[ace70]

Hey all,

Just new to the forum, long time listener, first time caller.

I am looking at a '94 M900, which has a crack in the crankcases around the pressure relief valve and earth strap, was wondering what could cause this. I haven't seen the bike in the flesh, but what i can see it hasn't been down the road, and it looks like the rest is in good nick.

I have seen posts in here talking about crankcase problems, trying to work out causes to how this could happen.

If only crashes cause this sort of damage, or over zealous spannerwork with pressure on engine mounts etc.

I am looking at either dismantling then welding, dismantling into other crankcases, or engine swap.

Any words of wisdom from the wise...

Cheers

 

[Speeddog]

That's a weak area in the early crankcases, not sure which year they beefed that up.
Does that crack go as far over toward the cylinder as it looks?

I've seen pics of crankcases with that kind of damage welded, and it was a successful repair.

I think one of the DML'ers in Australia or NZ did it.

 

[ace70]

Haven't seen the bike in the flesh, but the guy said he still rides it, so??

 

[Mark1305]

Yeah, a while back one of members over in the western Pacific had his crack from hitting a huge pothole IIRC. He got it welded successfully.

I've seen picks of weld repairs on other bikes too. If the crack goes all the way to the center seam in the cases, I would be less optimistic. At that point you might be able to pick up some cases or a junked motor with good cases for less than an extensive welding/machining repair.

I recently picked up the bottom half of a motor minus the case covers, flywheel, alternator etc. but with the oil pump and shift mechanism for under $400 before shipping. They are out there - especially on Ebay

 

[test-reg]

These cracks can be successfully repaired, but, IMO for me to buy a bike that needed that repair either I would have to be in love or it would have to be quite a bargain.

 

[ace70]

Going to do most of the work myself, which is secretly what I want to do.
Take a great big bite and chew like crazy.

Does a 900SS motor fit straight into the Monster. I checked the measurements between the frames of an SS and the monster in the workshop manuals and they are almost identical. A couple of very small differences in them. The space between the engine mounts going across the frame is larger on the monster frame by 0.017 of an inch (0.4mm). Every other dimension (that is relevant) is identical.

 

[Mark1305]

Yep, exteranlly they are identical. Pretty much internally too except for slightly different torque specs for some internals - no known reason for that other than possibly different engineers/tech writers doing the shop manuals. The carbs are spec'd for different pilot jets, too. But its an insignificant difference.

You will want to stick to the carbed motors with single phase alternator to avoid the extra stuff that has to be changed out on the bike because the ignition is triggered differently on the fuel injected motors. Three phase alternators have an additional output wire and use a different voltage regulator.

 

[MotoCreations]

Noticed the wire wheels -- more details? Looks like they have been on there for awhile.

The crack? As SpeedDog mention it is a known problem with early cases. I have heard of two others. Both were welded but required splitting the cases to do correctly. Factor in the money spent to do the work. Upgrade the head studs while you are at it with newer ones.

 

[Mark1305]

Good catch, Mark! I didn't even notice that in the pics.

 

[ace70]

You've got a good eye, i think the guy was getting the wheels detailed when he took the pic, has the standard alloys on it normally. Would be interesting to see a monstro with wires, but then again Ducati almost has with the new sport and GT range.

Does anyone know when and how they beefed up the Crankcases, especially in the rear offside pressure relief / engine mount area.