The Place

After some help,please!
Managed to hole a piston in practise this wednesday going round gerrards at mallory, left pot absolute lovely, right pot massive hole in piston.
Ignition is fine on both cylinders but right pot was "Dry" no oil film. Have used large fuel filters as header tanks for carbs, am i missing another "Trick of the trade", to stop fuel starvation and thus lean running on these long curves.
dont understand why one pot is worse than other. Happened on third session of practise.

Carb problem suddenly on that particular one ?? hence the lack of fuel ........ what fuel mix are you running ?

Could be where the pick-up for the fuel supply is on your fuel tank, if it is on the right side of the tank, then you may not get the correct fuel pressure round gerards. We had some similar probs when on the 2 strokes.

Wouldn't that emerge fairly quickly though ? rather than after a couple of previous sessions ??

What fuel system are you running? If you have Vac. pumps on, throw them along with the holed piston in the Bin!

The fuel system we found to work best is, simply a electric pump (facet) into a 'returning' regulator (malpassi) and then straight into the carbs! This was also used with great success by the likes of webbo. etc. on the 500cc 2 strokes (proper engines).

Enjoy!

Fuel system is a facet pump, BSR aerotek suppied fuel regulator et on "1" out of 5 into diesel fuel filters as header tanks as large volume and into carbs. Fuel mix is 25:1 using motul 800 which i have used for 5 years with no issues, am now on castrol A747 on the rebuilt motor.
Have jetted up enormously for now and will see what happens at cadwell.

For a 350 TZ a 30mm dia x 450mm long well fed sump to underside of tank with 10mm dia fuel pickup pipe fitting 150mm into sump filter king fuel regulator small facet fuel pump (lowest rated one) individual mercedes diesel filters to each carb and unrestricted return to fuel tank with 39mm mikuni powerject carbs with 350 main jets and 85 power jets with airbox A747 at 32/1 on an average day weather wise would get you nearley round Gerrards in 6th gear using 16 36 gearing on 350 primarys

wicked answer anp !!

Are you sure its fuel starvation?

I have been racing a solo TZ350 for three years now and have been suffering from holed right hand pistons due to detonation. They always appear dry following a seizure due to the heat generated. I have discovered that my problem was cured by reducing the ignition advance (the timing mark was wrong on the stator) and replacing my very old crank.

FYI, I normally use 50/50 avgas/vpower and A747 at 30:1.

Do you have a photo of the top of the piston? What ignition are you running?

Regards,

Simon

Thats a very good point how about a faulty coil ? I have seen that happen before