sheared flywheel key??... again?!?!?!??!

[4cfed]

iv put about 15 hours on the lt250r since i i got it back, and in exception of the clutch, and throttle cable its given me no problems.. ( replaced flywheel key the day i got it) i was out riding today, burnt up a tank of gas in just over a hour,

stopped to warm my hand sup, changed plugs, and it fired up on the first kick like always, i had to wait for my buddy to get his 400ex unstuck, and my machine stalled after idling for about 30 seconds, figured ehhh whatever i had the idle set low no biggy,

WRONG! i go to kick it and it kicks back and blows my foot off the kicker, figured hmmm ok.. kicked it again same thing, and again same thing.. WTF?? kicked again and it started, took off made it about 35 yard and it started to bogg and wouldnt rev or speed up, and it died, kicked and kicked and kicked, swapped inmy old plug thinkin maybe i had a junk plug, same thing... sooo a long boring tow home behind the 400ex,

i pull the stator cover and the flywheel is tight,( coulda sheered the key and stil be tight but timing out of wack?) i pulled the carb off to inspect the reeds, there fine, checked wiring fine.. kicked and kicked and kicked and it will back fire and shoot a flame out of the exhaust now and then, and when i did get it to start i could hold it wide open and it wouldnt get over 2-3k rpms

sooo pull the flywheel off and expect a sheered key? has compression.. obviously if it blew my 250 pounds off the kicker....

sheeered key or what??

 

[88' blaster]

same thing happed to my 83 kdx 200 but it could not blow me off because the rings were bad but mine was a sheered key

 

[4cfed]

well mine dam near sent my leg over the bars

 

[88' blaster]

well mine dam near sent my leg over the bars

like i said i had bad rings. almost no compression

 

[4cfed]

im gonna pull the fly wheel off sometime this week.. if the key is sheered ill replace it with a oem one again... if it shears again after that im making one out of a old wrench.. wont sheer then, will rust busting the keyway its self

 

[sicivicdude]

No No No, the key is only an alignment tool for the flywheel. What keeps the flywheel from turning is the taper and the friction between the crank and flywheel. If it is sheared, take valve griding compound and put it on the crank without the keyway. Turn the flywheel until you can't feel the grit anymore. Pull the flywheel off and look at the crank. It should have like a few shiny spots but mostly unused compound. Keep rubbing the unused compound on the shaft by spinning the flywheel until you can't feel the grit anymore. Once you have the whole shaft shiny, wipe all of the compound off and reinstall with a new key and the proper torque.

 

[Awk08]

thats some righteous info there civic, i'm dishin the green !!!!

 

[sheeblast]

the key does help turn the flywheel. if it didn't, then how would they shear?

 

[sicivicdude]

The key does not turn the flywheel. The key aligns the flywheel only. The taper turns the flywheel and the reason the key shears is because it's not strong enough to turn the flywheel without the taper.

Think about the last time you pulled a flywheel off with a puller. Did the key go flying when the flywheel finally popped off? No, the key is sitting in one groove or the other just like it was always in there... The taper is what holds the flywheel on and the taper is what turns the flywheel.

 

[sheeblast]

ya the key is for alignment. but what if the flywheel slips on the taper, this means the key is there to make sure it doesn't slip. it isn't the primary turning agent, but it is a back up. this is how they get sheared.

 

[sicivicdude]

They shear because they're in the way when the taper lets go. Use some valve lapping compound to grind the taper back to match the flywheel and you won't have any more trouble out of shearing keys.

 

[4cfed]

They shear because they're in the way when the taper lets go. Use some valve lapping compound to grind the taper back to match the flywheel and you won't have any more trouble out of shearing keys.

i did the valve grinding compound when i put aflywheel key in it 3 weeks ago, the only thing im wondering is it i had ti torqued enough, its hard to torque on a small engine to 65 foot pounds, , i had it in gear and afriend standing on the rear brake last time,

this time ill to the same but ill ratchet strap it down to get more weight on the wheels so it wont try to move when torquing

 

[Awk08]

thats what the clutch holder/flywheel tool is for, to hold it while you torque it
doing that against the tranny/internals cant be good

 

[sicivicdude]

What?! you're going to break out something else doing it like that.

Get a strap wrench, a chain wrench, a flywheel holder, hell jam a hammer in there to keep the flywheel from turning. Anything but relying on the gear train to torque it.....

How long did you use the grinding compound? You need at least 15-20 minutes of working that compound to work the high spots down to match the crank to the flywheel. After you've worked that first batch of compound down, reload it with fresh compound and keep working it. The signal that you've worked it long enough is when the compound goes immediately to not grinding anything. Once the crank and flywheel are matched perfectly that grinding compound actually acts like a lubricant instead of grinding because there are no low and high spots for the compound to work between when the two surfaces are worked perfectly matched.

 

[scotj77]

can you find this valve grinding compound at any autoparts store?

 

[Awk08]

can you find this valve grinding compound at any autoparts store?

yes, common valve grinding compound available at most auto parts stores

 

[sicivicdude]

If you can't find valve grinding compound at the auto parts store you're in, walk straight to the door and never go back in.

fed, come up off some of that money and buy the tusk flywheel/clutch holder.

 

[Awk08]

If you can't find valve grinding compound at the auto parts store you're in, walk straight to the door and never go back in.

fed, come up off some of that money and buy the tusk flywheel/clutch holder.

/\/\/\/\ word !!!!!!

 

[4cfed]

i wish i had some money!! im working on a auto parts store paycheck, with 2 kids.... i did the lapping for like 5 min.. il do it longer next time.. and a clutch holding tool is a no go, i work to hold the flywheel think my fancy aluminum clutch basket would like that.. ill get a strap wrench from work

 

[sicivicdude]

You can make your own flywheel holder. Take a piece of flat steel and drill two holes in it the same space apart as the holes in the flywheel. Put two bolts in it so you have two pieces of metal (the ends of the bolts) sticking out of your handle (the piece of flat steel) to hold your flywheel.