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Honda 1984 CR250R engine case damage :(

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I'm in the process of restoring a this bike. My boyfriend decided to "help" put the bearings in with his shop press. The result is illustrated below...

 

damage3_zps483826c6.jpg

 

damage2_zps3db7945f.jpg

 

See where that lip is supposed to be in the first image, and how it's not on there anymore in the second. He managed to push the bearing right though the case.

 

My question is can this sort of damage be fixed by an engine builder? Like a local shop or even a specialist shop like the kind that do welding on heads and cylinders? 

 

If I can't get it repaired, then do I have to buy cases as a matched pair? On some bikes like the Suzuki RG500 I'm aware the cases are machined together and must be kept as a set.

 

Other than that I'm just so grumpy about it at the moment that I had to tell someone.. arrrrgggh!

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Ouch!! I'm afraid to say that after carefully looking over the pics of the damage I have come to the conclusion it's time for a new boyfriend........ :goofy:

 

Most things are repairable. There is welding and machining involved with the repair of your broken casing, but finding someone that has the knowledge,

correct equipment, and the practical skills to carry out the task may be an issue, and the cost of the job may mean it is easier to source alternative casings.

 

Easiest way to fit bearings is to gently heat the entire casing so they expand slightly, and at the same time cool the bearing so they shrink slightly, then most times the bearings will just drop in easily and with no risk of breaking the casings with the use of either a press or hammer.

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Ouch!! I'm afraid to say that after carefully looking over the pics of the damage I have come to the conclusion it's time for a new boyfriend........ :goofy:

 

Most things are repairable. There is welding and machining involved with the repair of your broken casing, but finding someone that has the knowledge,

correct equipment, and the practical skills to carry out the task may be an issue, and the cost of the job may mean it is easier to source alternative casings.

 

Easiest way to fit bearings is to gently heat the entire casing so they expand slightly, and at the same time cool the bearing so they shrink slightly, then most times the bearings will just drop in easily and with no risk of breaking the casings with the use of either a press or hammer.

 

Thanks, but the boyfriend is like the case, I'm reluctant to part with either, although they are both have a fair bit of damage now.  :bonk:

 

I trusted him because he is a qualified diesel fitter.. I think he's been working with too much huge stuff. He was telling me all about how to fit a bearing that has to be lifted with a gantry and guided into place by more than one bloke. No wonder he broke the tiny engine case!! 

 

So does anyone know if they have to be replaced as a matched pair? Anyone? Because seriously, a common mistake with the RG is to buy a case or a couple of cases off ebay that aren't matched because they are all machined as a set so they all end up a little different. Are the CR engines like that or do folks replace separate parts of them successfully?

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So does anyone know if they have to be replaced as a matched pair? Anyone? Because seriously, a common mistake with the RG is to buy a case or a couple of cases off ebay that aren't matched because they are all machined as a set so they all end up a little different. Are the CR engines like that or do folks replace separate parts of them successfully?

 

I've seen people use only one case half without issue, and heard you should use a set.  Kawasaki sells cases as a set but Honda and Yamaha (IIRC) sell them separately. So if you buy a set, who can prove they were machined together?

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Cases are line bored. so even though it might work (used case half), its not running true. I had a yamaha dealer give me back my yz motor disasembled in a box because I wouldnt buy new cases.

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Cases are line bored. so even though it might work (used case half), its not running true. I had a yamaha dealer give me back my yz motor disasembled in a box because I wouldnt buy new cases.

 

I always presumed the cases were line bored as a matched pair, but having recently looked at the design of various engine cases I do now wonder if they are actually line bored as a pair.

Reason being is if one looks at the shape of the various profiles and diameters in the casings around the bearings and seals for the crankshaft, gearbox mainshaft, and gearbox counter shaft you can see that some have larger diameters internally through a given bore, whilst others have retaining sections (as per part broken off in OP's casing). Plus the dowell pins are in blind holes.This means it would be difficult to use a parallel diameter reamer to accomplish a final finish cut on a given bore.

Roller bearings can cope with a certain degree of misalignment so could it be each of the casings is just CNC machined individually and this gives an acceptable tolerance, and then the casings are mated together as a pair for a final finishing skim across where the cylinder sits, along with any other critical external dimensions such as engine mount boss and swing arm pivot points.

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Well, at a quick glance yamaha only sells them as a set, so either its a big scam, or they are matched.............however bike bandit lists honda case halfs seperately??????????????????WTF

Edited by ickfinger

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Ok, so if Honda sells individual cases then that looks promising that they don't line bore matched sets. If they haven't changed the way they bore them since 1984 then I should be in the clear.  :thumbsup:

 

Handy to know that about Yamaha and Kawasaki though, sounds like they might be matched and buying second hand at a wrecker then might be a risk too, because as Jeekinz said how do you know they're a matched pair? Only one half has a number on it so you really don't. I think that if the manufacturer is unwilling to supply the halves separately then that's pretty telling that they must be matched. It's a pain that they don't number both halves when they are a matched set (I wonder if there is a manufacturer that does?).

 

If it was an old bike and they didn't make the cases anymore then you'd virtually have to own the bike they came off and have reason to believe that no-one has bothered to split the cases before. Like my Honda - it had a total lack of tool marks on the halves. Also I can see the owner didn't even do the bare minimum of maintenance - someone was riding it with a piston that was well worn out, no front brakes and no resistance in the rear shock! 

 

I always presumed the cases were line bored as a matched pair, but having recently looked at the design of various engine cases I do now wonder if they are actually line bored as a pair.

Reason being is if one looks at the shape of the various profiles and diameters in the casings around the bearings and seals for the crankshaft, gearbox mainshaft, and gearbox counter shaft you can see that some have larger diameters internally through a given bore, whilst others have retaining sections (as per part broken off in OP's casing). Plus the dowell pins are in blind holes.This means it would be difficult to use a parallel diameter reamer to accomplish a final finish cut on a given bore.

Roller bearings can cope with a certain degree of misalignment so could it be each of the casings is just CNC machined individually and this gives an acceptable tolerance, and then the casings are mated together as a pair for a final finishing skim across where the cylinder sits, along with any other critical external dimensions such as engine mount boss and swing arm pivot points.

 

This is really interesting, I was wondering myself if you'd be able to tell from the where the holes are and the shape and size of them as to whether they are likely to be line bored or not. Unfortunately I don't have your level of engineering knowledge but I thought there might be some things that would stick out. Or just show them to someone skilled.  ;)

 

Cases are line bored. so even though it might work (used case half), its not running true. I had a yamaha dealer give me back my yz motor disasembled in a box because I wouldnt buy new cases.

 

Damn, that's handy! So is it still apart? It would be great to have a look at some pictures if you still have them apart. Sounds like rmxdan could tell you if they're likely to be line bored or not.

 

Thanks guys, all your contributions so far have been great :)

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