Small end explosion!

I have taken the top end off a friend engine and the small end bearing has eploded causing the engine to seize. The crankshaft is a worb5 special lip. The piston has some deep grooves and the ring is seized. The cylinder luckily is ok.

Does anybody have any suggestions on what to do now?







yes we had this problem with the delivered small end bearings they come with in the cranks of Mazzu.


Mazzu reacted on this problem and they changed us all the wrong bearings, only.


 The best service that we can do now for you is to give you a new crank (we pay for, not Mazzu)


But please understand that sip can not replace all the broken parts!

Mazzu does not give us big help in this problem.


Also to note is, that we made a newsletter that goes to all customers they get a crank with maybe the incorrect bearing.

And we have sent out the right bearings for free.

But for some engines it seems it was to late, like yours.

So, send us some pics of the damaged crank and we can send you a new one.


In all other parts we have to talk about a regulation in detail.



I hope this is the service you like and we can help you out in this prob.











Hi John, yes, the crank came from sip. Are you Kyle's dad?

I have bought a couple of mazzy cranks from sip in the past but never received any emails and neither did my friend Terry (the owner of the exploded one).

Looks like the piston will have to be replaced on the engine and it has only done 800 miles.

Oh and just to clarify, we had spare casings but if we were to look for replacement of all damaged parts this would include bearings, seals, crank, complete kit, complete casings, spark plug - as an item supplied not fit for purpose caused this damage perhaps we would be fully entitled to demand full replacement but we have been honest and would expect SIP/Mazuchelli to do the decent thing and compensate a young scooterist for a substantial loss due to failure of a trusted product.



A few photos

















Hi Max, this has happened to my son with a Mazuchelli crank bought from SIP, as you may have seen on the smallframe forum. I have since had an e-mail from SIP to tell me that Mazuchelli have found the small end bearing supplied with the crank was not up to the job, I have asked how SIP/Mazuchelli plan to compensate the loss of the kit and other parts - SIP have offered a new small end bearing.

I am shocked to say the least by this, I have used SIP regularly (including buying the replacement Malossi kit) and recommended them to many friends, however I think someone needs to take responsibility where a part has been supplied, which is not fit for purpose, and has caused expensive damage. I have let SIP know my opinion but I am still awaiting a reply 3 weeks later. Needless to say I have lost a lot of faith in SIP.



Hi and thanks for your reply.

Fortunately, the crank is ok. The damaged parts are the parmakit piston and ring and obviously the small end bearing which as you can see from the pictures above is completely gone. Also the head has some little damage but can be repaired.



Yes Max, Kyle's Dad[:D]


To Sip techy dude, crank was ok for running direct intake but not if it was running rotary. the main damage was to the piston, barrel and casing but caused directly by the collapse of the bearing, the piston had only done 500 miles. If you check my account you will see that I replaced the kit from SIP. I have emailed SIP and am quite dissapointed by the lack of reply as I have recommended SIP to many friends.


I can send pictures (as previously e-mailed to SIP) but the very least I would expect is for a replacement kit as this was the direct cost to my son as a result of being supplied with a part not fit for purpose.



So, how do we talk about this damage SIP???