spurs59 Posted March 30, 2012 Share Posted March 30, 2012 i have recently bought an 07 yamaha dtr 125 sm.it came with the standard exhaust and dep end can but bought a dep exhaust and had it fitted,whilst at the garage they looked at the powervalve and said it was set up correctly.there is a wire that looks like it comes from the speedo and is earthed to the battery (i cannot remember the colour without looking)regardless of all this the bike will not do more than 65 mph,why is this Link to comment Share on other sites More sharing options...
spurs59 Posted March 31, 2012 Author Share Posted March 31, 2012 anyone got an answer Link to comment Share on other sites More sharing options...
Moderator Cynic Posted March 31, 2012 Moderator Share Posted March 31, 2012 Because it has the aerodynamics of a barn door. Its primary purpose is crossing open country safely not going fast. Would you expect a landrover to perform like a porche. I have said it many times before but my TDR is very similar aerodynamically and has double the cc and over 4 times the hp, that is only good for 100. But the same engine, and i mean nigh on identical (different first gear) engine in the TZR250 will do 130mph. Link to comment Share on other sites More sharing options...
spurs59 Posted March 31, 2012 Author Share Posted March 31, 2012 Because it has the aerodynamics of a barn door. Its primary purpose is crossing open country safely not going fast. Would you expect a landrover to perform like a porche. I have said it many times before but my TDR is very similar aerodynamically and has double the cc and over 4 times the hp, that is only good for 100. But the same engine, and i mean nigh on identical (different first gear) engine in the TZR250 will do 130mph. i know it wont do the speed of a cagiva mito or aprilia rs but i though you would be able to get 75 mph from the sm Link to comment Share on other sites More sharing options...
Moderator Cynic Posted March 31, 2012 Moderator Share Posted March 31, 2012 Depends how windy, hilly, even your jacket and helmet make diferences, a stock Mito is still only a 70mph bike with 12hp and it has less weight and a lot less drag. If your getting a genuine 65mph from your dt you are not doing half bad. Having road tyres will help and missing the windjammer muddy on the front too but a cow born in a stable is still a cow. Link to comment Share on other sites More sharing options...
spurs59 Posted March 31, 2012 Author Share Posted March 31, 2012 Depends how windy, hilly, even your jacket and helmet make diferences, a stock Mito is still only a 70mph bike with 12hp and it has less weight and a lot less drag. If your getting a genuine 65mph from your dt you are not doing half bad. Having road tyres will help and missing the windjammer muddy on the front too but a cow born in a stable is still a cow. it has road tyres,if 65 mph is all that it is capable of doing then i have to accept this Link to comment Share on other sites More sharing options...
busyeddie Posted April 1, 2012 Share Posted April 1, 2012 I had this problem when I had my RXS100. I tried allsorts to try and fix it so that it would do 80mph, because thats what people said it could do. I eventually phoned yamaha and they told me the best way to fix a poor top speed that I should buy one of these http://www.yamaha-motor.eu/uk/products/motorcycles/supersport/yzf-r6.aspx Should help with your problem. Or the cheaper option is read pauls excellent sticky thread, all about speeding up a dtr. Link to comment Share on other sites More sharing options...
Ryan09 Posted April 1, 2012 Share Posted April 1, 2012 Try earthing the cable to the frame or the bottom yoke? You should see 75mph pretty easily, i wouldnt mess with it too much though as youll start affecting its reliability, Link to comment Share on other sites More sharing options...
AndyDtr08 Posted April 2, 2012 Share Posted April 2, 2012 It should be able to do 80mph on the DT clocks, although this wont be 80mph genuine. The wire coming out of the back of the speedo should be earthed to the frame. I put it around one of the headlight surround mounting bolts and tightened the nut over it. This will let it rev freely passed 7k rpm. Take the cover off the powervalve pulley which is down by your left knee. When you turn the ignition on, the pulley should turn. If it is pinned into place at the top the powervalve isnt operating correctly and you'll lose bottom end power but it shouldnt affect top speed. If the exhaust isnt on properly you could be losing power there. Someone must have been tampering with it to fit the DEP pipe. DEP claim an extra 10mph i believe which means it should do 90 on the clocks. Id be scared though. My DTRE would shake at the front end getting towards those speeds as the wind gets under the mudguard. Be happy with 65, do your test on the bike and move on Link to comment Share on other sites More sharing options...
Ryan09 Posted April 2, 2012 Share Posted April 2, 2012 The dep only seemed to improve acceleration on mine, the top end was near enough the same as before. Link to comment Share on other sites More sharing options...
AndyDtr08 Posted April 10, 2012 Share Posted April 10, 2012 The dep only seemed to improve acceleration on mine, the top end was near enough the same as before. Yeah thats what I had imagined. They look bloody nice though! Link to comment Share on other sites More sharing options...
Ryan09 Posted April 14, 2012 Share Posted April 14, 2012 Iv got a sticky on here somewhere about basic mods for a DT, might be worth a look. The dep does look pretty but is so hard to keep it shiney, it fades and rusts quickly if not kept on top of and dents really easily as well unlike the stock one. Lot of money for what it is but i did enjoy the difference it made on acceleration. Thinking back it makes me laugh a little how i used to try and squeeze every extra mph out of my dt then i upgraded to a bigger bike and thought 'wow this is so much nicer!' Link to comment Share on other sites More sharing options...
mark 88 Posted April 26, 2012 Share Posted April 26, 2012 year mine will get only 65 mph to and god i wish it would get more being trail bikes originally they must be geared more for talk than top end the sm version differs very little from its trail going brother is it derestricted fully ?. try (dtr.net) in google its a forum dedicated to the dtr they have a section on FULLY derestricting the bike they say it can go all the way to 80mph !!! Link to comment Share on other sites More sharing options...
blackhat250 Posted April 26, 2012 Share Posted April 26, 2012 but a cow born in a stable is still a cow. === Class jason class " Link to comment Share on other sites More sharing options...
spurs59 Posted April 28, 2012 Author Share Posted April 28, 2012 Try earthing the cable to the frame or the bottom yoke? You should see 75mph pretty easily, i wouldnt mess with it too much though as youll start affecting its reliability, the wire has been earthed to the battery by the previous owner Link to comment Share on other sites More sharing options...
FlyZanzibar Posted April 28, 2012 Share Posted April 28, 2012 I have a TTR600, and even that's only good for 90-100 at a real push. I'm going to get a smaller rear or bigger front sprocket, so that the engine will stop screaming at me on the motorway. I would suggest that that's your best bet, but be aware that you'll lose torque, so you'll have less acceleration. On a 125, this could be quite a serious problem... Other than that, just hang on to the back of a speeding lorry. You'll probably find that the aerodynamic problem is reduced dramatically Link to comment Share on other sites More sharing options...
AndyDtr08 Posted May 5, 2012 Share Posted May 5, 2012 It seems amazing the small difference in top end speed between a 125 and a 600, it must be a huge aerodynamic factor. I mean the TZR125RR Belgarda model ( italian import) manages to put out 33bhp using the same engine as the DT125. They appear to be able to get on the plus side of 100mph without mods. My RD350 YPVS claims 120mph and i can see it happening although have only taken it to 100 on clocks myself and dont't plan to take it that fast, yet a 600 in enduro style will be "only good for 90-100 at a real push". I suppose it's physics really, the faster you go the more air resistance and those style bikes are designed to cut through the air like the sportier models. They do after all have the "radiator scoops" catching all that air and chucking at the rad/rads. I still maintain that any year dtr or RE should be able to do 75-80 if looked after, with only a few small mods from standard. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted May 5, 2012 Moderator Share Posted May 5, 2012 Horses for courses, thats all. Hypothertical question.... I wonder if there are any people asking on Range Rover forums why their 4.0 Rangies are nowhere near as fast as a TVR Tuscan as they both have the same engine? Link to comment Share on other sites More sharing options...
Ryan09 Posted May 5, 2012 Share Posted May 5, 2012 Same engines but most likely different gear boxes, weight also plays a huge factor. A 600 single will have a lot of torque which is perfect for off roading which at the end of the days is what a dt and a ttr are made for, I know i wouldnt like to be pushing 80mph+ on the dirt! I get a bit miffed when people buy a dirt bike 125 and expect the speeds of an rs etc but id bet you that the acceleration on the dt is much much better than the rs, mine was for sure up to around 50mph. As for the TVR and Range Rover id say the main problem being weight!! Imagine a Range Rover doing 0-60 in under 4 seconds Link to comment Share on other sites More sharing options...
Moderator Cynic Posted May 5, 2012 Moderator Share Posted May 5, 2012 Same engines but most likely different gear boxes, weight also plays a huge factor. Exactly my point, the rangerover is for dirt and road, the tvr is pure sports road and track machine. Link to comment Share on other sites More sharing options...
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