any advice? about to swap my flywheel

[gl_s_r]

Didn't Benny run one this light for a good while?

[Tweety]

Inertia and rotating mass!

Markus what's you view on the less mass making the bike harder to start and easier to stall at idle. Everything has it's pro's and cons so it would be good to know what are the cons specifically with the big twins. These are big pistons to move around which requires energy and the rotating mass helps with that.

(:-})

Well... That depends entirely on the engine... On my "street" engine it makes no noticeable difference to starting, it tends to start on the second turn over, or third every time... I'm using a LiFePO4 battery, so first rotation is weak, second is good, and it starts easy... No problems with stalling either... But that engine has a comparatively mild tune... (135-140 Rwhp depending on the weather)

On the race engine, which has an entire different tune, it makes a difference... But that's more a result of the fact that that engine has quite a bit more aggressive cams, and different compression... It's not very easy to start, period... Doesn't much matter what flywheel you use really, it has a nasty morning temper regardless (or well, plain and simple a nasty temper really, come to think of it...) And it's very prone to stalling on idle, or having odd hiccups or carbfarts at just off idle... But that's a compromise I'm willing to live with... 150+ Rwhp has it's drawbacks...

Generally, yes, if your bike is a bit cranky (pun intended) it makes matters worse... But then I'd start finding the reason for that instead of compromising on the lightened flywheel... On a bone stock, or just carbtuned engine, it makes no difference what-so-ever unless the bike has other issues...

woah woah woah... hold it! youve got VTR engines pumpin 135-140hp and another pumping out 150ho??

are these two engines that you swap out on one bike? or is it two different bikes?

ive only heard of 150 hp when talking about moriwaki race bikes! i havnt heard of anyone whos got those kinda ponnies. maybe im just misinformed and its more common than i think.

im sure it takes a LOT of time and even more money to get there. really cool though. whats torque numbers and top speeds for those engines?

Since the flywheel discussion has already moved on, to where most points have been covered, I'll just answer this one...

Yes, two engines... Two bikes really, since decided I didn't like the idea of trashing my over time carefully built bike full of unobtanium bits on the track too much... Would be one hell of a bill to replace all the parts that where sort of rare to start with, and now are past extinction if I ballsed it up, which I'm likely to do, since I'm a mediocre rider at best, but with short bursts of delusion of grandeur every time I get passed on track...

So I built another one, replicating parts I had, or borrowed... And, it sort of spiralled out of control somewhere halfway through... Was supposed to be another 130+ bhp engine, but I got a bit greedy when I was doing it in one go, not spread out over ten years, like last time, and since it was for track duty only, I sort of started uhm... "refining" it, and removing compromises along the way... So, yes... It makes a bit over 150 bhp to the wheel... But numbers are somewhat subjective, since it's all from my own home-made dyno bench... (it was too expensive too pay for dyno time when playing, so I built my own...) It's not calibrated that well really, so I rather not put down specific numbers... It's better used to compare before and after when I fiddle, not compare to other peoples numbers...

Let's just say thought, that numbers aside, it's one hell of an interesting ride... It's still a VTR, it still behaves like one at heart, but imagine the most pissed of, nasty tempered version you can imagine, and it's a good start... It's NOT a beginners bike, I can tell you that... Whack the throttle either way with too much enthusiasm, and it will launch you at the scenery like a rag doll, no second warnings...

I wouldn't say it's very common for people to get that much power out of a VTR engine... Not because it's impossible, or even that hard really... I'd say it's mostly because it's expensive and time consuming, to the point where most just go and buy a more potent bike fresh of the showroom for less money... I'm a stubborn one though... I liked my VTR, and wanted more of the same, not something else... And it was mostly time, not money, since I have long, long track record of taking things apart, and putting them back together again, making them either go like stink, or go boom, crack, and clang...

And also apart from racing, or track riding, it makes no damned sense what-so-ever to do this, since riding this bike down to the local burger joint is a chore and a half... It's simply not fun riding it at anything less than full throttle, when it's tuned this way... It's not that it's un-ridable, or badly tuned in any way... It's just a handful, and unrewarding if you try too tootle around...

The "road bike" though, is another beast entirely... Sure, it's a lot more power than stock, but it's really a big pussy cat... Flog it, and it responds in kind, but you can quite easily go touring on it... Or, ass easy as with a stock VTR engine that is, same drawbacks apply, although contrary to popular belief, it's actually got a longer tank range than most stock bikes, if you baby the throttle a little...

[VTRDark]

Didn't Benny run one this light for a good while?

I don't think benny's was as extreme but had more taken off than Rogers spec.

I'm still away at the moment and should be back at the weekend. Hoping to get a rattle gun next week and sort the flywheel out. I shall take pics and report back on behaviour and feel. Watch this space

(:-})

[Jamoi]

Carlos, how will you hold the flywheel when you torque it up after reassembly? I've seen Tmon's exhaust clamp method but don't have a spare to use. I was hoping to use this..

But it's too small

I might try and fabricate a rubber lined strap

[Kev L]

Jamie would an oil filter strap fit? I've got one you can borrow if you need to.

[Ckennedy]

It would have to be a big one. I would reccomend putting a bit of rubber between the strap and the fly wheel to avoid any damage being caused

[8541Hawk]

If you don't have a strap you can put a 2X4 through the rear wheel and have it lock up to the swingarm to hold everything in place while you torque down the bolt.
Not the prettiest way to get the job done but it does work.

[tony.mon]

Carlos, how will you hold the flywheel when you torque it up after reassembly? I've seen Tmon's exhaust clamp method but don't have a spare to use. I was hoping to use this..

But it's too small

I might try and fabricate a rubber lined strap

Rlong's heading my way Saturday to have his cct's manualised; he's in Ilford I think which is at least the same county.
I can lend my ex clamp and get it back on the workshop day, if you want to arrange to meet up with him and collect.
Or just drop over to mine on Saturday....
Any use?

[Jamoi]

Cheers fellas

KevL, I may take you up on that if I can't find some strappy metaly stuff on site tomorrow.

Hawk, I read somewhere that it can put quite a bit of strain on the gearbox, although had I not read that, I would be doing it with 2x4" like you say and i'm sure you wouldn't recommend it if you thought it could damage anything, so that is another option after trying a strap.

Just figured, if I can find something for free to hold the flywheel then I'd try it 1st.

There will be plenty of things laying about on a building site I can use

[VTRDark]

Carlos, how will you hold the flywheel when you torque it up after reassembly?

I rekkon the rattle gun might be good enough on it's own to do it back up. I wont get the exact torque as it's not a torque wrench but it will be on there tight enough hopefully. Otherwise I will most likely use a bit of wood as Hawk says.

I bought a large flywheel holding strap tool like the one in your pic of ebay to try and it broke. Waste of money You need some serious tension to grip the flywheel so it don't spin inside the rubber strap. An oil filter strap would grip better but I would be concerned about the metal part where you attach a ratchet damaging the flywheel as that part tends to sit against the part being gripped and the strap fed through it and doubled over, if you know what I mean.

(:-})

[tony.mon]

Back to the weight discussion, the weight of the flywheel is only part of the weight and mass of the rotating assembly- you can start thinking about the crank next....
That's bloody heavy, and the mass of the flywheel on the crank end is only a small component in comparison.
Plus, as it's geared directly to it, but contra-rotating, the mass of the clutch assembly and its shaft. And the primary gears.

So reducing the flywheel feels like a big reduction, but considered as part of the whole rotating assembly it's not a huge reduction in rotating mass.

With my exhaust strap method the adjusting bolt is close to the outside diameter of the flywheel, and instead of using a lever at 90 degrees to the flywheel surface I jammed the bolt radially using a tube against a (can't remember, something solid like a footrest) so that is resisting a compressive force, much stronger this way.
It worked, so hey.

[VTRDark]

I finally got around to purchasing an impact wrench and got the lightened flywheel on.




What a beast the new impact gun is

A comparison of the two flywheels side by side.




Interestingly the part numbers are slightly different. Maybe one is the manufacturing batch code.




And here it is on the bike.




I thread locked all the bolts back on but didn't bother with new gasket. Used a bit of sealant instead. I also did not worry about torquing up the flywheel bolt to a specific torque and just let the rattle gun do it's job and tighten as much as it could. There was no need to lock the rear wheel or put the bike in gear or anything like that. The rattle gun is the way to go.....the right tool for the job.

Going for a test ride now.

(:-})

[lloydie]

That's going to spin up stupid fast and watch your nuts on deceleration !!

[Virt]

That's going to spin up stupid fast and watch your nuts on deceleration !!

Don't warn him! I'm hoping for a Countertenor solo when I next see him

[AMCQ46]

wow that is a very serious flywheel. will be interesting to see how that rides on the road.............it makes the bike less forgiving in low gear low speed stuff so take care on wet roundabouts