Need to make 350x faster. Anyone had 12:1 piston installed?

[sportvette]

did anyone have the 12:1 piston installed? do you have to run race fuel? what octane?

any drawbacks? does it make it harder to start?

i want to make the 350x faster. looking for suggestions. have a 250r to keep up with.

thanks for your help.

[lushatc200x]

they sure do have to run race fuel and its expensive. try and get a 10;1 or 11'1 where u just have to burn the high octane at the pump.

[hrc200x]

I have a '86 350x with 12.5:1 or 12:1 whichever it is, and I run 93 octain from the pump. It runs it, starts fine, but if I lug it in a high gear say 4th when I should actually be in 2nd it kind of makes a knocking/pinging noise. My cousin has a 200x with 10.25:1 and it pinged, but he added octain boost and that helped a ton.

I bought the 350x with the high comp piston installed, but comparing it to my stock '85 it helped the power tremendiously, but doesn't really seem must faster (havn't raced side by side). I'll take power over speed any day.

[lisnup65]

A 12:1 in the 350X will rewuire the use of racing fuel. The high compression on the motor with use of low -octane(94<) fuels was cause a short life. The engine will run mad hot due to the compressiom. High Octane fuels burn faster, but are cooler burning. The piston will beat the hell out of the sleeve causing pre-mature top end rebuilds. I know this because my 350 had a 12:1 in it that I did not know about. I always wondered why it ran so hot. I have scars from burns on my legs because on the heat generated. I posted about taking the top end of the motor apart and how I have to go from .020 bore to a .10(Final bore) because the cylinder is so warped.

The extra power it would create is worth it as an inexpensive mod, but the expense with that mod comes from the fuel you are required to run. Thus this is the reason that even the Wiseco site states that racing fuel must be used with a 12:1.

Good luck in what ever your choice. I would opt for a 10.25:1 and a new aggressive cam and springs to add what you are looking for.

[sportvette]

thanks for the replies so far. you all have been very helpful.

i am still not sure if i want to get the 12:1 piston. 100 octane near me was 4.00 a gallon a couple years ago. i wonder how much it costs now.

spending $4 everytime i ride is not a big deal to me. i dont know how much fuel i will be going through. havent been riding atvs for years now.

what octane is recommended for the 10.25:1 piston? is 94 good?

i am not interested in other performance upgrades, if i dont change the piston i was thinking about a larger rear sprocket to increase power. i missed one on ebay. dont know where they sell them new.

[lisnup65]

thanks for the replies so far. you all have been very helpful.

i am still not sure if i want to get the 12:1 piston. 100 octane near me was 4.00 a gallon a couple years ago. i wonder how much it costs now.

spending $4 everytime i ride is not a big deal to me. i dont know how much fuel i will be going through. havent been riding atvs for years now.

what octane is recommended for the 10.25:1 piston? is 94 good?

i am not interested in other performance upgrades, if i dont change the piston i was thinking about a larger rear sprocket to increase power. i missed one on ebay. dont know where they sell them new.


Just use Premium unleaded and you will be fine.

The larger sprocet will help. They are available at most any parts store. If not I have a number for a place that custom makes for you at around the same cost of a good sprocket.

The cam and springs is a serious option to adjust and increase the power of the machine. You can get them for different purposes such as lowend and midrange increase or for highend. With exchange of your cam it will run around $110.00, plus the heavy duty spring set at $120.00. You do the work and total increase would run around $270.00 with gaskets. The motor will come alive! I have a buddy that reworked his a few years ago with the race cam set-up. Night and day response and attitude of the motor.

Again good luck in your choices.

Dave

[Howdy]

I had a 12:1 in my 350x that got stolen. It made it very hard to start compared to stock. It kicked like a mule. How ever once running the power was nice. I did have to run premium fuel to get it to run correctly.

I have decided a 10:1 or so is a plenty for me. I currently am running a stock piston in my 350x. I must be getting old because it's enough power for me. lol

Howdy

[200x Basket]

1st of all high octane fuel burns SLOWER the ping you hear is preignition (detonation) and it WILL burn a hole in your piston or bust the top ring land. unless you race i would stay at the 10:1 piston. compression does make Horsepower but more can be gained from a cam, carb, exhaust, port and polish. i am sure some 350x's can keep up with a stock 250r but if he is modified i dont think it is possible. i would practice the launch and holeshot to beat him.

[plkmonster2]

i am thinking of goin to a 10.25 wiseco on my 225 dr. is that ok for sport use? i am going to run 91, which is about 2.20 right now (should go down after the war). is that ok too? also, after i do that, i was thinking of getting a web cam. finally, do you need to rejet after you go up in compression?

[lisnup65]

1st of all high octane fuel burns SLOWER the ping you hear is preignition (detonation) and it WILL burn a hole in your piston or bust the top ring land. unless you race i would stay at the 10:1 piston. compression does make Horsepower but more can be gained from a cam, carb, exhaust, port and polish. i am sure some 350x's can keep up with a stock 250r but if he is modified i dont think it is possible. i would practice the launch and holeshot to beat him.
Sorry about saying faster, I did mean slower.