stuck crankshaft worm gear

ILLF8ED · Mar 10, 2020

I’m trying to remove the worm gear on a ‘70 engine crankshaft timing side. I know the procedure just wanted to confirm this is a left hand (reverse) thread. It’s been soaked in penetrating oil and have been using my air impact. No luck so far. Not sure my impact gun is still giving 100 lb/ft of torque.

Mike B · Mar 10, 2020

Heat, then steady pressure with a breaker bar.
Mike B.

ILLF8ED · Mar 16, 2020

Still have not freed up the crankshaft LH thread worm gear. Soaked it in a rust remover for 12 hours, penetrating oil, heat, air impact gun and long closed wrench tapping it with a hammer. Someone said try HCl acid, but that would really attack the aluminum case if it got on there. Anyone have a success method?

gortnipper · Mar 16, 2020

Maybe try moving it the other direction first with the rattle gun. Might break it loose.

acadian · Mar 16, 2020

Make yourself one of these out of 3/16 aluminium flat stock and make sure you use the spindle support plate. It wedges diagonally between the idler and cam sprockets. The notched end fits under the plate, and the middle notch over the tensioner nuts. Flip it either way to tighten/loosen the worm nut, cam sprocket etc... This one has been in use for years and is getting a bit worn out, so I'll have to dig up a quarter to make another one soon

marshg246 · Mar 16, 2020

illf8ed said:
I’m trying to remove the worm gear on a ‘70 engine crankshaft timing side. I know the procedure just wanted to confirm this is a left hand (reverse) thread. It’s been soaked in penetrating oil and have been using my air impact. No luck so far. Not sure my impact gun is still giving 100 lb/ft of torque.

I had a similar problem with the camshaft nut. I tried everything including higher than normal air pressure on my air impact and when that didn't work, a long breaker bar and putting about 250 ft lb on it. I was about to cut it when my stepson stopped by said that he bet his electric impact gun would remove it. I laughed and said try it. Zip and it was off

ILLF8ED · Mar 17, 2020

Send over your son with that impact driver. Seriously though I may go and buy one of these.....Thanks.

Hortons Norton · Mar 17, 2020

Any chance I could get some dimensions on that tool?? I have something like that for the Buell and it works great.

acadian · Mar 18, 2020

Hortons Norton said:
Any chance I could get some dimensions on that tool?? I have something like that for the Buell and it works great.

RoadScholar · Mar 18, 2020

Acadian's plate is a great idea, the point of using the plate, I believe, is to lock the crankshaft so that the torque you apply to the hex on the worm gear isn't "diluted". The only down side I see is that the torque you apply to the worm's hex is felt on all the rotating parts in the timing chest; not being an engineer I can't say if there would be any residual adverse effects, I would think that a new cam chain should be fitted, and I have always wondered if just torquing the cam sprocket nut induces the chain to stretch.

I can only assume that you are removing the worm gear in preparation for splitting the cases, correct me if not. I use a length of bar stock that fits through the wrist pin bores of the rods then fit a block of aluminum across the cases. when the bar stock meets the block the crank is prevented from moving. The entire torque you apply to the worm gear is now felt where it needs to act and your impact gun's hammer strikes become fully effective.

Heat the gear, "freeze" the crank and I'd be surprised if your impact gun fails to back the offending gear off the crank.

Best.

acadian · Mar 18, 2020

I think the key is to use the support plate anytime you're playing with the cam or worm nuts, or adjusting the chain tension, I think this obviates any chain stretch but more importantly prevents the intermediate spindle bore from galling out. The aluminium plate indirectly locks the crank, but directly locks the cam & intermediate sprockets. IMHO the cam nut is what tends to be stubborn to remove (the crank worm nut is only supposed to have around 15lbs of torque after all).

This is just an alternate way to lock the timing gear without removing the barrels, or relying on the tranny/rear brake combo...

Here's a pic of the locking plate in use (the studs hold the gasket in place and help to align the timing cover during installation)

Hortons Norton · Mar 18, 2020

Thanks acadian, just what I'll need.

ILLF8ED · Mar 18, 2020

RoadScholar said:
Acadian's plate is a great idea, the point of using the plate, I believe, is to lock the crankshaft so that the torque you apply to the hex on the worm gear isn't "diluted". The only down side I see is that the torque you apply to the worm's hex is felt on all the rotating parts in the timing chest; not being an engineer I can't say if there would be any residual adverse effects, I would think that a new cam chain should be fitted, and I have always wondered if just torquing the cam sprocket nut induces the chain to stretch.

I can only assume that you are removing the worm gear in preparation for splitting the cases, correct me if not. I use a length of bar stock that fits through the wrist pin bores of the rods then fit a block of aluminum across the cases. when the bar stock meets the block the crank is prevented from moving. The entire torque you apply to the worm gear is now felt where it needs to act and your impact gun's hammer strikes become fully effective.

Heat the gear, "freeze" the crank and I'd be surprised if your impact gun fails to back the offending gear off the crank.

Best.

Immobilizing the crank isn’t the problem. I’m inserting a rod into one of the balancing holes with that bumping against a block of wood per the workshop manual. Yes I want to remove the crankshaft. This thing is stuck so hard I started to think it wasn’t LH thread. Kind of ignoring this problem for now to concentrate on reassembling my ‘69 750 S project.

ILLF8ED · Mar 19, 2020

Went after it again this afternoon. Air impact had no success. Propane burner heated it up then used my torque wrench, still nothing. Hammered impact driver seemed to start moving it. Hit it with the air impact again and off it came. What a stubborn thread.

RoadScholar · Mar 20, 2020

Congratulations on your victory; I was going to say success, but you fought that sucker tooth and nail, good job.

I did intend to weigh in earlier.

illf8ed said:
Immobilizing the crank isn’t the problem.

Yes, but it is part of the solution. If the crank is allowed to move, even a few degrees, the force of the impact gun diminishes greatly. The small hammers in the gun don't move much, to get the full benefit of the tool the object the gun is focused on must be quite stationary. The 1/2" bar in one of the balance holes is good, but always made me a bit uncomfortable about damaging the cases(s). Glad this worked out for you. Bravo!

Best.

Woody850 · Jun 24, 2021

I'm still struggling but this is how I'm doing it. I must bolt the engine stand to the bench first though.

SteveA · Jun 24, 2021

Looking forward to seeing the tool TW made for this, but here is my rough and ready one! I had a section of 52mm hex alloy and a Land Rover hub nut socket to hand.....I bored a hole alternator rotor size, and got a friend to broach a keyway!

I use a long breaker bar against the bench and normally manage the oil pump worm with a standard ratchet tool...remembering, at second try normally, it is LH thread...but a breaker bar on your 'half wit' socket should crack it....if you don't have an impact gun....I don't, but it is probably time I got one...

Of course you need your primary stripped....

I also use this setup to turn the motor when needed in the motor build, even just hand held when a timing disc is fitted, plugs out.

If the crank nut looks a little rusty....it contacted the tarmac at Pau after the fairing had worn through.....

Woody850 · Jun 24, 2021

That sounds a real niffty way of doing it.
Eventually I got the worm drive off using a socket on a breaker bar and an old fork stanchion stuck on the end excerting unearthly force until I couldn't manage more then........BANG
First thoughts whats broken or slipped but it worked.
Now posted in the pictures are nasty scratches from what looks like somebody took a screwdriver to scrape dirt off.
Having read about cleaning and degreasing the case a similar silver paint could be applyed by spraying on a rag and rubbing it in.
I must say this is only on the rear and hidden parts of the crankcase, to this I must add the cases will be split but have no intention to remove the bearings.
No doubt many will say if going this far then do it right, then tell me exactly what you would do.

stuck crankshaft worm gear

ILLF8ED

Mike B

ILLF8ED

gortnipper

acadian

marshg246

ILLF8ED

Hortons Norton

acadian

RoadScholar

acadian

Hortons Norton

ILLF8ED

ILLF8ED

RoadScholar

Woody850

SteveA

Attachments

Woody850

Similar threads