Flywheel - Impact Wrench Use

[Adam_Winstone]

Hi all,

I just thought that I'd raise an issue that I came across twice on this year's Euro Lambretta trip, which is the issue of people/dealers using pneumatic impact wrenches to fit flywheels in a garage environment but then finding that you cannot remove the flywheel to replace a failed stator on a rally. I came across 2 cases of this at the Euro and managed to twist/break the end off a socket adaptor whilst trying to get a flywheel off! Thankfully, the well stocked German assistance helpers at the rally had additional tools and long solid bars that allowed us to use a small lump hammer to get a flywheel to come free, however, it was touch and go as to whether it would strip the thread off the extractor or flywheel before coming free.

Sorry if it is convenient for people to use air wrenches to fit flywheels in the workshop put a correctly fitted flywheel, with matching crank and boss taper, should not be done up this tight. Considering that air wrenches are easily set to the correct torque setting, fitting to a higher pressure is a mistake that puts components, and ultimately riders, at risk!

Anyone who has had their bike worked on my others should ask themselves whether they will be able to remove a flywheel to replace a failed stator before they set off for such a trip. Thankfully, all worked out OK, other than me now being a socket adaptor down.

Adam

[soullad]

Wise words Adam.
Not only have you the possible "undoing" nightmare but there's also the possibility of crank damage by possibly twisting the Mag side crank cheek around the crank pin as the impact wrench jolts the nut tighter and tighter.
I would advise never using an impact wrench on the flywheel nut or crank side drive set up for those reasons.
Now, next we have the rear hub nut. I've seen these undone & tightened by impact tools. Again, is this necessary?

[Adam_Winstone]

^... agreed, hub nut is another example where this applies.

On the flywheel topic again, I wonder how many of the Indian aftermarket (particularly SX/LI boss) keyway failures have been the result of over tightening?

Adam

[coaster]

I have an cordless electric impact gun which is a fantastic help for undoing nuts and bolts but I generally go easy on assembly and use a torque wrench to finish off. The rear hub though requires a torque considerably in excess of the capabilities of my Clarke driver. Can't personally see any dange of twisting crank cheeks providing a holding tool is used.

[Adam_Winstone]

^... nothing wrong with using an impact gun to the correct torque settings but you're asking for trouble if you simply apply the 'good and tight' philosophy with a decent impact wrench as you can easily put it way over the correct torque setting. It is this 'abuse' of an air gun that concerns me as this year's Euro experience showed that it is all too common. Had the bikes in question not made it to the rally with their electrical problems, they would have been unable to get the flywheel off on the hard shoulder and they may well have stripped the puller/extractor threads whilst trying.

Like a dyno, an air gun/impact wrench is only as good as its operator... and you don't want to find that you've been over tightened when you are stranded at the side of the road, especially if you have a spare stator that you are unable to fit

Adam

[Warkton Tornado No.1]

I have a Milwaukee 18v impact gun & only ever use it for disassembly.

Over tightening is a common trait & a dangerous menace.

Slightly off-topic, but no apologies there, wheel fasteners on any vehicle should always be checked, specifically if having new tyres fitted.

Some time ago, I checked a car’s wheel bolts after it was shod with new rubber. Just by eye, you could see how much they’d stretched the bolts by over tightening. I made the supplier buy a full set of OEM bolts (including the security headed) for me as replacements. I also had the alloy wheels checked for cracks, but they survived.

[coaster]

I ................Slightly off-topic, but no apologies there, wheel fasteners on any vehicle should always be checked, specifically if having new tyres fitted.

Some time ago, I checked a car’s wheel bolts after it was shod with new rubber. Just by eye, you could see how much they’d stretched the bolts by over tightening. I made the supplier buy a full set of OEM bolts (including the security headed) for me as replacements. I also had the alloy wheels checked for cracks, but they survived.

I had a similar experience having a new set of after market alloys fitted. When he reached for the air gun I told him he should just use a brace and torque wrench but he insisted that "when you have been fitting tyres as long as I have you know how far to go". So just as he's finished, there were 3 sharp cracks in quick succession as 3 of the top hat type bolts snapped their heads off....the colour his face went was a picture

[JETEX]

I'm a professional mechanic, and I would never use an impact gun to assemble anything on a small engine such as a Lambretta. Always by hand, and always tighten with a torque wrench. Similarly, when I put car wheels on, I will run the nuts up with a gun, but tighten with a torque wrench. I always put locking wheel nuts on by hand so that the impact gun doesn't damage the key. Whatever you put on with an impact gun, some poor bugger may have to get that off at the side of the road with basic hand tools ( usually in the p*ssing rain ! ).

[Adam_Winstone]

^... a big thumbs up to that comment.

Adam

[Bettagetabrettabolti]

Duh! I may be missing the point but why the hell would you want to use an impact wrench working on a Lambretta I mean it's hardly like you are pushed for time and there are hundreds of nuts and bolts to tighten. Sorry just don't get it.
Do it by hand and stick with Innocenti torque settings.
Jettex comments are right on the money.
Bolti

[Eden]

loads of people do use them,
One of our lot had a stator failure at Cleethorpes and even though we managed to undo the nut, we had a right game pulling the flywheel off the tapper.
No idea if that had been gunned on though.