starting the engine

[r97]

you can skip the back story if you want

Ok, so a while ago i built a little, mini bike and entered it in the science fair. science fair did not allow me to work on it for several months, and now that i finally ahve most everything ready to go i need to start the engine.

my engine is a small, 50cc 2 stroke with no recoil, my original plan is to push start it (manual clutch), but i tried getting it to rotate the engine through the compression cycle (not trying to start it, just getting the piston to go up and down) but with the low gearing i have, the rear tire just skid. (engine can be turned easily by turning crank shaft by hand).

any how, I'm beginning to think i will need to install a homemade recoil, or kick start to start the thing. i though of a way to make a kick start, but there is one slight problem with it. the only accessible part of the crank shaft is a tapped hole, when you thread in a bolt to this hole, and then use the bolt to turn the engine over in its correct rotation, the bolt loosens, not good.

main question starts here,

so basically my main questions is, if i were to use lots of red lock-tite on a bolt threaded into the crank shaft, would it stay in place when i was turning the bolt counter clock wise (would usually loosen the bolt) with enough force to start the engine (only 50cc). also, lock-tite is supposedly loosened at 500* F, i'm pretty sure the crank shaft wont get near that hot right.

hope that makes sense, and hopefully someone with experience with lock-tie (i have never used it) will be able to tell me if this stuff will hold because i really don't want to make it impossible to disassemble. Thanks!

P.S. wasn't sure what section to put this in, has to do with engines, recoils/kick starter (all other parts), and tools.

 

[redsox985]

I used red on my PTO bolt and it was VERY tough to get backed out once it cured. I tried pulling the string out to keep it from turning and this wasn't working...it was GLUED in there. I finally had a friend hold the string while I put a crescent wrench on it and struck it with a rubber mallet a few times to break it loose with fast, blunt force.

 

[devino246]

Red locktite needs to be heated to remove the bolt. I think the temp is 500*F.

 

[r97]

Red locktite needs to be heated to remove the bolt. I think the temp is 500*F.

also, lock-tite is supposedly loosened at 500* F, i'm pretty sure the crank shaft wont get near that hot right?

not sure if you were confirming what i remembered, or just didn't see it. main question there is, an engines crank shaft can't get very hot right?

I used red on my PTO bolt and it was VERY tough to get backed out once it cured. I tried pulling the string out to keep it from turning and this wasn't working...it was GLUED in there. I finally had a friend hold the string while I put a crescent wrench on it and struck it with a rubber mallet a few times to break it loose with fast, blunt force.

ok, thanks, so i guess it should be pretty good, i will use a kick start, but i'm not going to hammer on it, and a 50cc engine doesn't require much force to go past the compression stroke.

looks like my question is pretty much answered, thanks redsox and devino for your help! hopefully i can get to work on my mini bike soon!

 

[Russ2251]

Crankshaft gets nothing near 500°F...not even internally.

 

[r97]

that's what i was thinking, but doesn't hurt to ask, and i really had no clue. Thanks!

 

[Rustydog2010]

Red locktite needs to be heated to remove the bolt.

Are you talking in general or just in this situation?

 

[r97]

IIRC, on the lock-tite website it says you must heat the bolt to 500* F and then remove while its hot. i think doing that is the easy way of removing it, the hard way would be just forcing it off.

 

[fowler]

usually u can just apply a breaker bar and crack it off

the only bolts i heat are very badly rusted/seized ones

 

[sideways]

If you lift the back wheel off the ground, run along holding it up in the air then drop it and jump on the bike it should kick over.

Locktite should hold it. Get a locking washer for some extra insurance.

 

[kendelrk]

make yourself a home made engine stand, kind of like the ones they have for some motorcycles so once the wheel spins it comes off the ground and goes, you put it on the stand, turn it by hand to start it drops off the stand and is running

 

[r97]

If you lift the back wheel off the ground, run along holding it up in the air then drop it and jump on the bike it should kick over.

Locktite should hold it. Get a locking washer for some extra insurance.

not completely sure that would work, i have tried coasting down hill then dropping the clutch (with me on it) but the rear tire just spins until it hits the compression stroke again and the tire skids. a kick start will add to the vintage feel anyway.

lock washer will be on there for sure!

make yourself a home made engine stand, kind of like the ones they have for some motorcycles so once the wheel spins it comes off the ground and goes, you put it on the stand, turn it by hand to start it drops off the stand and is running

uhhh.... not sure i can just turn the rear wheel by hand quickly and smoothly enough to start the engine.

 

[sexyvicta]

^ have a look on You tube at guys starting direct drive racing karts by hand.

What kind of engine is it? does it have a gearbox?

 

[r97]

^ have a look on You tube at guys starting direct drive racing karts by hand.

What kind of engine is it? does it have a gearbox?

gear ratio is 9.84:1 with an 8.9" OD rear tire. engine is a "bike engine kit" engine, 2 stroke 47cc, supposedly 3.5 HP @ 5000 RPM. engine has a built in gear reduction of 4.1:1 with a manual clutch, single speed.

i think low gearing, and the fact the tire isn't too accessible will make hand starting more difficult.

heres some pics to give ya'll some more info on the topic even though my question is pretty much answered.

 

[kendelrk]

ill have to try to get it my neighbor has a video of it, he was able to start his with a flat head screw driver

 

[r97]

did he put the flat head on the bolt on the end of the crank, and then turn it with an electric drill or something? or did he wedge it on a gear and press down quickly? anyhow, i'm not interested in starting it with a screw driver, and a kick start wont be tough to make.

 

[kendelrk]

no, he took a regular flat head screwdriver,stuck it inbetween two of the flywheel fins, pressed down while pulling out and tada, the engine was started, and after he had the recoil housing on, the starter cup came out a bit far, so he cut a small notch in the cup, right at the end, stuck it in pressed down and pulled out in the same method, and you didnt have to use much pressure

 

[r97]

interesting method, but i kinda doubt that will be very practical on the engine i have.

 

[fowler]

go the kick start

it just sounds cool

makes it look well done and make peolpe think u care

a screw driver makes it look like u just want it to run (mostly true but....)

 

[r97]

go the kick start

it just sounds cool

makes it look well done and make peolpe think u care

a screw driver makes it look like u just want it to run (mostly true but....)

that's about exactly how i was looking at this situation. i already had a method for starting the engine, just needed to know if one key component could hold together for it to work, LOL. unfortunately i'm off to camp for a week tomorrow, so (once again) progress will be slowed.... should have a couple weeks after that though.