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Discussion Starter · #1 ·
So I just pulled my engine out of my ninja 300 cause it seized at 100 mph in 6th gear with low oil. It was a 2014 and had 14,000 miles on it. Does anyone with any engine experience know what some key things to look at would be. I am kind of new to engine rebuilds so literally any advice will be greatly appreciated.
 

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84' Goldwing Aspencade, 91' EX500, 98' Ninja 250 w/ 17' 300 engine, 07 EX500
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My personal advice, don't. These engine are cheap enough used, than you will spend money and time to rebuild it. I've been messing with these parallel twin engines since the EX500/Ninja 500s, Ninja 250 days.

There are a lot of threads out there, most of them end badly. The few that do suffer more time and money than they originally thought it would be. Mislead by it's not gonna cost that much for bearings, etc.

I personally have a 98 Ninja 250, that after about 50k miles, just packed up, bottom end knock. Drained the oil, only to find A LOT OF METAL in the oil. So I needed an engine, then I found a whole 17 Ninja 300 engine complete with wiring harness, ECM, and fuel injection for only $600 bucks.

I'm not saying it's impossible to rebuild one of these engines, it's just not worth it in the long run.

Either or way we're here for you.

So first step, drain the oil, how does it looks? Sparkly? Metal, etc.. cut the oil filter open, and note what's in there.

After that, it's remove the engine, and split it open. Then examine all the parts, then make a list of what is needed to be fixed.
 
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So I rebuilt the top end of my 300 last season. Although it wasn't because it got damaged, it was just regular maintenance at 40k miles. I was mostly in there to inspect everything, but also replace the piston rings, hone the cylinders, clean the cyl head, all new upper gaskets, full new set of water piping, and a full clean out of the coolant and oil channels and lines.

Link to the thread I made back then, continue reading here for the TLDR essentially. I think I even described the emotional toll doing that work had on me in the thread, it was scary working on my only bike as a college kid. I don't have the cash for a new bike, lol. But I had an idea for what I was undertaking, and it couldn't have come out better IMO.


Had to take the motor completely out, and it lived on my bedroom table for about 2 months to do that. The work cost me about $400 in parts IIRC, but the cost was mostly time and effort. My story was a success story, it still runs beautifully to this day with mid 50,000 miles on it, and it's gonna be out on the track in the spring time for sure.

That said, I agree with Ghostt's sentiment to buy just a used motor. If you haven't undertaken similar projects in terms of time, space, cost, effort, or complexity, then I don't recommend it be your first. My 'simple' top end rebuild took up my entire house. I am not kidding, every room (including the kitchen) had bike parts everywhere. It took about 2 months of constant hand work. Things almost always break during maintenance, and you have to wait for parts in the mail. Everything was laid out in the orders/directions they came out of the bike. I hand washed every single part that came out and went into the motor, including the outside of the whole engine.

Not to discourage you if you want to learn. By all means, if you are prepared to undertake that level of work, I absolutely think you should, and we on the forums here can empower you with experiences and knowledge along the way. Just make certain you won't be the probably 95% of people who undertake an engine rebuild just to find out half way in that it's extremely complicated and detail oriented.

Here's the kicker. All that stress and strain and time and money was just for routine maintenance, not even a repair. My advice to you is that if you open it, and find transmission or crankshaft related failures, I wouldn't even try the repair, and just go for a used motor. Especially those problems, but obviously a ruined cylinder head is gonna be a costly fix as well. So unless you really want to learn and don't care about the time and money, and you find those serious problems, I wouldn't undertake the work.

But again, if you are here to learn and experience, I think there is priceless knowledge to be learned pulling apart any motor, especially one that might be unrecoverable. And in that same frame of mind, myself or anyone else here with the experience would be happy to guide you.

Good luck. Doesn't hurt to just get the motor out of the bike first. Follow the shop manual, it's free online if you haven't found it yet. Also, check oil and coolant reservoir EVERY time you fire up the bike, and you will avoid almost all serious engine problems!
-Mike
 

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Here's the kicker. All that stress and strain and time and money was just for routine maintenance, not even a repair
Definitely second this statement. A top end rebuild as part of a regular maintenance process is vastly different from a broken engine.
Low oil tends to lead to all sorts of major problems and would probably mean completely disassembling the engine, replacing most (if not all) bearing parts, and praying luck was on your side that only the bearings failed and none of the associated moving parts were damaged too.
Where it's a "cheap" bike with lots of relatively expensive plastic, you're likely to find a cost-effective, low-mileage, undamaged engine being sold off a "totaled" bike that had only (or at least mostly) cosmetic damage. A few pieces of cracked plastic and some scrapes to the muffler can be enough to "junk" one of these machines.

As a point of reference, my other bike was knocked down while parked less than a month after I bought it. I took in in for an assessment and the repair would have cost over $5,000 (the bike was over $10,000 new with all taxes and fees in). The damage was a bent lever, bent sidestand (not the stand itself, but the little knobby bit you kick to fold it out) and some scratches to the mirror housing, muffler and radiator. Zero functional problems (I did bend the lever and sidestand nubby-bit back to shape, but I was able to ride just fine before I did), and the repair bill was almost half the total cost of the bike new (over half the cost of the MSRP sticker price).
 

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From another point of view, if you like working on engines, it looks like a great fun project. I wish I had what it takes to takes apart the engine and rebuild it: time, skills, place, tools, ecc,
I think it wouldn't matter much to me if in the end I spent some more.
 

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From another point of view, if you like working on engines, it looks like a great fun project. I wish I had what it takes to takes apart the engine and rebuild it: time, skills, place, tools, ecc,
I think it wouldn't matter much to me if in the end I spent some more.
This is a valid observation.
If you want to ride the bike again in the least amount of time for the lowest cost, you're probably looking at a used replacement engine.
If you want to tinker, and can afford the time and dollar costs, go for it!

If it were me, I'd probably try and get a cheap replacement so that I could ride the bike, while also tinkering with the wrecked one when time and money allowed...
 

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It is a good learning experience, but not usually cost-effective in many cases. Plenty of things that can go wrong along the way.

The last project I did with my son, a new crank, before he took it (CRF150R Supermoto race bike) with him to live in CA -

Gotta have the factory service manual when you get to this point.



Before that, we had to repair a bent valve from the PO over-revving the snot out of it -





It's been solid now for dozens of races.
 

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I feel like where JKV is coming from with the CRF repair is honestly the best place to start a journey into engine repairs, as opposed to typical street bikes. Smaller size, lower complexity (relatively speaking) and lower costs and space needed. A lot of working on street bikes to me was just getting body work off and gaining access to assemblies by removing other assemblies. Then the actual 'job' you set out to do is 5-10% of the actual labor, for deeply embedded jobs.

Wish I had an old school off road machine just to practice all my engine rebuilding skills on. Maybe some day.

-Mike
 

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I agree Mike. I probably wouldn't dive into a Ninja the same way as we did the CRF.

Latest project, from the other son, is a KDX200 that needs cylinder repair from a broken wrist pin clip -



We did a head gasket and lapping on a Ninja 500, and it was a pain. Much prefer the simple single-cylinder engines.
 

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Discussion Starter · #10 ·
So I rebuilt the top end of my 300 last season. Although it wasn't because it got damaged, it was just regular maintenance at 40k miles. I was mostly in there to inspect everything, but also replace the piston rings, hone the cylinders, clean the cyl head, all new upper gaskets, full new set of water piping, and a full clean out of the coolant and oil channels and lines.

Link to the thread I made back then, continue reading here for the TLDR essentially. I think I even described the emotional toll doing that work had on me in the thread, it was scary working on my only bike as a college kid. I don't have the cash for a new bike, lol. But I had an idea for what I was undertaking, and it couldn't have come out better IMO.


Had to take the motor completely out, and it lived on my bedroom table for about 2 months to do that. The work cost me about $400 in parts IIRC, but the cost was mostly time and effort. My story was a success story, it still runs beautifully to this day with mid 50,000 miles on it, and it's gonna be out on the track in the spring time for sure.

That said, I agree with Ghostt's sentiment to buy just a used motor. If you haven't undertaken similar projects in terms of time, space, cost, effort, or complexity, then I don't recommend it be your first. My 'simple' top end rebuild took up my entire house. I am not kidding, every room (including the kitchen) had bike parts everywhere. It took about 2 months of constant hand work. Things almost always break during maintenance, and you have to wait for parts in the mail. Everything was laid out in the orders/directions they came out of the bike. I hand washed every single part that came out and went into the motor, including the outside of the whole engine.

Not to discourage you if you want to learn. By all means, if you are prepared to undertake that level of work, I absolutely think you should, and we on the forums here can empower you with experiences and knowledge along the way. Just make certain you won't be the probably 95% of people who undertake an engine rebuild just to find out half way in that it's extremely complicated and detail oriented.

Here's the kicker. All that stress and strain and time and money was just for routine maintenance, not even a repair. My advice to you is that if you open it, and find transmission or crankshaft related failures, I wouldn't even try the repair, and just go for a used motor. Especially those problems, but obviously a ruined cylinder head is gonna be a costly fix as well. So unless you really want to learn and don't care about the time and money, and you find those serious problems, I wouldn't undertake the work.

But again, if you are here to learn and experience, I think there is priceless knowledge to be learned pulling apart any motor, especially one that might be unrecoverable. And in that same frame of mind, myself or anyone else here with the experience would be happy to guide you.

Good luck. Doesn't hurt to just get the motor out of the bike first. Follow the shop manual, it's free online if you haven't found it yet. Also, check oil and coolant reservoir EVERY time you fire up the bike, and you will avoid almost all serious engine problems!
-Mike
My personal advice, don't. These engine are cheap enough used, than you will spend money and time to rebuild it. I've been messing with these parallel twin engines since the EX500/Ninja 500s, Ninja 250 days.

There are a lot of threads out there, most of them end badly. The few that do suffer more time and money than they originally thought it would be. Mislead by it's not gonna cost that much for bearings, etc.

I personally have a 98 Ninja 250, that after about 50k miles, just packed up, bottom end knock. Drained the oil, only to find A LOT OF METAL in the oil. So I needed an engine, then I found a whole 17 Ninja 300 engine complete with wiring harness, ECM, and fuel injection for only $600 bucks.

I'm not saying it's impossible to rebuild one of these engines, it's just not worth it in the long run.

Either or way we're here for you.

So first step, drain the oil, how does it looks? Sparkly? Metal, etc.. cut the oil filter open, and note what's in there.

After that, it's remove the engine, and split it open. Then examine all the parts, then make a list of what is needed to be fixed.
Wow I cant believe the response I have gotten on here already. Thank all of you for willing to help me out. I understand this project will be a challenge for sure. Im not to worried about the time it will take as this bike has already been sitting for a year and I have a sv650s so im not to worried about it sitting around for another 6 months or however long its going to take. Also not too worried about parts as I have a way of getting super cheap oem parts. This is more of a learning experience for me than me trying to save time and money by fixing it instead of buying a new one. Worse comes to worse if I open her up and its a shitshow Imma just get a new one but I want to at least give it a go I have been looking into it a lot. I have emptied the oil and it really had no flakes of metal or anything in it so thats kind of good going to cut open the oil filter next. Also how where you able to find a motor for 600 thats really good most i see are 1k-1.5k. Whats a good way also to make sure your getting what your paying for and not just some shit working engine. Again thanks to all that have responded I greatly appreciate it.
 

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84' Goldwing Aspencade, 91' EX500, 98' Ninja 250 w/ 17' 300 engine, 07 EX500
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Wow I cant believe the response I have gotten on here already. Thank all of you for willing to help me out. I understand this project will be a challenge for sure. Im not to worried about the time it will take as this bike has already been sitting for a year and I have a sv650s so im not to worried about it sitting around for another 6 months or however long its going to take. Also not too worried about parts as I have a way of getting super cheap oem parts. This is more of a learning experience for me than me trying to save time and money by fixing it instead of buying a new one. Worse comes to worse if I open her up and its a shitshow Imma just get a new one but I want to at least give it a go I have been looking into it a lot. I have emptied the oil and it really had no flakes of metal or anything in it so thats kind of good going to cut open the oil filter next. Also how where you able to find a motor for 600 thats really good most i see are 1k-1.5k. Whats a good way also to make sure your getting what your paying for and not just some shit working engine. Again thanks to all that have responded I greatly appreciate it.
I got it at that price by luck, I was searching for a pregen 250 engine, and found it on Facebook marketplace, I just had to drive to St Louis to pick it up, which was about 12 hrs round trip.

Here is the thread link Need some help with a project...

I always support learning about one's bike, ang giving all the information available, including personal experiences.

Like I said, worse case, you'll be buying a used engine, good luck and post your results here, don't start a bunch of threads, it's had to keep track of those, like I'm doing for my project
 

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I always support learning about one's bike, ang giving all the information available, including personal experiences.
I second this sentiment. My philosophy is always learn everything you can, especially if it interests you.
I've rebuild several small, simple engines as well as troubleshot a few car problems (usually sensors, etc.). Never rebuilt a motorcycle (or larger) engine (yet) but I'd be willing to offer any applicable experience, advice, opinions, theories, and utter lies/BS that I have if it could be in any way helpful.
 
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