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Discussion Starter #1
hey i couldnt find the correct place to ask this question so im doing it here for now, im sure someone knows where it should go but anyway...
i have a 74 MR 50cc that was supposed to be my 1st bike but parts were hard to find back then due to no internet access in my younger days so i learned on a 3wheeler haha.

Ive replaced the idle screw which had the head broke off and the air screw, got the correct spark plug, and gave her a new air filter, cleaned the carb (a few times), replaced the stripped kick-shaft and she will start after my 23 year life of never hearing her run but when i go to ride her the damn thing just boggs down like i weigh 400 pounds or something so i was guessing that the points are out of tune but ive never worked on this sort of bike and cant find them, any words of wisdom/ has anyone else delt with a similar problem?
Thanks
 

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Where is it bogging down, just when starting off from a stop or higher in the RPM range? When you replaced the air screw did you set it to the factory spec? If not, it will need to be set and then fine tuned to get the air/fuel mixture correct for the idle and starting off. Also, are you revving it enough when starting off? It won't be like a typical four-stroke with low-end power. I know on my MB5 I need to rev it pretty high (> 6000) when starting off from a stop or slow speed, if not it will bog.

Also, have you checked the compression? It could be low causing the engine to be down on power.

I don't have a shop manual for it, but here is an owner's manual and it goes over setting the ignition timing: http://honda-elsinore.alp-sys.com/manuals/MR5074/OwnersManual74mr50.pdf
 

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Discussion Starter #3
Hey thanks! that manual is way better than the link i was looking at i somehow missed the whole part about timing :oops: geez...
But its bogging down from a stop no matter how high i rev it before i dump the clutch even when i lift the back up and put it into gear the tire turns but its real gutless, as in not as fast as id imagine it should and when i drop it even without my weight on her it doesn't really wanna push its-self that much.
I dont really understand how to check the compression i mean the kick-starter seams to have a good resistance for a small engine if thats how I'd go about it, sorry newbie here...
Also the idle screw doesn't seem to want to go in all the way i can see a few threads poking out even if i crank her down, I'm afraid to push it more due to the fact that the old one was broke off in there nice and deep like and had to scratch a line it to back it out with a flat-head.
 

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Discussion Starter #5
yeah it could probably use some new gaskets too I'd imagine there is something like a vac leak going on somewhere.
ill go mess with the timing and see if i can get that pilot screw to go in all the way by cleaning the carb threads or something and see what happens after that.

Also i replaced the air box with a small k&n muffin filter do you think that its getting too much from that or should that not matter?
 

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Sounds like the typical long-neglected 2-stroke dry/brittle/hard crank seals that allow it to idle and rev just fine in neutral but bypass all proper flow at the instant any load is applied to the crankshaft.

Being able to hear it scream it's lungs out, thinking it will throw you with a wheelie the instant you release the clutch, sure is a let-down when all it does is bog like it's underwater.

Classic symptoms.
 

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Discussion Starter #9
i put the points directly in between .008 and .024 at .016 and checked the plug gap too and now the damn thing wont even start at all... :mad:
all i can do i guess is get a gasket set for her and clean the piss out of everything.
what size jet should i get then while im in there? a little bigger i would imagine?
 

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My thought was bad crank seals as well....But I'm not a 2-stroke guy.......
 

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I've been down that road too many times, that's why I immediately recognized the symptoms.

Go ahead and go through everything else, you'll be replacing the crank seals before it runs right.
 
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