Gearbox problem

[Charlynsane]

And the winner is.....









The MED flywheel!!!!!

For information, the flywheel had been ported with grinding past, and tightened to the right torque

Of course we adjusted the primary gear clearance

I'm really disappointed with MED products! I will never order anything else!

About the ring gear, I used a MED high torque starter as well, 9teeth, for inertia starter so, no error from the engine builder.

That what was causing the problem with the 2nd gear baulk

[hicklingmick]

Looks like wrong starter fitted for that flywheel and flywheel been insecure on crankshaft.

it still wouldnt make 2nd gear crunch

[imack]

So it looks like the flywheel has gone too far up the crank taper and 'pinched' the primary gear, but I would expect this to cause issues selecting all gears, not just 2nd gear.
This is a known concern and is something that needs checking during engine build.
Have you stripped the box and inspected all 2nd gear components?
Are the ring gear and starter motor compatible with one another?

[Spider]

I'm glad you have found something here, it would contributed to the issue you had, however, as imack has said, if that was the sole cause, all gears would grind, not jut 2nd, in particular, Reverse.

I take the approach of ' Assume nothing, Check everything '. New, Guaranteed, yr best friend's mother's own, what ever - check it. This isn't a slur on any supplier of manufacturer, just what I think is good practice.

Respectfully, this issue could have been checked for (and indeed should have been) at assembly. It's not difficult to do either.

It also looks like the flywheel wasn't fitted tight enough, though with it pinching on the Primary Gear, it possibly couldn't go on much tighter.

Is the Ring Gear soft ?

While you have it out and in bits, I'd strongly recommend at least checking the Gearbox, I still feel there's an issue there.

[Charlynsane]

Hello Guys

We ported the flywheel before fitting with grinding paste etc..

The starter motor is a powerlite sold by MED with the flywheel it has 9 teeth to work with the inertia flywheel..

We tightened it to the right torque, from my memories 115 lb/feet.

There is something we don't understand, the gearbox will be totally stripped, checked and we gonna fit Guess works baulk rings.

We gonna remove the KAD pinion support as well.

[Spider]

We tightened it to the right torque, from my memories 115 lb/feet.

Others here may have different views, but I've found that the factory figure here just isn't any where near enough. I tighten these to at least 150 ft/lb.

Odd as it sounds, but to make the flywheel come off easy and not let it do any damage, like the fretting you have, it has to go on very tight.

[Andrew1967]

Our torque wrench only goes to 110 ft/lb so it’s that plus a bit more.

Never had a problem with flywheels coming loose. Never lapped one in either.

So far anyway ...

[GraemeC]

Just to demonstrate how much the flywheel can move up the taper:
I run a crank with no c-clip groove and have to ensure I tighten the flywheel to the same torque every time to ensure I get the right endfloat on the primary gear. I tighten to 200lbft. I used to just go as tight as I could with a 2ft breaker bar - if I do that now the gear nips solid.

I would machine the recess in the middle of the flywheel deeper by at least 2mm - lots of room then but still plenty of taper to engage on the crank.

[Fanfaniracing]

I learned to lap the Flywheel in, and tighten to 200Nm plus Bonus

[Charlynsane]

I really think the MED flywheel cone angle is wrong, but very close to original

We lapped the flywheel before and we tightened it to up to 200nm..

Wait and see..

[Charlynsane]

I think I will go with a C-AEG421 flywheel,

what do you think? does it require balancing?

[imack]

I think minispare and MED flywheels may be from the same source.

[Charlynsane]

I think you're right! look identical, miniskirt flywheel as well

[MiNiKiN]

I think you're right! look identical, miniskirt flywheel as well

Lapping the tapper does not resolve (or it actually worsens) the problem of the flywheel touching/binding the primary gear.

Clearly explained in this video by HRE:

https://youtu.be/4lEbKGpZ4xw?t=417

[Charlynsane]

How Can I check the clearance between flywheel and primary gear?

Thank you

[MiNiKiN]

A lump of play dough is what I use in such cases. put it in the gap, assemble the lot, take apart and measure.
Tin solder in different thicknesses is the other "measuring device" to be used in such instances. Same procedure as above

[imack]

Just looked at my crank and minispares ultralight flywheel. Measured the depth of the taper in the flywheel and compared it with the length of taper from the c clip slot to the end of the crank - there'd still be 20 thou clearance between the c clip and the recess in the flywheel even if the flywheel was able to be bolted up flush with the end of the crank.

[Spider]

It has been a little while since I last bought a lightened flywheel, but I have fitted up a few of the Mini Spares C-AEG619 Flywheels and found them quite good. They fitted very well on the Taper, but I did lap them in to the Crank, as I would any other Flywheel. I don't know if these are made by the same firm as the C-AEG421 but I guess they would be. The only thing I found I had to do was to chamfer back the Ring Gear on a few as it would foul on the Flywheel Housing.

I made mention in my last post that from the Fretting on the Crank and Flywheel Taper, it was clear the Flywheel wasn't fitted tight enough. The Fretting maybe from a mis-match between the tapers or not fitting tight enough, though, if they were lapped together, they should match or there'd be clear evidence at that point that they didn't match from the finish on both tapers.

When fitting Flywheels, in order to get them together tight enough, I lightly lube the Taper with a very light grade Oil (3 in 1 is good) then assemble them together. The Oil Allows them to slip together tighter than if done dry. Using such a light grade of Oil for this, under the extreme pressure generated, the oil film then breaks down so they don't then slip any further. I've proven this technique does get the parts a much tighter fit than if assembly dry by measuring (as I suggested above) and also doing a trial removal, a much greater force is needed.

Usually, when they are run and with the Flywheel not tight enough, the Flywheel and Crank Fret (as has happened here), effectively 'dry welding' the parts together, then they become very difficult to separate and when they do, material is torn from one part or both. While this can sometimes be cleaned up, it does result in a loss of surface area contact between them. depending on just where on the Taper this occurs, if it's nearer the ends of is, it can mean there is a 'lesser' fit than there was in the first place.

How Can I check the clearance between flywheel and primary gear?

Thank you

At a point in the build before the Flywheel housing is fitted, I fit up the Primary Gear and fit the Flywheel as I would for final assembly (as above), then check the Primary Gear still spins free and has the same end float as when first set up. I then remove the Flywheel Bolt & Lockplate, then measure the depth from the Flywheel (the face that the Lockplate sits against) to the end of the Crank. When doing the final assembly, I check that depth again and before bolting up the Diaphragm, make sure the Clutch Plate can spin free,

[Charlynsane]

Here we go some more news

Thank you for your help guys

some bad surprises that we didn't notice during the rebuild







https://nsa40.casimages.com/img/2021/03/31/210331014942678916.jpg

[Andrew1967]

That's the reason it crunches .. was it a new baulk ring ??