Just purchased a 400ex! I would like to do some engine upgrades, I've read an awful lot of other forums looking for the answers on what to do but it seems I have a different path in mind than other members, can't find the answers to my questions. I believe its mostly stock, has a kn air filter lid and a white bros slip on exhaust, sounds good, decently quick, but I want faster. Thought about just saving up and buying a 450 of some kind but I want to weigh my options as I don't want to spend another 1-3 grand on something else. I see a lot of people looking to bore kits, but quite a few issues on 440, seems 426 is safer! I would like to go to 426 or stay at 397, don't know what brands are good. Seems a lot of people like the hot cams and je high compression piston. Was wondering where I should get a 426 kit and if stage 2 would be appropriate with a 12:1 Je piston would be a great route? Just wondering if this is the right route to go and what to shop for on the bore kit. Also wondering about adding a 05 450r carb?
99 400ex, Interested in engine upgrades.
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Sorry my answer is going to be short and sweet. I have a flu.
I would stay away from the 440, they tend to over heat. I have the 416 bore on my quad and I have never had a problem with it. Slammed ranger will fill you in with more. He has recently went with the 450 carb too. He's the man for the job
I would stay away from the 440, they tend to over heat. I have the 416 bore on my quad and I have never had a problem with it. Slammed ranger will fill you in with more. He has recently went with the 450 carb too. He's the man for the job
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4,390 Posts
My first question is what is your plan with this quad? Mx, drag racing, sand dunes, gncc, trail riding? 400's can be built to out run 450s. But you need to be ready to spend some money. The plus side is in the end you get an extremely reliable version of a 450. Which in the real world(not the 450 owners heads) is dang near impossible.
I have intensions of taking it to the dunes, but it will not be a everyday thing for me, maybe once a month depending on the buddies and I's schedules. I mainly ride at my place and a smaller gravel pit, few jumps and trails, racing each other, nothing serious. Occasional wheelies and donuts, just goofing around. Potential plans of taking it to the UP for some other trail riding type of situations.
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Gotcha. Well if you have any intensions of going to the dunes you will want some cooling mods if your going big bore at all. Honestly i would suggest a 416 kit. You can get the stock sleeve bored and it will save you some money that way. 100% gotta upgrade the head studs. With gt thunder or something like them, use cometic metal gaskets. You will be blown away the power difference from stock bore with a pipe and filter to a 416 even. The power difference is night and day. Add a cam and your really in business. And you want to ride the back of a monster get a fcr carb. If you grow out of the power and end up wanting even more down the road you can get the jug sleeved using LA sleeves and get the 426 kit put in. Im partial to wiseco for piston kits. But JE is good aswell. I would suggest avoiding namura.
Ru by chance in michigan? You mentioned the UP is why i ask. Were headed to bundyhill in jerome michigan on sunday for the first ride of the season.
Ru by chance in michigan? You mentioned the UP is why i ask. Were headed to bundyhill in jerome michigan on sunday for the first ride of the season.
Yes I am in Michigan, Stanton to be exact, 45 minutes North East of Grand Rapids!
I mentioned the 426 because I found a 12:1 je piston and that seems to be the highest compression in that area of bore. As far as boring I would have to find a shop to do it, don't really know who all would do it
around my area! What size fcr would I need? Would like to know how much about and honestly part numbers to certain parts that I would need, new to the sport quad world really. I am a Auto Tech at my local GM Dealership so I should have most of the tools and mind to understand hopefully how this stuff works.
I mentioned the 426 because I found a 12:1 je piston and that seems to be the highest compression in that area of bore. As far as boring I would have to find a shop to do it, don't really know who all would do it
around my area! What size fcr would I need? Would like to know how much about and honestly part numbers to certain parts that I would need, new to the sport quad world really. I am a Auto Tech at my local GM Dealership so I should have most of the tools and mind to understand hopefully how this stuff works.
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4,390 Posts
You can get 12:1 in CP also but JE is good. I got a 08 yfz450 fcr39mm on my quad. Getting you a part number for the carb isnt gunna help much. They are like 1500 dollars new. You can get a take off on ebay from a blown up yfz. (And there are alot of blown up yfz's lol). To be honest i buy alot of stuff on ebay. I got my piston kit, gaskets, cam, carb, and alot more on ebay. The one thing you will want to do is find a machine shop that can bore the cylinder and install the hd studs. Aside from that you will have to ship it all out. I do know that snure interlocking(which is the place that has the rights to make gt thunder studs) can do everything you need done. You would have to ship it all to him though. Hes in smithville OH. About 45 minutes from me. And i have driven my stuff to him a few times. But i know he is recieving parts from all over the world on a daily basis.
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Welcome to the forums. I do not get on here as much as I should........
One thing that has not been mentioned is the if you are going to bore your stock cylinder 87mm is the max you will want to go with out any heat concerns. If you decide on a 88 or even an 89mm DO NOT buy the KIT that comes with the cylinder. Buy the piston and gaskets separately and buy a 88mm sleeve and have the machine shop install it into your good cylinder. go to www.p4quads.com and get the head studs. This is Jeff's website. EBay occasionally has them. Have the shop install them when they fit the sleeve. The 440 (89mm) is very reliable when done properly (sleeve) there is almost no change in heat from OEM. Honestly you would make better power from a stroker build with a smaller Piston than if you went with a big bore kit only. Example: 74mm crank kit with OEM bearings and an 86mm HC Piston will get you 430ccs.
Either way you decide just do your homework and get the correct parts.
When you decide to move forward with your build, make a list of all of the parts you are replacing so that you do not forget anything. Here are a few parts that are a must IMO
1. Replace the timing chain with a 02-08 CRF450R/450X- 06-08 TRX450r/450er timing chain. Part # 14401-MEB-671
2. Replace BOTH timing chain Guides
3. Timing tensioner OEM or Manual (I prefer manual)
4. Oil Pump (New OEM ONLY)
5. OEM Clutch cover gasket
6. GOOD gasket kit w/ Good valve seals and a metal valve cover gasket (OEM) if COMETIC doesn't come with one? Some of their kits don't
Inspect the clutch frictions, steels and basket too while you have it apart. Use a good assembly Lube during installation. coat the cam, cam bearings liberally too. before you install the valve cover remove the 10mm check bolt under the oil lines and pour some oil in the cam chain hole until it runs out of the check hole. After assembly leave the spark plug out and crank the engine over for 10-15 sec to get the pump primed and fill the orifices in the engine. Check compression before break in then after. use a good JASO_MA/MA2 oil. I run Rotella T-4 15w40. Good luck and keep us posted on your progress.....
One thing that has not been mentioned is the if you are going to bore your stock cylinder 87mm is the max you will want to go with out any heat concerns. If you decide on a 88 or even an 89mm DO NOT buy the KIT that comes with the cylinder. Buy the piston and gaskets separately and buy a 88mm sleeve and have the machine shop install it into your good cylinder. go to www.p4quads.com and get the head studs. This is Jeff's website. EBay occasionally has them. Have the shop install them when they fit the sleeve. The 440 (89mm) is very reliable when done properly (sleeve) there is almost no change in heat from OEM. Honestly you would make better power from a stroker build with a smaller Piston than if you went with a big bore kit only. Example: 74mm crank kit with OEM bearings and an 86mm HC Piston will get you 430ccs.
Either way you decide just do your homework and get the correct parts.
When you decide to move forward with your build, make a list of all of the parts you are replacing so that you do not forget anything. Here are a few parts that are a must IMO
1. Replace the timing chain with a 02-08 CRF450R/450X- 06-08 TRX450r/450er timing chain. Part # 14401-MEB-671
2. Replace BOTH timing chain Guides
3. Timing tensioner OEM or Manual (I prefer manual)
4. Oil Pump (New OEM ONLY)
5. OEM Clutch cover gasket
6. GOOD gasket kit w/ Good valve seals and a metal valve cover gasket (OEM) if COMETIC doesn't come with one? Some of their kits don't
Inspect the clutch frictions, steels and basket too while you have it apart. Use a good assembly Lube during installation. coat the cam, cam bearings liberally too. before you install the valve cover remove the 10mm check bolt under the oil lines and pour some oil in the cam chain hole until it runs out of the check hole. After assembly leave the spark plug out and crank the engine over for 10-15 sec to get the pump primed and fill the orifices in the engine. Check compression before break in then after. use a good JASO_MA/MA2 oil. I run Rotella T-4 15w40. Good luck and keep us posted on your progress.....
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what they said .. the 440 can be reliable.. the issue is the 200.00 440 kits that are complete junk .. folks bolt these on then immediately try to sell the quad .. if you stick to quality parts then you will be ok .. i like the idea of staying 416 or so cc .. for extra cooling you can run the oversized oil tank , air scoops ,and or larger oil cooler .. even add a fan to the oil cooler .. also other then the fcr carb you can run a 04-05 trx 450r carb .. it is rather large and requires a dent to be pushed up in the fuel tank .. it can provide the same a mount of power that a 37mm- 39fcr will have but is a round slide carb so the throttle is less sensitive .. flat slides like the fcr make the throttle very snappy feeling ..
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\one of the best 400 ex upgrades is front shock replacement the 06 400/450 kawasaki front shocks bolt on with no mods and are nice ( ones with reservoirs ) and yfz fronts can be used with a little grinding on the upper shock mount. also honda 450 fronts with a little modding .. the stock 400 rear shock is great if in good condition. ( also some of the newer front shocks will be too tall . I do not know the exact years but want to say the 2010+ yfz comes with taller front shocks )
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\one of the best 400 ex upgrades is front shock replacement the 06 400/450 kawasaki front shocks bolt on with no mods and are nice ( ones with reservoirs ) and yfz fronts can be used with a little grinding on the upper shock mount. also honda 450 fronts with a little modding .. the stock 400 rear shock is great if in good condition. ( also some of the newer front shocks will be too tall . I do not know the exact years but want to say the 2010+ yfz comes with taller front shocks )
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