weld flywheel to crank?

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DvDRip

DvDRip

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I've got a near new yx140 but the stator shat itself, when I replaced it I didn't torque the flywheel down good enough and it came loose and sheared the keyway on the crankshaft.
So I wanted to bolt the flywheel on and have it welded in place, I'm not sure if this would work tho because the stator components might melt? So I was thinking maybe get an IRK and weld that on instead that way I can just remove the stator components while it's being welded and if the IRK ever fry's I can just get a new one and transfer the stator components over without removing the rotor.

What you guy's think?
 
dont do it . irk is alloy ,crank is steel wont work .
 
damn, do you know what the usual lifan flywheels are made of?

I've heard of another method where you get the woodruff key and stick it in there with a load of steel putty then bolt on the flywheel and prey the putty holds, anyone wanna back this up?

^^^ coolie was that you?
 
Last edited:
i have repaired them before . i used loctite bearing retainer .
 
standards are steel, but i have that feeling that the hub, the part youll be wanting to weld, is cast iron...if its cast STEEL, no problems(but keep reading), but if its IRON, welllllll... find something that youre 100% sure is cast iron, and just try welding it :p with standard rods/wire+gas.

maybe silver solder or brazing.... but then the heat tends to kill the magnets.... and destroy any temper in the crankshaft as well...if these chinas are even hardened/tempered in the first place....(and you also run the risk of snapping the crank clean off due to uneven tempering from the welding/brazing...)
you DO NOT want a kilo of steel spinning at 5grand to suddenly learn how to fly!!!!:eek:

plus the (rubber) seals burning...

new crankshaft. it is the ONLY way.:(

but the experience in changing one is good:)
 
get the shaft taper cleaned up, poke the key in place, apply large quantities of loctite, allow to cure, re assemble...and make a simple tool to hold the flywheel still while you do the nut up to the point its about to strip...
 
well I wanted to replace the crankshaft but I can't find a replacement, I've made a WTB for a stuffed YX140 bottom end with no luck. someone offered me a crankshaft but couldn't confirm that it was 100% from a YX 140
 
DHZ? still, its gunna be pricey....

IDK! :p

strip it all down and get an engineer to recut a keway? at 180 degrees? still pricey...
 
well it's basically a brand new engine so I don't mind spending a few bucks, I'm gonna call around a few shops n see what they can do.

dafunk check your PMs mate
 
DvDRip said:
well it's basically a brand new engine so I don't mind spending a few bucks, I'm gonna call around a few shops n see what they can do.

dafunk check your PMs mate
Click to expand...

pm sent bruz
 
probably would be best to do the irk, will put less stress on the keyway if you do decide to fix it, and if it does fly, there'll be less mass. fingers crossed.
 
good point, I'm back on the hunt for a crankshaft now if I can pull that off properly then it'll be a perfect engine
 
Forget welding it on ... Instead , buy an IRK and lap the rotor onto the crank with fine valve grinding paste ...

The taper is what holds the rotor from slipping ... the key is just there for locating the right position for ease of setting the correct ignition timing ... When both tapers are exactly the same the rotor will lock onto the crank and hold itself there ... IF there's any high spots beside the original key slot on the crank taper you'll have to file them off ... but DON'T touch anywhere else with the file ... Lap until there's even wear bands on both the crank taper AND inside the rotor bore ... When you put the rotor on you're going to have to guess the alignment of the the key ... that's IF the original key slot has been badly chopped up ... A bit of loctite taper lock will definitely give that added insurance against the rotor slipping ... but PVL doesn't mention using anything fancy so the rotors must say put ...

The WORST that could happen is that the engine will start running weird or cut out if the rotor slips ... and your pit bike will instantly morph into a push bike ... LOL ...

PVL Ignition rotors have NO key way at all ...

PENTON RACING PRODUCTS INC.

Check out section 5 ...

Section 5: TIMING PROCEDURE: Except for a very few PVL applications, no keyway is supplied. Keyways and woodruff keys are utilized by manufacturers for ease of timing during mass production. The woodruff key does not hold the rotor to the crank! If your PVL system has no keyway, then no woodruff key is used.

Before installing the rotor, clean both the bore of the rotor and the stub of the crankshaft with contact cleaner, acetone, or other suitable product to be sure that it is clean and free from grease, oil, or other residue.
 
thanks for that info cactus, do you think using a standard flywheel would be less reliable than an IRK in terms of possibly slipping on the crankshaft? I'd rather not go down the IRK road if possible but if it's allot safer then I'll do it.

I've been told to use Qbond steel adhesive (not sure of the actual product name) to hold a key in place. then use loctite bearing retainer on the flywheel to prevent it slipping. I guess this is basically what you've just told me to do just with a woodruff key as well and no mention of lapping.

Would bearing retainer be basically the same thing as taper lock?
 
Try it ! What have you got to lose ? ... You'll need to use a proper puller to get the flywheel off after doing the lapping ... Yes I meant to say use bearing retainer ...

Loctite Retaining by Moore International

IF you can't get the stock flywheel to stay put or get it timed right ... a Lifan ORK which has adjustable timing might be a good compromise ...
 
ok will do :D

stupid question but do you see any problem with using loctite 603 or they all pretty much same same? just it only has 0.1mm clearance and the others have significantly more, but that stuff is SO expensive and 603 is the only one in 10ml bottle.
 
Try it without anything first ... Once the tapers are lapped and you tap the flywheel on as described by PVL it might work out OK ...
 
hi all

a couple of years ago i heard of a product that was used to block up the ports on a rotary engines this stuff set rock hard like steel and can take the pressures combustion and heat. it's called DEFCON. not to sure how much or where to get t but it is worth a try or maybe google it
 
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