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Derbi Senda Cross City 125 Low MPH Please Help

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FU125
L Plate Warrior



Joined: 03 Jun 2018
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PostPosted: 20:24 - 03 Jun 2018    Post subject: Derbi Senda Cross City 125 Low MPH Please Help Reply with quote

I am new to this forum and I was just wondering if there is anyone that can help with my low top speed issue on the Cross City 125 (2016). As an upgrade from a 50cc which had a top speed of 55mph (Gilera SMT 50 - Derestricted + Sports Exhaust) I am severely dissatisfied with the same limitation for speed with the 125. Nothing has been altered with the Cross City so I know the exhaust would be a good place to start, but other than that and the sprockets, is there any way to de-restrict it or make it go faster??? Or is it simpler to just get a faster 125?
Thanks a lot.
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Teflon-Mike
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PostPosted: 21:08 - 03 Jun 2018    Post subject: Reply with quote

It's a four-stroke 125 single, that in tip top fettle, might have once upon a time, made a heady 12bhp... put into a dirt bike frame with high seat and wide bars, given a psedo-motard styling job and slick tyres....

A good two-stroke dirt-bike, might, with 20hp or so, just about reach 75-80mph. Learner-Legal ones? Well the Yamaha DT125 was electronically giverned at 65mph 'cos of stability. A four stroke, with a design spec of 12bhp, is unlikely to achieve even that... and one would have to ask why you would want to with such a tall CofG and short wheel-base....

Old rule of racing... before looking for MORE than standard... make sure you have all you should AS standard....

50-55mph doesn't sound like it does.... and oooh... little one-lunger learner-bikes.... dont tend to fair very well in the hands of learners, trying so often to run them on a shoe string, and with lary ideas, IF they bother to lift a spanner to them, of making them 'faster' rather than 'laster'... drilling holes in air-boxes removing the exhaust washer thingy restricter wotsit, putting monster-g-fast stickers all over it, and removing baffles from the exhaust..... rather than,,,, oooh... changing the oil, replacing the spark-plug, cleaning the air-filter or tickling the tappets.....

You want 'faster'.... forget ideas of tuning... just forget it!!! If you want fast, you bought the wrong bike.... a high wide dirt-bike mased machine just doesn't have the basic ingredients to go quick, and with a four-stroke single cylinder engine... you dont have a hope of giving it any more power to help.

SO!!!!

Start with a basic propper service.... change the oil, tickle the tappets, give it a new spark plug, A-N-D try and find all the botcxhes, bodges and 'go-fast' mods prior owners have attempted,...... probably very very badly... and put it back to standard.

Should go a bit quicker... but more importantly whatever fast you get will last!

If you want 'fast' buy a faster bike..... and that probably wont be a 125... even the fastest of the fast hot-snot two-stroke 125's are not exactly much more than a bit brisk in the greater scheme of stuff.. the homogation special, factory prepared 'race' bikes, JUST about managed to crack a genuine ton under FIM test regs.... which is pretty slow, if you look at the books, where almost anything over 125cc can get those sort of numbers and not go 'bang' in the trying!!! That is abouyt as quick as a thirty something year old Honda 250 four-stroke single 'commuter' bike!!!

A-N-D on a CBT you dont have a licence, you have a learner's permit... go get some savvy, save your cash for getting a licence, and prove you can handle the pathetic power of a 125....

Then, Oh-Kay, you might not be allowed to ride anything bigger or pokier than a 125.... and anything that can better 15bhp and about 75mph... which can still break all UK speed limits without too much effort, is going to be outside the limitations of a licence you dont even hold right now..... but, what the heck... not needing to display L-Plates that are probably missing, broken, under-size or non regulation, is a good reason NOT to get pulled, for a look-see, to see what else they can knoble you on... like a noisy pipe, or lack of insurance or riding other than in accordance, 'cos bikes not learner-legal....

YOUR CALL... but start with a basic, proper, thorough service, and finding all you should have as standard, before having silly ideas about making slow-bike, likely slower, less reliable and less valuable for the effort.

In the mean-time... enjoy the fact you are too young to have more... old age has little to commend it, big bikes is one of the few compensations.
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WmY
Renault 5 Driver



Joined: 21 May 2018
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PostPosted: 22:50 - 03 Jun 2018    Post subject: Reply with quote

Teflon-Mike wrote:
If you want 'fast' buy a faster bike..... and that probably wont be a 125... even the fastest of the fast hot-snot two-stroke 125's are not exactly much more than a bit brisk in the greater scheme of stuff.. the homogation special, factory prepared 'race' bikes, JUST about managed to crack a genuine ton under FIM test regs.... which is pretty slow, if you look at the books, where almost anything over 125cc can get those sort of numbers and not go 'bang' in the trying!!! That is abouyt as quick as a thirty something year old Honda 250 four-stroke single 'commuter' bike!!!


Hm. I had a Bultaco TSS125. About 24 BHP, top speed depending on various factors. I wanted to put it on the road. It had triangular tyres, a wonderful expansion chamber exhaust that "started" at the exhaust port, would do well over the ton, 6 speed, water cooled single. The Smiths rev. counter started at 5,000 RPM and finished at 15,000. It wouldn't run at all well unless it was on the clock (no speedo...). It was 196? Unsure of precise year. I do remember that it atttracted complaints, and could be heard running 1 1/2 miles away....

Urgh. You reminded me. I have just looked to see what they sell for, when they can be found. I sold mine for £1/cc.... Whurp! Grr! Still, there's only so much room in the shed. Still.
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Teflon-Mike
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Joined: 01 Jun 2010
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PostPosted: 23:06 - 03 Jun 2018    Post subject: Reply with quote

WmY wrote:
Still, there's only so much room in the shed. Still.

There only diddy... sure you could find space for one, somewhere.... the living-room perhaps?

Uncle used to have an MV Augusta Ipotesi as a piece of statuary in the hall at the farm, when my Gran died....... had to chuck out the Jacobean dresser to make room for it..... and the telephone had to go on the floor.... "Useless bit of furniture!" He grumbled... I wasn't sure whether he was talking about the dresser or the Ipotese!

Another acquaintance, actually had three ex GP125's in his living room... one was a Kreidler, I think, the other two probably Derbi's, co-incidentally.....

When he got married..... his missus told him she was NOT going to put up with a work-shop for a living-room... where his RC30 had usually lived... normally in bits.....

So he re-decorated!
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Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'
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WmY
Renault 5 Driver



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PostPosted: 11:43 - 04 Jun 2018    Post subject: Reply with quote

Teflon-Mike wrote:
WmY wrote:
Still, there's only so much room in the shed. Still.

There only diddy... sure you could find space for one, somewhere.... the living-room perhaps?


I'd love to, but I couldn't afford it now!

Near that time, I almost bought a BS SS80 with wicker sidecar all painted over again and again in black, like a badly "restored" Lloyd Loom laundry basket. I came across it in a car garage in Wales. The bloke wanted £800. Giutted, absolutely gutted. I could neither afford that nor fit it in the shed now. I'll have to start a "crying" thread when I snap out of it....
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Rogerborg
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PostPosted: 12:16 - 04 Jun 2018    Post subject: Re: Derbi Senda Cross City 125 Low MPH Please Help Reply with quote

FU125 wrote:
55mph

GPS 55mph, or speedo 55mph?

My 250 cruiser always felt slower than it really was because it had an accurate speedo. Every other vehicle I've ever owned has flattered to deceive.
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M.C
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PostPosted: 23:00 - 04 Jun 2018    Post subject: Reply with quote

Geared for 65mph and no screen/fairing (sounds familiar). I'm afraid that's all its got Neutral
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stevo as b4
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Joined: 17 Jul 2003
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PostPosted: 20:52 - 05 Jun 2018    Post subject: Reply with quote

In good condition and maintained right, I'd have expected a true 60mph maybe 62, so similar to a CG125. I never really found my own CG massively under powered because I never expected more than it could give, and you rode them flat out properly unlike owners of bigger bikes.

I used to be mildly impressed that it'd still get the drop on most mundane l cars from traffic lights to 25mph, and that it'd hold 50mph on long motorway inclines etc. I wasn't expecting it to be any better than that.

The same as when I had my 600, and found it couldn't do sudden warp speed 3car overtakes at 6000rpm, like an R1 etc.
I didn't expect it should be capable of 1100cc grunt.

As for the OP's previous 50cc, well sure it might have indicated 55mph+ but you didn't seriously expect that to be a true top speed from 49cc did you?
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Rogerborg
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PostPosted: 07:55 - 07 Jun 2018    Post subject: Reply with quote

stevo as b4 wrote:
As for the OP's previous 50cc, well sure it might have indicated 55mph+ but you didn't seriously expect that to be a true top speed from 49cc did you?

But it was derestricted and had a sports exhaust. Folded arms
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