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Discussion Starter #1
Looking at a TRX 400 that has a big bore 440 kit, from what I have read poking around the forum is there 440 big bores blow head gaskets like its their job, overheat cause not much material left to the cylinder and are not to reliable. I have read about a double oil cooler mod to make them run cooler.

The one I'm looking at has stage 2 cams with the 440. would it be possible to go back to the stock bore? I guess just buy a standard bore piston and cylinder? what about the cams?

Would it be more cost effective to do the double oil cooler mod to keep it running cool? or will I still have to deal with the blown gaskets.

This is the machine im looking at, can you guys tell what front shocks are on it?
 

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A 440 kit is very reliable IF it was done correctly the first time. Sleeving the cylinder with an 88mm sleeve then final boring to fit the 89mm piston. GT Thunder head studs are an absolute must on any 400 bore. Use a good multilayered steel gasket like cometic also. An oversized oil tank is required for 440 builds, the extra quart helps cooling. Have the head and cylinder surfaces machined too. This way your mating surfaces are true. With the GT Studs you can torque to 45 ft.lbs as opposed to the typical 33. Look at my thread on my build in my signature. Good luck and keep us posted

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I agree^^ to an extent. The 440 kit no matter how much extra work you do and cooling you add is still at the very limit of what the motor can do. You are going to go through rod bearings at an accelerated rate. A stock clutch is going to slip instantly with that much power. And no matter how much added cooling you add the cylinder is so thin its going to get hot. It will never be as reliable as stock bore or even a 416 or sleeved 426 period. But it can be made to not blow headgaskets as much and be a good bike needing rebuilt every few years. Those shocks to me look like stock 450 shocks that were sent to works and had a triple rate spring kit and im sure re valved.
 
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I agree^^ to an extent. The 440 kit no matter how much extra work you do and cooling you add is still at the very limit of what the motor can do. You are going to go through rod bearings at an accelerated rate. A stock clutch is going to slip instantly with that much power. And no matter how much added cooling you add the cylinder is so thin its going to get hot. It will never be as reliable as stock bore or even a 416 or sleeved 426 period. But it can be made to not blow headgaskets as much and be a good bike needing rebuilt every few years. Those shocks to me look like stock 450 shocks that were sent to works and had a triple rate spring kit and im sure re valved.
Man i know guys that have had years of great service from 440 builds.... They're not making much more than my 426.. Its 1mm you know how big 1mm is? Lol i can guarantee my head temps are just as cool as a stock 400 or better... Proper jetting will also play a huge factor with cooling..... Ive never heard of crank bearings failing because of a 440 build either... My spare engine is going to be a 440 stroker.. Thats a +4 crank on a 89mm piston .. May do 485 i havent decided.. Lol

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Thanks for the info guys, how much work would be to get it back to the stock 400 engine? would it even be worth it? guy is asking 2900 for the machine, may be able to get it for 2500. what do you think of that price with the beadlock and shocks and whatever else you can see on the machine that i cant lol

BTW its a 2006 if that makes a difference
 

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Thanks for the info guys, how much work would be to get it back to the stock 400 engine? would it even be worth it? guy is asking 2900 for the machine, may be able to get it for 2500. what do you think of that price with the beadlock and shocks and whatever else you can see on the machine that i cant lol

BTW its a 2006 if that makes a difference
You would need to replace the cylinder to get back to stock. Id leave the cam and add a 04-05 trx450r carb...

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Thanks for the info guys, how much work would be to get it back to the stock 400 engine? would it even be worth it? guy is asking 2900 for the machine, may be able to get it for 2500. what do you think of that price with the beadlock and shocks and whatever else you can see on the machine that i cant lol

BTW its a 2006 if that makes a difference
I don't want to sway you, just food for thought and to keep your options open. I sold this 2006 450R late last year for $2300. It had minor mods and pulled pretty hard. If I would have kept it I would have made the wheels match but other than that not too much.



Rob
 
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I would rather have a stock 450 (any of them really) than a souped 400ex

Rob
Them stock 4fitties do make for a good snack... Lol jk... I have an 06

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I'm not saying the 450s are the end-all quads, especially when pretty much stock, but $2900 for ANY 400ex is too much in my book. They normally sell for around $1500 here for a nice one.

Rob
 

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Discussion Starter #11
Thanks for the info guys, how much work would be to get it back to the stock 400 engine? would it even be worth it? guy is asking 2900 for the machine, may be able to get it for 2500. what do you think of that price with the beadlock and shocks and whatever else you can see on the machine that i cant lol

BTW its a 2006 if that makes a difference
I don't want to sway you, just food for thought and to keep your options open. I sold this 2006 450R late last year for $2300. It had minor mods and pulled pretty hard. If I would have kept it I would have made the wheels match but other than that not too much.



Rob
I have been looking at the 450s aswell. to be honest I live in Canada and prices up here seem to be way higher then what our southern friends pay. I have found some 450s cheaper then the 400ex, from what I understand there is no reverse and they require way more maintenance then their baby brother the 400. is there any 450s with reverse and electric start or are the 450s really just ment for racing?
 

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Agreed^^^ 2900 is over the moon! It better have another full 400ex for parts with it! And if it dosnt have a title its worth even less. People ask some pretty funny prices!
 

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The KFX450R, KTM 525XC and Polaris 525 race quads have reverse. All three are electric start. I also agree that $2900 is too high.
 

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unfortunately those are roughly the going prices around here:icon_ cry:

I wish I could find them for the prices you guys are paying but thats just not possible. and yes all the ones I am looking at have ownership, I wouldn't buy one without it
 

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Ah I didn't realize you were in Canada. I have heard prices are significantly higher for you guys.

Rob
 

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Ahh didnt realize you were in canada either. Someone local to me is trying to sell an 02 400ex says "Built" for 3700. My buddy responded just for fun and asked if it came with a titled 450 with nothing wrong with it that just isnt pictured or what? He never got a response sadly. LoL
 

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I agree^^ to an extent. The 440 kit no matter how much extra work you do and cooling you add is still at the very limit of what the motor can do. You are going to go through rod bearings at an accelerated rate. A stock clutch is going to slip instantly with that much power. And no matter how much added cooling you add the cylinder is so thin its going to get hot. It will never be as reliable as stock bore or even a 416 or sleeved 426 period. But it can be made to not blow headgaskets as much and be a good bike needing rebuilt every few years. Those shocks to me look like stock 450 shocks that were sent to works and had a triple rate spring kit and im sure re valved.
Man i know guys that have had years of great service from 440 builds.... They're not making much more than my 426.. Its 1mm you know how big 1mm is? Lol i can guarantee my head temps are just as cool as a stock 400 or better... Proper jetting will also play a huge factor with cooling..... Ive never heard of crank bearings failing because of a 440 build either... My spare engine is going to be a 440 stroker.. Thats a +4 crank on a 89mm piston .. May do 485 i havent decided.. Lol

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I would never trust a 440 no matter who built it. I would save the money and labor and crf450 swap and then destroy cities! LoL
 

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87mm bore on a +4 stroked crank with a Falicon hbeam rod.= reliability... Make more power than a 440 bore too

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