Guest brian0001 Posted October 23, 2009 Posted October 23, 2009 Hi All hope someone can help. My sons DT125R is getting petrol in the crank. I have sripped the top end and found petrol in the crank. The piston, rings and bore are all ok. not to much play in small or big end bearings. I did a de coke and put it back together, it started ok and run for a while, then conked out. took the spark plug out and it was wet with petrol. cleaned the plug and it started again. but conked out after a little while, same problem. any good advice would be great. cheers brian.
Moderator Airhead Posted October 23, 2009 Moderator Posted October 23, 2009 seems an odd one Brian, not familiar with the bike in question, how does it run before it conks out, is it 4 stroking, is the choke disengaging properly too?
Ryan09 Posted October 23, 2009 Posted October 23, 2009 Only way this could happen is petrol getting down the sides of the piston im baffled.
Guest brian0001 Posted October 24, 2009 Posted October 24, 2009 seems an odd one Brian, not familiar with the bike in question, how does it run before it conks out, is it 4 stroking, is the choke disengaging properly too? its a 2 stroke. i have also changed the piston and rings. still the same. when it runs it runs ok , but then backfires and conks out. just wondering if it could be a fault with the read valve or possibly the float in the carb. there is no knocking noise from the bottem end , so i don't think its the crank seals. i might strip the carb and clean it, set the float level and possibly get some new read valve. but if that don't work then im completely lost.
Ryan09 Posted October 24, 2009 Posted October 24, 2009 When he said 4t'ing i think he ment a technical term, I supose it could be your reed valves being stuck open, i didnt think of this, if its the float bowl wouldnt it be a pig to start and fload the carb?
Moderator Cynic Posted October 24, 2009 Moderator Posted October 24, 2009 When he said 4t'ing i think he ment a technical term, I supose it could be your reed valves being stuck open, i didnt think of this, if its the float bowl wouldnt it be a pig to start and fload the carb? 4 stroking is when the engine isnt firing cleanly, it fires badly on one stoke then some the excess fuel ignites on the second and repeat. Trouble is it generally fires late so you dont get a good blow down of the cylinder so it stagnates with bad gas (causing the bad power stroke where it doesent fire properly). Its self perpetuating and if you let it run like that it will flood out. You need to wind it on if it will and clear the cylinder(s). Typically, carb causes it with air leaks but a bad exhaust can do it too. Crank seals are in the mix but if that was the case it would run bad full stop. My money in this case and its only a feeling, ignition a bad plug/coil giving intermitant/weak spark added to maybe a bad float height. At most some sh1t in the float bowl floating around.
Guest brian0001 Posted October 24, 2009 Posted October 24, 2009 4 stroking is when the engine isnt firing cleanly, it fires badly on one stoke then some the excess fuel ignites on the second and repeat. Trouble is it generally fires late so you dont get a good blow down of the cylinder so it stagnates with bad gas (causing the bad power stroke where it doesent fire properly). Its self perpetuating and if you let it run like that it will flood out. You need to wind it on if it will and clear the cylinder(s). Typically, carb causes it with air leaks but a bad exhaust can do it too. Crank seals are in the mix but if that was the case it would run bad full stop. My money in this case and its only a feeling, ignition a bad plug/coil giving intermitant/weak spark added to maybe a bad float height. At most some sh1t in the float bowl floating around.
Guest brian0001 Posted October 24, 2009 Posted October 24, 2009 4 stroking is when the engine isnt firing cleanly, it fires badly on one stoke then some the excess fuel ignites on the second and repeat. Trouble is it generally fires late so you dont get a good blow down of the cylinder so it stagnates with bad gas (causing the bad power stroke where it doesent fire properly). Its self perpetuating and if you let it run like that it will flood out. You need to wind it on if it will and clear the cylinder(s). Typically, carb causes it with air leaks but a bad exhaust can do it too. Crank seals are in the mix but if that was the case it would run bad full stop. My money in this case and its only a feeling, ignition a bad plug/coil giving intermitant/weak spark added to maybe a bad float height. At most some sh1t in the float bowl floating around. thinking back on it, my son put diesel in it by mistake about 6 weeks ago. all i did was drain the tank and flush some petrol through the carb. maybe this has somthing to do with it. he did start the bike after putting diesel in it. it only ran for about 30 seconds, then he had to walk it home from the garage.i think my job tommorow is a carb strip. is there any way to check if the coil and spark are working correct? brian...
Moderator Cynic Posted October 24, 2009 Moderator Posted October 24, 2009 thinking back on it, my son put diesel in it by mistake about 6 weeks ago. all i did was drain the tank and flush some petrol through the carb. maybe this has somthing to do with it. he did start the bike after putting diesel in it. it only ran for about 30 seconds, then he had to walk it home from the garage.i think my job tommorow is a carb strip. is there any way to check if the coil and spark are working correct? brian... Diesel in the carb would have an effect very similar to water as the fuel will float on the diesel, but if the diesel gets into the jet then it will block momentarily. With the knowledge of the diesel mishap i would do the carb strip first, you more than likely still have some diesel in there. Leave the ig issue at the moment. Keep it simple and do the carb, that is more than likely the problem. If that doesent fix it then look at the ignition. You can get tangled up with different issues very quickly if you lose your focus.
Moderator mervin Posted October 25, 2009 Moderator Posted October 25, 2009 fuel in the crankcase on a stroker if it happening overnight /when standing is a float height/float needle not sealing problem i reckon. so strip and check carb, if it happens when running maybe the pilot jet has come out in the carb merv
Moderator Cynic Posted October 25, 2009 Moderator Posted October 25, 2009 fuel in the crankcase on a stroker if it happening overnight /when standing is a float height/float needle not sealing problem i reckon. so strip and check carb, if it happens when running maybe the pilot jet has come out in the carb merv Valid point Merv but it does it when its running and when it runs good it is great. Then it dies apparently. Whatever it actually is it is intermittant. If there is some derv floating about in the carb and drops washing about in the tank that could create some odd problems.
Guest brian0001 Posted October 25, 2009 Posted October 25, 2009 Valid point Merv but it does it when its running and when it runs good it is great. Then it dies apparently. Whatever it actually is it is intermittant. If there is some derv floating about in the carb and drops washing about in the tank that could create some odd problems. thanks for nall your inputs. not had time to do the card today. will do it tommorow and let you all know the outcome. cheers brian.
Guest brian0001 Posted October 29, 2009 Posted October 29, 2009 All. stripped the carb and throughly cleaned it and the read valves. stripped the valve out of the petrol tank and cleaned it. put new petrol in and a new spark plug. fingers crossed i took down the duel carridge way at full speed. 2 days on and it is still running well. thanks for all the advice and lets hope it's fixed.
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