menglovekai Posted December 5, 2016 Report Share Posted December 5, 2016 Today. I change the engine oil and transmission oil together .I notice there is very little amount of transmission oil came out . may be 200 cc. But the engine oil came out 800cc. So i fill new oil in and ride for 1 hour . i found engine oil level increase about 100cc per 1 hour of ride.Transmission side breather hose looks ok ,No oil came out the hose looks clean.Is this the Crank seal problem? Quote Link to comment Share on other sites More sharing options...
jimmyl Posted December 5, 2016 Report Share Posted December 5, 2016 Hi -I'm sure this has been raised before. If you search the forums I think the answer is on there somewhere. Good luck 1 Quote Link to comment Share on other sites More sharing options...
guys Posted December 5, 2016 Report Share Posted December 5, 2016 Here it is: http://www.trialscentral.com/forums/topic/60890-transmission-oil-seeping-into-engine-side-on-my-2012-montesa/ Quote Link to comment Share on other sites More sharing options...
2stroke4stroke Posted December 5, 2016 Report Share Posted December 5, 2016 Indeed it would have been useful if 12Mont had come back to let us know if he had any success. Is he out there somewhere? Quote Link to comment Share on other sites More sharing options...
menglovekai Posted December 6, 2016 Author Report Share Posted December 6, 2016 Thank you for your comment. 1 Quote Link to comment Share on other sites More sharing options...
menglovekai Posted December 16, 2016 Author Report Share Posted December 16, 2016 (edited) Update. Oil seal 's rubber deteriorate. No groove on the metal sleeve.I don't know how this happen but this bike parked for 2 years before i bought it. only 20 hours of use.after change ,I let the engine run at idle for 10 minute. engine oil level still the same Edited December 16, 2016 by menglovekai 1 Quote Link to comment Share on other sites More sharing options...
guys Posted December 16, 2016 Report Share Posted December 16, 2016 It would be interesting to know what kind of oil was used that caused such swellings. Or if the oil seal was made out of the wrong kind of rubber. 1 Quote Link to comment Share on other sites More sharing options...
jonnyc21 Posted December 16, 2016 Report Share Posted December 16, 2016 I would suspect it was using the wrong kind of oil based on only 20 hours of use. And yes if you know what type of oil was in the bike please let us all know so we can avoid it. Quote Link to comment Share on other sites More sharing options...
12mont Posted December 21, 2016 Report Share Posted December 21, 2016 Hi, I swapped out the crank seal and it rectified my problem of transmission oil leaking into engine compartment. 1 Quote Link to comment Share on other sites More sharing options...
chuck4788 Posted January 7, 2017 Report Share Posted January 7, 2017 I have two friends with earlier 4RTs and they have not had any oil migration issues. The CRF versions of these engines are known for shaft seal failures that allow oil to migrate between engine/tranny. Quote Link to comment Share on other sites More sharing options...
menglovekai Posted April 6, 2017 Author Report Share Posted April 6, 2017 3 months after crank seal changed. I notice the engine oil level is rising again. and the transmission oil is decrease. the engine looks clean ,no oil leak Is it possible that the engine oil pump's oil seal is defect ? Quote Link to comment Share on other sites More sharing options...
sportsawyer Posted April 10, 2017 Report Share Posted April 10, 2017 On 4/6/2017 at 7:42 AM, menglovekai said: ... Is it possible that the engine oil pump's oil seal is defect? May be possible, but I think it's unlikely because: 1) Pressure should be higher in the oil pump, which would push engine oil into the clutch / primary drive case rather than the opposite, and, 2) The oil pump seal is fairly high, above the transmission oil level (unless transmission is overfilled). There could be splash that gets to that seal, but it's also recessed and away from oil slung by the primary gears. Back to the first point, the pressure should be higher in the oil pump than the clutch / primary drive case. But if the transmission breather hose is blocked or pinched, pressure could buildup in the transmission / primary drive. That would increase potential for transmission oil migration to engine oil at the various seals or at the center-case gasket. Sorry... probably not much help. Quote Link to comment Share on other sites More sharing options...
jonnyc21 Posted April 10, 2017 Report Share Posted April 10, 2017 I would agree that a pressure issue caused by some kind of blockage sounds more likely the cause than the oil pump. The other option could be that you got a defective seal. Not common but can happen... Quote Link to comment Share on other sites More sharing options...
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