Can a Rocket III take down the establishment, and rule this island

DesertRat · Jul 27, 2025

R-III-R Turbo said:
Ok so got a few days off work and gonna try get this engine back together after sitting there in bits for a few months

Have to pull the head to replace the titanium retainers and also gonna change out the 8.2:1 pistons to the 8.0:1s.
One important job on the way is finding the missing tooth from the broken timing gear.

Can you spot it?

So after a bit of examination I think I know what broke the timing gear.
It was in the Stroker engine for several thousand trouble free miles and it didn't break.
So why did it break within 2000 miles when the Carpenter and TTS supercharger were fitted?
If the gear was just a dud then surely a random tooth would be the one to break.
But it was the tooth on the thinnest and therefore weakest point of the gear.
It just smacks of outward pressure like the crank expanded and cracked it.
Looking closely you can see a mark where the gear was pushed against the crank shoulder.

And if you look at the chamfer shape of the gear vs the radiused shape of the mating part of the crank.
Not shown here but the new gear won't go in quite fully to the shoulder because of this.

And couple this with the huge force the crank pulley mount puts inwards when you tighten up the big drive bolt.

I'm sure what happened was the gear didn't mate properly with the crank shoulder due to the different shape of chamfer vs radius, and the pulley mount had the gear pushed in on it hard (hence the mark).
The chamfered edge was being pushed hard against the radius, which acted like it was pushing outwards stretching the gear.
And there was no slight clearance there to allow for thermal expansion.
So while under this pressure the natural expansion of engine parts from the heat, well the crank expanded and cracked the gear.

So now I will sand the chambered edges of the new gear to make sure it mates nicely with the radiused shoulder.

Here's my .03 cents

More than likely this failure was a result of one of two or both of the following;

1) Tooling Shift or Tooling Wear during the Gear Production and/or;
2) Faulty Material to start with.

I wish I still had Chits owed to me around the Metallurgy World. A good NDT Tech could do an simple exam and tell you what caused the material to fail.

Here's a One-Dimensional WAG= I lean towards suspecting a tooling shift because of the fitment/non-fitment of two identical gears

A tooling shift is either tooling that wears during a production run and or an initial tooling set up flaw, (i.e. failure to zero your machine to the material at hand etc).

Small tooling shifts at multiple critical areas can lead up to a catastrophic issue, like what you've found.

This is why I prefer hand-fitted, Hand QC's Engine assemble methods.

Today's culture is lax at using and being proficient in the realm of "Attention to Detail."

Btw, Before I'd take any material off the Gear to fit to size, I'd determine the OEM spec's, sizing and dimensions, (including the Shaft OD and Shaft Chamfer).
There might be a bad batch of shafts and or gears still floating around. I'd then determine how much material is needed to be removed on a Mill.

Good job on the description and pics!

DesertRat · Jul 27, 2025

Turbo,

Sorry to hear about your Buddy.

We've all been there at 1 or multiple times in our lives.

R-III-R Turbo · Jul 27, 2025

Thanks for your thoughts.
Fairly certain the issue with the timing gear was because the crank was #1 custom made prototype stroker crank, the radius on the nose of the crank here the timing gear sits was a little on the larger side than stock, worked fine with a non supercharged motor but when bolting the drive pulley onto the end of the crank for a supercharger, it pushed the gear up onto the radius, putting it under expansive pressure.

R-III-R Turbo · Aug 12, 2025

Got another couple of days to get this beast finally back on the road. Engine off the bench and into the chassis, swingarm and back wheel on.

Justdad · Aug 12, 2025

R-III-R Turbo said:
Got another couple of days to get this beast finally back on the road. Engine off the bench and into the chassis, swingarm and back wheel on.

The world will spin a little slower when this gets back on the road.

R-III-R Turbo · Aug 23, 2025

So I finished the rebuild over a week ago and started it up, didn't get a chance to report back with the video since
Always a nervous moment. Especially when the oil light takes its sweet time.

Now time for the break-in spin.

Justdad · Aug 23, 2025

R-III-R Turbo said:
So I finished the rebuild over a week ago and started it up, didn't get a chance to report back with the video since
Always a nervous moment. Especially when the oil light takes its sweet time.

Now time for the break-in spin.

I was nervous for you on the start up.

rick danger · Aug 23, 2025

Justdad said:
The world will spin a little slower when this gets back on the road.

Depends which way he was facing when the clutch flew. .....if I lived in the UK my Rocket would be super charged by now.

Gerald · Aug 23, 2025

R-III-R Turbo said:
So I finished the rebuild over a week ago and started it up, didn't get a chance to report back with the video since
Always a nervous moment. Especially when the oil light takes its sweet time.

Now time for the break-in spin.

Guess we are all like expectant fathers when we start a fresh rebuild, doesn't matter if the first or many engines, until she fires and runs with good oil pressure and that sweet sound, hundreds of thoughts, doubts and questions run through our minds. I have enjoyed and gained knowledge following yours and other member posts. Thanks for taking the time.

R-III-R Turbo · Aug 25, 2025

Did the engine break-in yesterday. 75 miles. Warmed it up and used lots of varying rpm but nearly always above 2000rpm. Then as soon as it was warmed, wound it on more & more.
Max used was about 45% throttle and 5500rpm I think.

Was running on 2 cylinders for a while, was vibrating, sounding and going like a Harley.
Then the 3rd cylinder woke up and we were haulin ass again.

Idle needs some adjustment on fuel as it's a bit weak, and a few other tweaks but it's going great.
Break-in service now and those adjustments.

Can a Rocket III take down the establishment, and rule this island

DesertRat

.060 Over

DesertRat

.060 Over

R-III-R Turbo

Mine is the biggest :)

R-III-R Turbo

Mine is the biggest :)

Justdad

Turbocharged

R-III-R Turbo

Mine is the biggest :)

Justdad

Turbocharged

rick danger

Supercharged

Gerald

Turbocharged

R-III-R Turbo

Mine is the biggest :)

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Can a Rocket III take down the establishment, and rule this island

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