Rusty small end bearing

[Pat the Jawa]

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

[AlanJ]

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.

[Pat the Jawa]

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.

[Pat the Jawa]

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.

[Pat the Jawa]

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

[Pat the Jawa]

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.

[Pat the Jawa]

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

[DAVID THOMPSON]

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 "

[Pat the Jawa]

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

[DAVID THOMPSON]

what model and bet we can't buy one in the usa
dave

[Pat the Jawa]

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!