deputy dawg Posted January 12, 2019 Report Share Posted January 12, 2019 Hi all i have a 250 mar that I've restored, i had the engine rebuilt, new carb it fires up easily but it smokes quite badly, running 50.1 fuel, anyone any ideas as where to start? Quote Link to comment Share on other sites More sharing options...
b40rt Posted January 12, 2019 Report Share Posted January 12, 2019 I'd give it a chance to clean out any build up of old 2stroke in engine / exhaust before looking for a problem. Then wet side crank seal. Burning engine / gear oil looks and smells differently from 2stroke. 1 Quote Link to comment Share on other sites More sharing options...
pmk Posted January 12, 2019 Report Share Posted January 12, 2019 Agree with what B40 said. For comparison, my MAR, I had switched oils and all is good. However at a recent event, between the hill sections and immediate connector sections, my pipe was smoking pretty good. Laughing about it, we questioned if the bike was going to burn to the ground, which it did not. Merely residue built up from slower running. But do not rule out the oil seal, or retightening the case screws, though that should not be a concern with a fresh rebuild. Quote Link to comment Share on other sites More sharing options...
deputy dawg Posted January 12, 2019 Author Report Share Posted January 12, 2019 thank you for the replies, i,ll take it for a run over the weekend and see if it will clear and go from there Quote Link to comment Share on other sites More sharing options...
djr Posted January 12, 2019 Report Share Posted January 12, 2019 My own MAR starting smoking suddenly one day, but had been fine when ridden the previous week. turned out to be crank oil seal on clutch side had somehow got stuck to the crankshaft and was rotating with it ! { no idea how this could happen, but it did } fitted new seal with some adhesive and its been fine since, worst part of the job was removing the cush-drive off the Crankshaft to access the seal Quote Link to comment Share on other sites More sharing options...
deputy dawg Posted January 12, 2019 Author Report Share Posted January 12, 2019 well I've just been out on it and when its up to running temp it smokes excessively, with the engine stopped it smoke for quite a while afterwards, I've taken the plug out and its a nice biscuit colour would a crank seal not foul the plug if it was gone Quote Link to comment Share on other sites More sharing options...
feetupfun Posted January 12, 2019 Report Share Posted January 12, 2019 7 hours ago, deputy dawg said: well I've just been out on it and when its up to running temp it smokes excessively, with the engine stopped it smoke for quite a while afterwards, I've taken the plug out and its a nice biscuit colour would a crank seal not foul the plug if it was gone If you've still got smoke coming out the exhaust after you stop the motor, it means that combustion is happening inside the exhaust pipe which means that there is gunk in there. If you want to be smoke-free sooner rather than later, then take the pipe off and clean it out. A transmission oil leak into the engine produces foul-smelling white exhaust smoke and if that was your problem the spark plug tip would look oily and your primary drive case would be losing oil fast. Quote Link to comment Share on other sites More sharing options...
pmk Posted January 12, 2019 Report Share Posted January 12, 2019 6 minutes ago, feetupfun said: If you've still got smoke coming out the exhaust after you stop the motor, it means that combustion is happening inside the exhaust pipe which means that there is gunk in there. If you want to be smoke-free sooner rather than later, then take the pipe off and clean it out. A transmission oil leak into the engine produces foul-smelling white exhaust smoke and if that was your problem the spark plug tip would look oily and your primary drive case would be losing oil fast. Agree. As I posted, after switching oils and getting tne pipe pretty hot, just sitting there not running smoke was coming out the pipe. Plug was fun. After it did its thing, smoke subsided. Quote Link to comment Share on other sites More sharing options...
copemech Posted January 13, 2019 Report Share Posted January 13, 2019 get some heat into it on a regular basis and you will have/keep the excess oil blown out~! Quote Link to comment Share on other sites More sharing options...
deputy dawg Posted January 13, 2019 Author Report Share Posted January 13, 2019 thank you for the replies much appreciated, well i bit the bullet and took the pipe off and cut it open to clean it out, the packing was smouldering quite a bit by the time i had finished so i was glad i decided to do it. i cleaned it all out and repacked it and welded it back up, and so will have to wait until next weekend for a test run.Im very glad i didn't burn it out Quote Link to comment Share on other sites More sharing options...
feetupfun Posted January 14, 2019 Report Share Posted January 14, 2019 10 hours ago, deputy dawg said: thank you for the replies much appreciated, well i bit the bullet and took the pipe off and cut it open to clean it out, the packing was smouldering quite a bit by the time i had finished so i was glad i decided to do it. i cleaned it all out and repacked it and welded it back up, and so will have to wait until next weekend for a test run.Im very glad i didn't burn it out Why are you glad you didn't burn it out? Quote Link to comment Share on other sites More sharing options...
deputy dawg Posted January 14, 2019 Author Report Share Posted January 14, 2019 hi feetupfun basically my thoughts were that it is packed for a reason and burning wouldn't remove the wire wool that is in there so you would end up cutting it anyway, plus it would be pretty smokey. cutting it was a lot cleaner. 1 Quote Link to comment Share on other sites More sharing options...
section swept Posted January 14, 2019 Report Share Posted January 14, 2019 6 hours ago, deputy dawg said: hi feetupfun basically my thoughts were that it is packed for a reason and burning wouldn't remove the wire wool that is in there so you would end up cutting it anyway, plus it would be pretty smokey. cutting it was a lot cleaner. Wire wool? Thought you only used fibre glass wadding in the exhaust. Wire wool has a tendency to break up into smaller pieces and could get into the cylinder, not good. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted January 15, 2019 Report Share Posted January 15, 2019 12 hours ago, section swept said: Wire wool? Thought you only used fibre glass wadding in the exhaust. Wire wool has a tendency to break up into smaller pieces and could get into the cylinder, not good. Some Spanish bikes in the 1970s used wire wool as I discovered when I repacked my Cota 348 exhaust. The original arrangement was well designed with virtually no chance of causing problems. Yes I used some SMF to replace it 1 Quote Link to comment Share on other sites More sharing options...
deputy dawg Posted January 15, 2019 Author Report Share Posted January 15, 2019 yes wire wool was around the perforated pipe and fibre around the outer part Quote Link to comment Share on other sites More sharing options...
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