ciao cracking engine cases

I've done some searching and I can't find anything. The keywords seem too general.

I rebuilt the engine on my new ciao this week because I discovered a crack in the engine case. the next day it stopped running because of an air leak from a crack in the case.

I can figure it out myself but some ideas as to where to look would be helpful: it was along the top front engine bolt both times. Maybe the frame is too close together? Too far apart? I'm going to rule out vibration as that is barely noticeable at most rpms. I'll inspect the frame but I don't think there are any cracks.

for context, it's a small kit (maybe 65cc), stock portmatched cases, and a racing crank... New bearings and seal.

Re: ciao cracking engine cases

barney gierer /

Maybe the gasket wasnt in the corect posotion when you put the case together or the mating surfaces need cleaned

Re: ciao cracking engine cases

so the crack is in the same spot? Is there actually a crack or is there just an airleak?

Re: ciao cracking engine cases

***VANILLA BLUNDER*** /

Put some jb weld in it and rock and roll till it explodes

Re: ciao cracking engine cases

^^this. its just mopeds

Re: ciao cracking engine cases

Dirty30 Dillon /

Yeah, I'm confused as well. Is there an actual crack in the cases?

If so, new cases for sure. Or, if you're trying to diagnose why the crack happened????

Re: ciao cracking engine cases

I think he's trying to diagnose what could cause two sets of cases in a row to fail the same way, hoping that someone has experienced the same. For those of us that haven't, pics would help a lot, having trouble imagining where/how it cracked. (edited)

Re: ciao cracking engine cases

macelius, that's exactly right. Here's a picture of the crack. It's seriously tiny. I'm trying jbweld as the case half is already shot so there's nothing to lose. Tighten the engine bolts and cross fingers. I'll know tomorrow whether it holds.

IMAG0391.jpg

Re: ciao cracking engine cases

Dirty30 Dillon /

To me, it looks like that is right around where the bolt for the engine mount goes through.

I'd check your frame for severe flex or even cracks. Could be the engine cases are the only think holding the frame from twisting and that's why they keep giving up the ghost

Re: ciao cracking engine cases

No cracks, all the welds are solid, I can't get it to flex noticeably.

Re: ciao cracking engine cases

barney gierer /

Maybe it happened during disassembly. Or a bad surface imperfection during assembly.

Those two bolts are def structural points for subframe. Bummer.

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