Crankshaft seals T350

[joethebike]

My 1972 T350 picked the wrong time to suffer leaking crankshaft seals this week with the Broadford Bonanza only a few weeks away at Easter. The Broadford theme for this year is the Castrol 6 Hour Race and with my bike's history in the race it was definitely going to be a starter. Can you imagine the derision it would face though, smoking around the track in front of a thick cloud of gearbox oil smoke.

So a crank transplant was required with the options of rebuilding the current crank with new seals or replacing with a second hand spare one that has quite a 6 Hour history.

The replacement crank is one that did the first 6 Hour in 1972 and I then had it rebuilt as a precaution with new rods, crank pins, bearings and seals for the 1973 race. The rebuild was done by the old NSW Suzuki agent Hazell and Moore with the original used bearings, crank pins, rods and seals returned to me in a box with the rebuilt crank.

The bike then did the 1973 6 Hour and became my everyday road bike until the rebuilt crank suffered crank pin failure in 1981. The failure became noticeable on the way home from a ride with the bike sounding like a concrete mixer as I pulled into home with a 0.5 mm groove worn through the crankpin hardening.

I had a new crankshaft on hand thanks to open access to Hazell and Moores parts bins while they were in business, so in it went and that crank has now suffered the leaking seals.

After the rebuilt original crank had the crankpin failure I had Kevin Cass from Wollongong repay a favour by rebuilding that crank for the second time, using the original and still serviceable rods, crankpins and seals returned after the first rebuild in 1972. I had hoped never to have to use this crank and wanted to have it as back up for emergencies only but the time had come to use it with Easter not far away.
Over the weekend the engine was rebuilt with this crankshaft and, blow me down, it's up and running, sounding crisp, running as good as new and not blowing smoke.

It will be quite a buzz to circulate again with other bikes from the 6 Hour decade and I hope the Suzuki lives up to its record for reliability.

A new crank seal set is on the way from Paul Miller and I just have to find someone who can rebuild the leaky crank to have another spare for insurance against future failure.

A picture of the old failed crankpin is attached.

crank.jpg

[tz375]

Joe, Have fun at Broadford. I used to love the back straight with the blind turn at the end of it. I could never get the next downhill section just right though.

[Craig380]

Pretty amazing that the crank withstands a 6-hour endurance race, and then is a daily rider for 8 years before failing

And it's a nice piece of circular fate that you'll be doing the upcoming meet with original crank components from the first tome around! Hope it goes well for you

[Vintageman]

joethebike,

Do you think extra oil would have helped when running hard sustained?

You see this a common requirment for engines modified by factory for racing.

For example a T500 pump I think fits and puts out more oil.

I suppose you are suppose to be all stock

What did the needle bearing look like if they were still to be found

I try to run extra oil in my fuel tank ~64:1 even for everyday driving, just in case something fails with injection system (again)

[joethebike]

Vintageman, you have to remember we were running oils available in 1972 and they were not the equivalent of today's choice which would be a full synthetic racing oil.

You also have to remember the failed crank pin not only did the race but then did about 50,000 miles on the road, so Suzuki seems to have done their sums well with regard to oil flow.

The bike is running on its second oil pump now, not because the first one failed but simply because I had another new one and it seemed like good insurance to fit it.

The needle rollers must have stayed in their cage as I do not remember any damage to the piston and head which would have happened if any rollers had come loose. It sure did make a racket though over the last few careful miles to home as I hoped it did not self destruct.

The new/old crank has been given a good test and runs like new with no smoking and a bit less vibration. It just shows how these things slowly fail at a rate you don't detect until it becomes very obvious. Another benefit is a cured carburetion problem affecting the bike since putting it back on the road in 2000.

[Vintageman]

Thanks JoeTheBike.

50,000 is impressive and given its amazing history.

How about the piston and cylinders.... how many miles on a bore size?

For the 6 hour race did everything have to be 100% stock. I mean was it ever considered to add more oil or could not do that if you wanted to? Curious

Thanks again so much for your reply