motobecane woes

i just picked up this '77 motobecane and cant get it running. I have good spark, good compression, and recently cleaned the carb completely. when i try to start it it just turns over and nothing happens. i have even machined a coupling so i can use a cordless drill to get the motor to turn over in my small shop to no avail. one thing i am concerned about is the lack of a needle on the throttle. on my honda express there is a needle on the throttle but the motobecane doesnt have one - is this normal/correct? one reason i suspect this is the fact that when i am turning the bike over and give it a little gas, it just flows out of the exhaust (which is definately not good). any help would be GREATLY appreciated. anyone out there from cleveland? thanks for your help.

joe

Re: motobecane woes

If you have a barrel type throttle slide that goes up and down (by cable) when you turn the throttle and it has a small hole in it's center.. then you are missing the needle and clip (and possibly a retainer).

This would allow almost unrestricted gas flow into the intake.. and should wet foul your plug very quickly.. I would think that it would idle though, at least for a while (if the plug isn't already fouled).

Re: motobecane woes

i do have a barrel type slide, but there doesnt appear to be a place for the needle. in addition, there is a blown up view of my carb at http://www.themopedjunkyard.com/gurtner.html which indicates there is no needle. i am surpised that there isnt one, but i dont know about motobecanes, only hondas. any further ideas? thanks for all of your help.

joe

gurtner1.jpg

Re: motobecane woes

Ron Brown /

Joe,

I just got a pair of 78 Motobecanes running in Michigan. The carb does not use a needle, it seems to function like the old auto carburetors where the air flow controlls the mixture. I find it a little strage but it seems to work.

If you have a good spark, try this.

Remove the plug, with the gas turned off, spin the engine a bunch of times to clear it of residual gas/oil.

If the plug is not completely dry, wash it with carb cleaner or similar, then dry it well. Warming it in the oven is not all bad. Put the plug back in, turn the gas on, choke it and try to start.

If it does not at least fire a time or two on the first few spins, it will allready be flooded so turn the gas off.

If you have a good spark at the right time, the motor will fire on a little gas thrown in the intake. So if you can not at least get this to happen, you need to check the timing, fatness of the spark, and worry about compression.

Let us know how it goes,

Ron

Re: motobecane woes

If gas is running out of exhaust, crankcase could be full of gas mixture. Empty it out as best you can before trying anything else.

scott

aha!

the timing was off! i took off the exhaust and hooked up my cordless drill to the drive shaft and sure enough a plume of blue flame shot out of the exhaust port. after adjusting+cleaning the points, it runs!! but it wont idle even when the idle is turned all the way up. carb must have gotten dirty already. thanks for all of your help guys!

Re: aha!

What method did you use to clean the points?

What method did you use to check/set the timing?

Just curious.

Re: aha!

fred,

well, i wish i could say i used a scientific method and new what i was doing but i didnt. i was trying to use my cordless drill to turn over the engine and accidentally unscrewed what i guess you would call the flywheel. since it fell off, i took the opportunity to spray it down with carb cleaner and dry it off. i then noticed that there are dimples on the inside of the flywheel that correspond to holes on the driveshaft. after lining everything up and screwing the flywheel on, i tried to start it up again and it fired right up! i couldnt believe it. i know this isnt a very good way of fixing the problem but it worked. hope this helps.

joe

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