Double Trouble

[ATinkerer]

Always have wondered how any of us survived this long.

Gordon

[John H]

Yeh Gordon,
I'm reminded of that when it's painful to get around.

[Dragonknee]

Nice to see you still plugging away at the bikes... Keeps you young John. After being hit on my bike I feel older I would say but still not gonna stop riding... Love the project.

[John H]

Back to square one, almost. All the vital parts have been fitted for location and function so its time to take it apart and build build the engines. The engine mounting plates have to be separated before either engine can be removed.

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Engine #2 is not a matching pair of crankcases so after some measuring I found that the surface for the cylinder base was not parallel with the crankshaft. So into the mill to correct the misalignment. It took .006" to clean it up.

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[John H]

The motors are mounted between aluminum plates using 8 through bolts. Severe torque at the mounting points has caused considerable wear. To correct this I resurfaced each mounting point. This will require new spacers to keep things all lined up correctly. An equal amount of material had to be cut from both cases so the motor will stay centered between the mounting plates. Ironically, the 3 front mounting points are 1/4" wider than the other 5. This was due to the way the motor nested in its original Triumph frame. One motor done, one to go.

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[John H]

Back into hundreds of pieces preparing for the final build.

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Engine #2 got the treatment today. Decking and resurfacing the mounting lugs. I discovered a crack near the main bearing on the drive side so this will be the next item to address. Nitro is another name for a big hammer.

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[John H]

More surprises after removing the main bearings. On the drive side case of motor #1 the bearing retainer
bore was oblong fore and aft as you can see from the dimensions in the first photo. On motor #2 it's just the opposite with the bore being oblong up and down. See the second photo.
I can only imagine this has something to do with the configuration of the engines.
The fix will be to bore and sleeve the cases to fit the new bearings.

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[ATinkerer]

Abrasive wear from the outer race creeping, or actual distortion of the casing John?
If the latter, hopefully there is enough material to support a sleeve without the problem becoming more severe.

Gordon

[John H]

Thanks Gordon,
The bearings are in good condition and their dimensions are correct. It's not uncommon for a high compression "nitro" motor to hammer the main bearing housing out of tolerance. The drive side even has a 1/4" plate welded outside the case to increase support for the bearing. The bearing is 2.812" od and I have a 3" od tube that should to the job. There is lots meat around the bearing so it's strong enough when bored to 3". This was done to my Vincent race motor back in the 50s when they were first using nitro. Considering this bike will never see real competition again I could probably get by with high strength epoxy, But

[ATinkerer]

The increased surface area of the larger diameter sleeve may be enough to distribute the load so that distortion will take longer, even if you chose to go full bore nitro. Aluminum can react strangely to repetitive loads.

I've used chemical retainers (loctite 600 series) successfully, but not for that large clearance.

Gordon