Jump to content
Sign in to follow this  

Bottom end rebuild: Pics of the damage

Recommended Posts

So I'm doing a bottom end rebuild on my CRF250R ('04) because the crank bearings went out, and basically exploded into my engine, this is what I got from it...

DIGI0009.jpg

DIGI0007.jpg

DIGI0006.jpg

What do you guys think?

Need to replace the cases/piston?

Get the burrs machined back down and slap the new crank in?

Also, how do you guys suggest I go about flushing out all the bearing flakes?

Share this post


Link to post
Share on other sites

Those gol darn honda's! :thumbsup:

That is ugly! If it was me I would go el cheapo and just disassemble the cases, polish up the scars with some emery cloth, and wash them out thoroughly in the parts washer with some kerosene.

  • Like 1

Share this post


Link to post
Share on other sites

Well.... eww

There are a few problems that may arise.

First, if you machine the burs, you may take out too much material from the bearing seat and lose the interference fit. Or, if you're carefully and start at a known good seat point and only take up the burred/raised areas, you may be able to get away with it.

Second, you might want to start pricing out every bearing from inside that case. You don't want to take a chance at a flake messing with something after you've put your engine back together. If that's not an option, take some contact cleaner and hose everything out completely, until you're satisfied that there's no chance of any flakes being left.

It looks as though the bearing in the first picture can be removed without a puller, if so, then remove it and clean it thoroughly. Honda recommends that you never spin a bearing without grease in it, so clean it, inspect it, then grease/oil it back up before you tinker with it.

Now, check the crank to make sure nothing got in between the connecting rod and your.... crank lobes, obviously check it for warpage and such.

I would replace the piston and wrist pin while it's all apart. May as well start fresh.

Next, take a look at your cylinder, look for scars/marrs/holes in it. Take it to a shop that has a ball hone and run the hone through it a few times. Don't worry, it won't hurt the plating. It'll just remove the glazing/aluminum from the old piston.

Other than that, go through everything with a fine toothed comb, make sure there's no trace of metal where there shouldn't be.

and LOL at crash bandicoot

  • Like 1

Share this post


Link to post
Share on other sites
Well.... eww

There are a few problems that may arise.

First, if you machine the burs, you may take out too much material from the bearing seat and lose the interference fit. Or, if you're carefully and start at a known good seat point and only take up the burred/raised areas, you may be able to get away with it.

I'm going to get some Emery paper, and get the burrs out of there and see where I go from there...

Second, you might want to start pricing out every bearing from inside that case. You don't want to take a chance at a flake messing with something after you've put your engine back together. If that's not an option, take some contact cleaner and hose everything out completely, until you're satisfied that there's no chance of any flakes being left.

Thanks, my brother has a parts cleaner he can use at work... So he's going to bring my cases in tomorrow and clean the shat out of it...

It looks as though the bearing in the first picture can be removed without a puller, if so, then remove it and clean it thoroughly. Honda recommends that you never spin a bearing without grease in it, so clean it, inspect it, then grease/oil it back up before you tinker with it.

Now, check the crank to make sure nothing got in between the connecting rod and your.... crank lobes, obviously check it for warpage and such.

I ordered a whole new crank... So I shouldn't have to worry about any of that right?

I would replace the piston and wrist pin while it's all apart. May as well start fresh.

About that piston, it has about 4 hours on it... thats why I was trying to salvage it.. I would doubt the cylinder even has a glaze on it..

Next, take a look at your cylinder, look for scars/marrs/holes in it. Take it to a shop that has a ball hone and run the hone through it a few times. Don't worry, it won't hurt the plating. It'll just remove the glazing/aluminum from the old piston.

My cylinder is good, although I will clean it with contact cleaner and make sure there is no glaze on it..

Other than that, go through everything with a fine toothed comb, make sure there's no trace of metal where there shouldn't be.

and LOL at crash bandicoot

HAHAHAHA I knew somebody would catch that Crash Bandicoot disk... dangit!

I just wanna ride!!

Share this post


Link to post
Share on other sites

Ok, if you're replacing the crank, you shouldn't have to worry about the above crank part.

Now, it's your call on the piston. When you get your new crank in the mail, try installing the old piston and pin on it, check for wobble in the pin area. If everything there is smooth, then you "should" be ok. I would still recommend picking up a ring set at the least

It's really what you feel comfortable with. Look at the rings and see if there are any marks on the outside, if there aren't, then make the decision.

Good Luck and keep us posted.

Oh yeah, Crash was an awesome game, it was really tough if you tried to get the best ending.

Share this post


Link to post
Share on other sites

I sure as heck wouldnt re-use that chewed up piston with a nice new crank!!

Share this post


Link to post
Share on other sites
First, if you machine the burs, you may take out too much material from the bearing seat and lose the interference fit. Or, if you're carefully and start at a known good seat point and only take up the burred/raised areas, you may be able to get away with it.

I'm not recommending this per se but in my limited machining experience I was instructed that if your opening for a press fit was slightly too big (.001"- .002") you could use a center punch and make a few small punches around the machined area to regain the press fit. I would probably buy the new bearings then go get it cleaned up at a machine shop and see how much they have to take off. I'm sure the machinist could point you in the right direction.

Share this post


Link to post
Share on other sites
I'm not recommending this per se but in my limited machining experience I was instructed that if your opening for a press fit was slightly too big (.001"- .002") you could use a center punch and make a few small punches around the machined area to regain the press fit. I would probably buy the new bearings then go get it cleaned up at a machine shop and see how much they have to take off. I'm sure the machinist could point you in the right direction.

You're on the right track. That is called "peening."

You would have to hope that after cleaning up the area, that it wasn't too loose, you'll then run into the situation of the bearing hole being .001" off, now that may create a problem. Or it could work. Depends if you want to take the chance.

Share this post


Link to post
Share on other sites

You guys are starting to scare me again..

what exactly happens if the clearence is too big?

I don't understand I guess, the clearence doesn't seem like it has anything to do with how the crank operates to me... because the crank rests in the bearings on both sides... aaaand then the wall is just there..

Clearly you guys seem to know more than me, which is why I'm trying to allow you guys to help me understand this :thumbsup:

Edit: After re-reading this, it sounds like you guys are talking about the crank needing to be pressed in, which would directly be affected by the tolerances...

If this is the case then I would like to inform you that 4-stroke cranks aren't pressed in, rather they just rest in the bearings basically. And if that's not what you're saying then I'm sorry, I feel like an idiot haha.

Share this post


Link to post
Share on other sites

Maybe I'm not seeing the pic well enough. I believe we are both going off the assumption that the damaged area is where a bearing would be pressed into, which judging by your response is not true...?

Share this post


Link to post
Share on other sites

haha, didn't mean to throw you off. The bearings are press fit into the case halves, that is the interference fit.

The issue that was brought up was, if you mill/sand down the burrs in the bearing seat area, you *may* enlarge the hole just a bit, therefore reducing the interference.

From that point, we seemed to have digressed into a spin of how to correct that one situation.

Don't get worried. Continue with your plan of removing the burrs. When you're ready to install your new bearings, you shouldn't be able to push them into place with the pressure of just your hand. They should require the use of a bearing driver and softblow hammer.

If, they fall in super easily, then there might be a slight problem, and you'd have to take measures to ensure that the bearing doesn't move from its seat.

Share this post


Link to post
Share on other sites
haha, didn't mean to throw you off. The bearings are press fit into the case halves, that is the interference fit.

The issue that was brought up was, if you mill/sand down the burrs in the bearing seat area, you *may* enlarge the hole just a bit, therefore reducing the interference.

From that point, we seemed to have digressed into a spin of how to correct that one situation.

Don't get worried. Continue with your plan of removing the burrs. When you're ready to install your new bearings, you shouldn't be able to push them into place with the pressure of just your hand. They should require the use of a bearing driver and softblow hammer.

If, they fall in super easily, then there might be a slight problem, and you'd have to take measures to ensure that the bearing doesn't move from its seat.

I'm not sure where you're going with this? haha...

What bearings are you talking about? There isn't any bearings in the area that was affected, it is just a plain, metal wall that surrounds the crank, and creates the cavity that the crank sit in, but no bearings on those walls.. ( I think I'm trying too hard to explain this)

Those walls run perpendicular to the rod, if that makes anything clearer?

So what I'm saying is that as the rod spins, these burrs (if sticking out any further) would rub.

Share this post


Link to post
Share on other sites
Well theres your problem.

You lost me buddy... haha what's my problem again?

Share this post


Link to post
Share on other sites

oh geez, I was totally off. You mentioned that your crank bearings went out. I thought you were talking ball bearings or something of that nature. haha

If nothing is touching those walls with the burrs, then just clean them up.

disregard the bearing install portions of my posts then.

Share this post


Link to post
Share on other sites

To add to the confusion.

It looks like in the picture the burs are on the crankcase halves.And not in the bearing races.Apply heat(propane torch) to the area around the retaining screw's that are holding the bearing(s) in.They will have Loc-Tite on them.It is easier the remove the screw's this way.Then heat the case around the bearing and tap it out with a hammer.Install them the same way..

If for whatever reason a bearing is loose fitting in the case it can be peened as mentioned or use the red Loc-Tite.It work's i've done this many times.Also use Loc-Tite on all the retaining screw's.

The rest of the sage is to dissasemble everything. Cylinder head,oil pump and all and flush all of the oil passages and cavities,holes,etc in every part of your motor and look for damage.You just grenaded you motor and there is schratnel everywhere.

Some motors have small orfice's(jets) in the oil passage that usually sprays the piston that can also become stopped up.

I hope thats a good start and it's not raelly as bad as it sounds.

Look at some parts fiches and try yo get a service manual somewhere

Good luck

Doug

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×