motorcycle rev limiter(a.k.a:CDI unit)

[an2]

Please some one give me some references to build my own high performance CDI unit for my bike.. The installed one is suck, it make my bike run only 120kmh for 125cc bike.. hope u guys can give me the detailed circuit and component taht ineed to find.. Please

 

[akg]

it make my bike run only 120kmh for 125cc bike..

then how much u expect from a 125cc ?

 

[manz]

base on my experiences (for 2-stroke engine) it can go well untill 180km/h : ).but if it is a 4-stroke, 120km/h is quite good already.

 

[phalanx]

Rev limiters are not used to limit the speed of the motorcycle. They are there to limit the speed of the engine so your valves don't end up kissing the top of your piston. Your valve springs can only shut the valves at a specific rate. Rev the engine too high and the valves will not shut completely leading to poor compression and valve train wear for a mild over rev. A large over rev will cause the valves to hit the pistons which certainly leads to severe top end damage and there is also a good chance that the bottom end will be damaged as well. The only easy way to get around the rev limiter is to intercept and modify the tachometer signal going to it. You would trick it into thinking it is running at a safe RPM.

The other limiter some higher end motorcycles have is a speed limiter which prevents the bike from going faster than 186MPH (300KMH). Depending on the bike you have, this is implemented in a few different ways. Some manufacturers sense you are in high gear and compare that to your engine RPMs. Others go by your spedometer signal. The bike's ECU then leans your fuel mixture or retards the timing which decreases the engine's power so you can not go faster than 300KMH. This limiting is different then a rev limiter where every other cylinder (for multi cylider bikes) is fired.

In summary, unless you really (and I mean really) know what you are doing, don't mess with your rev limiter. If you have a speed limiter, which is very unlikely for a 125cc bike, there are a number of easy ways to get around it, the easiest of which is installing a speedo-healer.

 

[Hero999]

base on my experiences (for 2-stroke engine) it can go well untill 180km/h : ).but if it is a 4-stroke, 120km/h is quite good already.

That's right, I have a Honda CG125 and it gets to 100km/h easilly, 110km/h is a push and 120km/h is only possible downhill with the wind on my back.

Want it to go faster?

Buy a bigger bike!

It depends on what you want, a 125 is fine as a run around as it's fast enough to keep up with the traffic (apart from on the motorway) and acceleration is similar to a small low powered car.

If you want speed then get a 600 or something but be warned it'll be more thirsty, if you want the best of both worlds then go for a Ninja 250 great fuel economy and does more than 160km/h.

I'm thinking about buying a new bike but I'm not too bothered about speed, just something cheep to run and has lots of storage space. I'm considering a scooter, maybe a Vespa GTS250, I've given it a test ride the performance is acceptable and it's comfortable too, I'm still not sure it's what I want, can anyone recommend anything?

 

[Nigel Goodwin]

I used to usually have two stroke bikes, my fastest was a Suzuki 380, three cylinder two stroke - seriously nippy bikes. You could easily blow off Porshe's and Ferrari's (up to about 100mph) - but with a 380cc engine only giving probably low to mid 20's mpg they weren't cheap to run!.

There's nothing 'magic' about two strokes, they give much greater power, but only because they drink much more fuel!.

 

[Hero999]

That's because lots of it remains unburned causing polution leading to two stroke engines being banned in some countries.

 

[hizzo3]

this is what i have learned about motorcycles since i got mine.....

1) do you have enough power to get you to your 125kmp? if so look at a smaller final gear or larger diameter tire.... $200-400
2) you can always buy a turbo with the smaller gear.... $1500
3) try porting the valves $400
4) install a radical cam $500
5) pipes.... $400
6) Stroker kit $400-1000

Ok with all this aside, what do you think you will gain from all those mods? maybe an extra 20 hp on your already small 30 hp...... for $4200 not bad.... i really think you should have a new frame made too out of magnesium too...only an extra 5000 bucks, but and extra .25 sec off your quarter is so worth it......


Oh wait.... you arent a complete fool? then buy a bigger cc bike lol..... my vulcan 750 tops out at 125 mph (i dont use metrics) with rev limiter......but does a qtr in about 11 sec flat...... $4200 used for 1 yr.....

 

[hizzo3]

I used to usually have two stroke bikes, my fastest was a Suzuki 380, three cylinder two stroke - seriously nippy bikes. You could easily blow off Porshe's and Ferrari's (up to about 100mph) - but with a 380cc engine only giving probably low to mid 20's mpg they weren't cheap to run!.

There's nothing 'magic' about two strokes, they give much greater power, but only because they drink much more fuel!.

This has nothing to do with it.....its actually they get less power per stroke, but have 2x strokes per revolution of a 4 stroke...... hence y they have more power per size, but much worse fuel mileage

 

[an2]

hmm.. in my country,someone can make a honda 4stroke 100cc machine goes 250km/h and it run more faster now.. how? and how can the rev limiter doesnt make bike go faster when the racing one were installed..

here were so hard to find the racing accs.its sooo cost a lot of money bro... the only way is modified them, like installed another higher cc machine part,bigger piston,carburetor and the one thing that more interesting is we make our own cams by grinding and polishing it back with our own design..

 

[akg]

hmm.. in my country,someone can make a honda 4stroke 100cc machine goes 250km/h and it run more faster now.. how? ..

hmm..maybe using nitromethene

 

[an2]

hmm..maybe using nitromethene

nitromethene? no bro.. it run just use the ordinary fuel.. do you know that Drift King from Japan also defeated by malaysian driver? just use ordinary street car with some modifications..

 

[Hero999]

But they're highly tuned sporty engines, we're talking about an average run of the mill 125cc engine here.

By the way how many mile can a 100cc bike do at 250km/h before it falls to pieces?

with all this aside, what do you think you will gain from all those mods? maybe an extra 20 hp on your already small 30 hp

30bhp?
My Honda GC125 only has 10, the most you normally get from a 4-stroke is 15, aren't you talking about a 2-stroke 125, or a 4-stroke 250 here?

Oh wait.... you arent a complete fool? then buy a bigger cc bike lol.....

That's probably a better option.

my vulcan 750 tops out at 125 mph (i dont use metrics) with rev limiter......but does a qtr in about 11 sec flat...... $4200 used for 1 yr....

What do you mean by "does a qtr in about 11 sec flat"?

 

[akg]

What do you mean by "does a qtr in about 11 sec flat"?

covers 250m(or 400m) or in 11sec

 

[manz]

hmm.. in my country,someone can make a honda 4stroke 100cc machine goes 250km/h and it run more faster now..

hmmm i doubt that. and even if its true,how much do u think it`ll cost you.isn`t that as the same as buying another high cc bike? other is that you can`t get anywhere with that speed on that bike,except straight.the engine chasis (it should be a single frame due to small capacity engine) just could not keep up with the speed. and i am so very sure that the engine will not last at all because the parts of the engine did not design to withstand that amount of torque and power.it is so not save for the rider (you) also.

just a little advise, you can modified the bike but just dont over do it. anything that runs at full,max,over, its limit just will simply wont last. it just the nature of everything. and just dont simply listen to others` idea on what to do, think-study-and consider, and then make dicission.just as simple as that. it will realy worth it.

 

[Nigel Goodwin]

covers 250m(or 400m) or in 11sec

I suspect it's a quarter of a mile?, the standard distance for dragster racing.

 

[manz]

i think it should be 400 meters or 0.25 mile, coz 1 mile equals to 1.6 kilometer.
so quarter mile means 0.25 out of 1.6 km.

but anyway, both also the same,400m and quarter mile

 

[Nigel Goodwin]

i think it should be 400 meters or 0.25 mile, coz 1 mile equals to 1.6 kilometer.
so quarter mile means 0.25 out of 1.6 km.

but anyway, both also the same,400m and quarter mile

But it's not EXACTLY the same, and considering it's timed down to at least mS resolution (might be even smaller?), it's important that it's a quarter of a mile, and not 'almost 1/4 mile'.

 

[manz]

hmmm ?????

i just dont get it

1/2 = half
1/4 = ____????

i think it`s quarter.

so if it is quater, quarter mile means 1/4 of a mile, and to convert it to kilometer its 1/4 of 1.6km = 400meters.

dont u agree ?

 

[phalanx]

If you want to be precise, 1/4 mile is equal to 402.317 meters (1 mile = 1.609269 KM)

No 4-stroke 125cc bike that I know will even remotely reach 250KMH. You would be very hard pressed to reach 100mph (160kph) with a stock 125. They simply do not have the power to do it. 250kmh is more the realm of 600cc and larger sport bikes.