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Hi, last year i melted a hole through my piston at finke running a 172 main. Sure dont want to make that mistake again so I have gone back to a stock barrel with no porting and cast piston both oem. Can anyone please advise me on which main would be the best going by the following pics? I followed "spanky's jetting 101" to set the pilot and airscrew then did plug chops using 178, 180, 182. All started with clean plugs and I held it full throttle through all gears until it topped out and held the kill switch. The lighter side of the plug was facing the exhaust port. I think the 178 and 180 are a bit lean and the 182 a bit rich which will prob be fine for finke as there is a fair few sections where your ringing its neck. Just after some others opinions as i'm definately no expert. Last year I was running 30:1, These tests were done using 50:1 fully synthetic. Carb is a PWK 39.5mm
Next question, Does anyone run 50:1 or should i drop it back to 40:1? 40:1 will lean it out a little i guess

Cheers


182


180


178

In order to read plugs correctly, you have to be able to see down deep, they say you can use a 10X loop, most just sacrifice the plug and cut it to remove the threads and expose the entire porcilin.

Here is a little info, http://www.strappe.com/plugs.html


If the pictures don't work, you can see them here http://www.pilotodyssey.com/PO/viewtopic.php?f=9&t=870

Hope this helps, if it were me, I would get it where you think it is right and fatten it up a little

Thanks for the reply and info, Unfortunately im running the shorty plug which are over $50 a pop in Aus. I will grab some cheap normal plugs and just leave the tank loose for the testing. That way I can cut them up with out crying

Cheers

50 bucks for a fucking spark plug? you gotta be shitting me?!? someone is getting paid bank for extortion!

Can fill a suitcase be their soon how many does the great land down under need
NGK $2.95 a piece
USA
USA

If you went back to stock everything a 172-175 should be since.

It maybe the needle, try riching the 3/4 range of that. cgj to a dgj or 1368 to a 1468.

for what finke is a 172 main jet is no where near big enough i run a 175 for mx in western australia to put finke into context for our american friends finke is a desert race 170kph+ top speed

For the Americans 170kph is about 105mph Or FAAST!!!!

gregrobo wrote:for what finke is a 172 main jet is no where near big enough i run a 175 for mx in western australia to put finke into context for our american friends finke is a desert race 170kph+ top speed

Agree entirely . . . there's something about West Aussie air, I reckon. Mine nipped up on a 172 main in the Lancelin dunes. 175 is crisp, 178 makes me breath easy, so I'd be running 180 for Finke or the Gas Dash . . .

Everyone needs to remember a few things....

1. In OZ, our winter is their summer.

2. In OZ, their gasoline may be completely different.

3. In OZ , they all ride "Upside Down"

4. In OZ, Repairs cost 3x as much as here in the States.

A old racing proverb states.... " In order to finish first...... one must first finish"

I say run her rich..... and hang on!!