Flushing A Crankcase?

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#1
Hey Guys,

I had a set of rings overheat and the bottom ring end gap hooked on the intake opening and snapped a piece out of the piston. I had to replace everything but I have no idea where the piece of piston went?

I decided to flush out the crank area to be sure nothing got down there ready to raise hell when I get her running again.

My question concerns flushing methods. I noticed that there was a small amount of oil on the crank as I spun it around. I was under the impression that the crank was dry? Does it get lubrication from the fuel mixture?

I decided to use my 2-stroke premix as a flush which is going ok but now I am starting to feel the crank getting a little tighter. This is probably because I am removing the trace oil that was in there. If this is the case, what should I use to lube the crank area again? Should I dump a little 2-stroke oil in there just to keep things slick?

Cheers
Bernie
 

IndyMX

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#2
Yeah, the oil in your mix is used to lube the bottom end..

If you really want to make sure you get it all out, you better split the cases. It's really not that hard. And if you decide not to, and you didn't get the piece out, you will be later anyway.
 
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#3
Thanx for the info.

I probably should take the advice and split the cases just to be sure. I do not have an actual repair manual for this bike yet so I am curious about what I need to do?

Looks like I can take the generator and sprocket off the left side of the engine and then remove the left side engine cover. Going to go poke around with it this AM.

Any tips on doing this would be appreciated.

Cheers
Bernie
 

IndyMX

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#4
Yeah, you can do it that way... Invest a couple dollars in a flywheel puller, it will save many gray hairs. I picked mine up at the bike shop for 10 bucks. it's a 27 mm left hand thread, and will fit almost all jap bikes. For actually splitting the cases, I used a $12 steering wheel puller I got at Autozone. I had to get a couple of 120mm long 6mm bolts from Lowes, plus a couple flat washers, but that was only a couple extra bucks.


When you reassemble, just take it slow and it'll all go together pretty easy.
 
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#5
Hey Indy,

Thanx for all of the great advice you are offering up. It is greatly appreciated!

I already have the puller for the generator so I am good there.
Can you give me a quick rundown on what I need to do to that cover off the engine?

Just not clear on where you are using the steering wheel puller and the bolts etc?

I will also do a search on the forum for any info that might already exist.

Cheers
Bernie
 

IndyMX

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#6
when you get the flywheel off, you then take off the stator plate below it.

There'll be two bolt holes on either side of the crank shaft that are straight inline.

Put your long 6mm bolts in those, and your case puller on.. Start crankin down slowly. (err.. make sure you have all of the case bolts out. there's about 10 of em. all on the left case side.)

I had to tap lightly with a deadblow hammer to get it all to release, but not too hard, don't want to knock anything out in the gearbox, and not know where to put it back in.

Clean the old sealant from the case halves.. Don't use a razor or knife.. nothing hard and sharp.. Perhaps a plastic putty knife, or a scotch brite pad.

Once everything is clean and dry, use some Yamabond 4 (if you can find it) or equivalent. Let that skim over and join the halves. Go slow, incase you have binding in the gear box..
 
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#7
yeah its easy to gouge up flywheel if u just cram a gear puller on it. Make sure you use the right size phillips head on the stator bolts if they arent hex heads. this is a 2 stroke engine? so how would a piece of metal get into the trans?
 

IndyMX

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#8
He's got a flywheel puller, no issue there.. They are phillips head screws, be careful on them, you may need an impact to get them loose. It's a 2 stroke, but he never mentioned that there was anything in the trans. It could be in the bottom of the crankcase though, splitting the cases is the only 100% sure way of knowing it's not in there, ready to do more damage.
 
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#9
Thanx for the tips guys.

Yeah, its the crankcase that I am worried about.
The transmission is alright.
I am missing about a 1/2" piece of piston. It may have gotten
blown out the exhaust for all I know but I do not want to find
out the hard way that it somehow worked its way into the area of the crank ready to jam at the worst possible moment.

Time to get to it i guess.

Should be back for more Q's later....

Thanx
Bernie
 
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#10
IndyYZ85 said:
when you get the flywheel off, you then take off the stator plate below it.

There'll be two bolt holes on either side of the crank shaft that are straight inline.

Put your long 6mm bolts in those, and your case puller on.. Start crankin down slowly. (err.. make sure you have all of the case bolts out. there's about 10 of em. all on the left case side.)
Hey Indy,

I have the flywheel, stator assembly off.
Just to be clear, you used 2 long M6 bolts (I found 90mm but couldn't find 120mm) with a set of washers.
Then you used the steering wheel puller to grab underneath the washers and press against the end of the crank?
I just realized that my pullers are three arm and not two arm which I am assuming you are referring to. Might have to go out and pick one up tomorrow if I cannot figure it out another way. I think I could make one by drilling and tapping a piece of flat steel.

Cheers
Bernie
 

IndyMX

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#11
razorboy said:
Hey Indy,

I have the flywheel, stator assembly off.
Just to be clear, you used 2 long M6 bolts (I found 90mm but couldn't find 120mm) with a set of washers.
Then you used the steering wheel puller to grab underneath the washers and press against the end of the crank?
I just realized that my pullers are three arm and not two arm which I am assuming you are referring to. Might have to go out and pick one up tomorrow if I cannot figure it out another way. I think I could make one by drilling and tapping a piece of flat steel.

Cheers
Bernie
You should be able to use a three arm.. as long as you can get it to pull straight.

And I only suggested 120mm bolts because that's what I have. And they seemed to be about the right length..
 
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#12
I made a flatbar puller from a piece of aluminum.
Drilled 2 x M6 holes for the 2 bolts and a threaded M10 in the middle to put the pressure on.
It won't come apart?
I counted 9 bolts to take out of the case. There are 4 under the stator and then 5 around the outer perimeter of the motor. If I pull on the case, it does move as if the Yamabond seal is now broken but it still won't come off?
What holds it in place besides the Yamabond and maybe a few guides?

Cheers
Bernie
 
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#13
I believe the puller is flat,with slots in it,and a threaded spindle. Back the spindle all the way back,the 6mm bolts are to small of a head,add washers to keep them from pulling through. The puller needs to be tightened evenly and as many bolts as possible. Thread the spindle in and watch that the cases remain parallel at all times. This is where the dead blow comes in handy to keep the countershaft side equal. If you are real handy take a piece of metal that will not bend too easy,1/4 or 3/8 aluminum,basically the size of your engine. Mount 2 spindles,crank and countershafts,drill holes for the case bolts you can utilize. Make sure you put the bolts in the left case,not the right,damage can occur! I like this one, http://www.motionpro.com/images/groups/84.jpg
 
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#14
razorboy said:
If I pull on the case, it does move as if the Yamabond seal is now broken but it still won't come off?
Bernie
razorboy.

Try a little heat. If you don't have a torch, go to your local hardware store and buy a butane plumbing torch. They are pretty cheap. Heat the case in a circular motion around the bearings until you can sizzle a drop of water on the case. This will expand the case and release the grip on the bearings.

When you put the cases back together, seal your crank in a large plastic baggie and put it in the freezer for a couple of hours. Then heat the case with your torch and the crank will drop right in. Be careful not to overheat the cases. Only heat them until you can sizzle a drop of water on them. Be sure to tap on the countershaft while you push on the crank to keep the cases even like foxforks said. This will keep them from binding when separating them.
 
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#15
Thanx for all the help guys,

Got It!

Cheers
Bernie