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SAKs YAMAHA

Bottom end mods

28 posts in this topic

I recently picked up a non running 2010 yz450 super cheap. It only needed valves adjusted to get it running. Anyway it has a really bad grinding sound in the bottom end so I am splitting the cases and replacing all bearings while I am in there.

Now I don't ride MX, I like to stick to single track and slow trail riding on weekends. Since I got it so cheap I can afford to throw some money into it. I want to make it more like the 2016 WR. Does anyone know if the crank and flywheel will drop in? How about the gears? This is my first fuel injected model so I am a little in the dark about theses parts. Thanks.

Edited by SAKs YAMAHA

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The transmission should interchange, but since the WR is made up for an e-start, the crank is longer on the left side to accommodate the starter drive.  You would likely have more to change if you wanted to use a WR crank.

 

Absent the electric start, however, there's no real reason to want the WR crank.  The flywheel can be weighted, and the magneto puts out plenty of power as is. 

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Agreed. If you decide to go with the trans swap keep us updated on your progress. I plan to do my YZ whenever I split the cases.

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The transmission should interchange, but since the WR is made up for an e-start, the crank is longer on the left side to accommodate the starter drive. You would likely have more to change if you wanted to use a WR crank.

Absent the electric start, however, there's no real reason to want the WR crank. The flywheel can be weighted, and the magneto puts out plenty of power as is.

I wanted the WR crank because I was under the impression it is heavier. Good call on the e start though. I will be skipping that part of the swap and just make a weight for it. Thanks.

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Agreed. If you decide to go with the trans swap keep us updated on your progress. I plan to do my YZ whenever I split the cases.

I will try, I have a habit of just blowing through a build and forgetting take pictures and documenting stuff. Just hound me once in awhile if you dint see any new content next month.

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Just swap the wr 4th and 5th to your yz transmission unless you want the tractor like 1st gear the wrs have.

I did a yz\wr hybrid transmission in my 07 wr450 and love it.

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I will try, I have a habit of just blowing through a build and forgetting take pictures and documenting stuff. Just hound me once in awhile if you dint see any new content next month.

Please do take photos and update. I'll send you a sixer of San Diego IPAs for the trouble.

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so rocky mount atv has the gears listed but they aren't available until some time January. i am also going to try an get away with just buying 4th and 5th primary and secondary gears for $210. hopefully save a little money.

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so rocky mount atv has the gears listed but they aren't available until some time January. i am also going to try an get away with just buying 4th and 5th primary and secondary gears for $210. hopefully save a little money.

2 gears gets 2 beers.

It was a couple years ago but I put together a shopping list at an online OEM parts distributor. I think the difference on the entire transmission was over $100 from what ThumperTalk and Rocky Mountain wanted. Maybe shop around.

Edited by WouldsAssassin

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I ordered all of my rebuild parts from rmatv except a carillo rod.

Its nice that they give out the 10% off coupon codes after every order + you get frequent buyer points. I think i saved over $500 on $2000 in parts between the codes and points.

Everything took about two months to get here but i used oem for everything in the bottom end and most of it was back ordered.

If you do order from rmatv im pretty sure i got a 10% off coupon coming in the next couple days if you want it, i just placed an order through them yesterday.

Heres a link to my build if you want to check it out.

http://supermotojunkie.com/showthread.php?171234-Pic-heavy-bottom-end-rebuild-Looking-for-60whp-or-close-to-it

Edited by knuckleduster271

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I ordered all of my rebuild parts from rmatv except a carillo rod.

Its nice that they give out the 10% off coupon codes after every order + you get frequent buyer points. I think i saved over $500 on $2000 in parts between the codes and points.

Everything took about two months to get here but i used oem for everything in the bottom end and most of it was back ordered.

If you do order from rmatv im pretty sure i got a 10% off coupon coming in the next couple days if you want it, i just placed an order through them yesterday.

Heres a link to my build if you want to check it out.

http://supermotojunkie.com/showthread.php?171234-Pic-heavy-bottom-end-rebuild-Looking-for-60whp-or-close-to-it

Definitely! I will be replacing almost the whole bottom end as well. Thanks.

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Don't forget the Carrillo rod doesn't come with the pin or bearing. ( big end)

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If the crank is good I won't change it. If it's out of limits I am going to buy the whole assembly.

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Its nearly impossible to check. It could seem nice and tight 5 min before grenading. Better to go by the amount of time on it

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I'm gonna put it on stand with a dial gauge, it should be good. I haven't seen the crank end fail yet, only the piston end. I have bought countless toasted bikes, almost all the same.  I have no idea how many hours. I am the third owner and the original owner was a MX racer. I watched his videos on youtube, it was ridden hard.  so probably a lot and really hard hours too.

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Big end bearing clearance is simple to check, but you need a dial gauge.  Measurement "F" below:

 

In most cases, the only thing that would happen to a big end bearing that was still in spec is a cage break, which usually seizes the engine, but doesn't normally break the rod or piston. 

rod.png

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Big end bearing clearance is simple to check, but you need a dial gauge.  Measurement "F" below:

 

In most cases, the only thing that would happen to a big end bearing that was still in spec is a cage break, which usually seizes the engine, but doesn't normally break the rod or piston. 

 

That's what I was planning.

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I have to vent! Even though the bike was cheap, I didn't expect what I found today. I started tearing the engine down and found a whole world of s**t.

1. The "new" piston skirts are beat up and prematurely worn.

2. The cylinder has never been re-honed which is apperente in the fact that there is a mirror finish in the cylinder and the nikisil coating is worn completely through in one spot.

3. The wrist pin was seized in the con rod

4. There is so much play crank/rod journal that I don't even need to put a gauge on it and the cam chain drive teeth are sharp as a knife.

4. The oil was not changed and any interval cuz there is a 1/4" deep sludge build up in the bottom of the engine.

5. The chain guide was just floating around in there.

6. Finally, after the previous owners so called "fresh top end" he didn't even torque the head bolts they were hand tight. The bolts on my seat were tighter! The head gasket and base gasket look brand new, like they've never been clamped down.

I knew there were issue cuz it smoked a little when hot and the oil was black after a couple minutes of riding, but holy cow this thing is messed up.

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