Pop goes the Motorized Bicycle.

[bairdco]

Re: Pop goes the MB.

i'm almost 41. i still think i'm young and invincible. if i didn't, i wouldn't be riding a 70 year old bicycle with a chinese hand grenade bolted to it at 45mph in traffic...

 

[spit_fire]

Re: Pop goes the MB.

well said bairdco i hope im still how you guys call it.........HIP WITH IT once i hit my 40s im just worried everything is gonna be electric and digital by then, i really enjoy the good old mechaincal stuff but it seems i missed that era, even on all the new cars everything is electric powersteering on some of the new gm, brakes on some of the new vw can you belive you will need a software to make the pistons retract into the calipers as they wont b hydraulic anymore so no more pushing them back in manually thats pretty bummer tsk tsk new and fancy stujff suck apparently even the Harley,s with the fuel injection suffer alot got a coupld of buddies that own them and i swear theyre fixin them more then riding them, you can almost call them Hardleys too bad cuz man wut a bike

 

[spit_fire]

Re: Pop goes the MB.

SRRY FOR JACKING YOUR THREAD RCFLIER back on topic any luck with your bike??? have you tried pedalling with the gas off ?

 

[exavid]

Re: Pop goes the MB.

These little engines are just like a slightly larger model airplane engine, when they get badly flooded the easiest way to clear them is to shut off the fuel, drain the carb bowl, remove the spark plug and spin them over with the throttle wide open. Much easier with a MB because you can just pedal the bike to spin the engine over. After a hundred yards or so the engine should be pretty well dried out and cleared. Just put in a clean plug and try starting it again.

 

[fasteddy]

Re: Pop goes the MB.

Spit-fire, I dried a distributor with WD40, slapped the cap back on and started it up.

Real good thing that there weren't the usual bunch of guys leaning on the fender watching. Plenty of shrapnel for every one.

Steve.

 

[noco]

Re: Pop goes the MB.

hey before his is diag'd is this a 2 or 4 stroke....hey by the way these guys arnt steering you wrong

 

[rcflier500]

Re: Pop goes the MB.

SRRY FOR JACKING YOUR THREAD RCFLIER back on topic any luck with your bike??? have you tried pedalling with the gas off ?

Haha. No problem. You guys have been a ton of help as it is. I lowered the piston to bdc with the plug out and am letting it sit open for a couple days while i have class. Thursday ill try to get it started. Ill let you know how it is then.

 

[spit_fire]

Re: Pop goes the MB.

I got some bad new brother all of a sudden im in the same boat as you, i whent on a long trip today and was planning at fueling at a gas station and just adding some 2 stroke oil to it but instead i used my buddies premixed gas wich he claims was 25/1 and after about 6 mph at WOT it sputtered fir a split second then the engine lost power and as i pulled in the clutch it seized solid, i had some tools with me so i tried tightening up the clutch to keep it from slipping at all and it still wouldnt turn over the engine afterward i pulled out the plug poored a little bit of gas/oil from the tank using the fuel line to the piston to add some lubrication let it sits for 2 minutes and lucky the piston was at TDC so i just pushed down on it with a screwdriver as it still wount turn over and it let go but when trying to start it was backfiring threw the carb but no weird noises were coming out i decided to lock it up instead of keep trying and possibly damadge the carb its a dellroto and it has a plastic throtle plate, so im waiting to get a ride right now to go pick it up i was just curiouse as to what everyone thinks is the problem i cant wait to take a peak inside, you guyz think its fuel related not enough oil and it just seized my buddys not to good with oil fuel mixtures or you think something let go???

 

[GearNut]

Re: Pop goes the MB.

If you are getting backfiring out of the carb then I would suspect a broken piston ring and a gouged cylinder. With these piston port engines, the intake passage to the carb is closed off by the piston moving downward just before the transfer ports open up to let the fresh intake charge transfer into the cylinder. The only way you are going to get combustion into the carb is if somehow the flame front is travelling into the flywheel area and then travelling back out through the intake manifold and carburetor. I can also reason that if something bad happened to the wrist pin bearing then that would alter the port timing in relation to the piston movement. FYI the wrist pin is what connects the piston to the connecting rod. The last variable I have dealt with was extremely messed up (advanced) ignition timing, Still the engine did not backfire, it just ran backwards.

 

[spit_fire]

Re: Pop goes the MB.

well i brought my baby home took the head off to take a peak inside cant say the cyclinder wall was looking it greatest but it wasnt destroyed either, the cluprit happen to be the intake manifold gasket it had dissapered (disintigrated due to heat and vibration) therefore allowing a gap between the manifold and engine wich extra air got threw causing a horribly lean condition causing the engine to overheat and seize and thats where the smoke/flame was coming out of assuming there was extra fuel everywhere as i used the fuel line from the carb to poor gas direstly on top of the piston to lubricate the seized motor in order to break it free once again as i was 30 mph away from home, so after siliconing the intake and tightening it up the bike runs once again but when cold the compression feal way way low the motor is really easy to turn over (today i had clucth apart in order to clean the clutch as it galzed in attept to brake the motor free and was slipping) and i could turn the motor over with the plug in by hand by just turning the big gear wich should even make it harder but it was not difficult at all, overall the bike starts easier and i feal runs the same, i did 3 consecutive compression tests each one gradually faster first once was 60psi second was 90 and 3rfd was 120 im assuming it goes up becouse of air/fuel being sucked into motor causing a better seal and im turning the engine faster and faster every time i thought that was pretty good so i left it alone havent had problems sice

 

[GearNut]

Re: Pop goes the MB.

120psi is good.

 

[spit_fire]

Re: Pop goes the MB.

its wut i figured i mean when it comes to cars ill c anywhere between 90-110 maybe 120 psi so i figured if this little engine can do that it must be good and it was done ith a MAC tools compression tester not some cheap pos

 

[GearNut]

Re: Pop goes the MB.

Try it "wet" Pour a teaspoon of 2-stroke oil down the sparkplug hole then test it again. If the compression reading goes up considerably then it means that the piston rings and/ or cylinder have taked a real beating. Still 120, is good so if it goes way up then I would be very suprised.
Yes, I figure that you know this already, but others here may not.

 

[spit_fire]

Re: Pop goes the MB.

good old run down test i was thinking of doing it but i figured the bikes is only easier to start still runs good and its got good compression y bother but thanx anyways, oh today i asked my shop foreman about the sticking the torch down the sparkplug whole and he said in a 4 stoke it can blow the head gasket but a 2 stroke he said it should be fine ( hes got over 25 year of experience) and he also said to never clean a distribuitor with bake clean or wd40 as fasteddy did as it will blow ( he blew one of a honda last year using brake clean) but thats because a distrituitor is not made to handle any kind of internal compustion and the distribuitor cap is made of plastic, but i must admit you guyz got me scared to do it now and here i thought i was young and invincible

 

[GearNut]

Re: Pop goes the MB.

Do what you feel is necessary, just be carefull! If you must do that again, I recommend wearing a bomb squad suit...

 

[spit_fire]

Re: Pop goes the MB.

lol thats funny you crack me up i think ill just do it the good old fashion way just peddle with no plug and no fuel

 

[flybytaco]

Re: Pop goes the MB.

So i let it sit over the weekend and after cleaning the plug and making sure there was a good area for spark i tried to fire it up and after pedaling and dropping the clutch for about 500 feet i stopped and checked the plug again to find it was fouled like no other. Could my crankcase just be filled with oil and gas and need to be drained?

make sure your main jet didnt unscrew

 

[exavid]

Re: Pop goes the MB.

It's likely that the piston skirt was scuffed. Normally on an overheat the piston will expand until it gets too tight in the bore to run. If you didn't see any aluminum on the end of the plug and the piston top looks okay especially adjacent to the exhaust port the engine most likely doesn't have any major damage. If it still starts the same as before and seems to have the same power all is probably well. in 1964 I had a little 50cc Yamaha two stroke motorcycle. Running it uphill in some deep grass seized the engine up tight. I couldn't kick it over until it had cooled down for and hour. Once it loosened up I started it and ran that bike a couple thousand more miles with no problem before I sold it. So odds are your motor will do the same.

 

[spit_fire]

Re: Pop goes the MB.

yah i figured plus in the summer im planing on rebuilding the motor just so i can polish the ports and change some seal and get rid of the gasket at the bottom of the jug so ill just use a brake caliper honer to hone the cyclinder wall and throw in some new rings while im at it just to give the motor a fresh start as well as remove 1/4 off the piston skirt on the intake side so it will open up the intake port as the skirt covers lots of it, i herd this will increase the engines rpm

 

[exavid]

Re: Pop goes the MB.

Cutting a 1/4" off a piston skirt even just the width of the port might add vibration at higher rpms, it's got to throw off the balance a good bit. If you have the piston and crank out and rebalance them by drilling out the crank counter weight it should keep things running smooth.