Jump to content
Sign in to follow this  

a little powerband like a 2stroke

Recommended Posts

if i put a inner rotor kit on my 4stroke will it let my bike take off faster!!! and have little powerbands!!! something like two strokes!!!!

any ideas??

Share this post


Link to post
Share on other sites
and have little powerbands!!!

That would depend entirely upon what your interpretation of little is.

You need to post a couple of illustrations of what sized powerbands you have, in order to give an honest appraisal of the inner rotor kit, and whether or not it will help you...

......otherwise.......

ThisPostSucks.gif

Share this post


Link to post
Share on other sites

If you install some of those bow flex bands you could possibly end up with power bands, and or get a three stroke motor, its a cross breed between the two.

Share this post


Link to post
Share on other sites
if i put a inner rotor kit on my 4stroke will it let my bike take off faster!!! and have little powerbands!!! something like two strokes!!!!

any ideas??

All engines have a powerband , it's just that 4 strokes have a much broader and smoother powerband than two strokes fitted with expansion chambers and raised port timing . Two strokes get a supercharged effect from sonic pressure waves stuffing extra fuel /air charge back into the cylinder over a certain rpm range as governed by the shape of the expansion chamber . At that point the filling of the cylinder rises above atmospheric pressure at a rapid rate and that accounts for their savage "powerband" ! In other words , a 125 two stroke for example actually becomes more like a 250 engine , that's why they have to race against 250 4 strokes to be fair . 4 strokes basically operate at atmospheric pressure all the time so they have a flatter more useable "powerband" ! If expansion chambers were not allowed on two strokes , they would suffer a dramatic drop in power and become more like a 4 stroke engine powerband wise . This is how an expansion chamber works .

http://www.liebold.com/rumipages/espansioni/twostroke.html

http://www.motorcycle.com/mo/mcnuts/em-pipes.html

http://en.wikipedia.org/wiki/Expansion_chamber#How_it_works

Here's some valuable info on inner rotors I received and saved , from a VERY knowledgeable and experienced XR 100 racer . The same could be applied to horizontal pitbike engines ! I hope this helps .

The good- Inner rotor ignitions allow a much quicker rev up. They allow modified engines to make more power & RPM than the same engine with a stock or modified stock unit with "rev box". They also allow much quicker shifting & easier braking.

The bad- They allow the engine to kick back much harder when starting & the weak kick assembly takes the shock. They have no real RPM limiter so the top end needs to be bulletproof & the rider must be RPM aware. To get the bike to launch well you must launch @ about double the RPM of a stock flywheel & it's much harder on the drive parts, particularly the clutch, basket, & output gears/shafts.

Share this post


Link to post
Share on other sites

....like to add that it's 100x easier to stall a motor with an inner rotor and with big bore high comp motors the power gets almost violent, like an on-off switch. The more ponies your motor puts down, the harder it is to ride with an inner rotor in a 50-style bike....that's my opinion anyway.

Share this post


Link to post
Share on other sites

Okay dude... you can't put a powerband on a bike. Plain and simple... it doesn't exist. lol.

Second... the inner rotor DOES make it rev quicker, but you may run into problems. On low horsepower bikes it really perks them up, but they tend to go out a little quicker than a stock rotor setup. If you bump up to like 8HP and it's a chinese bike with a clutch on the crank, you're gonna snap the crank. Plain and simple. I wouldn't put it on a bike with over 5hp if the clutch is mounted on the crank. If it's off the crank, go for it Dude.

It all matters on the bike. Let us know what you ride. I have full blown race engine, and the inner rotor was actually TOO much snap. I opted for a lightened stock flywheel. So it can go both ways...

Share this post


Link to post
Share on other sites
Okay dude... you can't put a powerband on a bike. Plain and simple... it doesn't exist. lol.

That's dead right ! You can't put a "powerband" on a bike unless you are getting a dead motor running again . You can only alter the characteristics of it's existing powerband with cams , pipes , ignition advance curves , lightening crank and flywheel weight etc . When you hear two strokers ranting "wow man , it's got band", it sounds really dumb but it's good for a laugh .

Crank clutch motors are 60's or thereabouts technology and OK on a posty bike delivering the mail but have several disadvantages as far as racing goes . For instance , stall the motor and you'll be frantically searching for neutral to get the bike started again . Having the clutch spinning at crank revs was never a good idea and they disintegrate very quickly with an inner rotor ignition fitted . Mainshaft clutches spin at around one third of the speed of the crank revs , so they are way less stressed ! (ie crank revs divided by the primary drive ratio).

Also , I forgot to mention that flywheels act as harmonic balancers that help dampen out harmonic frequencies created by the power pulses and prevent them from traumatizing the crank and rod . Harmonic vibration is mostly responsible for stress crack failure of cranks , rods and big end bearings ! The crank vibrations are also transferred to the valve train via the cam chain where they can cause valve sealing problems at high revs . Harmonic buzz causes the valve springs to momentarily lose tension . Inner rotors don't have enough weight to absorb harmonics adequately !

When you use an inner rotor ignition , the crank really should be internally rebalanced to suit it .

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×