QuestionQUESTION: I have a 1987 Honda cr125r dirt bike. I just picked it up today and am working on getting it running. The topend was "said" to be rebuilt. Anyways i checked the spark plug and i do have spark. The compression seems good, but after kicking the darn thing for 10-15 mins the plug is still dry. I did take the carb apart and cleaned the jets but that seems not to of helped. maybe i didnt do a good job at cleaning it? anyways what do you think is the problem. btw i am getting fuel to the carb bowl... i was told by another guy that i could have a massive leak at the crank shaft seal? how could i check to see if thats the problem.. other than that what else could be the problem?
ANSWER: Aaron,the seal leak could be the problem,if it is its usually the left side under the flywheel as it dries out from sitting a long time. The one on the right can leak but usually it will suck in tranny fluid and smoke like crazy. There is a test that called a crankcase pressure test that some shops will perform to see if the crank seals leak. The other thing you could test is the reed cage. pull the carb then the intake boot and inspest the reeds and cage. Some reeds will split or break off or even warp making it almost impossible to start let alone run right. Think of it as having a valve out in your car. If they are bad look into the Boyesen Pro Series reeds they are 1/2 carbon fiber and 1/2 composite. They give tremendous mid range and throttle response but may cost about $60.00. If you choose to change them outfor any reason but have the seals checked for your peace of mind.
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QUESTION: Thanks for all of your help, you got me thinking about the reeds so i went ahead to checked them out.. one thing i did do before i took the reed cage out was to check if i have vacuum. i did this by placing my hand over the intake rubber pipe and pressing the kick starter over with the other... i did feel it suck my hand in but i also felt alot air forcing my hand off the intake. i thought the reed kinda worked like a one way valve? anyways upon removal of the reeds i noticed that there is a small rectangle spacer that is between the reed block and the two reed pettels on each side. because of this the reeds cannot seal around the block but only on the front... is this normal
ANSWER: Aaron, The reed cage should have metal reed stops on the upper side and the lower side. You are correct you should feel some suction as the piston goes up in the cylinder. But you should not feel the air rush back out as the piston comes back down. This is where the compressed gas mix is forced into the transfer ports along side of the cylinder wall untill the piston uncovers the port. Try to look up the parts on "powersportspro.com" . When you get to the Honda link look under crankcase 87-89 and it should show you a breakdown of the parts. #5,6,7, may help you.
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QUESTION: you have been a great help! once i rebuilt the reeds the bike fired right up. but not to my surprise another problem has occurred. the bike will only start on 1/4 throttle and will not rev at all and black water was dripping out of the header... while i was scratching my head i decided to change out my clutch fluid and the fluid was like milk.. so here we have another problem. im thinking maybe a head gasket? or the water pump seal or maybe even the crank gasket. either way im a lil worried about the crank internals being subject to that fluid. what do you think?
AnswerAaron,The water pump seal may be bad,there is a weep hole on the bottom side of the water pump to allow the leaking fluid out on some models to keep it out of crank case oil. The internal crank parts are lubricated with the fuel oil mix even the crank bearings.So this shoud be ok. There really is no oil at the top of the head just coolant. Pull the right covers off and replace the waterpump seal and brg put on a new gasket and put in your fresh oil run it then change the oit again this should get the water contaminated oil out. The not revving up may be a carb adjustment problem.
