Rusty small end bearing

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Rusty small end bearing

Postby Pat the Jawa » Fri Jul 22, 2016 2:57 pm

Was wondering if anyone else has come across this problem? My MZ TS250/1 had developed a metallic rattle from the engine - louder when under light load. I removed the head, barrel and piston and upon inspection of the bits found the gudgeon pin and internal surface of the conrod little end to be quite well pitted. The little end bearing itself also showed signs of damage. I can only assume that the little end had suffered a rust attack in the bike's past which had been cleaned off by a previous owner. I have tried a replacement little end bearing with the original pitted gudgeon pin and found it pretty tight so I am hoping I can get away with gentle honing of the internal surface of the conrod little end and reassembling it all with the new little end bearing and a new gudgeon pin . Any thoughts and comments would be greatly appreciated - thanks :-)
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Re: Rusty small end bearing

Postby AlanJ » Sat Jul 23, 2016 2:46 pm

Hi Pat, I am right on the end of a refurb to my 1977 TS 250/1 and one of the things I had to look into was a seized clutch, now, when I finally got to the parts they were seized up with a furry rust area, it was on the main clutch drum and on the bearing and the wavy plate on the kick start ratchet. I have never seen rust quite like this. Mind you the bike has been sitting in the garage for 28 years. Hope you get it sorted Pat Take care Alan.
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Re: Rusty small end bearing

Postby Pat the Jawa » Sat Jul 23, 2016 4:03 pm

Thanks for your reply Alan. My MZ had already been refurbished but judging by a few of the problems I've encountered not by a good mechanic. MZ's are renowned for being simple and hardy so I'm hoping that I can get away with the previously mentioned repair. Within days of buying the bike I saw a new old stock conrod kit going cheap on eBay which I grabbed just in case but don't really want to fully strip the engine to fit it. I had a 4 speed MZ 30 years ago which had an engine that I could strip and reassemble blindfolded but I made the mistake earlier this year of buying a Jawa 350 engine to rebuild to fit my other bike but it's been such a nightmare of problems it's knocked my confidence somewhat.
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Re: Rusty small end bearing

Postby Pat the Jawa » Mon Aug 01, 2016 11:51 am

Further to my first post I have now fitted a new small end bearing and gudgeon pin which were a tight fit in the little end eye and have reassembled the engine. All has not gone according to plan as have still got the rattle so can only conclude that the big end bearing must have also suffered from rust or perhaps is just worn out. Luckily soon after buying the bike I saw a conrod set on eBay for £26 including postage so bought it just in case. I'm going to keep riding the bike until autumn as can't do any more damage and will strip the engine and do a full rebuild including a rebore whilst it's all in pieces.
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Re: Rusty small end bearing

Postby Pat the Jawa » Mon Aug 08, 2016 4:00 pm

Have now ridden a friend's Supa 5 which has only done just over 20,000 miles and has a similar rattle though not so loud - am I to conclude that the rattle is perhaps piston slap? Any thoughts/help would be much appreciated :-)
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Re: Rusty small end bearing

Postby Pat the Jawa » Sat Sep 03, 2016 12:13 pm

Having gently rotated the flywheel back and forth I can only conclude by the free play and slight clicking that the big end is knackered. Looks like it's a major engine strip and refurb coming up - at least it'll be like having a new engine when I'm finished.
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Re: Rusty small end bearing

Postby Pat the Jawa » Wed Oct 26, 2016 4:16 pm

Further to my last comment - I'm continuing to ride my MZ and it still rattles but is running fine so I'm going to just keep riding until it gives in. I've already got the bits necessary for a complete engine rebuild but whilst the engine runs I'll ride the bike. According to the speedo she's done 48,500 miles which can't be bad :-)
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Re: Rusty small end bearing

Postby DAVID THOMPSON » Wed Oct 26, 2016 5:57 pm

i am understanding why uk riders like the MZ 2 strokes

"According to the speedo she's done 48,500 miles which can't be bad "

:smt023
Dave 2002 MZ RT125+1995 Saxon Tour(500cc)
1997 MZ 660 Traveller+6/13/09 WV USA
"IN the end times the IDIOTS will be in charge
of everything"
"I like the road less traveled if it's PAVED!"
wd8cyv at yahoo dot com
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Re: Rusty small end bearing

Postby Pat the Jawa » Tue Nov 01, 2016 5:09 pm

I know it's obviously not an MZ but my Jawa has done 30,500 original miles from new and is also running fine and all at just over 30 months old :-)
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Re: Rusty small end bearing

Postby DAVID THOMPSON » Wed Nov 02, 2016 3:09 pm

what model and bet we can't buy one in the usa
dave
Dave 2002 MZ RT125+1995 Saxon Tour(500cc)
1997 MZ 660 Traveller+6/13/09 WV USA
"IN the end times the IDIOTS will be in charge
of everything"
"I like the road less traveled if it's PAVED!"
wd8cyv at yahoo dot com
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Re: Rusty small end bearing

Postby Pat the Jawa » Sat Nov 12, 2016 5:15 pm

The Jawa I ride is a 2014 Retro bought from the only Jawa importer at Wisbech. I doubt if you can get one in the US as your emissions laws are pretty strict!
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