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2007 Engine seized diagnosis and rebuilt help

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I have a 2007 that I trail ride, rarely do I bounce it off the limiter. Last year my headgasket failed and filled the cylinder with coolant. I fixed that and rode a few times for a couple hours at a time. Last ride it was acting/sounding a little funny so I pulled over and it quit while it was idling. I pushed the kicker and it was a little hard but it kicked through so I started it again. At idle it quit again. This time it was a seize. I assumed the timing chain tensioner had failed and the valves hit the piston. I got it home and pulled the head and the timing chain and valves were great so I pulled the oil filter to look for brass shavings. There was a little copper colored powder in the oil but no shavings. Am I still looking at a failed main bearing? I haven't pulled the engine and split the cases yet, I need a splitter and I assume a crankshaft puller/installer. If there is anyone in the Metro Detroit area that is willing to loan/rent them for a week or so please message me. I bought the shop manual and will be working on this over the winter. 

 

So I guess the questions are:

 

Am I wrong assuming it is the Main Bearing? Where else should I look? 

Do I just buy a bottom end rebuild kit or wait until I get the bottom end apart to diagnose?

How do I know if the crank needs to be replaced/rebuilt?

Because it seized do I need to replace the piston? 

How about the cylinder?

 

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It will probably be the connecting rod bearing. You can do without a splitter if youre really careful but you will need a flywheel puller, once the cases are apart the crank should come right out.

You may as well get a rebuild kit and do everything while youre in there. The cylinder may be ok but you wont know without measuring it, replace the piston.

Edited by CRFRida1605

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It is the connecting rod bearing CRFRida says.  You really don't need a case splitter.  You can easily tap the cases apart with a rubber mallet.  A flywheel puller is pretty inexpensive but given that you are going to replace your crank assembly, you can use a regular puller to remove the flywheel.  A regular puller will damage the oil orifice in the crank but who cares when you are replacing the crank anyway.

 

The work you are going to do in splitting the cases is not hard but it is involved.  Honda publishes a great manual and builds an even better engine that is very intuitive to put back together.  I would absolutely replace the piston and rings given all the work you are doing.  Once the cylinder is off you'll almost surely be able to tell if it is good or not.

 

The bigger and more expensive issue is the head.  Before you take stuff apart, get a good measurement of your valve lash.  If it has already been reshimmed a time or two and the clearance is under tolerances it is time for new valves and for the head to be cleaned up.  There are many options for the head but you need to know its current condition before you can start selecting the best options.

 

You will be really happy you are doing your own work and will learn a lot about your bike.

 

Henryrifle

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Thanks guys, I just ordered a case splitter and crank puller. I already have the service manual. I know it is possible to split the cases with a rubber mallet but I am just going to make the investment in the tools. I can be ham-fisted so it probably will save me money in the long run. Also ordered a clutch holder and flywheel puller. I'll take it apart and pay particular attention to the con rod bearing. The piston has no carbon build up. I bought the bike from a guy that bought it from a buy that just rebuilt it. He was having problems starting it so he sold it cheap. It always started right up for me, I am pretty sure the guy thought the hot start lever was a compression release so he would kick it all day and not start. Usually started on the 2nd kick for me. Last year the head gasket failed and when I had it apart the piston looked brand new, I'll measure and decide if I will replace it. It probably only has 6 hours on it since I replaced the head gasket. I hate to replace good parts but I would hate a failure more. I might just do everything while I have it apart.

 

Weird thing is the guy sold it to me as a 2007. Dual exhausts so I took his word for it. When I checked the VIN the frame came back as 2004. Basically a 2007 engine in a 2004 frame. I think the frames are the exact same between 2004 and 2007 but I might take the opportunity to get a 2007 frame and transfer everything over to it, that way I can say I have had fingers on every inch of the bike.

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You are right. The '04 - '09 bikes use the exact same frame.  there is no difference.  There is a difference in the subframes.  The '04 and '05 bikes had single exhaust and a different airbox, and, as such, used a different subframe.  There is nothing to gain by switching to an '07 frame except eliminating some confusion when ordering engine parts for the next owner.  I do think you could make the swap without loosing any money as you should be able to sell your existing frame for what you pay for an '07.  It would also represent an opportunity to really clean the frame and refresh the steering stem bearings.

 

I have created a similar situation by installing an '08 engine in an '04 frame.  I have the '04 engine and will rebuild it as a spare should one of the other bikes (I have 3 - two sons ride with me) need a rebuild during the riding season.

 

The flywheel puller is a good investment if you ever need to pull a flywheel off a good crank.  Likewise, the clutch holder is very useful.  I have never needed a crank puller to get the crank out.  It easily slides free of the bearings after the cases are split but you can never have too many tools!  The most difficult item to put back on and torque correctly was the flywheel.  I used a strap wrench the first couple of times but ultimately found the Honda tool on eBay for around $40.  Now it is super easy.

 

Good luck with the tear down and rebuild.  It is a fun project and unlike some similar projects, you can complete it with a very high degree of confidence that the job was done right because it is so intuitive.  I always find it fun to work on something that was so obviously well engineered and this is one of those kinds of things...

 

Henryrifle

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Hey guys a quick question. After splitting and watching for thrust washers. One musta slipped out without me seeing

Where does the purple/blue looking thrust washer go!!!

I think it goes on one of the tranny shafts. One was on and the other shaft didnt have a thrust washer...

Any help...

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Hey guys a quick question. After splitting and watching for thrust washers. One musta slipped out without me seeing

Where does the purple/blue looking thrust washer go!!!

I think it goes on one of the tranny shafts. One was on and the other shaft didnt have a thrust washer...

Any help...

 

 

When this happens to me, I look in the service manual and parts diagram. The parts diagram may have the dimensions listed in the part description and then it is a matter of measuring to ID where it goes.

 

Do you have the service manual?

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Yes i do have the manual. It shows a thrust washer on both trans shafts. It only had one. This blue in color washer seems to go on the other shaft. I will di the measure thing. I just thought with its blue color someone might know exactly where... Thx.. Love watching your teardown crf250 video

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Matthew:

 

Thank you for posting a PDF Service Manual.  I do own the official manual but It is great having the electronic one to look at while at work :naughty:  or out in the garage on an old laptop that is out there.  I've watched the free video and if the rest of the series is similar it looks like a great aid to a new engine rebuilder!

 

Thanks again,

Henryrifle

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Matthew:

 

Thank you for posting a PDF Service Manual.  I do own the official manual but It is great having the electronic one to look at while at work :naughty:  or out in the garage on an old laptop that is out there.  I've watched the free video and if the rest of the series is similar it looks like a great aid to a new engine rebuilder!

 

Thanks again,

Henryrifle

 

No problem. Yes, the video is a great aid. It walks you through the process step by step and has helped many people so far.

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I bought a Wrench Rabbit full rebuild kit, WR101-022. I figure that should take care of everything. Need to get a look at the cylinder to decide if I need to send it out or replace it. In several places on the internet, including Amazon the WR101-016 kit was listed as a fit for the CRF250R but it is actually for the CR250R, can't believe everything you read on the internet I guess. As I get further into the engine I'll post more.

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That brass/ copper is a connecting rod crank bearing, believe me I just finished a whole rebuild on my bike and the same thing happened. The good thing is no special tools are needed to split the cases and get the crank out. From there you have 2 options, get a whole new assembly from Honda which will do the same thing again in about 50 hours or (like I did) rebuilt the crank with a forged connecting rod and a aftermarket needle style race proven bearings. Note the higher compression the piston the faster this will fail from the added stress.

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That brass/ copper is a connecting rod crank bearing, believe me I just finished a whole rebuild on my bike and the same thing happened. The good thing is no special tools are needed to split the cases and get the crank out. From there you have 2 options, get a whole new assembly from Honda which will do the same thing again in about 50 hours or (like I did) rebuilt the crank with a forged connecting rod and a aftermarket needle style race proven bearings. Note the higher compression the piston the faster this will fail from the added stress.

Most will get way more than 50 hrs out of the crank/rod bearing. A fast B or A MX rider may need to replace often , but not the average rider.

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