GS1000SZ knocking crank ....??

[LAMA]

Hi all,

I am a frequent visitor to The GS Resources and have spent many very long hours being educated and entertained by the posts of the various members. It is for this reason that I feel I am in the right place to present the following. I am the happy owner of a 1982 GSX1000SZ Katana UK spec since 1986. In the last few years I have rebuilt this bike and tried my best to bring it to a condition that will allow it to live for a further 30 something years. However I am experiencing a problem that I would like to share with you and hopefully with your help find the reason and eventual remedy. About 20 yrs ago I experienced a very noticeable but not particularly loud knocking sound coming from the engine under acceleration. After dismantling the engine I found that ALL the main bearing outer races together with the bearing supports of the cases had patches of "hammer" marks. I went through my genuine Suzuki service manual for this model and checked all wear limits and tolerances pertaining to crankshaft, big-end,small-end,pistons and just about anything that I considered could play a part in this issue. EVERYTHING was in spec. I suspected at the time my alternator rotor as it had span on the end taper and I thought that maybe it was creating an un-balaced load by virtue of the fact that it was no longer sitting snug and correct. In the end I replaced the engine with an 1100 but kept the now retired 1000 engine. This last rebuild of mine has had the 1000 engine stripped down and rebuilt with the taper cleaned up, keyed and the alternator rotor checked for correct positioning on the crank with the use of a dial gauge and rotating the crankshaft slowly to ensure no wobble. It runs absolutely true and again my crank tolerances are correct. I have run this engine for about 1000 km since the rebuild and from the get go the mild knocking sound re-appeared (together with a vibration). It doesn't appear to get any louder or worse and once again is an issue that surfaces only upon acceleration. When just cruising along there seems to be no problem.

So the question is this. Has anyone experienced this problem? Did you find out what it was? Did you resolve it? How, and for how much ????

Thank you all in advance for any help you care to offer.

 

[Nessism]

Did the crank bearing webs look like the photos below? If so, I was told by a couple of knowledgeable folks here to not worry about. Reassembled the engine with some bearing loctite on the saddles and the engine is running well.

I suspect there is clearance between the bearing and the cases, and the bearing is fretting some. Maybe your engine is worse, or mine is going to start making noise some day.

 

[LAMA]

Hey Nessism,

That's exactly what I've seen. I thought that maybe there might have been play between race and cases and had considered having the cases skimmed but in the end changed my mind in case I opened up a whole can of ugly worms. Thanks for your quick response and the pics. If I'd had any sense I would have taken some pics of my own crank but I was too eager to get it all back together and go riding. The NAPA store round the corner from where I live stocks a bearing installation liquid that I believe is made for this very type of issue. I'll use the bike for now and strip the engine down in the fall.

Thanks again and have a safe and pleasant riding season.