Mark Haycock with a page of tips.
Our very own wizened sages, Messrs Mark Haycock and Steve Cooper are here to answer all of your woes, be they mechanical or spiritual. Every month we will be giving advice, as well as some general tips. Don’t forget to send in your own tips too.
1999 Yamaha YZF-R6
Q. I recently bought an R6 with 30,000 miles on the clocks: standard with the exception of a race slip-on silencer and race-style air filter. It ran a little rough at the bottomend of the rev-range and would slowly die while idling and become difficult to start from hot. I initially thought it may be dirty carbs and so thoroughly stripped, cleaned and balanced the carbs. This improved matters slightly but the problem was still there at low rpm. I did however notice quite a plume of white smoke coming from the crankcase breather that feeds back into the air-box. It was suggested that these engines on the R6 5EB are notorious for cracking the bore plating. I duly stripped the engine and found the bores in one and two had cracked. Yamaha were contacted and they stated that this was a problem they were not aware of. I am now in contact with over 500 owners of this particular machine and find its alarming at the high number of owners who experience the same problems and have found cracks in the bores effectively rendering the engines as scrap. Is this something that you are aware of? We are collectively asking your opinion as to why the bores may crack. Could a combination of race-can and air-filter without the jetting cause this? It seems that more and more people are coming forward to say they think their bike has problem carbs and are finding cracked plating and I fear that very soon there will very few usable first generation R6 5EBS left! Sean Cunningham
A:I’m surprised that Yamaha are not aware of this issue with the 5EB engines as everyone else seems to be! I think it most likely that the way the cylinders were constructed was not satisfactory and differential expansion of the various parts puts excessive stress on the cylinders, causing the cracking. I think your best course of action would be to speak to an expert in the field of cylinder repairs with a view to producing a permanent and effective solution. One such is Langcourt Ltd in Weston-supermare on 01934 612226 who should be able to do the job for you – at a price. So you would need to assess whether all this is worthwhile or whether you would be best to sell the bike as a ‘spares or repairs’ project and move on.