Anditover

I'm using an android phone. None of the windows menu items are available.

At the bottom of the page there is no icon indicating "attachment". After a row of various social media choices, all I can see is an email envelope, a printer option, and a download icon. When I tried to post a photo in the gallery, it said the photo exceeded the maximum size, with no option to resize. So I'm stuck with text. I even added the graph to my clipboard, but the forum doesn't allow clipboard items to be inserted. Anyway, if a moderator wants to email me at the above address, I'm happy to put the data out there for reference.

Thanks, I just thought it was about time someone got some base figures, as well as checking on carburation to see if part of the restriction was over jetting or whatever. The Lambda sensor basically told us that whilst yes, it is a tad rich at the top end, it's the sort of rich that keeps you out of trouble if you rag it on a chilly morning. I would love to post the graphs, but my membership level doesn't let me post attachments. Whilst at the tuners, we compared runs with other DTs. There was one which produced 19bhp, a 1990 bike if I remember. It had a race exhaust, no air filter (brave), and 3, repeat 3 bhp up to about 6,500 rpm, then the graph went up at about 60°. Utterly horrible to ride, and likely to spit you off if you hit the power band mid corner, no other details, but presumably the bike has expired by now. Nice work on the rubber manifold Airhead, it fooled me for a second into thinking it was a factory version, perfect symmetry. The next step is to borrow a bendy camera from a friendly mechanic I know, and have a look down the exhaust header. I feel sure that at least one restriction at the mouth of the expansion chamber has fallen off, but if I can get a good look to confirm, then I think we'll have cracked how to derestrict a standard bike without blowing a stack on pipes, jetting and hi-flow air filters. And more importantly, keeping the reliability.

I used a tuning shop called Dyno Tech, they're experienced (that's code for middle aged) and support alot of teams in BSB and enduros. Fuelling wise the DT, on factory settings, is lean at tickover (where no harm could be done), spot on in the midrange, and reassuringly rich at full throttle. That was part of the reason I took it in, having found that on some days it got its second wind at 8,000+ rpm, I wanted to be sure it wasn't running lean (which would crispen up the throttle response before crispening the piston). I was quite prepared to rejet, but the advice was stay stock. Also, the well intended advice to cut off the rubber protrusion from the carb gasket to the reed block, would appear to be misguided. I took mine off, measured the diameter, and concluded that it was the same as the exit from the carb, and the point of the protrusion was not to restrict the fuel mix, but to guide it at a constant velocity directly at the reeds. Widening the route at that point would result in reducing pressure and velocity of the fuel/air mix. Probably not helping performance.

Just like to add, since my last post, I've had the DT dynoed. I was curious to see what was really going on in mine, and to make sure that when it was revving hard, it also wasn't running lean. Unfortunately I can't seem to add an attachment to show the graph, but I am happy to email it if people are interested. It was done on Tuesday 5th of May, barometric pressure was about 989mb, in other words pretty awful. The tuners said it was so bad it was probably robbing me of a whole horsepower. All figures are RWBHP. 5,000rpm: 7.25bhp 7.5 ft/lb torque 6.000rpm: 9.50 8.5 7,000rpm: 14.50 10.7 8,000rpm: 14.50 9.5 between 7 and 8,000, the power dipped to 13.5bhp as the torque dropped from its peak. 9.000rpm: 16bhp 9.5ft/lb 10,000rpm: 13bhp 7.0ft/lb peak output was 16.98 at 9,500rpm, and 17.58 on two different runs, peak torque was 10.73 at 7,000 rpm. Stock pipe, airbox etc. Only the reed switch moved out of the way. A rattle in the front expansion chamber, would indicate that one of the restriction crescents has dropped off. Result also indicated that the airbox, carb manifold and silencer is NOT restricted by the factory. I don't know why no one else has done it before, I can be emailed on [email protected] if anyone would like to see the full report. Estimated top speed ( with wheel slip from the knoblies in the dyno was 75mph).

Name: Kawasaki KH250 (1977) Date Added: 07 May 2015 - 10:08 PM Owner: Anditover Short Description: KH250 B2 Chassis S1c pipes and gearbox S2 Top end, clutch, oil pump. View Vehicle

To help clarify what a DT125R can actually do, I have had my bog standard 2002 model dynoed. It's done about 5,000 miles, I've owned it since it was 13 months old with 1,100 recorded miles. The only things different to new are the infamous "reed switch" has been moved out of the way, and there is a rattle in the front expansion chamber which could mean that one of the restriction tabs has fallen off. Sorry, but as a biker of more than 30 years, there are a lot of myths out there. I've owned RD350YPVS, and TDR250, and have owned a KH250 (with S2 350 top end swap) since 1990 so consider myself a BS free zone. My conclusion, from talking to the very nice chaps at Dyno Tech, who run the dyno shop, is that stock is best. We looked at some very interesting curves, including a dep pipe and no filter effort that produced 19bhp at 10,000 rpm, but only 3, yes 3! at 7,000. Very fast in certain circumstances, unridable the rest of the time. And likely to go pop at any moment. I wish there was a way to show the graph as an attachment. Suffice to say peak torque was 10.73 ft/lbs dropping to a steady 9.5 ft/ lbs until 9,500 rpm. Peak rwbhp was a healthy 16.98 at 9,400 rpm. Mixture was a tad lean at tickover (where no harm could be done), spot on in the mid range, and healthily rich right at the top. Torque up to 6K was a remarkably steady 8ft/lbs, before rising to the peak at 7k. Power dropped by about 1hp between 7,250 and 7,750, before rising steadily to a peak at 9,400. If someone would like me to email them a copy of the curve, I'd be happy to, but for some reason I'm not even been given the option to post it directly. I've seen 80 mph on the clock, with a gps verified top speed of 82. However, the dyno indicated that both of those may be subject to error, and a more realistic top speed (according to an acceleration through the gears, is about 75mph. I did take the carb off and check out the "restrictions" at the reed block. Then I measured the diameter of the rubber manifold against the diameter of the exit from the carb. And found that they are the same. My conclusion is that the rubber protrusion is actually aiming the fuel mix at a constant velocity directly at the reeds, adding a slight curve to the route, and that removing them will only increase the internal diameter, reduce the pressure and flow speed, and result in poor running. Either way 17 rwbhp with no mods proves that Yamaha DIDN'T go all out with restricting the induction side of things, and that the exhaust front pipe is probably where most of the inbuilt restrictions are located. Almost forgot. The best run of the day produced 17.58 bhp, chasing gears (in fifth), and the barometric pressure was about 985mb, in other words pretty awful, and the suggestion was that in normal pressure (1020-30) with cool air, there was the potential for another bhp on top of that. But that's pub talk really, the important thing is that torque was consistent from 4,500rpm to 9,500rpm making for a really strong midrange, and making the peak power easy to get at, as opposed to trying to spit you off if you're in the band and trying to take a corner at the same time, which is not unheard of...

For those of you after a bit more speed, I just did a winter spruce up on the DT: New head bearing, fresh fork oil, fresh brake pads and fluid, and then a new genuine air filter (they're washable but mine looked a bit tired), and a new chain and sprocket kit. Since fitting the last 2, there is a noticeable difference. The engine note is more crackley, tickover is steadier, and it feels more willing. The other morning I cracked open the throttle in 1st to get past a car turning right, and it lifted the front wheel in both 1st and 2nd gear. Not by much, just enough for me to feel the wheel touch down twice, but I reckon renewing the transmission got me at least 2 bhp, and swapping the filter got me useful torque everywhere. My old chain and sprockets actually looked fine, but when you got the old chain off and compared tight links, and how well it flowed, you could see it was power sapping. I used a genuine kit, but it was made by DID (with O rings and split link). Hope that helps.

OK, keeping the Yamaha small bike theme going, and respect to the guy who posted the (removed) comment about loving a Z1R, back in about 1992, I was offered a Z900 as a direct swap for my mint 18 month old RD350YPVS. I turned it down. I don't regret it, the way I still see it is that yamaha developed the RD series, and the YPVS to run rings around those old dinosaurs - and they did. As a fast and forgiving ride the RD350LC and it's descendants were far superior, if I wanted vast and heavy, I had my KH. I've now owned 3 YPVS powered bikes of different capacity. The TDR was a thrill, but I sold it after 18 months from new. Too buzzy and a one trick pony. The RD I kept for 5 years from new, but at 35,000 miles after rebuilding it, I realised it was gonna cost me a fortune. I've had the DT for 9 and a half years. More grins per cc than any other bike I've owned. And only £ 16 a year road tax. You never forget your first DT.

I'm down in Newbury. Was on the KTC a couple of years ago, helped me out when bloody ethanol melted the protective resin I'd put in the fuel tank just 3 years earlier. It needed a complete engine strip, and I ended up meeting Alan Smith (one of Ricks network of people who know what they're doing), who sorted it out and then was able to hook me up with a S2 engine Rick had brought back from the USA and we canibalised the barrels, carbs, clutch, and oil pump. If you do a Google for "kh250 s2 conversion" sometimes my post on a US site comes up as top suggestion, I think I may be the only one to have posted the dyno curves of a before and after 250/350 conversion using the same dynometer. In case you're wondering, with S1c pipes and standard air box, and Boyer Bransden ign it gave 27.7 bhp, and now it puts out 35.25 at the rear. I've owned it since 1990 and it's been a flaming albatross around my neck ever since. Never a dull moment. H2 and a Z900? Kawasaki got the styling exactly right with those bikes, if not the handling...

Thanks for the welcome, specially from a fellow triple owner on a Yamaha site! Ennit amazing, this thread's been dead for 4 years and then all of a sudden it gets 6 new msgs. Just shows how good the OLD DTs were. Arguably the best learner 125 ever. I mean, Aprillia RS125s are great and fast, but you ever tried getting the rear sliding on one... In the mud? And DTs are built for crashing too. I wonder how that bloke who had the interview at Silverstone got on?

What a great thread. Having owned a TDR and RD350YPVS (F2), can confirm that their standard top speeds were about 107-112; and 125mph respectively. My present 2002 model DT125R runs on castrol fully synthetic, and is completely standard, except for the relocation (just taped up and moved out of the way) of the block connector in the back of the speedo. On a good day (and because it has a carburettor ambient air humidity and temperature play a huge part) it's revved to 10,000 rpm in top, with the needle hitting the stop beyond 80 MPH. I thought that although it felt quick, we were probably looking at a real speed of 72? Then I got GPS. I couldn't believe it, my ACTUAL top speed is 82. Just 1mph slower than my old KH250 before I put a S2 top on it. What's more, the speedo is never more than 2mph out. It's more accurate than my Jaguar (X-Type). Totally bog standard, and owned by me since 2004. I do believe that they can nudge 85, if they can hit 10,500 rpm in top, but I find talk of 90 mph hard to swallow, unless you go down the road to big bore kit, bigger carburettor, race exhaust. At least the air boxes don't need changing, I understand that they used the same ones in the DT200. I love mine, at least I can max it out, chin on the tank, try that on my GSX-R750 and I'd end up in the back of a Volvo driven by Mrs Myopic. I hope that that has helped clear things up. Although I understand that the 2002 model was both one of the slowest and hardest to fully derestrict. There...All cloudy again.