing the 6 hex-head bolts around the inside of the flywheel and remove the weight.

 

Aprilia Tuono flywheel removal

 

 

Aprilia Tuono flywheel removal

Reinsert the primary drive gear into the flywheel and place the flywheel weight inside your buddy's bike somewhere he won't see it.


Aprilia Tuono flywheel removal
There was a lot of residual Loctite on my flywheel retainer bolt.  I chased the threads with a die before reinstalling it.


Aprilia Tuono flywheel removal
Coat the 6 flywheel bolts with Loctite and install while still wet. I used red Loctite here but you should re-use the same type that came from the factory - Locktite 648 green.

Aprilia Tuono flywheel removal
Tighten the 6 nuts you purchased onto the back of the bolts.  Set to 22.13 FtLbs of torque.

Aprilia Tuono flywheel removal
Again, you'll want to use Locktite 648 green, despite what you see here.  Apply Loctite to the taper between the crankshaft and the flywheel, as well as the retainer bolt, which should be tightened to 95.88 FtLb of torque.

Aprilia Tuono flywheel removal
When re-installing the cover, be careful not to pinch the neutral gear indicator wire.

Aprilia Tuono flywheel removal
Tighten the 12 alternator cover screws to 8ft/lbs. And of course don't forget to refill your engine with oil before firing her up.

 

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