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If you want a serious power gain, then both are necessary with the MSX, a larger fuel injector and a controller.
You need the controller not only to control the AFR ratio, but also to improve the ignition timing from the MSX and to make it possbile to make RPM's.


Honda have made the 4th gear, and final drive sprockets way to heavy, they have installed a camshaft not mentioned for RPM's, limited the RPM's with a fuel cut on 9400 and didn't designed the ECU with the eye on performance.



If you want to tune your engine properly you will need to pay attention and correct these items.


To give you and idea, the top speed from the Yuminashi 150cc light bore kit in combination with the standard 125cc head with genuine (small) valves and ports is 144Km/h (89.47Mph).
Top speed sitting up straight is 135Km/h or 83.88Mph with our Twin-Cone GP exhaust and 31mm throttle body installed.
Test driver weight is 90Kg and 1.80Mtr tall (not Asian).


Total Light Bore high performance setup:


Cylinderhead: Standard MSX125, standard valves, standard ports.
Front sprocket: 14T (1 teeth smaller as original)
Rear sprocket: 36T (2 teethes larger as original)
Gearbox: Yuminashi 4th gear short overdrive gear set (23471-K26-025) with 25T gear sprocket (1teeth larger as original).
Cylinder: Yuminashi 150cc Light Bore Kit (12103-K26-572A)
Camshaft: Yuminashi SX270 (14100-K26-270A)
Manifold: Yuminashi 31mm light bore manifold set, to be installed on the original head (17111-K26-031A)
Throttle Body: Yuminashi 31mm Light bore throttle body with high performance light bore injector for MSX125 (16400-K26-031A)
Air Filter: Yuminashi High Velocity Stack for 31mm throttle body (17570-K26-031)
ECU: Standard ECU corrected with our tune-up box (correcting ignition and injection degrees)

hope this helps!!!!
 

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Nice write up. Thanks.
 

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I doubt your going to get near 90mph on a 150 single. Ninja 250s in race trim top out just above that.

I'm not saying it can not be done, I'm just saying with a four speed and stock small valve head it might take half the day to get there.

I mean come on a Moriwaki 250 is tough to get over 110mph and it is making lots more power with a extra gear, wide ratio trans and way better aero.

I'm pretty surprised people are reporting 65mph out of them stock.
 

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I doubt your going to get near 90mph on a 150 single. Ninja 250s in race trim top out just above that.

I'm not saying it can not be done, I'm just saying with a four speed and stock small valve head it might take half the day to get there.

I mean come on a Moriwaki 250 is tough to get over 110mph and it is making lots more power with a extra gear, wide ratio trans and way better aero.

I'm pretty surprised people are reporting 65mph out of them stock.
Use a GPS unit to get real speed, use your iphone gps and a Garmin then take the average and you'll get close to true mph vers looking at the digital read out.

My 1999 Hayabusa has a 220mph speedo but when I hit that speed the corrected is only 193-196mph.
 

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I am told that all motorcycle speedometers in the U.S. are 7% slow. They always indicate faster.

Now, what is this ECU tune-up box and where can it be had?
 

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The amount they are off depends on lots of things. Which wheel they read for one, most are off the engine now but used to be a lot on the front axle.

The faster you go the more the rear wheel is slipping. Back in the day the R1s aero was so bad that its top speed was 187mph as it would just spin the tire after that. It did not have enough weight and or down force to get more traction above those speeds. This comes from isle of mann racers quoted in British motorcycle mags.

The Busa is aero dynamic and heavy for a reason both are needed for the speeds it gets to. There is some pretty crazy math that gets done as speed and drag increase. You start needing insane amounts of power and downforce pretty quickly.
 

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I have used my Garmin watch on my minibikes during track-days you get some pretty cool graphs. I will see if I can find one to post up.
 

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That is a mph graph from a Garmin watch. Each low dip in the graph is the tightest turn on the track the one real low dip was when a friend crashed right in front of me. Neat info I was getting the CRF150R up to about 50mph on a very small kart track its geared very short. Has 5 gears in the transmission and 24ish HP(just a guess, never been on a dyno). Pretty basic bike 17inch slicks, high compression piston and Yosh cam, stock pipe.
 

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bump for moar info.
 

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Hi If you look on the Grom Net forum you will see that someone fitted the Light bore kit and had problems with the kit. He is waiting for replacement parts. Returned his bike to standard - but left in the high flow injector - did not run well - so returned fully to standard including the injector.

Someone else just fitted the injector (they have a modified intake and exhaust) - as per Yuminashi web page - but it did not run well. - Returned to standard.

So so far things are not going as well as hoped on the BB front.

Sure there will be some more updates in the next week or two.
 

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Your a godsend! Thanks for the details, I am sure everyone is eager to see the gains.
 

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Not a reliable products as they mention iv got piston broke in the first 200 mile
Bent valve oil leaks + the most important thing they don't have a customer support
I ordered some product payed by bank and receive nothing
So they owe me money its a long story i will open a claim soon
If you want to get a good product just wait for t.b. or contact Mike he is the best
Soon he will release some of them just need time the bike still new
 
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