I'm prepared to get shot down in flames here because this could be a very stupid question but is there any chance the rotor/flywheel on my 1997 XT600 could be threaded? I ask because it refuses to move despite me following all the great advice on here about using heat and a hammer with a pulling rig and protecting the end of the crankshaft. But when I look at the image on the parts page on MSP (shown below) it seems to show a thread pattern inside the central hole. Is this some kind of stepped taper or could it be thread?

If not I’m guessing I need to heat it more or hit it harder – can anyone tell me which is least likely to cause serious damage to the bike? I’m concerned that too much heat might deform the rotor or cause it to blue.

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Not threaded.

A friend of mine had one that really had to take a beating with a big sledgdehammer, if flew across his worshop when it let go.

With my own, i just put some tension on the puller, gave it a few whacks, and repeated that 2-3 times, and of it went. I was really surprised at how easy it was. So its very different from bike to bike.

My guess is that a good puller, with even tension so its not pulling slightly "sideways" will help alot.

No, not threaded, it's a taper fit - basically jammed in place with a nut to stop it coming off. If the male and female halves of the tapers are a good fit (as they should be) it can sometimes be a real struggle to get them apart. That's where the heat idea comes in - if you can get the flywheel warmer so it expands it'll release its grip on the shaft slightly (until the shaft heats up). You don't need to get it glowing in the dark but hotter than touchable should be somewhere about right. Remember it gets hot every time the engine runs so it's designed to take a bit of heat.

I've rarely (read never) had much luck with the two or three legged type of puller on flywheels. For what the proper puller costs it's worth buying one and even then it's sometimes tough (or it'll fall off straight away!). Heat it up, tension the puller (protect the end of the shaft with a sacrificial nut) and if it doesn't come off tap the end of the puller with a hammer. That's tap, not breaking concrete with a sledgehammer.

If you've got to this stage and everything is under tension do whatever you have to from the side, not in the direct line of fire if the flywheel comes off. The rear wheels of one of my cars are held on by the same method except everything is twice the size and they're always tough to get off. I've had the whole hub and puller assembly fly across the garage with some force before now. If you're in the way it'll hurt.

Thank you for the advice guys. The puller being to blame is something I hadn't considered enough, but it makes sense. I'm using a home made puller (now on the third version after the thread stripped on the first one and the plate bent on the second) that fixes into the threaded holes kindly provided by Yamaha. I've tried to keep it parallel with the rotor but I guess if it is even a few mm out it could cause one side to bind on the shaft. I'll make a stronger v4 tomorrow. It's good to know I'm not fighting against some high tensile thread through.

Be carefull when you tighten the puller, I always meassure the distances on four points from magneto to puller, up to 0.5mm accuracy should be good enough.

I wasnt carefull once, and new crankshaft had to be ordered

Wow. I've been working on anything within 2mm being good enough so that could be where I'm going wrong. I'm thinking that my homemade rigs are not good enough and I should invest in a proper good quality puller, preferably one I can use for other jobs on the bike like splitting the crankcase. I'm seeing 'harmonic balancer pullers' on ebay that look like they will do the job but all seem too cheap to be any good on a job like this. Can anyone recommend a quality tool that is likely to last? The Yamaha one is stupid money at 150 euros plus, especially as it only does one job.

KEDO - Performance Products item no 30270

KEDO - Product Details

Had a friend who built a copy of this, and the copy was great (it was the one I used) so id guess the original would be too =)

https://yambits.co.uk/flywheel-puller-p-12977.html

How frequently are you really likely to use it?

If it is very seldom then could you hire it from the local Yamaha workshop? OR if forced .. take the engine to the workshop to have the flywheel removed.

A tip when refitting the rotor.
The taper on the crankshaft and inside the rotor must be dry when refitting.
If there is oil or grease, the lubricant will allow the rotor to be pulled on further than it should be, and become tighter on the taper, making removal next time more difficult.

Bob

__________________
Remember that Assumption is the mother of all f**k-ups.

Oil or grese could also be the cause of spinning the flywheel and breaking the key.

So make sure everything is clean and dry, an torque down properly!

When you're refitting it the two halves of the taper must be a good fit. It doesn't take much - a slight burr on the metal or a bit of grit - to stop the two halves mating properly and you'll run the risk of the flywheel moving. It's the metal to metal contact that stops the flywheel spinning on the shaft, not the metal woodruff key. That's just there to make sure everything goes back in the right position.

If there's any doubt then lap the two together with some fine valve grinding paste. You'll very quickly see which parts are in contact and which are not.

guys, thats plain cruel, he can not take it apart and you are telling him how to put it together?

here's my tool
important to use a fine pitch M12 bolt, a coarse pitch will generate less pull
distance between M8 bolts is 75mm, just draw a triangle with a compass

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Haha thanks turboguzzi. That tool looks great compared to mine (pic below) and made me realise I need to make a much stronger rig. Mine uses 8mm threaded rod which is distorting under the pressure and two bits of 3mm plate which are bending outwards.

This is a tool I want to have because I'm having so much fun learning how to fix this bike that I'm sure there will be another in the garage as soon as it is finished. But I'm reluctant to spend the 52 euros on the Kedo one and concerned that the cheap Yambits one might not be up to the job. So I've ordered some high tensile bolts and now just need to find some steel plate. Is yours mild steel or do I need something special?

And thanks guys for all the advice about putting it back together - you saved me making some costly mistakes because I had imagined it would be a straightforward case of just whacking it on and tightening up the bolt.

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Huh, this is seriously "lightweitgh" puller Not sure if this would even take it off mine 50cc scooter

You need a lot stronger stuff, I used 10mm thick steel, ok I am maybe going a little hard, but it has done the job easily a few times. I'll take a pic later.