Engine rebuild advice

10/11/2017 5:16am Edited Date/Time 10/12/2017 7:21am
Our racing season is coming to a close, and I'll have plenty of time this winter to rebuild my ride. I've never owned a bike this long prior to this one, so rebuilding it has never been an issue before.
I have a bone stock 2013 KX450 with nearly 140 hours on it. I race MX in the +40 class. The bike only gets used on motocross race weekends. I have changed the oil every 10 hours. The valves have been inspected and adjusted as necessary. I replaced the piston at 80 hours, but that was just a precautionary measure. The bike runs perfectly, but I don't want to push my luck. What should I replace over the winter, and what company/services should I utilize to do the work?

OR...

Am I better off just selling it and forking out 9 grand for a new one? Problem is, as a 6'4" motocross rider, I really like the layout of the chassis on this bike. Plus, believe it or not, Factory Connection has my air forks working great for me.
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Pirate421
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1778
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MA US
10/11/2017 5:43am Edited Date/Time 10/11/2017 5:45am
If it were me I would leave it as is. With 60 hrs on that new piston I would think you have at least another 40hrs left in it. I would hope that bottom end would be good for 200 hrs with regular maintenance. At 200 hrs you're in a pickle I believe. You could sell it but I'm not sure what a 2013 450 would be worth with 200+ hours on it? Personally I would never consider buying a 4 stroke with over 50-75 hrs on it, but there is a buyer for every seat. If you love the bike I'd ride it to 200 hrs as is and save some more money. Then either do a full rebuild or try to recoup some $$ with a sale and buy something new. Rebuilding now is just throwing $$ away imo, and this is all what I would do if it were my bike.
10/11/2017 6:02am
With 140 hours on the lower end and 60 hours on the piston I would urge you to check crank and likely replace the rod and piston. Even if the stock parts are in good condition think of peace of mind. The last thing I want happening when I get to the track is to have a mechanical. Pushing a rod through the cases is far more expensive to rebuild then replacing a rod without going through the cases.

Last winter I sent my 2015 yz250f motor to Motor Medic Racing and was thoroughly impressed with the end product. He replaced the rod and piston, cleaned up the head, removed the counter balance, and super polished the transmission. None of this reduced the reliability. The transmission treatment was probably the most impressive treatment. It reduced the engine braking to a point where it is now nearly non existent. Coupled with removing the counter balance the bike now revs much faster. It also allows you to use more of the low end power because the internal drag of the engine was drastically reduced.

John with Motor Medic Racing does sweet work, he will take care of you.

http://motormedicracing.com/
r.sal923
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564
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Location
CA
10/11/2017 6:31am
I would buy new in spring and sell old. If you decided to rebuild and put 1500-2000$ into it. New tires , bars , grips, chain , sprockets , because it always happens when you are trying to build a fresh bike for spring. if you were to rebuild you will only recover 1/4 the amount you spent on the rebuild . Remember it is not a home for you and your family to live in, it is a dirt bike.
walent215
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2365
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12/6/2014
Location
Ridgecrest, CA US
10/11/2017 7:38am
Keep the bike! Unless you are racing with Doug Dubach and Ty Davis i wouldnt worry about the motor . If your using a good synthetic oil and keeping a clean air filter the piston you put in will get you through another 40 hours. Of course an arguement can be made the other way but for me and the experience with the 450s ive had / worked on is that well maintained 450s will go alot further than most like to admit. Not gonna be the popular advice here but I've never "blown" up one of my many 450s ....

The Shop

kNewc
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IN US
10/11/2017 7:50am
With 140 hours on the lower end and 60 hours on the piston I would urge you to check crank and likely replace the rod and...
With 140 hours on the lower end and 60 hours on the piston I would urge you to check crank and likely replace the rod and piston. Even if the stock parts are in good condition think of peace of mind. The last thing I want happening when I get to the track is to have a mechanical. Pushing a rod through the cases is far more expensive to rebuild then replacing a rod without going through the cases.

Last winter I sent my 2015 yz250f motor to Motor Medic Racing and was thoroughly impressed with the end product. He replaced the rod and piston, cleaned up the head, removed the counter balance, and super polished the transmission. None of this reduced the reliability. The transmission treatment was probably the most impressive treatment. It reduced the engine braking to a point where it is now nearly non existent. Coupled with removing the counter balance the bike now revs much faster. It also allows you to use more of the low end power because the internal drag of the engine was drastically reduced.

John with Motor Medic Racing does sweet work, he will take care of you.

http://motormedicracing.com/
How much did that end up costing you?
sgrimmxdad
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1494
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7/23/2013
Location
Farmville, NC US
10/11/2017 7:59am
With 140 hours on the lower end and 60 hours on the piston I would urge you to check crank and likely replace the rod and...
With 140 hours on the lower end and 60 hours on the piston I would urge you to check crank and likely replace the rod and piston. Even if the stock parts are in good condition think of peace of mind. The last thing I want happening when I get to the track is to have a mechanical. Pushing a rod through the cases is far more expensive to rebuild then replacing a rod without going through the cases.

Last winter I sent my 2015 yz250f motor to Motor Medic Racing and was thoroughly impressed with the end product. He replaced the rod and piston, cleaned up the head, removed the counter balance, and super polished the transmission. None of this reduced the reliability. The transmission treatment was probably the most impressive treatment. It reduced the engine braking to a point where it is now nearly non existent. Coupled with removing the counter balance the bike now revs much faster. It also allows you to use more of the low end power because the internal drag of the engine was drastically reduced.

John with Motor Medic Racing does sweet work, he will take care of you.

http://motormedicracing.com/
kNewc wrote:
How much did that end up costing you?
How much did that end up costing you?
Wondering same
IWreckALot
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Location
Fort Worth, TX US
10/11/2017 8:07am
Anybody else's radar go up when you have a newb start a thread and a newb reply with a link?
10/11/2017 8:12am
With 140 hours on the lower end and 60 hours on the piston I would urge you to check crank and likely replace the rod and...
With 140 hours on the lower end and 60 hours on the piston I would urge you to check crank and likely replace the rod and piston. Even if the stock parts are in good condition think of peace of mind. The last thing I want happening when I get to the track is to have a mechanical. Pushing a rod through the cases is far more expensive to rebuild then replacing a rod without going through the cases.

Last winter I sent my 2015 yz250f motor to Motor Medic Racing and was thoroughly impressed with the end product. He replaced the rod and piston, cleaned up the head, removed the counter balance, and super polished the transmission. None of this reduced the reliability. The transmission treatment was probably the most impressive treatment. It reduced the engine braking to a point where it is now nearly non existent. Coupled with removing the counter balance the bike now revs much faster. It also allows you to use more of the low end power because the internal drag of the engine was drastically reduced.

John with Motor Medic Racing does sweet work, he will take care of you.

http://motormedicracing.com/
kNewc wrote:
How much did that end up costing you?
How much did that end up costing you?
sgrimmxdad wrote:
Wondering same

John even had to redo valve seats as one seat had a tiny chip. The turnaround was about four weeks, but I lost a week each way with shipping the motor from Illinois.

I was referred from a friend so I don't know if I got a friends and family discount, but all in it was $1,700.00. That included all parts, and shipping the motor back to me. I feel like it was a good deal, especially considering the fun factor.

captmoto
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Rancho Cucamonga, CA US
10/11/2017 8:18am
IWreckALot wrote:
Anybody else's radar go up when you have a newb start a thread and a newb reply with a link?
You were never a noob? How else do you expect he's going to get to get over 8000 posts?
10/11/2017 8:28am
You don’t need to rebuild it. I ride Honda so maybe that’s why but my two previous bikes (2011 2013 450) I put close to 200 hours on them in about 2 years or less and never an issue. I ride tracks and sand pits. Currently own 2016 450 going on about 40ish hours.
10/11/2017 8:40am
IWreckALot wrote:
Anybody else's radar go up when you have a newb start a thread and a newb reply with a link?
captmoto wrote:
You were never a noob? How else do you expect he's going to get to get over 8000 posts?
Fair enough. Just to clarify, I have no vested interest in promoting any company within the moto industry, just sharing an experience.

Oh, and I've been prowling this site since before you were a noob. Rubber side down.
IWreckALot
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Location
Fort Worth, TX US
10/11/2017 9:15am
Fair enough. Just to clarify, I have no vested interest in promoting any company within the moto industry, just sharing an experience. Oh, and I've been...
Fair enough. Just to clarify, I have no vested interest in promoting any company within the moto industry, just sharing an experience.

Oh, and I've been prowling this site since before you were a noob. Rubber side down.
It's all good man. I've just seen a lot of instances where the OP and responder are the same person promoting a business. My opinion doesn't matter though. It just always sets off my BS radar regardless of circumstance anymore.

I like those yellow YZ's. A buddy of mine races one that looks pretty similar to yours. $1,700 isn't too bad for an engine rebuild and all you got. I miss the engine braking on my 4 stroke the most. That was the hardest adjustment on the 2 stroke for me.
Acidreamer
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1797
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8/25/2015
Location
Mansfield, OH US
10/11/2017 9:31am
id check your crank for any play and keep an eye on it. If theres no play then throw a fresh piston in and run it till the 2019 kawis are released and buy a new one. Im sure the next gen kx450s will be phenomenal.

10/11/2017 10:28am
IWreckALot wrote:
Anybody else's radar go up when you have a newb start a thread and a newb reply with a link?
I'm no newb here, junior. Been on this site since '08. I just don't think everyone necessarily wants to hear my opinion on every topic.
kNewc
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1106
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Location
IN US
10/12/2017 7:21am Edited Date/Time 10/12/2017 7:21am
kNewc wrote:
How much did that end up costing you?
How much did that end up costing you?
sgrimmxdad wrote:
Wondering same
John even had to redo valve seats as one seat had a tiny chip. The turnaround was about four weeks, but I lost a week each...

John even had to redo valve seats as one seat had a tiny chip. The turnaround was about four weeks, but I lost a week each way with shipping the motor from Illinois.

I was referred from a friend so I don't know if I got a friends and family discount, but all in it was $1,700.00. That included all parts, and shipping the motor back to me. I feel like it was a good deal, especially considering the fun factor.

Thanks for the reply! That's actually a really good price. Did he give you how much labor was? I know http://www.finishlineengines.com/ charges $350. I'm starting to learn rebuilding myself.
walleyeguy
Posts
459
Joined
5/9/2011
Location
Centerville, PA US
10/12/2017 7:48am
With 140 hours on the lower end and 60 hours on the piston I would urge you to check crank and likely replace the rod and...
With 140 hours on the lower end and 60 hours on the piston I would urge you to check crank and likely replace the rod and piston. Even if the stock parts are in good condition think of peace of mind. The last thing I want happening when I get to the track is to have a mechanical. Pushing a rod through the cases is far more expensive to rebuild then replacing a rod without going through the cases.

Last winter I sent my 2015 yz250f motor to Motor Medic Racing and was thoroughly impressed with the end product. He replaced the rod and piston, cleaned up the head, removed the counter balance, and super polished the transmission. None of this reduced the reliability. The transmission treatment was probably the most impressive treatment. It reduced the engine braking to a point where it is now nearly non existent. Coupled with removing the counter balance the bike now revs much faster. It also allows you to use more of the low end power because the internal drag of the engine was drastically reduced.

John with Motor Medic Racing does sweet work, he will take care of you.

http://motormedicracing.com/
I'm not a pro mechanic but I've rebuilt a number of yz250fs. I'm at a loss on how polishing the transmission could reduce engine braking. Make it shift smoother sure but engine braking?
CarlinoJoeVideo
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7271
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11/30/2013
Location
Portland/Los Angeles, CA US
10/12/2017 7:54am
Our racing season is coming to a close, and I'll have plenty of time this winter to rebuild my ride. I've never owned a bike this...
Our racing season is coming to a close, and I'll have plenty of time this winter to rebuild my ride. I've never owned a bike this long prior to this one, so rebuilding it has never been an issue before.
I have a bone stock 2013 KX450 with nearly 140 hours on it. I race MX in the +40 class. The bike only gets used on motocross race weekends. I have changed the oil every 10 hours. The valves have been inspected and adjusted as necessary. I replaced the piston at 80 hours, but that was just a precautionary measure. The bike runs perfectly, but I don't want to push my luck. What should I replace over the winter, and what company/services should I utilize to do the work?

OR...

Am I better off just selling it and forking out 9 grand for a new one? Problem is, as a 6'4" motocross rider, I really like the layout of the chassis on this bike. Plus, believe it or not, Factory Connection has my air forks working great for me.
The bikes have come a long way since 2013. Depends on your financial situation. If you can sell the bike for $2,500-$3,000 and put another $5k in, go buy a new Kawi.

If not, am I crazy to think that 140hours on the bottom end is a lot? Being that you have time off the bike, id get that whole thing rebuilt. But that's me...
Hallzilla
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941
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1/21/2011
Location
Langtown, CA US
10/12/2017 5:29pm
IWreckALot wrote:
Anybody else's radar go up when you have a newb start a thread and a newb reply with a link?
I'm no newb here, junior. Been on this site since '08. I just don't think everyone necessarily wants to hear my opinion on every topic.
Totally agree with you.! To bad most everyone else doesn't think that way.


PFitzG38
Posts
1559
Joined
11/6/2009
Location
Newport Beach, CA US
10/12/2017 5:39pm
Our racing season is coming to a close, and I'll have plenty of time this winter to rebuild my ride. I've never owned a bike this...
Our racing season is coming to a close, and I'll have plenty of time this winter to rebuild my ride. I've never owned a bike this long prior to this one, so rebuilding it has never been an issue before.
I have a bone stock 2013 KX450 with nearly 140 hours on it. I race MX in the +40 class. The bike only gets used on motocross race weekends. I have changed the oil every 10 hours. The valves have been inspected and adjusted as necessary. I replaced the piston at 80 hours, but that was just a precautionary measure. The bike runs perfectly, but I don't want to push my luck. What should I replace over the winter, and what company/services should I utilize to do the work?

OR...

Am I better off just selling it and forking out 9 grand for a new one? Problem is, as a 6'4" motocross rider, I really like the layout of the chassis on this bike. Plus, believe it or not, Factory Connection has my air forks working great for me.
You could throw another piston at it. I've seen lower end bearings and seals go twice as long as your at, but it wouldn't hurt. If valves are in spec I'd just do a piston and cam chain and verify with a leak down test. High maintenance 4 strokes are a myth.

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