Mastiff Posted June 21, 2012 Share Posted June 21, 2012 My son's really enjoying his bike, since he got the drivers licence last week (after so much training with me that he spent 1/3 of the average you'll have to pay for that lisence in Norway - yes, I'm proud of both him and myself!), except for one thing: We have a 40 km long stretch of highway between our house and our cabin, where he spends much of this summer. The speed limit there is 100, and he can't stick to that in the hills. Another strech of that road is 90, and even that is a problem if the wind's against him. So is there a simple/easy (read: cheap...) way of giving him just a few more horsepowers to manage those hills and the wind? It's an 81 DX that was bought in Sweden. I think everything's stock, and it has around 16 horsepowers now (11-12 kw). Does that mean that it's restricted, so I can just remove something to make it go that little bit faster? I must say, just so it's said, that I trust my son, and he's not going to use the extra muscle to play crazy. We have a 40 kmh zone near the house, and he's been raced past by tuned 50 ccm's on several occasions. Not once have I seen him even try to go above 40 to keep up or show them who's boss. I did not have his self control when I was 16, I can tell you! Then again I've spent two years hammering safety, safety, safety into his head, with protective gear, back protector, knowing the road and all that. But that was a digression (or maybe a disclaimer?). I think the one year later RD 125 LCII and the YPVS models has around 23 or hp when they're not restricted, can the difference be that large in a comparable engine? I guess the water cooling has to mean something, but still... Link to comment Share on other sites More sharing options...
NEV Posted June 21, 2012 Share Posted June 21, 2012 A DEP full exhaust system wouldn't go amiss, and maybe a bigger carb,, and the usual reed block de-restriction, sorting those out would give him a bit more umph, I reckon Mastiff, plus a properly set up powervalve too. Link to comment Share on other sites More sharing options...
Mastiff Posted June 21, 2012 Author Share Posted June 21, 2012 Thanks! But I don't think the DX has the YPVS system. Do they make DEP for the 125 DX? I don't think I've seen that. Also there are two cabs, maybe it's possible to just use bigger jets? As for Reed Block, does that mean buying something like this? Link to comment Share on other sites More sharing options...
NEV Posted June 21, 2012 Share Posted June 21, 2012 It does mastiff, look on the barrel on the left hand side circular cover with 2 cables going into it, that the powervalve cover, yes you can get the DEP exhaust for the DTX its the same as the DTRE one but not the same as the DTR older version, although over in Norway they seem to favour the Gianelli exhaust system for some reason, and the reed switch is a white plastic plug on the rear of the clocks, you unplug it then isolate it. as for carbs yes you can upjet it, but to get more HP that your after, but I suggest going from a standard 28mm Mikuni, to a 32mm Mikuni, same as I've got on mine, that gives a fair bit more power. AAAAAAHHHHHHH just noticed its not the DX as in DTX is it, its the MX if its an 81 bike, my mistake I should have read it properly. I shall chant the idiots mantra 10 times to make amends. " owaar tannaar syam " Link to comment Share on other sites More sharing options...
Mastiff Posted June 21, 2012 Author Share Posted June 21, 2012 I think you misread the first post a bit hear, mate. DX, not DTX. That's what confused me, you are describing stuff for a DTX! I have two 350 YPVS, and I know what an YPVS should look like, and I knew I hadn't seen one like that here. Oh, and they only make those for water cooled bikes, I think. The DX is air cooled. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted June 21, 2012 Moderator Share Posted June 21, 2012 Back in the stone age i lusted after one of those little 125's. The favorite tuning method was a 200 motor but thats a little naughty. The difference between the old stuff and anything 83 on is astonishing. Yamaha REALLY sussed out the 2 stroke with the water cooling and the powervalve etc the engine make massive power for their capacity. Tuning, strictly old school if you skip the 200 barrels (which swap i think cough cough). Pair of microns or allspeeds would be sweet if you can find them and sound superb, make a noticable difference too. Matched with a set of hi tec or boysen reeds (not the 2 stage gimmiky ones) and a good filter you could gain maybe 5 solid hp. Nev, he's talking about an RD125 DX a twin cyl road bike , not a DT. Link to comment Share on other sites More sharing options...
Mastiff Posted June 21, 2012 Author Share Posted June 21, 2012 Cynic, weird how somebody with that screen name can be so sentimental! Thanks! 5 hp should be enough to do what I want. So I guess it's on to eBay to chase. Do you by any chance know if I can use the same pipes as some other models? Except for the DX 200, of course. They usually have the same parts. Btw the 200 barrels could be a nice thing. If I just swapped those, do you think I'd get about the same increase? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted June 21, 2012 Moderator Share Posted June 21, 2012 Cynic, weird how somebody with that screen name can be so sentimental! Thanks! 5 hp should be enough to do what I want. So I guess it's on to eBay to chase. Do you by any chance know if I can use the same pipes as some other models? Except for the DX 200, of course. They usually have the same parts. Btw the 200 barrels could be a nice thing. If I just swapped those, do you think I'd get about the same increase? The place to go for the real experts would be the Aircooled RD club, what they don't know you won't need to. They may have help with the parts too. As to the 200 barrels, i may be wrong but my understanding is the 125 is a 200 with smaller pots so in theory the 200 head and barrels (with proper jetting) will give you the 20 odd hp a 200 did. Bit like a Dt125 mx and a Dt175mx, bar the head barrel and piston its the same bike almost exactly. Link to comment Share on other sites More sharing options...
Paulwhite Posted June 21, 2012 Share Posted June 21, 2012 just an idea as i dont know about the bike itself, but could you fit either a bigger or smaller sprocket to gain more speed / torque? if he cant get up a hill then the cheapest solution would be to play with the final gear ratio...(i say smaller rear sprocket as he will have to drop down a gear to gain more torque but it could climb the hill faster...) just out of curiosity what is the top speed of the bike on a flat road? could you drop the top speed (put a bigger rear or smaller front sprocket) to gain more torque which would translate into speed on a hill? im just thinking its a 125cc with "16 horsepowers" ...??? surely he should be able to hit 60mph up a hill? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted June 21, 2012 Moderator Share Posted June 21, 2012 Its a peaky 16hp, on a flat it will romp 60mph, but a headwind or a grade will hurt it. A sprocket change won't help all that much as you will either lift the gearing out of the reach of the motor or on the days the wind drops she will be spanking the limiter. Same as the DT175 really, that officially has around 15hp but anything over 60 is possible but dangerous for more than breif periods. 50 is about it on any real grade. A liquid cooled DT125 of any age would destroy it performance wise. Link to comment Share on other sites More sharing options...
Paulwhite Posted June 21, 2012 Share Posted June 21, 2012 i was just comparing to my bike which has 14 / 15 bhp (4 stroke liquid cooled .....which could be the main difference and the reason why) but it can climb a hill at 60mph and hit 70/ 75 on a straight.........all this is due to me playing with the sprocket ratio, plus im thinking if mine is 14bhp and can do 60mph as standard then why cant his 16bhp motor do the same if not more? Link to comment Share on other sites More sharing options...
Mastiff Posted June 22, 2012 Author Share Posted June 22, 2012 Thanks for the tips! I will pop in to the Aircooled RD forum and see what they have to say, since they are the experts. I must (embarassingly) admit that I didn't even think about the sprockets. That may work, I need to check what's on the bike. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted June 22, 2012 Moderator Share Posted June 22, 2012 Thanks for the tips! I will pop in to the Aircooled RD forum and see what they have to say, since they are the experts. I must (embarassingly) admit that I didn't even think about the sprockets. That may work, I need to check what's on the bike. Just a thought but when was the last time it had a full decoke, as far as cheap tuning goes thats about as good as it gets. If the pipes are choked and the cylinders are mucky that will kill the performance. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 22, 2012 Moderator Share Posted June 22, 2012 another easy check is to remove the reed cages and inspect the petals, they should be perfactly flat and you shouldnt be able to suck air through them Link to comment Share on other sites More sharing options...
blackhat250 Posted June 23, 2012 Share Posted June 23, 2012 Hers what your lookn for,,,, Link to comment Share on other sites More sharing options...
Mastiff Posted July 25, 2012 Author Share Posted July 25, 2012 Well, I have been waiting since this thread was started for answers on the air cooled RD forum, but I guess they don't like big dogs there.. Anyway he needs new sprockets and a chain, so we'r going to put a 38 (standard 39) rear and 16 front (standard 15) on it to see if that helps. I'm opening another thread because I'm wondering if I can use one rear sprocket I found on eBay. Link to comment Share on other sites More sharing options...
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