Flywheel fun

One of the coolest bits about the NSR250 MC28 is the smart card PGM IV ignition.
One of the least cool bits about the NSR250 MC28 when it comes to tuning is the smart card PGM IV ignition.
All you need is an hrc P-030 card and the bike is fully derestricted. With a wire splice you even get your lights back.
Unfortunately hrc cards are like hens teeth and even if you did find one, the speedo becomes one big temp gauge so making the bike even less popular with the law on the road.
Clearly the thing to do here is to bin the PGM IV unit and buy a programmable ignition unit like the one offered by Zealtronic. Plug it in, book some dyno time and happy days your bike isn't only derestricted, it now has an optimized ignition curve with exup valve opening times to match!

But that does away with the smart card and that was one of the coolest things about the MC28 wasn't it?
The HRC card might be an idea for the future but for now there are a few things I can do.
First off we need to know what the HRC card actually does. This being advanced ignition timing and EXUP valve operation.
So how to emulate this?
Exup valve timing isn't going to be easy to change but we can advance the ignition timing changing the flywheel over to that used on an NSR250 MC21. The benefit of this flywheel is that you get 3 degrees (just went to check where I thought I read this exact figure and it wasn't there so not gospel) of timing advance. You can use an MC18 flyweel that offers a slightly lower advance or opt for an advance/retard woodruff key like those offered by Tyga Performance.
I bought my flyweel on ebay for £15, this was allot less than I thought I'd get one for. I then went on to look into removal refit. I had done this before on some commuter 125's but with little concern for engine casings as I wedged levers behind the flywheels to hoy them out.
The NSR wasn't getting this treatment so I went searching for a flywheel extractor. Initially I was lured in by the multi purpose (for the mc28 that is) extractor available form Tyga. However the cost and immediate availability of the Laser 4267 Motorbike Fly Wheel Puller from machine mart made for a more tempting offer.

With the fairings already off I removed the coolant reservoir followed by the the retaining bolts so the flywheel cover could be removed. This also partially covers the drive sprocket to prevent crap from being thrown all over the engine and the back of your leg so unsurprisingly this was full of old chain lube and associated dirt. I stuck this in soak whilst eyeing up the now exposed flywheel.

As I do not own a flywheel holder I opted for a chain wrench to hold the flywheel steady as I undid the flywheel retaining bolt. Engine compression alone is not enough to react this action. A strap wrench would be a better idea (less the correct tool of course) but 1 I'm replacing the flywheel anyway and 2 as it turns out these things are nails and didn't take any damage.

With the bolt out I was able to screw the outer barrel of the extractor into the flywheel. This is a reverse thread, good for catching some people out. With this in the cross piece can be screwed into the outer barrel till it stops. Now it is a case of giving the flywheel a few taps (being careful not to demagnetize it though) whilst turning the cross piece in. What you are trying to do is overcome the sticktion of the flywheel on its tapered shaft.
All of this is quick and easy to explain but took an age as that thing was on there!


After a bit of fighting I realized I was bottoming the cross piece out on its threads not on the crank shaft wasn't pushing the flywheel off as I was supposed to.
My fix was to use a flywheel cover bolt in the hole as an extension as you can see on the left. From here I was able to re attach the extractor tool and the flywheel came off right away.
Well that was easy!




Before proceeding I gave the generator coils a glance over, they weren't looking bad at all considering how long she had been supposedly standing in Japan.
With the mc28 flywheel off it was a simple matter of taking up the mc21 flywheel, locating the keyway and slipping it onto the shaft in line with the wood ruff key.
I was then able to slap in the flywheel retaining bolt and torqued it to 57.9 ft-lbf (8 kg-mf) after finding a torque chart on dreamgate. This is a useful resource to bookmark since I am still waiting on being able to join NSR world as their admins appear to be asleep.
Due to having the front head off I haven't been able to run the bike up yet but am hoping for a freer revving bike for 20th the price of an HRC card if I was ever able to find one.

In review of the Laser 4267 Motorbike Fly Wheel Puller, I had mixed feelings for it.
Confusingly it offers multiple different thread options on the cross piece when only one arm of this will screw into the outer barrel as the others are either to large or small. So I have no real ideas as to what purpose the other 3 legs offer other than as very uncomfortable levers to turn the correct leg in when pressing out the flywheel. A better alternative to this would be to do away with the cross piece and have flats so a spanner can be used. Not only would this be more comfortable but you could also use a hammer to tap it around (as it stands you would just damage the other threads). Of course we can't forget that the treads aren't long enough either so generally not good with this part.
The body of the sleeve does have two external thread sizes to screw into the flywheel so this does offer some universal applications. It is also pretty robust with strong threads as well to its credit.
 I can see how, in its lack of need for spanners, it is a simpler and tidier tool to use on low capacity motorcycles and those extra threads may well have other applications on simpler flywheels.

Flywheel extractor design aside the job itself is a simple one and will hopefully aid in freeing some well hidden ponies. Just read the above, avoid the time wasting bits and do it quickly and properly. I hope this is helpful.