whoever said a YZ426 motor fits in a R frame is Wrong...

[LT250Racer609]

So I got my motor today with the plans to throw it in my 86 250R frame to make a hybrid. I researched this for a good amount of time and everyone says its a nice fit...well I dont see whats So nice about it? The motor basically sits on the front motor mounts, and the rear motor mount on the actual motor that the swingarm bolt is supposed to go through, well thats not even close. Does anyone have any actual pics of a yz426 motor in a 250R frame?? Also, the shift lever doesnt come out far enough from the motor to clear the frame enough to shift.

[theTman]

i hope you didnt expect it to bolt right in.....its obious that frame mods are gonna have to be done for a totally new motor to fit!

[racerx573]

Much modification is needed if you want it done RIGHT!

I put one in a Laeger 250R frame. Which is all the same except for the CR500 linkage and narrow front rails, but as far as engine mounts.. it's the same..

I have an awesome machinist/welder who has done many conversions, so we knew what we were getting into, and it took quite a while to get it all right.

We cut the pivot bolt tab off and relocated it, so that the pivot would go through the engine. We machined an '89 style CR500 link swingarm so that it would go around the engine and the pivot would go through. We machined some custom bushings for the engine so the 250R pivot bolt would fit.

We cut the 2 "V" looking braces off of the bottom and put a cross bar in and made mounts for the 426's lower mounts. Then we cut out the upper shock braces for the rear shock and put another cross brace in, and redirected the shock braces to this crossmember. Then we made a custom headstay mount which utilizes the stock headstay brackets from a YZ dirt bike. A headstay is MANDATORY if you want your frame to last. Lastly after the major mounting issues were handled, we made the front motor mounts.

http://img.photobucket.com/albums/v377/racerx573/04-05%20Projects/conversion3.jpg

http://img.photobucket.com/albums/v377/racerx573/04-05%20Projects/YZ3.jpg

http://img.photobucket.com/albums/v377/racerx573/04-05%20Projects/conversion2.jpg


http://img.photobucket.com/albums/v377/racerx573/04-05%20Projects/YZ1004.jpg

[jrspawn]

Well, the number one question Everyone has when wanting to build a hybrid is the classic what engine. CRF, YZF, or KTM. And the first answer for the easiest conversion is the YZF.

The YZF fits the best out of the bunch into any frame for the most part. But most people fail to understand that by No means does that statement mean that it bolts up, or all you need to do is fab a couple little spots. The statement means its the easier of the bunch to use becuase of the size for the most part. You still have to modify Alot to get it close to where it should be. And even after that, you run into many problems with clearences, locations of multiple things, oil tank spot(pretty tight in an R conversion frame normally if one can even be fitted)and several other headaches.

This is one of the main reason i personally do not like to mess with conversion quads. I dont have anything against them in general, and im not downing them. But you woulnt catch me with one. Using a chassis designed for the engine and having the exact geometry right(which in alot of conversion isnt) is critical in my opinion. Yes you can slap an engine into anything and make it work, but having something done right and the way it should be, well i shouldnt have to say anymore.

My advice would be to get the complete chassis and engine to a good fab/atv shop and have them do what they can. Just make sure it is going to be cost efficient first. You might be better off finding a good YZ chassis already done for a better price.

Sorry for the long post also:D Just trying to shed a little light on the subject.

Thank you
Justin

[LT250Racer609]

Well I just got the rear of the motor bolted up to my rear swingarm bolt, and its sitting nice right now. The top sits very close to the gas tank, but the gas tank still lays down on the frame fine.....Im gonna hafto tweak the exhaust pipe in a little bit to give my my clearence behind the frame rail....

I dont hafto use a External Oil tank...I just installed the Wet sump kit today into the motor....so that saved a few oil lines, and alot of space and less of a headache for me....

I will Fab. up the front motor mounts tomarrow. The hardest part put of this whole thing is trying to make a good head stay mount....On the right bottom side of my R frame, I could cut that cross member section out right before where the swingarm mounts, to make the motor drop down another 2-3" but I dont think I wanna go weakening my frame like that....

I will figure it out...at first, I thought there was no way to make it work, but i walked away from it for a little while, came back and I got it mounted pretty well....Just need to figure a few odd's and ends out...

[matt250r21]

Good luck getting the YZ carb to clear the stock 250R upper rear shock mount. If you get sick of trying to make it work, I have a 2002 Laegers YZ426 pro trax frame, fliptop subframe and CR500 link swingarm for sale. Frame has 250R geometry but is made for the YZ426 motor.

[LT250Racer609]

Originally posted by matt250r21
Good luck getting the YZ carb to clear the stock 250R upper rear shock mount. If you get sick of trying to make it work, I have a 2002 Laegers YZ426 pro trax frame, fliptop subframe and CR500 link swingarm for sale. Frame has 250R geometry but is made for the YZ426 motor.

yah for 2500 correct?? No thank you.

[400exrider707]

It's generally never a good idea to try and make a four-stroke motor work in a frame that was originally designed for a two stroke. For the most part four strokes are taller motors making it more difficult than it needs to be to get things to mount up, and generally speaking two stroke frames are not up to the task of handling high torque situations that a four stroke will throw at it... I'd expect a lot of broken frame pieces

Also dont forget to fab up a good way to mount a radiator for that beast too... keep posting pics as you go along, I love these builds.

[LT250Racer609]

Originally posted by 400exrider707
It's generally never a good idea to try and make a four-stroke motor work in a frame that was originally designed for a two stroke. For the most part four strokes are taller motors making it more difficult than it needs to be to get things to mount up, and generally speaking two stroke frames are not up to the task of handling high torque situations that a four stroke will throw at it... I'd expect a lot of broken frame pieces

Also dont forget to fab up a good way to mount a radiator for that beast too... keep posting pics as you go along, I love these builds.

my radiator is already mounted...thats not affected in any ways...

Im gonna pick up a 400 ex frame I think...that will make things much easier and everything will switch over from my 250R chassis.

I broke motor mounts with my CT350....I dont expect this YZ426 to be making more power then that.

[ss440ex]

PM me you e-mail if your going to use the 400ex frame.
I got a few pics....

[LT250Racer609]

PM sent.

[250x_kyle]

Originally posted by 400exrider707
It's generally never a good idea to try and make a four-stroke motor work in a frame that was originally designed for a two stroke. For the most part four strokes are taller motors making it more difficult than it needs to be to get things to mount up, and generally speaking two stroke frames are not up to the task of handling high torque situations that a four stroke will throw at it... I'd expect a lot of broken frame pieces

Also dont forget to fab up a good way to mount a radiator for that beast too... keep posting pics as you go along, I love these builds.

well first of all he was using a 250r frame wich means he wouldnt have to fab new radiator mounts.seconds of all he would more than likely gusset the frame.

you will have to find a new place to mount the stock oil tank or an aftermarket one because the radiator gets in the way of the stock 400 oil tank mount

[LT250Racer609]

Originally posted by 250x_kyle
well first of all he was using a 250r frame wich means he wouldnt have to fab new radiator mounts.seconds of all he would more than likely gusset the frame.

you will have to find a new place to mount the stock oil tank or an aftermarket one because the radiator gets in the way of the stock 400 oil tank mount

Not being a *** but I already stated this...

I DONT need a External Oil tank. I installed the WET SUMP kit into this motor, which Eliminates all the oil lines, and external oil tank.

And I bought a 400ex frame....I will switch everything over off my R chassis to the 400ex frame....

[ALAMX37]

I will tell you this I had my CRF in a 400ex chassis that was gusseted to hell and back and I still broke the frame every two or three rides. Got my LSR 400ex geometry frame tfor the CRF and have had 0 problems.

[matt250r21]

Thats my point ^. If you are going to go thru the trouble of building a Hybrid, why not use a frame that will last and is made for the motor. A 400EX frame is mild steel and has inferior geometry compared to the 250R. $2500 is a lot for my Laeger's frame and parts, but it is rare, is made by one of the best builders and most importantly will LAST.

I'm sure you know what your doing welding and fab wise, but your working with mild steel tubing. I just think you will be pulling it apart a lot to weld up cracks. Good luck with it though.

[stocktires]

Originally posted by matt250r21
Thats my point ^. If you are going to go thru the trouble of building a Hybrid, why not use a frame that will last and is made for the motor. A 400EX frame is mild steel and has inferior geometry compared to the 250R. $2500 is a lot for my Laeger's frame and parts, but it is rare, is made by one of the best builders and most importantly will LAST.

I'm sure you know what your doing welding and fab wise, but your working with mild steel tubing. I just think you will be pulling it apart a lot to weld up cracks. Good luck with it though.

For Real!
Please don't build another oem framed hybrid, they don't last AT ALL. You will spend more in time repairing it & converting it (the right way) than money you will save to buy a very nice strong aftermarket frame. Also your quad will be worth something when you sell it...
I'm just trying to help you. If you disregard this, which it seems you will with the immature and cocky attitude you have, then so be it.

[LT250Racer609]

Originally posted by stocktires
For Real!
Please don't build another oem framed hybrid, they don't last AT ALL. You will spend more in time repairing it & converting it (the right way) than money you will save to buy a very nice strong aftermarket frame. Also your quad will be worth something when you sell it...
I'm just trying to help you. If you disregard this, which it seems you will with the immature and cocky attitude you have, then so be it.

Please show me where my "immature and Cocky attitude" comes into play, please.....

I Bought a 400ex frame. Im 20 years old, and work full time. I took welding for 3 years, I can weld with my eyes closed, so a crack here and there is nothing to me. Fabricating, is nothing to me as I Fabricated and welded a whole Forward flowing turbo Header kit for my car...

I dont have the Money right now to go diving into a 2500.00 Investment when the only time I use the quad, is at race night. When **** starts breaking, I will fix it and look into a aftermarket setup...untill then, I dont have the money so its NOT a option.

[2muchquad]

When **** starts breaking, I will fix it and look into a aftermarket setup...untill then

I agree totally.Why spend 3 grand for a frame when you wouldnt get anything in return unless your a pro racer who gets paid to race.For me if i break a weld i can break out the mig anytime i need to..For the haters out there,just keep dumping money into the aftermarket and leave building to the ones that know what they are doing.:D

[timsmcm]

matt250r21





Thats my point ^. If you are going to go thru the trouble of building a Hybrid, why not use a frame that will last and is made for the motor. A 400EX frame is mild steel and has inferior geometry compared to the 250R.

Man I dont know where you get your info but the 400ex has some of the best geometery of any quad ever I have had mine on the track for years and the only thing wrong with the ex is it is heavy and underpowered but setup right it will carve and fly better than anything I have ever come up against.

[Groves187]

I have talked to a kid on here with a 400ex framed CRF Hybrid and he said he has raplaced so many frame rails and belive he said he went threw a few frames as well.. I found a really good deal on my LSR frame brand new.. ther out there and you dont need to pay 2500 for it... O and have fun grinding off your PC everytime you find a crack...HAH

[racerx573]

Originally posted by timsmcm

Man I dont know where you get your info but the 400ex has some of the best geometery of any quad ever I have had mine on the track for years and the only thing wrong with the ex is it is heavy and underpowered but setup right it will carve and fly better than anything I have ever come up against.

Take a spin on a Pro Trax 250R, or even a stock geo R with a good LT front end and rear end.. you'll change your mind, haha.

Although you are right, compared to a lot of other sport quads a 400EX does have excellent geometry, especially when done right with front/rear ends. It is very closely based to 250R geo.


Another thing to keep in mind when doing a conversion is to have your suspension revalved for a heavier (or lighter) engine. having a good suspension set up will increase the life of your chassis components. Even with this done though, things will still break depending on how hard you are on equipment, trust me. I've cracked a Laeger frame on one of my old 250R's. That is the frame I did the YZ conversion on. The part that cracked was removed though during the conversion. I have firm belief though that my YZ's frame is stronger than when it was built though. Simply because my welded/machinist is godlike when it comes to fabrication. His welds are better than the original Laeger welds.

[korniev]

Originally posted by jrspawn
Well, the number one question Everyone has when wanting to build a hybrid is the classic what engine. CRF, YZF, or KTM. And the first answer for the easiest conversion is the YZF.

The YZF fits the best out of the bunch into any frame for the most part. But most people fail to understand that by No means does that statement mean that it bolts up, or all you need to do is fab a couple little spots. The statement means its the easier of the bunch to use becuase of the size for the most part. You still have to modify Alot to get it close to where it should be. And even after that, you run into many problems with clearences, locations of multiple things, oil tank spot(pretty tight in an R conversion frame normally if one can even be fitted)and several other headaches.

This is one of the main reason i personally do not like to mess with conversion quads. I dont have anything against them in general, and im not downing them. But you woulnt catch me with one. Using a chassis designed for the engine and having the exact geometry right(which in alot of conversion isnt) is critical in my opinion. Yes you can slap an engine into anything and make it work, but having something done right and the way it should be, well i shouldnt have to say anymore.

My advice would be to get the complete chassis and engine to a good fab/atv shop and have them do what they can. Just make sure it is going to be cost efficient first. You might be better off finding a good YZ chassis already done for a better price.

Sorry for the long post also:D Just trying to shed a little light on the subject.

Thank you
Justin



Yeh, I would agree with that one! Companies just put some R&D into those things.....