Paulwhite Posted July 14, 2010 Share Posted July 14, 2010 hi iv had 2 bikes (4 stroke 125cc v twins) and both have had the bottom end fail so just wondered what can cause this? i know the 1st one decided to die cause of the oil....well...lack of it. but as to the second one the only thing i can think of is cause iv re-jetted the carb??? but surely the crank and everything connected to it shouldnt fail cause of that? both the bikes were under 10 years old so i cant get my head around why they died. could someone shed some light on this problem? cheers. .Paul. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 14, 2010 Moderator Share Posted July 14, 2010 hi iv had 2 bikes (4 stroke 125cc v twins) and both have had the bottom end fail so just wondered what can cause this? i know the 1st one decided to die cause of the oil....well...lack of it. but as to the second one the only thing i can think of is cause iv re-jetted the carb??? but surely the crank and everything connected to it shouldnt fail cause of that? both the bikes were under 10 years old so i cant get my head around why they died. could someone shed some light on this problem? cheers. .Paul. The only thing pops to mind is you chopped the latest one about with some different bits and pieces like heads and such. That can have an effect on oil pressure, the sachs may have a bigger or more efficient pump. Either way oil starvation is still the most likely. If you can be arsed check the shells and see how they failed. Link to comment Share on other sites More sharing options...
Paulwhite Posted July 14, 2010 Author Share Posted July 14, 2010 The only thing pops to mind is you chopped the latest one about with some different bits and pieces like heads and such. That can have an effect on oil pressure, the sachs may have a bigger or more efficient pump. Either way oil starvation is still the most likely. If you can be arsed check the shells and see how they failed. well iv taken the engine out and dismantled it to see whats gone off, the conrod for the front cylinder has worn to the point where it will happily wobble and can be pushed up and down by about 1-2mm (with the crank being perfectly still) from just looking at it, it seams that both the xv virago (thats in the sachs) and the dragtar 125 engine internals are exactly the same appart from the cam timing and the cam chain. the oil pumps look identical with regards to size but the dragstar one could be more efficient? im in the process of trying to take the round magnet that goes round the stator off but am finding it difficult as its a tapered shaft with a keyway and just wont budge. im gonna get a second hand bottom end but dont want to have the same problem a year down the line. plus when it went i noticed that some oil was burning as white smoke filled the crank case but the pistons and barrels were fine and there are no marks on the valves. what do you mean by shells? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 14, 2010 Moderator Share Posted July 14, 2010 well iv taken the engine out and dismantled it to see whats gone off, the conrod for the front cylinder has worn to the point where it will happily wobble and can be pushed up and down by about 1-2mm (with the crank being perfectly still) from just looking at it, it seams that both the xv virago (thats in the sachs) and the dragtar 125 engine internals are exactly the same appart from the cam timing and the cam chain. the oil pumps look identical with regards to size but the dragstar one could be more efficient? im in the process of trying to take the round magnet that goes round the stator off but am finding it difficult as its a tapered shaft with a keyway and just wont budge. im gonna get a second hand bottom end but dont want to have the same problem a year down the line. plus when it went i noticed that some oil was burning as white smoke filled the crank case but the pistons and barrels were fine and there are no marks on the valves. what do you mean by shells? The bottom ends on engines can be ball, taperd roller or white metal bearings. White metal bearings don't use any kind of roller but rely on an accurate covering of oil ( in microns) to remove friction. They are excellent for diagnosing engine failure causes as an free material will be stuck to them and poor oil or lack of it also shows clearly. They are typically used as big end bearings where they have forced lubrication. The top end is more likely rollers as they are far happier with splash lubrication. Link to comment Share on other sites More sharing options...
barkwindjammer Posted July 14, 2010 Share Posted July 14, 2010 All-Bran or fresh orange does it for me Link to comment Share on other sites More sharing options...
Paulwhite Posted July 14, 2010 Author Share Posted July 14, 2010 jalapino peppers normally does it for me lol but yeah so were saying that a lack of decent oil could be the main cause of the failure? see i thought that it could be the extra power caused by the different heads, timing and carb settings that caused extra stress on the conrods causing them to wear down at an increasing rate. so in theory if i put it back together with a new bottom end and a better grade oil then it should last? do you think it would be wise getting a fast flow oil filter? or even putting the dragstar oil pump in? i know the filter that was in there was pretty much fooked and the oil was drained then filled up with fresh 10w40 a couple of days b4 it went but when i came to drain the oil again it was black and not as thick as it was. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 14, 2010 Moderator Share Posted July 14, 2010 Paul, so this was a good engine before this right? how long have you had it / rode it? seems a bit drastic good one minute fooked the next...like something catastrophic, like not pumping oil. Now i'm wondering if you fitted the right oil filter, or whether it HAS to go in one way rather than the other? or less likely that the oil pump is not working? Link to comment Share on other sites More sharing options...
Paulwhite Posted July 14, 2010 Author Share Posted July 14, 2010 Paul, so this was a good engine before this right? how long have you had it / rode it? seems a bit drastic good one minute fooked the next...like something catastrophic, like not pumping oil. Now i'm wondering if you fitted the right oil filter, or whether it HAS to go in one way rather than the other? or less likely that the oil pump is not working? i cant realy say if it was good or not as iv had it for 2 years and only rode it for 6 months due to the piston rings failing. it started and road fine but wouldnt reach 60mph so thats when i re-jetted the carb and it went boom. but i think the filter might of restricted the oil flow as it looks like it hasnt been changed in a while. but surley that would mean that there was hardly any oil getting to the heads as the crank goes through the oil in the sump? i havent touched the oil filter since i got it but i have changed the oil. as to the pump im not sure if its working or not but it all looks ok. Link to comment Share on other sites More sharing options...
root Posted July 14, 2010 Share Posted July 14, 2010 I dont think them thar derbyshire hills are very freindly to 125s Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 14, 2010 Moderator Share Posted July 14, 2010 i cant realy say if it was good or not as iv had it for 2 years and only rode it for 6 months due to the piston rings failing. it started and road fine but wouldnt reach 60mph so thats when i re-jetted the carb and it went boom. but i think the filter might of restricted the oil flow as it looks like it hasnt been changed in a while. but surley that would mean that there was hardly any oil getting to the heads as the crank goes through the oil in the sump? i havent touched the oil filter since i got it but i have changed the oil. as to the pump im not sure if its working or not but it all looks ok. 1, you should have fitted a new filter to this old unknown quantity of an engine (easy to say now I know...but still!) 2, crank goes through the oil in the sump?..Does it? you sure?...ohh no youre not are you? I dont know either Link to comment Share on other sites More sharing options...
Paulwhite Posted July 15, 2010 Author Share Posted July 15, 2010 1, you should have fitted a new filter to this old unknown quantity of an engine (easy to say now I know...but still!) 2, crank goes through the oil in the sump?..Does it? you sure?...ohh no youre not are you? I dont know either yeah i am sure, now iv had a look and it goes through the oil in the sump and the pump looks like it cleans the oil and pumps it up to the heads, then back into the sump again. Link to comment Share on other sites More sharing options...
Gas up - Let's Go! Posted July 15, 2010 Share Posted July 15, 2010 All-Bran or fresh orange does it for me I resisted this for so long........ Dodgy prawn curry, bottom end with some top end issues too! Link to comment Share on other sites More sharing options...
Paulwhite Posted July 15, 2010 Author Share Posted July 15, 2010 lol it was inevitable ! but yeah just payed for a new crank and a fast flow oil filter from e-bay just got to save up for the gasket set now anyone know how to take the round magnetic thing off? and the clutch? i need to take them off to split the engine plus anyone know about the gear ratios of the xv and xvs ? was wondering if its worth swapping some gears over. Link to comment Share on other sites More sharing options...
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