Cracked Gear-Case ETZ 250

[AlanJ]

Hi again Les,
Please forgive me if I am overstepping things here, but I wouldn't feel right if I did not mention it, so, if I was welding that crack I would drill a small hole at the absolute ends of the existing crack and then V the crack from hole to hole thus allowing good penetration with a stress reliever at either end.
As I said Les please forgive me If this is known to you but better safe than sorry. Take care Alan.
]

[nice2day]

Thanks Alan...After you suggested what type of filler rod I did some searching and also found that 4043 seems to be the best one. I'll phone first and if he doesn't have any, I'll buy some and give it to him to use . From videos it looks particularly good at flowing and matching motorcycle type cast aluminium...I appreciate your friendly help Alan...All the best....Les

[nice2day]

Just an update. I took the engine case and something else in for welding 10 days ago with a promise of getting it back the following Wednesday (3x days) ...Now I'm afraid to phone again as the guy is likely to get annoyed that I'm pushing him....

Les

[Puffs]

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[nice2day]

Many thanks Puffs...Nothing worse than not knowing when the work will get done ...I'm desperate to get the parts back so I can continue the rebuild plus there is a morbid fear about the safety of the parts...it's giving me heart-burn...


Les

[AlanJ]

Hi Les,
So sorry to see you being mucked about, as you say, especially when you want to get on with the rebuild, sad, some people.
.
Wish you well Les. Alan.

[Blurredman]

Where did you say you lived again nice2day? (put it in your profile info?)

Scratch that- West Somerset. I had a feeling you were closer and could advise.

[nice2day]

Well I eventually did get the crankcase back. The welding wasn't too bad but not easy areas to get to in all fairness. Well I used a Dremel with Carbide burrs and cleaned it up so I'm reasonably happy with the weld (Noting it would be an unusual event if I was entirely happy )

I just have to get the layshaft bearing removed now but can't shift it by heating to at least 200 C and slamming the case down on the bench so I have had to order a blind bush extractor set...still waiting for that to arrive.

I also thought it would be worth matching the crankcase transfer ports. The right side one was badly matched where the port met the the machined area at the neck of the opening which left a sharp 2mm deep right angled step which would have impeded gas flow on one side. If they were both the same (with a step) maybe I would have left them but there was a large difference and its crucial on a two stroke that the transfer gas flow is near as identical as you can get it.... Using the Dremel carbide burr and then wearing away my thumb flesh, I managed to get both ports with a similar smooth curve.

Les

[Blurredman]

That looks pretty awesome!

[breakwellmz]

That all looks good.
Have you got appropriate bits and pieces to make up a slide hammer to pull the bearing out? You can do it with a grease gun and some fiddling and fittings but i`ve not done it myself.

[nice2day]

Thanks for your comments Blurredman & breakwellmz. I'm happy to say the bearing is now out. The puller kit is a great set with lots of sizes and a very hefty slide hammer plus a screw puller should you wish to do it that way. I had a horrible dread that even with all the different sizes of pullers there would not be one that fitted that bearing but there was it fitted very nicely and after a quick blast of heat on the cases and around the rear side of the bearing housing a few hefty whacks the bearing quickly came out. So I'll do a little more cleaning on the outside of the cases with acid (wish I had an aqua-blaster locally) and then set about the re-build.

Moving on then,...I'm a big fan of Wellseal but I'm tempted this time to try Loctite 518 as the case joints are a touch damaged by the original factory assembly where a slither of something hard was trapped between the crankcase which caused an indentation that is nearly right across the joint seam and then one side of the case has quite a few porosity holes along the joint face too. Any views on sealants just out of interest please?... I reckon the original MZ sealant is not the same as Wellseal...it might have the same colour but it sets quite hard whereas Wellseal remains a very thick goo and never hardens like the MZ stuff does.

Oh yes one other question. As regards the left side case what is your preference on fitting the main bearings?...As per factory video (bearing into case and then fit the crankshaft) OR fit both main bearings to the crankshaft first and then install this into the left side case?

Look forward to the replies.
Les

[Puffs]

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[nice2day]

Hi Puffs. Yes the weld seems sufficient and it's pretty tough hard aluminium, hopefully the cases fit back together again well as no precaution as regards distortion could be taken. Aluminium is extremely good at heat conduction so I just hope heat was dissipated well enough and things cooled down as one. I will find out when I screw it together. The JB weld sounds a good idea I think I will use that.

The indentation was caused by a small piece of something trapped in the joint. It was slightly yellow so it might have been a brass slither or fragment but certainly hard enough to put a dent in the joint. I dropped it and lost it after prising it off the other side so can't be sure but whatever it was it was certainly from the original build as it is obvious the bike has never been stripped before.

I have decided to use Loctite 518 this time which can seal up to 0.25mm gaps.

Thanks for telling me of your preferred build method, I reckon I will choose that way....I just hope the crank slides into he bearing OK after heating the inner race...I hate banging the ends of crankshafts as its very possible to distort the alignment...

To Follow of course

All the best

Les