well, what would cause THIS?

[300rman]

i am at the end of my rope with this piece of shat. if one thing isnt broke, its another, and its never an easy fix.

SO. i have a problem with my flywheel shear key. it has sheared off 2 or 3 times now, causing it to not run (DUH) the thing is, it has almost 20 hours total riding time on it since i bought it, so obviously there is a problem.

my question is: what would cause the shear key to consistently shear off so often?

This wont be a simple fix at all, as the flywheel nut threads are GONE. i will need to thread the end of the crank with a different thread, and either find or make a nut that will work before i can re-assemble the damn thing.
any tips on how to fix this as well?

i am about ready to throw in the towel, burn this damn thing, and go get a new quad, even though quads suck.

[thefox]

i am at the end of my rope with this piece of shat. if one thing isnt broke, its another, and its never an easy fix.

SO. i have a problem with my flywheel shear key. it has sheared off 2 or 3 times now, causing it to not run (DUH) the thing is, it has almost 20 hours total riding time on it since i bought it, so obviously there is a problem.

my question is: what would cause the shear key to consistently shear off so often?

This wont be a simple fix at all, as the flywheel nut threads are GONE. i will need to thread the end of the crank with a different thread, and either find or make a nut that will work before i can re-assemble the damn thing.
any tips on how to fix this as well?

i am about ready to throw in the towel, burn this damn thing, and go get a new quad, even though quads suck.


I think you answered your own question. Bad threads let the nut loosen up, if the nut is lose the key and then shear. I had it happen on my atc70, I thought the threads, although not very good, would still hold the nut. I ended up having to swap cranks.

[money89tractors]

Could be as simple as the flywheel wasnt tight or worked loose.

-Phil

[200x newby]

Here's a bad but still a solution to your problem! I know some idoit will come in here and say DONT DO IT! But that is why I said its a bad solution. You could put the flywheel on and weld it on there after you get it where it needs to be, then put the nut on and weld it to. Since the crank has bad thread anyways you could run it that way and shouldn't have any problem until your next bottom end rebuild.

[300rman]

yeah, i thought about welding it, but my luck, my stator would short out a week later. i think ill be able to run a tap over it and put a different nut on it.
i aint swappin cranks. if it comes down to it, ill weld it, and cut it apart upon disassemby, i got another crank layin around, it just needs a rod kit, and i just rebuilt this one........

ill try a re-thread, then ill throw a weld on it if that goes sour, or just cant be done.

i should probably have it TIG welded though?

[200x newby]

actualy from my experiences wire welding is stronger than tig.

[300rman]

ok, i will go with that. thanks for the input!

[money89tractors]

Another solution is to cut the treads off and drill and tap the end of the crank and use a bolt and washer to hold it on.

-Phil

[Dirtcrasher]

Something came loose from the beginning. The taper of the crankshaft or the bore of the flywheel, running with a bad key or a loose nut. Either way, something is worn and until it's all tightened up again, it will keep shearing keys.

Threading the crank isn't a bad idea either internally or externally, but it would have to have the case split either way which of course is allot of work. If you put intermnal threads in the crank you probably can't get much larger than 8MM before the wall gets to thin. Stock OD threads are probably 10mm OD.

[cr480r]

You need a some threads... welding alone will not work it will just sheer off at the weld... welding will not hold any tension on the tapers... Flywheels tend to keep shearing keys after coming loose the first time because damage is done that keeps them from fitting together properly... re-thread the crank... file out any high spots on the crank snout and flywheel...and then seat them together using valve lapping compound...

[300rman]

well, i am not splitting the cases again. if i cant re-thread the OD without taking the crank out, this thing will sit there until i feel like touching it again. i have had the motor in and out countless times for different, stupid stuff, and i've bout had it. the crank was just rebuilt with a new rod kit, which was a hundred bucks to have put together, plus the 40 for the rod.

i can tighten the nut up some, it will hold for ?? time, but it doesnt instantly break. if i can get tension on the nut again, and get it tightened down, i will weld the nut to the crank and the flywheel to the nut. ill just grind it all apart when it comes time for a rebuild.



unless someone here can re-rod a crank for cheap? ill start a thread on that.

[300rman]

the thing is, ive got too much into the damn thing to part it or burn it........IF it ever gets done, it will be all new.......everything has been replaced, but they are always really odd issues, nothing mainstream at all.

[Erics350x]

Rethread and put just alittle JB weld on the key and torque the nut to specs.

If you want to weld it will hold, i've done it several times. Hell its been holding my front sprocket for 2 yaers and i ride very hard

[cr480r]

well, i am not splitting the cases again. if i cant re-thread the OD without taking the crank out, this thing will sit there until i feel like touching it again. i have had the motor in and out countless times for different, stupid stuff, and i've bout had it. the crank was just rebuilt with a new rod kit, which was a hundred bucks to have put together, plus the 40 for the rod.

I dont see the need to split the cases... I would just pull the motor, and pull the clutch cover and basket assembly off... then you would have a flat suface to reference from when you drilled the crank.. a good machinist could get it close enough.. I wouldnt split the cases unless I was going to replace the crank with a new one..


Threading the crank isn't a bad idea either internally or externally, but it would have to have the case split either way which of course is allot of work. If you put intermnal threads in the crank you probably can't get much larger than 8MM before the wall gets to thin. Stock OD threads are probably 10mm OD.

I would cut the old externaly threaded section completely off and tap the remaining snout for a bolt or stud.. that way you could keep the same size hardware as stock..

[300rman]

ill drive up to PR racing and ask a few questions. if they want to spit the cases, ill do it myself, they want a ton to do that.

[300rman]

but, beside the nut being loose, there arent any other possible underlying causes that would do this?

[Tryzeedudeman]

you can always get a nice new motor rieady to bolt in an ride of ebay for 5 or 6 hundy, sell yours for 2-4 hundy and be done with it. Just something to think about again, since you probably already have. Good luck though!

[icp4life162005]

Hundred.<--(Correct Spelling)

[300rman]

yes, i could do that.....but then again, i would have to put my 300 top end on the new motor......and, considering i have 1 near complete bottom end, and another set of cases/complete tranny, i dont think this will solve the problems lol.

[TrailerRider]

Agreed, flywheel may be loose. In my experience of rigging things together (when I was a broke mofo) I would end up spending more then fixing it the right way to start with. I say whatever you find to be the exact problem, fix it correctly and then you have nothing to worry about. Since you have replaced almost everything you will have a good running bike again. just my 2cents.