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| godlygaz |
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godlygaz
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| Teflon-Mike |
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Teflon-Mike
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 Posted: 13:32 - 13 Jul 2011  Post subject: |
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Err, yeah.... sounds like some tit has done a half arsed de restrict on it!
The speedo has a pretty rudimentary speed governer in it, that retards the ignition beyond 'about' 55 to restrict top speed to 65...
Simply snipped, though, rather than NOT telling the CDi to retard the ignition beyond 55, it tells the CDi to retard it all the time!
Restriction in DT motor comes mainly from the power valve program, and the carburettor, if memory serves, not an exhaust restriction.
Old ones had exhaust restrictors and fitting after market expansion chamber could find a few extra top end bhp, at the expense of a lot of mid range ones, and tweeking power valve pegging could make it loose even more mid range for a couple of extra top end bhp, making the power band come in 'harder', the rate of change of power convincing so many people that they 'must' have SO much more power than before... when in fact they often got maybe 3-4bhp extra for teh effort at the top end, for a sacrifice of perhaps 5-6bhp in the mid range, hence teh screaming power band WAS ramping up 'like' they had liberated and extra 10bhp, because thats how much power increased from 6K to the red line, when in fact half of that was simply getting back the hole they had made in the mid range!
Check the web, your starting point will be to try and put that speed governor circuit to rights.
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
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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| godlygaz |
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godlygaz
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Posted: 15:17 - 13 Jul 2011  Post subject: |
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ok, i have had a fiddle and will test it out later, many thanks 
based on that the power valve opens at 5400rpm, is this standard ? or should i put it back to normal ?
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| godlygaz |
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godlygaz
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| unitynotsocri... |
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unitynotsocri...
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| Posted: 21:02 - 13 Jul 2011 Post subject: |
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Check the sprockets hav'nt been changed for mad off roading.?///???
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS |
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| Teflon-Mike |
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Teflon-Mike
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| Posted: 01:29 - 14 Jul 2011 Post subject: |
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| godlygaz wrote: | OK so had a whirl and i now think the speedo may be wrong ?
the bike can easily rev up to redline
and in top gear aparently doing 55mph at about 7500rpm
or 55mph in 5th doing about 9000rpm
that dosent sound right to me? plus few cars were actually overtaking, i was keeping up with the cars on the dual carriage way.
who does 55mph on the dual carriage way ?
dunno sounds wrong, could the speedo be wrong ?
G |
The DT Speed governer doesn't introduce a rev limiter.
It works by changing the ignition advance 'map'
When the governer oprates at speeds UNDER 55, it tells the CDi to use the more advanced ignition timing, which allows more power.
When the govener 'activates' over 55mph, it brings into play another CDi map, with less advance, which limits the power, without it 'stuttering' or machine gunning, like a rev limitr, simnply killing the sparks... sparks still hapn, just later in the combustion cycle, so you cant burn as much fuel so quick, hence get less power.
If the govrner is by passed 'wrongly' it defaults to the retarded low power map, ALL the time.
Engine will still rev out, but it wont take as much load, because it wont be making as much power.
So could still be the govrner....OR could b some on has tweeked the spedo, tightning the needl return spring to make it under read, so the govrner isn't actuating so early....
You'll have to clock it against a GPS to see...
And many people do 55 on duel cariageways.... it saves fuel!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
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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| godlygaz |
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godlygaz
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| unitynotsocri... |
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unitynotsocri...
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| Posted: 16:33 - 14 Jul 2011 Post subject: |
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Speedos on small bikes are inaccurate.A trial bike usually has a lower top speed than a road bike because of the gearing,and its a 125 not a 350lc ,so ,other than wear and tear,there's nothing to worry about.
we usually get let down by our own expectations.
You could change the sprockets for an extra 7 to 10 mph ,but it would turn it into a scabby dog with an even narower power band.be happy with it.
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS |
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| Teflon-Mike |
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Teflon-Mike
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| Posted: 16:56 - 14 Jul 2011 Post subject: |
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| godlygaz wrote: | Okay I did a speed test against my car , and the car was reading about 65? , yet the 30mph reading was correct.
The front sprocket is a 16T which I think is standard.
Behind the speedo I have taken out the restrictor which madr no difference and I can't see anything that may seem like someone has done a bodge derestrict.followed down the speedo cables, found noting.
Btw bike is , 2003 model |
https://www.yamahaclub.com/forums/
is probably your best place to look.
As I understand it, the speed governer on post 90 something DT's is a red switch behind the speedo, and is normally 'closed', and opens when the speedo needle gets round to about 55mph and the magnet lines up with reed.
But I am as likley as not to be wrong, My DT is thirty something years old, it's lucky to have reed valves, let alone reed switches!
If it does 65, then sounds like it's working OK.... and if speedo is reading 55, some-one has messed with calibration.
Thinking through; if reed switch opens to retard ignition, then if some-one had 'snipped' the wire, it would be as though red was permenantly open... and bike would be down on power throughout rev range, and not go faster than 65.
If some-one else, boght bike, and was dissapointed it never went more than 55, and decided to recal speedo, to circumvent governer, would just make speedo under read, becouse snipped wire, anywhere in circuit, would be the 'problem'... sold on, you have two bodged attempts to make the bike go faster to sort out....
BUT bottom line is, DT125 is governed for a reason.... even in full power form, the governer is fitted for many markets, because they are not very stable bikes....
But, you have a 'problem' with your's and you need to find the root cause....
DT is a loverly little bike in either restricted form, or full power, but they are a nightmare when folk dick with them trying to be clever and make them faster... unfortunately most owners have a go at it... usually badly!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
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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