+4 timing and 21cc domes, any jetting changes

[ScEaMin BaNsheE 305]

64mm stock pistons, no porting chariot cool head with 21 cc domes, vf4 reeds, chariot intake manifold, k&n pods, +4 timing, running 93 octane. So I already put a hole in a piston but to avoid the same shit from happening again, do I need to change the jetting to richer when running +4 timing and 21cc domes or did I fuck up by running 93 gas. thanks

[trickedcarbine]

What does the strap on the plug look like? If it was on a decent tune up, it is probably ok on 93.

[Keno]

If you holed a piston, you either have too much timing, too little octane, or are lean.  21cc domes you are probably okay on 93. Try jetting up and check your plugs.

[tfaith08]

21cc domes are just fine at sea level with +4 timing on 93 PENDING JETTING.

[rubberneck]

I didnt see what pipes you are running and if you post it up guys can get you a good starting place.  Before i had my 350 ported i ran T5s VF3s k&n pods 21 cc domes +4 timing on 93.  I had 340 mains and 27.5 pilots running at sea level. It was a safe tune.

[ScEaMin BaNsheE 305]

cpi small bore in-frames, 27.5 pilot, 4th clip on needle, 330 mains. Im pondering if its possible that a float needle could be adjusted wrong and starve the engine of fuel at WOT, I did mess with it trying to get the fuel to stop pouring out the overflow, the other piston looks good so im thinking that the root of the problem lies in the float adjustment of the carb on the side of the blown piston, I appreciate the feedback, btw I did a leak down before riding and after I blew the piston and it held 6 psi for more than 10min. Thanks

Edited December 30, 2015 by ScEaMin BaNsheE 305

[tfaith08]

Get some carb rebuild kits and set the floats as per the manual.

 

Good to see that you're doing a leak test.

 

Remember that an engine that's just a hair lean may present with detonation once you add timing. Get the jetting right (via plug chop), THEN add timing.

 

Make sure you have your filter clean and oiled and that you use E10 93 gas if you ever switch back and forth. Jetting with E10 and running mogas is fine. Jetting for mogas and then running E10 will make it a tad lean (by stoichometry, about 4% lean). Jetting with a dirty filter will make you leaner once you clean it.

 

None of these is major, but all of these going wrong at once and them adding timing will probably start eating the piston.

 

 

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Edited December 31, 2015 by tfaith08

[carlosg54329]

 

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[carlosg54329]

some wannab mechanic told me too much fuel, I say lean,opinions

 

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[sheerider11]

some wannab mechanic told me too much fuel, I say lean,opinions

 

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Opinion. Stop going to that mechanic.

[ScEaMin BaNsheE 305]

I dont use mechanic, it was a neighbor(homemade mechanic) i showed piston to, banshee hq is my mentor and I learn from mistakes

Edited January 1, 2016 by ScEaMin BaNsheE 305