I was talking to someone at the races last night and they said if I ran 110 octane in my 400ex even though it doesn't have a high compression piston it would give it more throttle response and maybe 2 or 3 hp gain. Has anybody heard of this and is this true? Because if so I'm gonna start using it. Also, I have heard that the 440 kit on the 400 is not very reliable if you push it in moto-x. Anybody know about this? What about JE pistons? Any help would be appreciated.

 

Actually, you would probably lose throttle response with the high octane fuel. Octane doesn't help really help combustion. The reason it is used in high compression engines is that it prevents detonation, which occurs when the fuel ignites before it is supposed to. Detonation destroys the engine if left alone for too long, that is why many people blow holes in their pistons. If you are running a stock 400ex, then Premium gas is fine, I think that the max you would want to run would be about 100 octane, which you can achieve with additives. But this really isn't necessary.

 

Do not use race gas! You are wasting your money if you do. My 440's compression is 11.5:1 and I run 100 octane. Any higher and I would be wasting my money. JE makes excellent pistons. I have been told they are lighter than Wiseco which makes for a quicker reving machine. I haven't heard any problems with 440 kits. It's the most popular engine conversion for any make and size of engine on the off-road market, so it's been tested. Before you drop about $1000 for the 440 you might want to try a 400 high compression piston, race cam, pipe, K&N and a rev box. Thats gonna get you 33-35 hp, a 7-9hp gain. In addition, it will rev much quicker and higher. Your average 440 kit will put out 36-38hp and if you really hop it about 44hp. that's over $2000 for that kinda power. good Luck. -RT

 

To start standard combustion style engines with less than 200 pounds of compression cannot effectively burn more than 100 octane. So yes it is true you would be wasting some money. Try a 50/50 blend of race fuel and premium unleaded. Race fuel DOES NOT CREATE HORSEPOWER, it simply causes the motor to combust more effectively, unleashing power that the motor has been able to produce all along. So it is there you just did not know it. A race fuel has a longer burn so when the piston is on the down stroke it is being forced at a greater rate (due to stall from the longer burn) when it goes down faster, it comes back faster and so on. If you were to set 87 octane fuel and say Torco 110 octane race fuel side by side and lit them both on fire, the 110 would still be lit when the 87 was out. Now 440 big bore kits are very effective and not quite as much money as reported. To start Wiseco and JE pistons are owned by the same company named Dover Enterprises. Most your 440 big bore kits will come with a JE piston because they have a slipper piston skirt design which allows the piston to rev a little more. Big bore kits (piston,gas. set, sleeve) are $270.00, race cams $150.00, black box rev kit (1200 more rpm's) necessary for this mod $110.00 + add pipe of your choice and some machining labor. Get the 11:1 no matter what kind of riding you do!

Matt Sheldon (Magic Racing Sales Manager)

 

Hey motomatt, do you have JE pistons at Magic Racing? I just want to go to a 426 though. Do you have cams too? If not, where do you recommend that I get them from. I am in the process of saving money right now to make my 400 into a 426 with a race cam, rev kit, 11:1 compression, and I think the DMC exuast. I am going to do it all at once though, because I don't want to lose a lot of riding time tearing it apart a couple times. Thanks.

 

Matt,
Could you tell me where in Michigan I can take a stock 400 and have them install a 440 kit? Just how much will it cost? I want an exhaust system that is race quality that includes a head pipe to maximize my engines new potential. What about gearing? What about a K&N? What about a Jet kit? Everything together must be significantly cheaper than a $1000.
Basically Matt, a 440 kit is gonna cost the average guy about a $1000 when you include the pipe and the labor. Are you gonna run stock gearing? No. You need a new sprocket or sprockets. What about a K&N filter and a Jet Kit? You'll need both of those. So as reported, you're gonna spend about $1000 for a 440. And for 99% of the population a few hundred more because WE have to have it done through mail order. -RT

 

Rob,
If you include the pipe then yes you will be at about or under $1000. But the pipe really should not be estimated in the 440 kit because the majority of people are going to purchase a pipe of some sort any way whether the 440 kit is installed or not. It is the 440 kit we are pricing and not the pipe! To efectively run the 11:1 std. size piston you are reporting (which can run very well) will only save the average guy (your terms)$100-$120 in parts and at the most $130.00 in machining labor. If your stock cylinder was worn you would need to spend another $40-$50 for a bore job so now you are at only another $50-$70. Why? well to start the 11:1 wiseco really needs a high lift cam of some sort to flow properly and the cams are the same price no matter which lift you choose. Second a rev box is necessary the minute you install a pipe anyway. The 16T sprocket is only $19.95 and recommended by most your pipe manufacturers. (Do the 440 kit when it is spkt kit replacement time and this will be basic maintenance). A K&N filter is $39.95 and the necessity of a jet kit is not that great! For 90% of altitudes the stock needle is perfect (it is a little rich so this works with this mod) so spend $4.00 for a larger main (158-165) and $4.00 for a pilot (40-42) and be happy. Heck most companies give you the main jet with the purchase of a pipe. I was in no-way intending to criticize your intelligence, I simply was correcting some of your pricing (only from everyday experience) My comments at this site have nothing to do with my business. I simply am trying to help educate those who need help on my OWN time. I could care less if you buy anything from me I just want people to do it the right way the first time. I welcome anyone to ask me any questions they might have.

Sorry if I offended you,

Sincerely,
Matt Sheldon (Magic Racing Sales Manager)

 

Is it feasible to install the cam and hi-compression piston by myself on my quad with my tools at home. Ive never worked on a quad but i have built motors, adjusted valves, etc.. on regular cars, so i am somewhat familiar with the basics, if at all it is that basic.

 

Yes, it is entirely feasable for you to do the work yourself. A service manual is a nice help. The only items you will have to have done elsewhere is the cylinder boring/resleeving, and you will have to have a shop change the cam gear mounting flange for you. The rest is cake for someone with some mechanical ability. I did it myself, and I laugh at these $1000 to $2000 numbers.

 

Compression ratio increases are possible with higher octane fuel. While octane numbers are cheap and easy to get, getting the fuel to burn properly and most importantly effectively during the few milliseconds while it is compressed and then ignited is the important part.

I really doubt that "slower" burning fuel is going to creat the power. As the crank rotates the once compressed and now expanding gas is losing pressure, not creating more power. Everything has to jive within a VERY short amount of time. You've got to get the maximum potential out of the very short power stroke before the valve or exh. port opens and pressure is lost and the motor has to free wheel around again to the next cycle(s).

That's why higher compression ratios create more power, the "bang" is greater due to it being more compressed thence is creates more force on the piston crown, creating more power. If you have a fuel that burns too slow, it's not going to completely combust within the given crank rotation and power is going to be lost. The crank is going to rotate independent of whether or not the mixture is fully combusted.

Higher compression ratios make HP and torque...higher octane fuels facilitate that.