bhima Posted June 11, 2010 Report Share Posted June 11, 2010 Hi All just got me a 04 beta rev3 250 . i pxe'd my cota 315r with a dealer. It sounded like the little/big ends had gone when started and cold. He said this was a little piston slap and would go when hot. Yes it does seem alot less 'tap tap tap' when warmed up. Also on an incline i heard a 'knock knock'! Any need to be concerned? I have read about ''knocking'' what is it ? when does it happen and why? what is piston slap. i have just read through the online manual and realised i should have put superunleaded in which i will do next time. Why ? Seems all good. All bikes take some getting use to! Gear box seems a bit lose?! not as tight/nice as the monte. Quote Link to comment Share on other sites More sharing options...
houseape1000 Posted June 11, 2010 Report Share Posted June 11, 2010 As far as the knock goes, I know the monts have a knock if using regular unleaded.....not sure about the Betas though. Quote Link to comment Share on other sites More sharing options...
tt5th Posted June 11, 2010 Report Share Posted June 11, 2010 You put in super unleaded as the higher octane rating reduces the knocking (pinging) - which is pre ignition of the fuel. Beta's aren't known for knocking so I'd suggest you might need new piston rings. Quote Link to comment Share on other sites More sharing options...
feetdown Posted June 12, 2010 Report Share Posted June 12, 2010 i have just read through the online manual and realised i should have put superunleaded in which i will do next time. Why ? Super has a higher octane which resists ignition, a lower octane fuel is simply igniting on compression before tdc (pre ignition) Piston slap is caused by general wear causing a slight movement in the piston this could be worn rings , or at the other end of the scale could be a tired big end, or indeed anything in between from main bearings through to small end bearing. first step would be, whip the barrel and piston off carefully remove the top ring and taking care not to score the barrel slip it inside the barrel to just above the ports and measure the gap with a feeler gauge (I forget the tolerence but lampkins should be able to help) if the gap is only just out of tolerence new rings should sort it, inspect the gudgin pin if there is any wear on the pin replace both the pin and bearing now take hold of the conrod and shake it around you should expect a small amount of side to side movement but NO up or down play if there is any play to determine whether its big end or mains take hold of the flywheel and try to move that if that moves in anyway your mains have had it Quote Link to comment Share on other sites More sharing options...
jamersby Posted June 12, 2010 Report Share Posted June 12, 2010 Another thing that causes piston slap which I had on a 270 gas gas was, that the chrome had worn away at the bottom of the barrel making it sound like the little ends had gone, had the barrel re-chromed and new piston it was so quiet and increased the power of the engine considerably, as mentioned above take the head and barrel off and check all parts. Quote Link to comment Share on other sites More sharing options...
bhima Posted June 14, 2010 Author Report Share Posted June 14, 2010 i have just read through the online manual and realised i should have put superunleaded in which i will do next time.Why ? Super has a higher octane which resists ignition, a lower octane fuel is simply igniting on compression before tdc (pre ignition) Piston slap is caused by general wear causing a slight movement in the piston this could be worn rings , or at the other end of the scale could be a tired big end, or indeed anything in between from main bearings through to small end bearing. first step would be, whip the barrel and piston off carefully remove the top ring and taking care not to score the barrel slip it inside the barrel to just above the ports and measure the gap with a feeler gauge (I forget the tolerence but lampkins should be able to help) if the gap is only just out of tolerence new rings should sort it, inspect the gudgin pin if there is any wear on the pin replace both the pin and bearing now take hold of the conrod and shake it around you should expect a small amount of side to side movement but NO up or down play if there is any play to determine whether its big end or mains take hold of the flywheel and try to move that if that moves in anyway your mains have had it very helpful thanks all. Today i used the proper fuel. it seemed to run better but knocked more! i want to run it for a while before i take the head off and will probably need some help to do so. Am i doing any damage running it with a knock/tap tap . tap tap when cold seems ok when hot knocking while working up a slope who shall i order the parts from? Quote Link to comment Share on other sites More sharing options...
nzralphy Posted June 18, 2010 Report Share Posted June 18, 2010 Most Beta Rev3's will knock going up hill on a constant heavy load. I did heaps to get rid of mine and reduced it a bit. Check the jetting is correct. Polish the head and top of the piston. Clean the exhaust out. Retard the ignition a little (3-4mm) on the plate. And then it is still there......get used to it. Quote Link to comment Share on other sites More sharing options...
embalmer Posted June 18, 2010 Report Share Posted June 18, 2010 (edited) none of my rev3 done this, personally i wouldnt ride it until you have found the cause or you may make it worse. i had some fuel pinking on one but jetting was out that got sorted. knocking doesnt sound good. piston slaps when worn ie worn barrel coating, worn piston or rings or bearing. id strip top end off and check piston barrel and bearing its 45 min job tops. and the beta gearboxes feel nakered compared to others thats what i found. good luck Edited June 18, 2010 by embalmer Quote Link to comment Share on other sites More sharing options...
bhima Posted June 20, 2010 Author Report Share Posted June 20, 2010 i had some fuel pinking on one but jetting was out that got sorted. knocking doesnt sound good. piston slaps when worn ie worn barrel coating, worn piston or rings or bearing. id strip top end off and check piston barrel and bearing its 45 min job tops. and the beta gearboxes feel nakered compared to others thats what i found. good luck 'i had some fuel pinking' what's fuel pinking? Quote Link to comment Share on other sites More sharing options...
embalmer Posted June 20, 2010 Report Share Posted June 20, 2010 wrong mixture, wrong jetting wrong octane fuel etc etc. Quote Link to comment Share on other sites More sharing options...
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