ESE's works engine tuner

[twotempi]

So I take it that is a "NO" then ??

[husaberg]

So I take it that is a "NO" then ??

the idea has some merit.......for the greater good.........

[speedpro]

MBs are the same. If you disconnect the balance shaft or take it out with no other mods they vibrate like crazy. As I pointed out, without the balance shaft the counterbalance is too light. People then put the balance shafts back in. I've rebalanced my crankshaft. It's dead easy, all I've done is drill 2 8mm holes and 2 10mm holes around the big end pin area of each crank web.

[husaberg]

MBs are the same. If you disconnect the balance shaft or take it out with no other mods they vibrate like crazy. As I pointed out, without the balance shaft the counterbalance is too light. People then put the balance shafts back in. I've rebalanced my crankshaft. It's dead easy, all I've done is drill 2 8mm holes and 2 10mm holes around the big end pin area of each crank web.

I have heard that before. Dave maybe?
My old H100, which i guess is more subtly different than most people would expect was fine without it(in a MB5 frame).
I also remember pulling apart a AC CR80 and noticing it was actually machined for a balancer shaft (i guess betraying it true design origins)
But in my opinion the tiny possible gains are far outweighed by the negative aspects. I personally wouldn't do it again. But each his own you have 30hp and i have er..... i have a pile of bits. My theory is even with design margin the crankcase are designed to have them and i guess are pared down a it accordingly material wise.
But shove a CR500 in an alloy frame then after a 30 minute ride. A balance shaft or a more suitable balance factor would be a welcome addition. They are much more acceptable in the steel frame. As suitable Balance factors are off course effected by both frame material, design and engine inclination as well.
Of course some people's engine vibration problems relate more to the engine mounts sloppiness and untrue crankshafts as well.........

[SS90]

When Honda added balance shafts to Rs125's, the differenece was phenominal, I was always of the opinion from then that the advantages from having one, far outweight any disadvantage.
The early stuff was terrible for cracking chambers and rooting stators (although the flywheels where quite heavy)

As always, I feel a new set of tyres and correctly set up bike will be a far greater advantage than faffing about trying to get it close to correct after removing a balance shaft in the forlorn hope of less weight/ minute gain in power.

Russel Bleach always used to (helpfully) lecture me about "tuning to a standstill", as always, he was right.

[Grumph]

I've only ever found one motor that gained from balance shaft removal - the big kawasaki four ZX/ZZR family - and that was only because the shaft spent a lot of it's time under the oil level. Churning losses were significant.

Unless you have a really good handle on balance theory and practise, leave it in.

[Henk]

I took one out, rode it for a day then put it back in, didn't seem to make any difference powerwise but man it shook.

[wobbly]

As always its a combination of factors that makes any modification worthwhile or not.
The old RS125 was based on a MX case, and when used in the roadrace frame the balance factor was wrong for the rpm it was expected to pull - but that was because it used the original MX crank.
The stators were a shit design and doomed to fail even if it didnt vibrate, and the pipe had a slip joint at the end of the header, another shit design doomed to fail.
But in a kart, the old MX based engine was as smooth as any, and with expoxyed or better later model stators, and a pipe with a proper header design they were able to be tuned harder than the new engine.
Especially if you fitted a new solenoid PJ carb and Ignitech to drive it.

The newer RS125 was specifically designed for the roadracer, and had a very laydown cylinder layout.
But for people to believe that removing the balance shaft would be a performance enhancement,due to reducing the rotating inertia, are sorely mistaken.
The small inner rotor flywheel, doesnt have sufficient inertia, and if you remove the balance shaft, and or remove the rotor to convert to total loss, the engine simply will not rev, using a stock crank.
Its been proven hundreds of times, and Honda and VHM offer high inertia cranks specifically for use without a rotor.
ie remove the shaft,then you have to add weight back into the crank to get it balanced - so the point was????
Rebalancing the crank to reduce the vibes in the power range used, all but adds as much inertia back into the system as was there before, and except for reducing some balance shaft support bearing drag , removing the
shaft really is of no advantage.
But a balance shaft in a small single simply isnt needed anyway if the crank is correctly balanced for the chassis its used in.
Plenty of single MX and kart motors are perfectly fine without any balance shaft.
Big clunkers throw alot of big amplitude vibes around, and as everyone knows a CR500 would be wonderful if it had one.

[richban]

I took one out, rode it for a day then put it back in, didn't seem to make any difference powerwise but man it shook.

Best one I saw was a guy who just removed the balance drive gear but left the shaft in. The front wheel nearly left the ground when he gave it a rev. Is that even possible. Well thats what he told me anyway. crazy vibration.

[Henk]

I'd have thought that the saft without the gear would just swing gently as it pleased and occasionaly bang into the crank as it was spining, scary thought.

[richban]

I'd have thought that the saft without the gear would just swing gently as it pleased and occasionaly bang into the crank as it was spining, scary thought.

After just splitting my engine I think it would miss the crank. But my balance shaft is a little smaller than normal.

[F5 Dave]

A commuter bike is of course set up for doing 8000rpm max so all bets are off when raced. They will spin another 4000 & not have to cope with learner riders in slow traffic.

I took the balancer shaft off my MB50s back in the day because everyone was doing it. My H100 came without one as PO had the bearing fail & took it out to fix it. The MB in RS chassis I never put it in, partially to see how it went & on new cases I used the area for the Case reed. None of them have vibrated much at all & I hate vibey bikes. - Like really hate them.

I've been a bit lucky I guess (also paid attn to using anti vibe mounts) but the latest MB crank I have followed Mikes lead with some drilled holes. Seems to vibrate a bit more down low. Can't complain up top.

I've had mate who had done the cut the rotor off the side of RS125 crank, but of course not bought a HI crank, so it is interesting to read Wobs explanation & shows the folly of following the trends without understanding the full story. A little knowledge, as they say.

[husaberg]

Yeah it was a single crank four rather that a twin contra-rotating crank. So as result of the layout the engine was obviously wider but........
The weight was also further forward. less weight shorter and less losses....
Doohan reckoned the heavy balance shaft inherited from the initial big bang motor helped the handling...... makes sense. contra-rotating.
Ever noticed most bigger cc'd engined bikes seem harder to turn as a general rule even in the same frame those flywheels are effective gyros.....

Successful design it guess is about achieving the best possible compromise...........bucket loads of cash does of course, not hurt either

Not sure why then they make the twin crank 250 though.........................

i guess its the early 70 degree nsr250 (the real one not the roadie) can anyone confirm.......

[TZ350]

Fitted an air box and lost 2.5 horsepower so I had to try and get the motor working properly with my carb cover come spilled fuel catch tank thing again.



The quick change air jets worked a treat.

Torque curve runs for 5k, 8 to 13, and at 13 its starts to detonate, I guess because of insufficient blow down STA at those rpm.



In the end I managed several good runs @ 30hp, I hope I can do that again in a back to back test with Riches bike tomorrow night.

[ief]

Came across the smartcarb and understood Wob tested them, are they all that is claimed or just a good carb and, if any, what's the secret?