12:1 stock bore or 440

[Dubs_Tech]

What do you guys recommend? I have no problem running race fuel but i cant decide whether or not to just go with the standard bore high compression piston or the big bore 440 kit at 11:1.

[XXXRACER165]

440;)

[Dubs_Tech]

HAHA ok, why though, id like the pros and cons before i make a purchase.

[gcart2]

OK I GOT OFF THE PHONE WITH SOME1 FROM DUNCAN AND THEY SAID THE 440 IS NUTHING. ALL IT IS IS MAKING UR PISTIN A LITTLE BETTER. IF U R DESPERATE FOR SPEED DO IT. WHAT R U RIDING? I CAN LEAD U IF U TELL ME WHAT U DO WITH IT?

[Colby@C&DRacing]

depends on the type of riding you are doing I would do either a 416 or a 426 is you go with 13:1 compression I would also add a heavy duty rod. I have noticed the guys that are heavier tend to like the 426 better, make sure you add a cam airfilter and full exhaust to compliment the high compression piston.

[Dubs_Tech]

Well i do alot of aggressive wide open riding out here in Arizona. Most people i ride with have 450s. Id like to have a set up somewhere stronger than them. Im a technician for volkswagen & building motors is my specialty, so buiding the actual motor wont be a problem, but making my decision on what internals to go with are confusing. I need something strong though as i ride hard, especially since i ride with quads that are faster than mine.

[gcart2]

WANA HERE THE TRUTH? UNLESS U R WILLING TO REBUILD UR BIKE EVERY MONTH STAY AWAY FROM A BIG BIG BORE. A M416-426 IS GREAT. PUT A 426 DO A FULL EXHAUST DO SPRINGS AND CAM. ALSO GET PORT AND U WILL BE READY TO ROCK AND ROLL. I HAVE A 400EX IN THE PROCESS OF A TOTAL REBUILD. IM GETTOING 426 CUZ IM "POOR". I CAnt afford to tare down all the time. stay small bore and do everything else and u will crooooooze.

[Dubs_Tech]

How does having a bigger bore make it less reliable?

[GPracer2500]

Originally posted by Dubs_Tech
How does having a bigger bore make it less reliable?

Smaller sealing surface between the head and cylinder for one. Maybe other reasons too. But building it properly and not taking shortcuts is more important than bore size for maintaining reliablity, IMO.

To be honest, I'd re-evaluate your expectations for your 400EX. Or, think about how else you can get there. It would take one hellva 400EX to be "somewhere stronger than them [450s]". Of course, it depends on the 450s to a degree. Some are stronger than others depending on what years they are and what mods they may have. There are plenty of 400EXs out there than can run with and beat showroom stock TRX450Rs, for example. But the 400EX was never meant to be a 450 killer. Sure, anything is possible with enough money, know-how, and skill. But ask yourself--do you really want an no expense spared 400EX? Or do you really just want a quad that can run with and possibly beat your buddies' quads?

To do what you're wanting to do: I think you'd be happier in the end if you sold your 400EX and bought a newer, faster, higher performance oriented quad. In my experience, the 400EX is a bit of a slippery slope. You start modding it to try and reach a lofty goal but you're never quite satisfied. And the further you go the harder it is to cut your losses and start fresh.

Now I know some folks are going to chime in to defend their 400EX builds and tell us how fast and reliable they are. That's fine. But where I'm at I don't see 400EXs competing in the way you're describing, Dubs-Tech.

I love the 400EX but I think it looses its luster when we try and turn it into something it's not. Modding them is fine--good even. But once you take it past a certain level, only do it for the sake of doing it, NOT because you're trying to build the fastest quad around. In other words, if you love building engines and want to challenge yourself by building the fastest and most reliable 400EX you can, that's fine and a valid pursuit. But that's a different goal than just wanting a faster, better quad.

Personally, I like the basic 11:1 416, cam, intake, exhaust 400EX build. If you've got extra money then get a carb and do some head work. If you need more out of the 400EX then maybe consider a stroker, but probably it's time to start thinking about a different quad. Before, all there was (for four strokes) was the 400EX so we built them to the max and were happy. But now there are more options.

And don't forget the suspension!

$0.02

[XXXRACER165]

Idk, my 440 is stone reliable. With my setup you could can it in first gear for 300 yards to the rev limiter and still would be in shape for a race. You just have to rebuild it the right way. Oh and you were right GPRacer about others chiming in, LOL:p

[Dubs_Tech]

Yeah im not looking to build the fastest quad around, nor am i looking to sell mine, but all i do want is to be able to ride with them and not have to beat the living hell out of mine to do it. Get my drift? So would a basic 11:1 416 w/ cam etc at least make it fun for me instead of a loosing battle.

[XXXRACER165]

Yeah probably.

[Got Boost]

a jump of 40 cc is quite noticable, and when you throw a good cam,450 r carb, and a hc piston and full exhaust, I will keep up with or beat any 426 unless its ported. I was racing ported stock bores at sand mountain utah, on the face and staying right with them if not winning by a bike length, it is all on how and who builds your motor.

[Dubs_Tech]

So is it in your opinion better to keep stock bore but higher compression or increase bore size? Which would yield more useable power.

[XXXRACER165]

A 440 will have more controlable power. On the other side, stock bore and 12:1 will give you more of a powerband hit to it.

[Dubs_Tech]

Should i do the 440 kit at 12.5:1 or 11:1? Id have to run race fuel in the 12.5:1 right?

[GPracer2500]

Originally posted by Dubs_Tech
Id have to run race fuel in the 12.5:1 right?

Yes

[davetheslave]

If you dont mind using race gas, go with the 12.5:1 440, I have one on my bike, and it keeps up with the 450's. But make sure you do the heavy duty head studs.

[Dubs_Tech]

Yeah using race gas wouldnt be a problem as its all i can run in my race car as well. Theres a gas station right down the street from my place that sells 101 unleaded VP gas. Would this be a high enough octane or would i need higher? If so id probably just go with the 11:1. Is there that big of a difference in power between the 12.5:1 & 11:1?

[gcart2]

im goin threw same prob mystelf. keep me posted =)

[XXXRACER165]

12:1 will give you more juice than 11:1, and I'd run aviation fuel (110) octane

[GPracer2500]

Originally posted by XXXRACER165
....aviation fuel (110) octane

There's no avgas I'm aware of that is 110 octane. And even if there was, 100LL is the only avgas that's available anymore (except for rare cases). 100LL = about 100 MON (99.5 is the minimum spec but most will test slightly above that). For reference: premium pump gas = about 88 MON, most "110 octane" race fuels are around 105 MON.

[XXXRACER165]

There is 110 av gas in MN as for AZ idk

[GPracer2500]

Originally posted by XXXRACER165
There is 110 av gas in MN as for AZ idk

What gas is it? Specifically, what is it called? Is that 110 number a MON rating, RON rating, Lean Mixture Rating, Rich Mixture Rating, or what?

Avgas is a very universal product. It doesn't change by region as you suggested (unlike mogas). I'm aware of 11 different types of aviation gasoline that have been used since the 1950s. Most of them have disappeared completely. 100LL is BY FAR the most common and even among the 2 or 3 others that are still being made, none of them have a knock rating that corresponds with the number 110.

If you can support your statements with something that's meaningful and able to be corroborated, then great--I'll be happy to listen and learn. Otherwise I kinda have to assume you don't really know what you're talking about. If that's the case, don't take it personally. Most people don't know there *** from their elbow when it comes to how octane ratings are assigned to avgas. You wouldn't be the first person who's been fed a load of crap about gasoline (I'm assuming someone told you "such and such avgas is 110 octane").

Look, I'm not trying to be a jerk. But if someone says "do this" and I respond with "that doesn't make sense, and here's why" and they say "your wrong, I'm right" then I'm gonna ask them to back up their position. I'm particularly senstive about gasoline topics because there's so much mis-information about gasoline that gets spread around by people who don't know any better.

:uhoh:

[XXXRACER165]

RON rating

[GPracer2500]

Originally posted by XXXRACER165
RON rating

So what fuel is it? Where are you getting your information?

I have to believe that the fuel you're talking about is 100LL. It is not normally tested for RON though--only MON (ASTM D2700) and the Rich Mixture Rating (ASTM D909).

Nonetheless, I do have a study performed by Conoco Phillips that found the RON of 100LL is ~106.5. The only reason 100LL was tested for RON in that case was as part of a study on an experimental, ethanol based aviation fuel. RON is not a specification that defines aviation fuel.

But regardless of the accuracy of your 110 RON figure, we shouldn't be using RON anyway. MON is the superior test method for our engines and is more widely used. If you are going to throw around RON ratings you should specify it as such. To do otherwise is misleading (and a tactic used by some racing fuel maufactures to make the labeling on their fuels look better than the actual deto resistence of the fuel can support). It is always appropriate to specify which type octane rating you're refering to. Otherwise the number looses meaning. A single fuel could be 95, 100, or 105 (for example) octane depending on which type of octane rating you're using. The only exception is pump gasoline which in North America is always assumed to be the average of RON and MON.

Again, it's not my intent to bust your balls. Rather, I'm trying to encourage you to be specific so I (and others) will know what it is you're talking about.

[XXXRACER165]

oh ok

[Dubs_Tech]

Hey guys how about we get back on topic here.

[XXXRACER165]

It depends on what cam your gonna use. If you go 12:1 440 and a stage 1 Hot cam, you will need more than 100 octane fuel. It will detonate. A longer duration cam (stage 2), will lower the compression a little and should be fine. I went 11.5:1 and stage 2 cam on mine and it has tons of smooth torquey power. I still run aviation fuel just to be safe though.

[davetheslave]

I have never tried 101 octane, I have always ran Sonoco 112 and have never had any problems. You will need to to a bigger oil cooler though, the stock one just isn't big enough.

[gojk]

How about rod reliabilty with going to 12.5:1. I have kicked around going that high, but I have to assume that since the stock rod is already known as a weak spot in the engine, that 12.5:1 would easily push the stock rod to its breaking point.

Please correct my if I am wrong.

[XXXRACER165]

Nope your totaly right

[davetheslave]

you should do a rod when you go with that kind of compression, but if you put all the solid parts in it the first time, it will be pretty reliable. I haven't had any problems with mine at all, starts every time, and runs great