12:1 350x guys, I need your help

[p26575r16]

I have an '86 350x with a 12:1 piston in it. What are you 12:1 guy's running for gas? When I originally built the engine I was running VP leaded 110 octane in it, but found I had some issues with the "perfect condition" head I bought for it off of ebay (valves seats were messed up, leaked compression. Lesson learned: Alway's double check). I have just got around to replacing the head and was wandering if I really need the 110 (It's like $7 a gallon out here, and that's the cheapest I can find it). I know I can just try it on 93 and see if it knocks, but the dunes are 90 miles away and there are no gas stations close to them that sell 110 (I know I can also get away with 93 on the trails here, but the dunes ask for a lot more out of your engine). I have been told 93 will be fine by some locals here, but I thought I'd ask some of you that actually have 12:1 350x's. Thank you

[300rman]

take some of both fuels. try a half-tank of 93, and if it knocks, fill the other half with VP, therefore you run a 50/50 mixture of 93/race fuel.

or, you can go in smaller increments, say try 25% race fuel, 75% 93, then add more race fuel as/if needed.

[p26575r16]

I was thinking of doing that. I do love the smell of race fuel, just hate the price.

[Tecate 50]

I agree....take both to offset the price, it can get expensive! You are right the Dunes are demanding when it comes to the motor! I run C-12 and it smells good.....but its so damn expensive! I always wanted to ride a 350x with the big compression, must be a stump puller!

[p26575r16]

It ran good with the 8:1 piston in it. I really have not got to ride it with the full 12:1 yet due to the fact that the head was junk. It was considerably more powerfull (and loud) with the 12:1 even with the leaking valves though. I cannot wait to get it back out. This trike is pretty much just going to be run only at the dunes, I don't have a spark arrestor on it and the forestry cops don't like that here in Reno. The local dunes are pretty much the only place I can run it legally.


I agree....take both to offset the price, it can get expensive! You are right the Dunes are demanding when it comes to the motor! I run C-12 and it smells good.....but its so damn expensive! I always wanted to ride a 350x with the big compression, must be a stump puller!

[Tecate 50]

Thats cool.....me and my buddies are heading to Little Sahara in Oklahoma in April. We went there last year for the Rampage, it was a blast!

[eyecekold1]

I have run 91 in mine but it gets way hot, way fast and fuel economy goes down. Jetting also changes between the 2 fuels. On race gas I am a little lean on 91 way rich. I find that the bike has better performance on the race gas too. My race gas is 111 and is about $5-$6 a gallon at a local place called Rhinehart oil. Smells amazing. I can run up to 3 days on 5 gallons of race gas. Its about $35 to fill my 6 gal container.

[Dirtcrasher]

I just get 5 gallons of race gas $$$$$$ and mix it with 93 octane, then it doesn't hurt so much.

I'm using 12:1 too, just on a 200X and not your 350X.

[audioworks04]

12:1 is kind of borderline, you may be able to get away with 93, but would probably be best off with a 50/50 mix of 93 and 110. I run straight 110 in my 450 but I am not sure on the compression of it as i bought the motor used with a fresh rebuild, and all the guy I got it from could tell me is that it is a high compression piston. Have not tried a 50/50 mix, but I only ride it at the dunes burn less than 5 gallons each trip in it, so not that big of a deal.