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I have a 01 yz426 with a broken crankshaft and I have the opportunity to buy a 03 low miles engine from 450. I know that I'm going to have to make new upper headstays and making a new collar for swing arm pivot. Is there anything else that is going to present an issue with the engine running in my bike? Carb should switch over and if I have to be a little creative with air box I won't mind working with that. Am I missing something that would make this swap not worth it over just holding out on finding a good used 426 engine? BTW does anyone have or know of a 426 complete engine in good shape. I have no problem doing the work to mount the engine in the frame (I have done mustang 5.0 conversions including a 328i and Honda swaps), but if economically it will be alot more expensive I don't want to fool with it. 

 

 

 

 

 

 

 

 

Edited by dtaylor0728
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Thank you, and I took pictures down. Is there anything specific I should watch out for other than headstay and swing arm mount? 

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There shouldn't be very much.  You probably know they are a 4 speed, and they have been prone to wearing the gear dogs on 4th gear to the point where they skip.  Some '03's had rod bearing troubles.

Just about everything should be a near bolt-in.

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Thanks for your help. I knew about the gearset, but not about common issues. The engine seems to be in very good condition and low hours, so I went ahead and bought it. We will see how it goes.

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WP_20170414_09_22_25_Pro.jpg.a0cd8af5f478740056ff664f17b3a6e6.jpgengine came in on 13th and started fitting in frame. I got the swing arm pivot hooked u and began to mock up additional mounts using the previous mounts. So far I have templates holding the engine in frame which I can use to make my new mounts from (to improve appearance and look more OEM). I have the radiator halfs mocked up and have got the dry sump lines hooked up. Still have to figure out what to do about bottom mount (probably going to cut tabs off and weld in correct spot) I've already had to cut mounting point for skid plate off frame to clear crankcase drain.

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426 wiring harness seems to work fine. Clutch cable is routed differently and you can just switch the trans side bracket. 426 coil wire seems to fit ok. Kick start lever has different diameter for splines than my 426 or buddies 04 yz450f, but my 06 ktm 250sx-f works fine. I have another ktm lever ordered due to ktm lever being found for $69 versus $130+ for new or used 03 450f lever.

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The bike is essentially finished and has been running good. Still have little stuff I'm going to replace (couple bearings, rear caliper, drive sprocket, clutch perch), but seems to ride pretty good, almost feels "factory". I'm not aware of anyone else completing this conversion, if anyone needs specific information just ask.

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bike build has been finished and then restarted a couple times. Went yz450f cdi, harness and coil. Alot more space without coil and wire and like the complete engine wiring (stator, cdi, ignition at plug etc.) being consistent. with my mounting position 450f cop impossible to service engine tight in frame, I had to clearence old head stay to frame with ginger to make service clearance. I was running yz 426 headpipe with fmf slip on. Have switched to 450 headpipe which seals up much easier when oriented to line up with exhaust, 426 header bend makes total seal against head, while also keeping orientation to exhaust, very difficult. carb to airbox boot is a PIA against the shock, better with.no 426 coil in the way. A few new plastics and tires, waiting on carb parts to do full re build to minimize future dealing with airboot and carb lining up against shock as much as possible 

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On 4/27/2017 at 7:16 AM, dtaylor0728 said:

The bike is essentially finished and has been running good. Still have little stuff I'm going to replace (couple bearings, rear caliper, drive sprocket, clutch perch), but seems to ride pretty good, almost feels "factory". I'm not aware of anyone else completing this conversion, if anyone needs specific information just ask.

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Great work man! I'm doing a winter rebuild from the floor up on my 99 yz400f and was wondering if you know if I could put a 450 engine in that frame? I was adjusting the valves and just started taking shit off and next thing I knew I had ordered a ton of stuff and had the frame stripped to bare metal lol. You think I could do what you did but using a 99 yz400f to put the 450 in? Here she is in pieces, pardon the language I get carried away some times lol. Thanks in advance for any information on the possibility of it being a bolt in and go job or something I'm gonna have to do some fab work on to make it work. 

https://youtu.be/uAlyu5qmDzk

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17 hours ago, Yammyhammer said:

Great work man! I'm doing a winter rebuild from the floor up on my 99 yz400f and was wondering if you know if I could put a 450 engine in that frame? I was adjusting the valves and just started taking shit off and next thing I knew I had ordered a ton of stuff and had the frame stripped to bare metal lol. You think I could do what you did but using a 99 yz400f to put the 450 in? Here she is in pieces, pardon the language I get carried away some times lol. Thanks in advance for any information on the possibility of it being a bolt in and go job or something I'm gonna have to do some fab work on to make it work. 

https://youtu.be/uAlyu5qmDzk

My understanding is that the 400 and 426 frames are identical. It sounds like he had to do a little fab work to make it fit.

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On 2/26/2019 at 4:58 PM, Yammyhammer said:

Great work man! I'm doing a winter rebuild from the floor up on my 99 yz400f and was wondering if you know if I could put a 450 engine in that frame? I was adjusting the valves and just started taking shit off and next thing I knew I had ordered a ton of stuff and had the frame stripped to bare metal lol. You think I could do what you did but using a 99 yz400f to put the 450 in? Here she is in pieces, pardon the language I get carried away some times lol. Thanks in advance for any information on the possibility of it being a bolt in and go job or something I'm gonna have to do some fab work on to make it work. 

https://youtu.be/uAlyu5qmDzk

For the 03-05 YZ450 engine to fit in my bike and I assume probably yours as well, you will need to make new headstays and front mount brackets, the tabs on bottom frame will need to be cut and off and then welded about inch back on frame from where they were for the bottom mount bolt, and you will need to either use a 02+ swingarm and pivot shaft or modify your swingarm for the 02+ shaft. The 02 426 and 03+ 450 have a larger pivot shaft than 01 back bikes. You will also run into little things like "massaging" oil lines to fit, you will need a new kick start lever, modify coil boot to fit/ convert to COP,  etc. For someone with experience doing engine swaps, it should be fairly simple 

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On 3/4/2019 at 6:30 AM, dtaylor0728 said:

For the 03-05 YZ450 engine to fit in my bike and I assume probably yours as well, you will need to make new headstays and front mount brackets, the tabs on bottom frame will need to be cut and off and then welded about inch back on frame from where they were for the bottom mount bolt, and you will need to either use a 02+ swingarm and pivot shaft or modify your swingarm for the 02+ shaft. The 02 426 and 03+ 450 have a larger pivot shaft than 01 back bikes. You will also run into little things like "massaging" oil lines to fit, you will need a new kick start lever, modify coil boot to fit/ convert to COP,  etc. For someone with experience doing engine swaps, it should be fairly simple 

Thanks for the info. I decided to just stay with the 400 tho, it barely knows im on it anyway lol. Thanks again..

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On 3/11/2019 at 11:51 PM, Yammyhammer said:

Thanks for the info. I decided to just stay with the 400 tho, it barely knows im on it anyway lol. Thanks again..

It isn't a particularly hard swap, but if you have a good running 400 engine than I agree that you should keep it. The 450 is awesome, but if my 426 had not spontaneously ceased to live, then I would have not spent the time and money for the 450.

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On 3/22/2019 at 7:26 AM, dtaylor0728 said:

It isn't a particularly hard swap, but if you have a good running 400 engine than I agree that you should keep it. The 450 is awesome, but if my 426 had not spontaneously ceased to live, then I would have not spent the time and money for the 450.

Yeah i agree, im gonna run this engine till it pukes then ill get me a 450 for it. Iv almost got her buttoned back up and riding now. If the weather was a little nicer id be in more of a hurry but iv took every last bolt loose and rebuilt it over the winter so a week or so more aint going to hurt me lol. It still runs really strong as is so im happy with it, and now im as happy with how it looks as i am with how it runs 😜

Hard to believe all that started from doing a valve adjustment lol. Thats what happens when you just need to do a valve job and smoke a joint before you put it back together haha...

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On 3/25/2019 at 9:03 PM, Yammyhammer said:

Yeah i agree, im gonna run this engine till it pukes then ill get me a 450 for it. Iv almost got her buttoned back up and riding now. If the weather was a little nicer id be in more of a hurry but iv took every last bolt loose and rebuilt it over the winter so a week or so more aint going to hurt me lol. It still runs really strong as is so im happy with it, and now im as happy with how it looks as i am with how it runs 😜

Hard to believe all that started from doing a valve adjustment lol. Thats what happens when you just need to do a valve job and smoke a joint before you put it back together haha...

Yea...... I have also been known to start out with a relatively minor task and it snowball into a multi month endeavor. One "well i might as well since im here already" turns into another and than hours turn to weeks. Lol

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On 4/2/2019 at 5:15 AM, dtaylor0728 said:

Yea...... I have also been known to start out with a relatively minor task and it snowball into a multi month endeavor. One "well i might as well since im here already" turns into another and than hours turn to weeks. Lol

Then weeks turn to months lol. 

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