Modern Vespa

Ugh... To make a long story short, I WAY over torqued my transmission cover screws. It took me 30 seconds to figure out what I had done (I read the wrong torque setting in the manual), and I removed the screws and replaced them. Now, 2 of the new screws (or the old screws for that matter) will no longer tighten. The other 8 screws seem fine. So:

1. Are the other 8 screws okay?

2. Does anyone have any ideas as to how I can tighten the 2 screws? Locktite? A slightly larger diameter screw?

It appears the transmission cover tightens into the crankcase. I'd rather not replace the crankcase piece. That would suck. And be expensive.

80% is a pass in my book.

RDWRYS
(Relax, don't worry, Ride your scoot)

When the workshop tightened the crank case cover using an impact wrench, it stripped 4 of the bolts holding the cover.

had to tap the engine bolt threads to fit something slightly larger.

The female threads are deeper than the screw is long. Get a couple of replacement screws about a quarter of an inch longer than the originals. Worked for me.

Brilliant. Bend a coat hanger straight and test the depth of the hole against the screws.

People break more things using a torque wrench than by not using one. I don't know anyone who would use a torque wrench to put the variator cover back on. You just tighten it.

some people install an oil filter like its holding the bike together.

Whats the torque rating... about 10 ft lbs? A seasoned tool handler could get real close by feel and nobody would die & parts wont fall off!

I'm amused that a stripped thread requires case replacement!

all we need now is some SAE recos by an english engineer!

Oh FYI... dont spin the 8mm bolts on with a driver... guaranteed way to break the head off! 8)

As the guys say, try some longer screws but check the depth of the holes first like wasp is saying. The second thing to do it make sure to get longer bolts with the same pitch to the thread not just the right size bolts. Often it's not the overtightening that causes the stripping of threads, but the fact owners put in the wrong pitch threads which strips them out very effectively. Either way this is not a disaster of any kind and is an easy fix even if the longer bolts don't do it. Re-threading any stripped holes is easy using a Helicoil kit. Just make sure to read the instructions first. Good luck and let us all know how you get on.

ps. Helicoil kits are available from Ebay or Amazon at good prices.

[quote="turboblew"] And that's one of the reasons for using a torque wrench. Not everyone is a seasoned tool handler. Even still, I've been using tools for decades but my hand is not calibrated and I have no sense of how tight 10 Newton-meters is, for example. I always use a torque wrench if the manufacturer specifies a torque. Why not?

This from Wikipedia Best Miguel

I went with 35mm screws, and they seem to work so far. Original screws were 30mm. Thanks for the suggestion. If you don't hear from me, assume it worked! I'll let you know if they wriggle free! Thanks all.

Sounds silly I know but std. small size wrenches are short and larger ones are longer. Hmm. Could they be self calibrating? foot-pounds is easier than Nm. Bag of sugar is what 5 lbs and a 8mm wrench is about 1/2 foot so exerting a bag of sugar with a 8mm wrench is 2.5 foot pounds.

Socket head or Allen wrenches are L shaped. Maybe the short side is for tightening and the long side for loosening?

Then again really large wrenches go short again and are tightened with a large hammer.

Mike, I know you are right but having destroyed a $200 carbon bicycle seat by "over-torquing" by hand. Now I just go for the torque wrench every time so I don't have to guess. I've never regretted doing it right the first time and always regret it doing it the wrong way if it breaks. Also, ther his common sense that plays a role too in making sure you don't under-tighten or way over tighten, even when using a torque wrench. If it doesn't feel right, I go back and double check the spec. I don't know who said this to me years ago but, "there's never enough time to do it right but there's always enough time to do it over." Also, small bolts and nuts probably have less tolerance. Being lb over on a 10 ft-lb bolt is more forgiving than with 4 foot lbs.

Best
Miguel

Yep for some things one needs a touch like a midwife

Is the cover structural at all?

I have often wondered. I'm thinking slightly. Otherwise it would be plastic.

Metal helps with the heat dissipation?

I think the cover holds 1 end of the starter.

I over-torqued the screws as well... 2 have no thread in cases (metal vs alloy), try thread tape (get the GAS version, it's far thicker & easier to work with)... if that fails, get out the loctite... ohh... do those screws up by hand, then you get a better feel for what's going to be too tight

Loctite makes a special product. Form a Thread. about $16

Next time?

Has anyone heard of Helicoil? You can buy a kit online. Also, don't buy cheap torque wrenches. My 0-25 ft.lb. dial torque wrench cost $180, I only use it on the engine. Pay's for itself every time I use it.
I use a 1/4 drive ratchet for small bolts(8-10mm heads), it's hard to strip a bolt with that tiny ratchet.

Post 8!

I saw that the OP used longer bolts, but I would add another vote for using a Helicoil. I've used them countless times on various stripped aluminum threads and they have saved the day every time. I Helicoiled rocker arm bolts on my Montana with 160K miles and it held up fine until it sold with 250K on the clock. My LX 50 motor pulled out a cylinder head stud and a Helicoil got it back on the road.

Not if you read the torque setting correctly and set the torque wrench correclty. Never saw a bolt broken when doing it right.

The quality of the fastener must be taken into account, I once borrowed a very expensive and correctly calibrated 3/8 drive torque wrench from my work when I was re-fitting my transmission cover. I snugged up all the fasteners, and then started with the torque wrench. Before the recommended torque had been reached I could "feel" the fastener stretching. I dispensed with the torque wrench and just tightened them up by "feel".