petrg Posted February 21, 2016 Report Share Posted February 21, 2016 How easy a job is it to change the big end bearing on my Beta 250? I realise the cases need splitting and the crank then needs splitting to get to the big end, but am guessing there is some expertise or special tools required along the way. My engine sounds rattly and just taken the piston out to check the little end, whilst that seems not too bad, there is definitely play in the con rod.Or do I just send it off to somebody??? Quote Link to comment Share on other sites More sharing options...
lineaway Posted February 21, 2016 Report Share Posted February 21, 2016 Simple enough to split the cases and do the main bearings. You can then ship the crank for the rod work. There should be no up and down movement on the big end. Quote Link to comment Share on other sites More sharing options...
sirdabalot Posted February 21, 2016 Report Share Posted February 21, 2016 I've done a few rod renewals, but not a Beta. You need access to a press (up to 20 ton) a lathe, a DTI, feeler gauges, vernier calipers or suitable micrometer and a big copper mallet. If you don't have all of those, hand it to someone who rebuilds cranks. Quote Link to comment Share on other sites More sharing options...
goudrons Posted February 21, 2016 Report Share Posted February 21, 2016 (edited) There often quite a bit of side play in the big end that can be mistaken as wear. It's hard to test, but you can often get the crank to TDC and grab the rod near as possible to the crank pin/big end, hold it straight and try lifting and pushing it up and down (without the crank turning) against the crank pin and feel for any movement, then try again at BDC. If you are going to replace it, you'll need a new con rod kit and gasket set (and while it's apart, buy and replace the main bearings and seals). I think you'll struggle to get the old rod apart and the new one needs truing up carefully, so hand it to a motorcycle engineer to swap the rod and big end out for you and true it up, it doesn't usually cost much if they have the right tools and know what they are doing. There a few tools needed to tear down the engine. A flywheel puller And something to hold the flywheel to undo the nut (and primary nut), you also need to hold the clutch centre too. A tool like this http://www.demon-tweeks.co.uk/Product.do?method=view&n=678&p=547524&d=124&c=4&l=2&utm_source=Google&utm_medium=Base&utm_campaign=Hand%20Tools&gclid=CIy2_qbAicsCFQMcwwodfNUNRQ One side (with the studs) will hold the flywheel, the other (with the bent ends) will hold the clutch centre. Using something else to jam these will usually end in tears! The rest are just usually tools. Edited February 21, 2016 by goudrons Quote Link to comment Share on other sites More sharing options...
worldtrialchamp Posted February 21, 2016 Report Share Posted February 21, 2016 There's plenty of diy vids on poo tube....will give you an idea what's involved Quote Link to comment Share on other sites More sharing options...
lineaway Posted February 22, 2016 Report Share Posted February 22, 2016 The Techno crank was easy as it still was all steel. I`d leave the crank up to someone with the right spacers since all the crap plastic on the new cranks. Used to be a noob would be lost doing a job like splitting the cases. With video and forums like these the job is much easier. Flywheel, clutch and primary gear is much easier with the top end still in place, unless you have air tools. Quote Link to comment Share on other sites More sharing options...
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