steve
New Member
Posts: 1
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Post by steve on Aug 13, 2006 19:27:39 GMT -5
i got an 02 400ex and next year i am planning on a build, i dont kno wut engine to use, the crf 450? or the yzf 426? my 400 just dont got the power no more but the engine is brand new built by baldwins so im gonna run it for the reast of this year and most of next year then start the build, im goin to a joint voational skool and this will be my first year and i can bring my quad in and work on it so i figure next year i will do it when i have the time and the money cuz im broke from a-arms now..give me ur opinions on which engine would be the best
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Post by gtilley45 on Aug 13, 2006 19:44:58 GMT -5
A lot of people like the power of the CRF. I have one and I have no complaints about it. I have also heard a lot of good about the YZ motors. The power is a little snappier and the ones that are 4 speeds are supposedly one of the best motors for MX. Apparently, the 4 speed doesn't have to be shifted much at all. I like the thoughts of this but I have never ridden a YZ hybrid. Whichever motor you decide on, I highly recommend getting one of the conversion kits so the engine will fit right. JB racing sells a nice one and there are other brands too. I have just heard a lot of good about the JB conversion kit for the 400EXs.
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Post by justanobody on Aug 13, 2006 19:45:55 GMT -5
Pesonally I wouldn't put a big thumper in a 400ex frame cause It will break all to pieces, I had a buddy that did that and his lasted 7 months and it broke in like 10 different spots, and the frame was done by JB racing. I'm not telling you not to do it but in my opinoin i would NOT. As far as what motor to run I have only owned crf's and I have rode 1 yzf 426 punched and stroked to 450 and the both have awsome power but I like the power of the crf better. That is just my opinion, i do know the crf will be more reliable. Not trying to scare you but I will post some pictures of my buddys bike that was converted to a crf that broke in half.
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Post by gtilley45 on Aug 13, 2006 19:52:38 GMT -5
i do know the crf will be more reliable. Mine hasn't been. Actually mine has been quite the pile of chit. After riding it for about 20 minutes, I had to spend 2 thousand dollars on it to get it fixed and running right. I thought it was all fixed until today after I ran a few laps and noticed I had an oil leak.  But I think I just got screwed on mine, all the others I've seen have been good motors. |
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Post by justanobody on Aug 13, 2006 19:55:04 GMT -5
where is it leaking oil?
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Post by gtilley45 on Aug 13, 2006 19:58:02 GMT -5
At the back of the motor, somewhere around the swing arm bolt. I was so pissed when I saw it, I didn't even look for it much. I just put it on the truck and came home. I haven't even washed it or unloaded it yet, I was too pissed to even mess with it.
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Post by jrspawn on Aug 13, 2006 21:43:36 GMT -5
Hey, i have owned MANY YZ's and crf's, and i can personally tell you from expeirence, the yz's are a more reliable engine by far. The CRF's put out a little more power out of the box, but.... Have alot of small problems always happening, they are a good engine dont get me wrong, and all engines have problems now and then, but if your looking for a reliable all around engine, the YZ400,YZ426,and YZ450 is the way to go. If your looking for brunt power out of the box, the crf would be a choice.
Thank you
Justin
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Post by getdrunk on Feb 2, 2007 21:28:54 GMT -5
The yz is more reliable. It uses a oil tank so you can ride longer at less you remove the tank and go wet sump then the oil needs changing every half hour. The yz motor is a little hard to get started but theirs a kicking technike to it and once figgerd out it starts after a couple kicks.
As for power the crf i heard has a little more low end but the power drops off fast and the yz motor keeps pulling till rev limiter which is around 12 thousand. The motor runs hotter than a ex motor too. Mine has a pwr raddy and engine ice and it boils over all the time and my jetting is even a little rich.
The yz motor is known for tranny problums. Well so far my tranny problums were a broken clutch basket cause one of the fins broke and also the clutch is grabby. Like its always gripping a little when i have the clutch lever pulled in so it dont start as easy while in gear.
The ex frame is not going to crack from the extra power if it cracks its from the way its rode. I hit big jumps and nothing is cracking but i am having it gusseted just for more streingth.
The 250r frame and 400ex frame are not much differance except for the front by the raddy other wise their pritty close.
From what i heard and see is that the 250r frames crack easier than the ex frame.
I wouldn't go buy any kits cause its easy to make mounts for the thing and you still need to mod the frame after the kit.
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Post by ktmquad on Mar 15, 2007 19:19:21 GMT -5
If I was you I would be looking into a KTM power plant. I have an '03 525exc in a leager chassis, that I built in 03 with awesome power. I can pull holeshots on some of the top built motors out there. I tore the engine down last year and completely rebuilt it to '06 specs. The only extras I have is a 12-1 piston and a WhiteBrothers titanium exhaust other than that it is stock. The new 450sxf dual overhead cam would make a great engine, or maybe the new 505sxf. I am trying to locate one myself for another build. I put a ktm 50 in my daughter's Lem and it finally runs great. A buddy of mine built a '96 KTM 550 2-stroke in a 400ex chassis (out of control) had to bigger than mine!!
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