YZ250 Motor in a YZ450F Aluminum Frame


142 replies to this topic
  • stimps

Posted March 24, 2010 - 02:19 PM

#61

Reality is the YZ250 frame was all new in 2005 and was a massive development program. Can't recall details but there was loads of variations of frames tested with lots of diffferent flex characteristics etc. The likelihood of bolting on a frame designed for a much heavier engine with totally different power delivery and achieving an improvement is probably slim to none. If they could produce a generic frame or even use common radiator shrouds I would think it would lower manufacturing costs and be worth while for them. The reality is that the latest model already uses the latest technology finely tuned to the latest 2 stroke engine they produce. The fourstroke frame is no more advanced. On the flip side this is just such a cool project, like yourself I'd build one just for the fun off it. Go for it, it will be different, I bet still handle as good as most people can ride and super super cool. Well Done Dude.

  • ulmanb

Posted March 24, 2010 - 03:55 PM

#62

Lots of custom aluminum frame cr500's in 4-stroke frames, never heard of complaints of pushing in corners.

  • mxjosh

Posted March 24, 2010 - 04:01 PM

#63

crf250's aren't known for pushing to begin with so why would they suddenly push with a 500 motor? The YZF's are known for pushing and its unknown as to whether or not a different motor will change that.

  • ulmanb

Posted March 24, 2010 - 05:16 PM

#64

crf250's aren't known for pushing to begin with so why would they suddenly push with a 500 motor? The YZF's are known for pushing and its unknown as to whether or not a different motor will change that.


There are a lot of 500's stuffed into crf450 frames too, this guy is putting his engine into a YZ450 frame if I am not mistaken.

  • mdkcrf250r

Posted March 24, 2010 - 06:18 PM

#65

Thats my exact point! The 450 already pushes and dont turn. I have rode them along with th e2 stroke the last 4 years. Then your taking a 2 stroke motor that has a lower center of gravity and weighs less. Which is only gonna make it push more. The reason I say this is you have a 450 motor with a higher center of gravity. That is gonna put more weight towards the front end, to help weight the front wheel I feel. I love the effort he is going about building this. I just don't see how it will be better at all, if anything it will be worse. I personally would like to see a CR500 moto stuffed in a YZ 250 2stroke frame. :thumbsup:


It would push less than the stock 450...The COG has very little to do with the reason a 4 stroke is such a front wheel turning machine...Its mostly due to the engine braking which the 2 stroke has less of which will result in a bike that pushes less...

  • mxjosh

Posted March 24, 2010 - 09:30 PM

#66

There are a lot of 500's stuffed into crf450 frames too, this guy is putting his engine into a YZ450 frame if I am not mistaken.


makes no difference, one pushes one doesn't. Service Honda uses crf250 frame.

  • djmamayek

Posted March 25, 2010 - 04:19 AM

#67

I like the project, I think it will look cool. Furthermore, all the nay-saying here is likely from people who are too lazy or not skilled enough to undertake this project, but constantly complain that Yamaha never updated the YZ's to the YZF plastic and graphics. I'm sure the bike will handle great, and it is going to look great!

Furthermore, the "four stroke push" phenomenon is, as had been said before, a result of engine braking on entering a corner. You can make any bike push in a corner by grabbing a handful of front brake.... :thumbsup:

  • mxjosh

Posted March 25, 2010 - 09:05 AM

#68

With clutch in and no front brake, it still pushes so it's not 4t engine thing. What I'm hoping is the lower cg helps him out. No cams or tall motor up top. When's the first ride?

  • MaddogYZ

Posted March 25, 2010 - 12:44 PM

#69

With clutch in and no front brake, it still pushes so it's not 4t engine thing. What I'm hoping is the lower cg helps him out. No cams or tall motor up top. When's the first ride?


NO bike will ever turn coasting, you have to be on the gas and the suspension loaded for a bike to turn well. Enough of the handling debate this is about a really cool project bike, back on topic!

  • mdkcrf250r

Posted March 25, 2010 - 01:02 PM

#70

With clutch in and no front brake, it still pushes so it's not 4t engine thing. What I'm hoping is the lower cg helps him out. No cams or tall motor up top. When's the first ride?


Yeah my mountain bike pushes in the corners and I hate...lol come on with the clutch pulled in its essentially a heavy bicycle. It does not push with the clutch pulled in or the engine off....

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  • mxjosh

Posted March 25, 2010 - 03:15 PM

#71

Sheesh do you guys not read about other bikes? The YZ450 pushes at the exit of corners, right about the time you gonna accelerate so the engine braking thing makes no sense for the pushing. Front brake is usually not applied, maybe dragging, but not locked on acceleration. Until we hear a ride report, there's no need to get bent out of shape about it. I'm hoping it works. Just have to be realistic and there's nothing wrong with pointing out potential issues with it.

  • Rude Riders

Posted March 25, 2010 - 08:26 PM

#72

Who really cares how this thing is going to end up turning. I think its F-ing awesome no matter what, and i want one lol! Like he said before, he's doing it for the cool factor, to be different, cause no one else has one!

......any recent photos on updates?

  • del250

Posted March 26, 2010 - 04:25 AM

#73

To tell you the truth, I really don't give a s**t about it pushing in the corners, it is not going to be a motocross bike, it will be a woods/offroad play bike. Like I said, I was never fast when I raced, and I am too old and fat to be fast now, so lets stop the bickering and focus on the project.

On the other hand, I should have the frame back today with any luck. I need to work on the airboot tonight, even if I don't get my frame back from the welders. I will keep you posted.

  • yamasaki

Posted March 26, 2010 - 11:07 AM

#74

sweet project man!

i had an 03 yz450f, an 06 yz450f, a yz250, and now my 06 yz125... this is like a yamafrankenha! i love it!

  • BRM

Posted March 26, 2010 - 03:59 PM

#75

To tell you the truth, I really don't give a s**t about it pushing in the corners, it is not going to be a motocross bike, it will be a woods/offroad play bike. Like I said, I was never fast when I raced, and I am too old and fat to be fast now, so lets stop the bickering and focus on the project.

On the other hand, I should have the frame back today with any luck. I need to work on the airboot tonight, even if I don't get my frame back from the welders. I will keep you posted.


Well said Del250, Keep up the good work. Looking forward to the finished product.:thumbsup:
Cool project

  • busted bones

Posted March 26, 2010 - 07:38 PM

#76

Sounds like it should be moving along pretty well

  • del250

Posted March 27, 2010 - 06:12 PM

#77

Well I got my frame back from the chopper shop, wasn't exactly what I was thinking, but I think it will work good anyway. Check out the pictures.

Posted Image
Posted Image

They moved the bottom rails back and up a little to accomodate the pipe. The pipe has a nice clearance now and fits great on the motor. I acid washed the frame before I put the motor back in and it turned out good. It got the aluminum nice and bright again. I think I will do that to my 4 stroke when I rebuild the motor in that here shortly. I got the motor planted in the frame but an still undecided on how I am going to mount the electronics. I did however get the radiators mounted, they fit great with the Dr. D radiator lowering kit. It moved the radiators just enough that there wasn't any interferance with the frame or motor.

Posted Image
Posted Image
Posted Image

I got a little anxious today after work and took it out and blasted it up the street without the airboot. I forgot how much I love the smell of race gas and 2 stroke oil. It filled my lungs and now I am addicted again. I would just start it to smell that smell again. I did get my new carb vent hoses on today after the ride up the street, and then went in and started on the airboot. Hopefully I will get a few more layers on tomorrow and work and getting that installed early next week. I think I have all of the parts that I need to finish, just need some time and patience now. As always I will keep adding photos as I progress.

  • RCannon

Posted March 27, 2010 - 07:22 PM

#78

That looks really good. I cannot believe how well the motor fits.

Hurry UP!!!!!

  • 02WR426Cali

Posted March 27, 2010 - 08:06 PM

#79

It's looking awesome! I can't wait to see and hear it in a video

  • CaptDan

Posted March 28, 2010 - 06:06 AM

#80

Fantastic!





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