TT1 4 Hour Endurance racing

Jo said:
Thanks for the report! You've summed it up well, that can happen when you're doing endurance racing. Pity that the engine broke, I'll keep my fingers crossed that the repair won't be so expensive and that things will go better at the next event!
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Did crankcase pressure blow that primary gasket?
Paul
 
I love to hear the blow-by-blow so to speak, I was talking to the blokes at a recent club night and apparently, quite a few have fitted TPSs, that is throttle position senses, that connect to the Ingatec ignition, pretty easy to do so they were saying. I remember Cape doing it ages ago and getting significant improvement in his MPG. Better than 50mpg and has smoother power application. Thats got to be better than the usual 30 MPG or worse at racing speeds
 
Thanks for the comprehensive report. Not the result you would hav e hoped for - bloody racing!! Any idea why the inlet rubber would have imploded? Having first-hand experience of lean-outs and piston failure, it's not a cheap and easy fix. Good luck with the rebuild and look forward to the next round.

I'm starting to think exhaust gas temp gauges could be a wise investment for racers ... and me ... alike.
 
I am going to do exactly that, The bung was done years ago when I bought my big bore exhaust from Red. The last time I melted the ring landed off a couple of pistons were there was zero warning till the mass exhaust smoke happened. NOT FUN
 
When I was dialing in my Westfield I used an O2 sensor and it was amazingly helpful to watch the mixture change at various throttle positions and loads. It made a long frustrating job a matter of a few hours over a weekend. This was a Weber carb on an over bored BMC A-series. I just ran the wires out the bonnet to a meter taped to the instrument panel. After I was finished I removed it all including the sensor and plugged the bung. Job Done!
 
I was going to write a lot story about my circumstances but some recon BLA BLA BLA so to avoid causing another dispute I like the idea of permanently fitting an O2 Sencor and dash instrument and maybe getting an early warning before melting shit. The hard bit is the bung in the collector and it's been there capped off for years so I might as well use it.
 
The problem is that O2 sensors are physically so damned big. At least the car ones are, I assume the ones used on EFI bikes are more compact, but I’ve never actually seen one! More than likely, as the size goes down the cost goes up….
 
That was a tough one. A lot of travel, time and energy without the sweet result.
A blown out gasket often caused by too much pressure behind it but not so easy in the heat of battle.
Well done for your perseverance and enthusiasm.
 
I know Red didnt find much pressure variation in 120s but adding an extra breather might help.

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nick7 said:
Possibly, but its a common issue even on engines in good condition when revved ( not for those of sedate disposition plodding about on their points fired 750😉)...there have been posts by Phil Todd and Red on that subject.Phil described variously using a morini baffle thing in the breather, and creating a breather from the rocker cover I think? Red was designing a different breather, I seem to recall. I wonder if this was an issue for the Jota racers back in the day? I first came across the problem 20 years ago when revving my newly bought Jota...and for sure though shiny it was a smigeon away from self destruction internally, worn bores , rings etc causing blow by.
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I decided to design a 2nd breather after monitoring the crankcase pressure on a 180 degree triple on my test bench, I set up a 0-10psi transducer installed in the dip stick hole and ran the engine
Having been involved in drag racing in the past where they use Vacuum pumps to scavenge the crankcase cavity to gain horsepower I was interested to see what was going on

You could watch the gauge on the software go crazy, up to 6 psi fluctuation depending on revs whereas do the same on a 120 and the needle barely moved
Is caused by those 2 pistons going up/down and the poor old middle piston trying to keep up so I machined up and installed a 2nd breather bolted to where the Starter motor should be and which has a Kawasaki 125cc 2 stroke Reed valve inside of it
Works really well

I doubt that anyone else has ever taken the time to set up and record the crank case pressure on a Laverda triple
Shit you do when trying to find power out of these old clunkers
 
My first race bike was powered by an iron BSA B33. Effectively an iron Goldie. Breather was a pipe into the timing case. Which, once it started to wet sump. was below oil level. The old man coined the phrase "Lubricated by external splash"
Only way to fix at the time was to raise the takeoff level inside the cases.
Now, every single,360 twin v twin or 180 triple I build has a reed valve to pump the case pressure down. When it starts working properly the plug colour changes about two jet sizes. You're burning less oil.
Britten pic shows the pyramid on top of the gearbox just above the final drive sprocket which holds a four petal Yamaha reed valve. Nothing special, just an old RD or DT steel petal setup. Solved all the breathing problems. Later customer bikes used a big PCV valve. I was told those are a bugger to get the rings bedded.
 

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The reason for failure was due to an inlet rubber splitting . The only way one would have seen the cracks developing is if the clips had been completely removed. Piston on No1 cylinder gone ! Complete strip and rebuild started. Donington 5/6th Oct next 3 hr endurance race.No1 inlet rubber split.JPGNo3 piston gone No2 running too lean.JPG
 
There is an alloy bracket holding my Mikunis up mounted off the rear of the rocker box. Before that, it had heavy-duty cable ties, before that I had the carbs wiggle back and drop down a couple of times. They need some support, especially if you're not using the airbox.
 
I'm sure I've seen a pic of an American semi works Triumph twin with rubber bands supporting the bellmouths.
Can't find it but it's a simple solution.
 
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