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Discussion Starter #1
i was driving my quad and in fifth gear the thing just stopped driving like the clutch was pulled in and made a loud grinding noise. only fifth gear doesnt work anyone know what happened?

I figure i am just goin to pull the engine out of my crf because i never ride it and it takes space in the shed. I am going to put the 250 engine in the trx450 frame. has anyone done so or is this just a bad idea?

I am scared it will just be a gutless pig.

So i need t know

1. why doesnt fifth gear work?

2. Would this engine swap be a good idea?

3. Is the quad gonna be way underpowered or have the same amount but just a different feel of power with the 250 engine?

I am going to put a high comp piston and low end cam in the 250 engine if it's a good idea because i want to be able to race the rest of the year.
 

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hmm i would like to see it done but not sure if it would be a waste of time or not, my friends CRF250r is a beast and is FAST

the tranny will need to be replaced, you can get full sets of tranny gears for 200 bucks then + all the other stuff you might wanna change out while your in the cases

but the tranny would IMO be a easy fix
 

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id say its a baddd idea.

the 250 engine is not anywhere near built to handle to loads a heavy 4wheeler will put on it...
IMO if you want a project and want to get rid of your 250... sell the crf and use the money to buy a good used 450 engine and rebuild it. etc... whatever you chose but i would not put that engine in your 450r frame... you'll be burning up gears and clutches like no tomorrow.

edit: or another simple option i looked over haha... just rebuilt your current 450r motor top to bottom and your good to go!
 

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crf250 engine is NOT in the same class as the 450R engine....

and with that being said.... split your cases on your TRX450.....and lets fix the issue at hand......apparently your 5th gear....


jmho....
 

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Discussion Starter #6
i think i am goin put put the 250 in my frame becaues whats the difference if a 300 pound guy was on the crf and i put the engine in my quad and im only 160 wouldnt it be the same weight ratio.

me on trx with 250 engine = 400-500 lbs total weight

big guy on bike = 400-500 lbs

i think it sounds the same or am i missing some big picture?
 

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i think i am goin put put the 250 in my frame becaues whats the difference if a 300 pound guy was on the crf and i put the engine in my quad and im only 160 wouldnt it be the same weight ratio.

me on trx with 250 engine = 400-500 lbs total weight

big guy on bike = 400-500 lbs

i think it sounds the same or am i missing some big picture?[/b]
your math makes a tiny bit of sense. but with a 300 pound guy on the 250 i guarantee it would not be the rip snortin bike it was with a 160 lb guy on it.
you will be seriously disapointed with a 250 in a 450 frame, especially if you want to run with other 450 class machines
bad idea IMO
 

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CRF250R = LOW TORQUE/LOTS OF REVS
TR450R Quad Likes - Lots of torque and revs too of course! LOL!

This would be a fun swap to do.... However on days when the track is muddy, you will miss the torque.... JMO...
 
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dont be puttin a 250 motor in a frame where a 450 should be. if anything put something like a crotch rocket motor in thur
 

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IMO that is a stupid idea.

FIRST the crf 250 motor is built for fast high revs....WITH ONE TIRE.
THrow that motor under twice the load of two tires+ the added weight and it would really have problems. Especially once you hit and sort of mud or sand or anything. The CRF motor is not built to handle the load of the stress and added weight of a trx. YOu would have a lot of issues IMO.

Fix your 450 motor....there is nothing like it.

-Kip
 

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Yeah..think about it like this..You at 160 lbs racing other guys at 160lbs ..you have a 250 motor they have a 450 motor..who do you think is going to win. ..If you wanna do a swap sell the crf and buy a crf450 motor and swap that!..Or just fix yours..
 

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BAD IDEA, Not only willl it probably be a PITA to do, it will have less power than your 450 motor. Take the time and effort you would use to put a weaker motor in and use it to repair your R motor. JMHO

Grey
 
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