125sx "electronic restriction"?

[TS2Fifty]

Hi all, A friend has asked me the other day whether I knew how to derestrict his 125sx (approx 4yrs old). He said that it's electronically restricted or something.

Does anyone know if this is the case & if so how to get round it? Also, is there any other form of restriction in the exhaust/airbox etc? (as you might be able to tell, I haven't seen the bike yet!)

Any help on this would be appreciated as He says it will only do 50mph as it is, not much fun that... (it's a UK bike I think, if that makes any difference)

[Igor]

Yes, all MZ 125ers do have electrical restriction at 10,5kRPM. If you want to eliminate this restriction, I think you have to change CDI.

AFAIK 4-stroke machines don't have restrictions on exauhst or airbox.

[DAVID THOMPSON]

i put a 52 tooth sprocket on my rt125 made it pull better on hills

but mods to this bike are not practical as it is tuned to the max from the factory

yes it can be made to go faster but the money spent is better spent on buying
a bigger bike
ar dave rt125 in wv usa

[Igor]

What top speeds are you able to get with 52 tooth sprocket in fifth and sixth geard?

[TS2Fifty]

Alright, cheers folks. I will tell him to change the sprocket size then.

Didn't realise it was a rev limiter, thought he meant power restriction. Maybe would be better to leave the limiter alone,
do they hit the limiter in top gear easily enough? Maybe I could look at some form of tricking the CDI with a small resistor or similar though if he really wants it doing.

[DAVID THOMPSON]

into the rev limiter at 69mph
but max speed limit is 65 where i live and 45 to 55mph over most of the area i ride
the sprocket i used was an sx 52 tooth so on an sx a 56 should do about the same
or use a 15 front
but if not in Europe lots of luck on finding one
tisjot i think is a brand made in germany they may list one
or check the uk parts guys grahams
all the mods i have tried do both of 2 things make it use more gas and go slower
dave

[TS2Fifty]

Right, so on standard gearing you hit the rev limiter at 69mph?

So far as I know, said bloke's bike will only do 50 but I've yet to test it myself. He did say he read something online about taking the restriction off to get to 70mph (British national speed limit = 60 on major roads, 70 on motorway, although general flow of traffic on clear stretches is about 90) but didn't know how to.

I'll see if I can get a test ride on the actual bike to see what's what with it, my bet is that in an attempt to make it faster he's maybe done something to the exhaust or airbox which is making it underfuel & miss at higher revs...

I'll let you know what happens & also if by some strange miracle, I manage to get any more speed out of it I'll let you know what to do.

Cheers, Dan

[DAVID THOMPSON]

in new form this is a very tight motor and does not rev good till about 4000 miles of use
69 mph is my top after sprocket change 16x49 stock 16x52 after mod

on an sx the rear sprocket is hard to find
but grahams may be able to supply a 15 front that will make it pull better

click on the link below and download and print the poster for your friend
lot of useful info
in the link click the picture for a full view as site crops it till you click on it

viewtopic.php?f=4&t=804

[TS2Fifty]

Nicely. I'll see what sort of mileage it's done, but as it's four years old I suspect it's done more. (maybe even worn out to the point of losing power!).

I'll give him a knock when I get home, see if the bike's there.

Cheers, Dan.