steve1979 Posted October 19, 2008 Report Share Posted October 19, 2008 Hi guys, my fantic 307 does not idle too well and have been told by someone possibly the crank seals are worn. I have a friend who is a mechanic who also does scrambling so is used to stripping his motocross engine i was thinking of asking him for a hand, While the engine was out i was thinking to replace the piston rings, smallend bearing, gudgeon pin as she seems to have a slight rattle at the top end. Another friend of mine has a 307 also and says his make's the same noise but it's never bothered him and his idle's perfectly, do the seals come out from the outside of the engine as in a tap in fit or does it require splitting the engine. Thanks for any advise Steve Quote Link to comment Share on other sites More sharing options...
lee harris Posted October 20, 2008 Report Share Posted October 20, 2008 (edited) Hi Steve, all reed valve motors rattle. Some when new, some very shortly after. Its the window that upsets the piston balance. Dont worry about it. The seals can be replaced with the motor in the frames. The flywheel side will be wet if it is worn. If it is not then it is not...worn that is. The gearbox side will only need replacing if the motor empties the gearbox of oil. Very smokey.... I think probably the carby is causing the rough running. Either buy an overhaul kit or borrow a good carby to test. If the slide anodising is visually worn, then the carby is awol. Buy an OKO or mikuni or new dellorto. You choose. (Okos from classictrial will fit staight on and i rekon the best solution,) If you do wanna replace the seals, take off the clutch, flywheels and gubbins. Grind the hooked end of two spokes to make a gaff and push them into the seal at 180 degrees from each other. Use the nipples and two mole grips and pull the seals out. Make sure the replacements are for petrol or they wont last I would bet a fiver that the carby is the cause, unless the engine is just worn out...... HTH Lee Edited October 20, 2008 by Lee Harris Quote Link to comment Share on other sites More sharing options...
steve1979 Posted October 20, 2008 Author Report Share Posted October 20, 2008 Hi Lee, thankyou for your advice it is very much appreciated, i'm glad to hear all the engines are a bit rattly i feel a bit more reassured now. Its good to know replacing the seals can be done in situ if and when they need doing, the bike is a wee bit smokey on alot of revs over a small distance, i do this as i read somewhere it helps clear the engine out. But as long as she doesn't dump the oil out i think i will leave the engine alone. The fantic 307 is a great bike, really good fun. Thanks again Lee Cheers Steve Quote Link to comment Share on other sites More sharing options...
steve1979 Posted October 20, 2008 Author Report Share Posted October 20, 2008 Hi Lee, thinking about your advice i have e-mailed classic trials about a replacement oko carb as there is definate wear on the throttle slide in the original dollerto, here's hoping Cheers Steve Quote Link to comment Share on other sites More sharing options...
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