Moderator Airhead Posted December 30, 2009 Moderator Share Posted December 30, 2009 Recently took off the top end from my bike, had a look into the exhaust header and found a subtle restriction lurking in there. Cant understand why Yamaha would have done this unless it was for a foreign market for some reason. This flies in the face of any good tuning practice as it will give rotten gas flow characteristics. ....Now...wheres my hole saws? Any how heres some pics Link to comment Share on other sites More sharing options...
duaneage Posted December 30, 2009 Share Posted December 30, 2009 The idea that any restriction in the exhaust that a manufacturer went to the trouble to insert is a mistake would fly in the face of what they are trying to accomplish which is a good running bike that performs properly. I would call the feature an anti-revision port and guess that it's purpose is to allow expansion past a certain point to prevent reversing flow. Honestly I would leave it alone and worry about other things. It's a small bike to begin with and you're not going to see big performance gains from a small motor no matter what your do. More likely it'll be cantankerous as hell. A wise man once told me that deviating from stock was a sure way to end up with trouble. Unless you're versed in retuning carbs, jetting, and all that stuff I would leave it alone., My .02 Link to comment Share on other sites More sharing options...
Moderator Cynic Posted December 30, 2009 Moderator Share Posted December 30, 2009 Just been out and had a look at my pipe, 46mm outside diameter, 42mm inside which actually matches up to the exhaust port quite nicely. Thing is mine also has the pipe in a pipe thing going on. Its about 2inches long, must have something to do with the dynamics of the pipe. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted December 30, 2009 Moderator Share Posted December 30, 2009 A wise man once told me that deviating from stock was a sure way to end up with trouble. Unless you're versed in retuning carbs, jetting, and all that stuff I would leave it alone., My .02 Bet he never owned a aircooled DT though . They are like fruit pastles, you just got to chew em up. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted December 30, 2009 Author Moderator Share Posted December 30, 2009 The idea that any restriction in the exhaust that a manufacturer went to the trouble to insert is a mistake would fly in the face of what they are trying to accomplish which is a good running bike that performs properly. I would call the feature an anti-revision port and guess that it's purpose is to allow expansion past a certain point to prevent reversing flow. Honestly I would leave it alone and worry about other things. It's a small bike to begin with and you're not going to see big performance gains from a small motor no matter what your do. More likely it'll be cantankerous as hell. A wise man once told me that deviating from stock was a sure way to end up with trouble. Unless you're versed in retuning carbs, jetting, and all that stuff I would leave it alone., My .02 But the supposed dynamics of an expansion pipe is precisely to do just that, ie reverse the flow of gasses and push the unburned fresh charge back into the cylinder before the port is blocked off by the rising piston, so i dont see any benefit to leaving this in there and i think it has origins in de-tuning more likely. There should be as little as possible obstuction from the exhaust port to the header to cause turbulance. Just been out and had a look at my pipe, 46mm outside diameter, 42mm inside which actually matches up to the exhaust port quite nicely. Thing is mine also has the pipe in a pipe thing going on. Its about 2inches long, must have something to do with the dynamics of the pipe. Cant figure the differences in sizes here Jason, dont tell mee there is a different part number for a 125 and a 175 pipe !! and unbeknown to me i've got a 125 pipe here Bet he never owned a aircooled DT though . They are like fruit pastles, you just got to chew em up. Love that comment...too true Link to comment Share on other sites More sharing options...
Moderator Cynic Posted December 30, 2009 Moderator Share Posted December 30, 2009 Cant figure the differences in sizes here Jason, dont tell mee there is a different part number for a 125 and a 175 pipe !! and unbeknown to me i've got a 125 pipe here Oh no master, mine be Gianelli, the once pipe of choice for the disscerning 80's headcase. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted December 30, 2009 Author Moderator Share Posted December 30, 2009 Oh no master, mine be Gianelli, the once pipe of choice for the disscerning 80's headcase. I had a Gianelli once but i used my bike a lot back then and didnt regularly paint it, so like all the others it ended up rotten, you just dont see them any longer, even on ebay, last one i saw on ebay had been powder coated...as the Americans might say...go figure! You say your Gianelli has a pipe in a pipe, but my stock one has a big air gap between the two like this Link to comment Share on other sites More sharing options...
Moderator Cynic Posted December 31, 2009 Moderator Share Posted December 31, 2009 I had a Gianelli once but i used my bike a lot back then and didnt regularly paint it, so like all the others it ended up rotten, you just dont see them any longer, even on ebay, last one i saw on ebay had been powder coated...as the Americans might say...go figure! You say your Gianelli has a pipe in a pipe, but my stock one has a big air gap between the two like this Thats it, couldn't have drawn it better myself. I'll measure it properly tommorow, it was a quicky with a tape measure earlier. As to powder coating an exhaust, only in America. Although how many bikes have been lost to the monsters that never use them except to put on a trailer for a show. I'll admit i dont take the TDR out at this time of year but if the DT was running it would be up and about. I've been wet and cold often enough to know how stupid it is to walk past a perfectly good car when the floor is so slick you can hardly stand though. Seeing as i've started waffling i'll continue, i have orderd all the components i need to build a new loom FROM SCRATCH for £26. Can't go wrong really. When i stripped mine out it had 2 broken wires and some of the internal loom conections were loose. Pluss a lot of the wire especially over the engine has gone hard. Link to comment Share on other sites More sharing options...
little dave Posted January 2, 2010 Share Posted January 2, 2010 could it be, and this is just my opinion mind you, that the double pipe area is there to act as a heat sink/fin to keep the pipe from burning up at the point there where it exits the engine? there are really hot gasses (read flames) exiting continuously right there, a double wall would protect the pipe by allowing it to dissipate the heat it absorbs without doing much to cool the exhaust gasses themselves. just my 2 cents.... Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 2, 2010 Author Moderator Share Posted January 2, 2010 could it be, and this is just my opinion mind you, that the double pipe area is there to act as a heat sink/fin to keep the pipe from burning up at the point there where it exits the engine? there are really hot gasses (read flames) exiting continuously right there, a double wall would protect the pipe by allowing it to dissipate the heat it absorbs without doing much to cool the exhaust gasses themselves. just my 2 cents.... Happy new year Dave. That exact thought did occur to me, but if thats is so its not all that effective as its only about two inches long. and still requires painting often, the most serious damage done in the uk is the rain that is thrown against the header pipe...not something that you suffer from so much eh? Link to comment Share on other sites More sharing options...
little dave Posted January 3, 2010 Share Posted January 3, 2010 the most serious damage done in the uk is the rain that is thrown against the header pipe...not something that you suffer from so much eh? What is this "rain" you speak of? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 3, 2010 Author Moderator Share Posted January 3, 2010 Was looking on a DT125 website about de restricting And lo and behold...what do i find there...the same bloody restrictor and a piccy of it, seems like us 175 riders are a tad behind the times here http://www.dtr125.net/tuningf.htm Link to comment Share on other sites More sharing options...
Moderator mervin Posted January 3, 2010 Moderator Share Posted January 3, 2010 Was looking on a DT125 website about de restricting And lo and behold...what do i find there...the same bloody restrictor and a piccy of it, seems like us 175 riders are a tad behind the times here http://www.dtr125.net/tuningf.htm boils down to not being a spotty 17 year old trying to extract every las .00000001 of a bhp out of the bike to make it go .0009 of a mph faster and last less than 50% of its normal life Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 3, 2010 Author Moderator Share Posted January 3, 2010 boils down to not being a spotty 17 year old trying to extract every las .00000001 of a bhp out of the bike to make it go .0009 of a mph faster and last less than 50% of its normal life Its coming out merv heaven forbid...are you really suggesting i should go through my whole motorcycling life wondering....WHAT IF! Link to comment Share on other sites More sharing options...
Moderator mervin Posted January 3, 2010 Moderator Share Posted January 3, 2010 Its coming out merv heaven forbid...are you really suggesting i should go through my whole motorcycling life wondering....WHAT IF! oh yes get it put Paul, no points in wondering what if mate, iwas just saying why we wrinklies are behind the 125 owners merv Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 12, 2010 Author Moderator Share Posted January 12, 2010 A few more pics Link to comment Share on other sites More sharing options...
Moderator mervin Posted January 14, 2010 Moderator Share Posted January 14, 2010 Paul Mick Abbey has replied to your post about this on the RD forum, in his opinion you will not make a huge difference removing it Hi Paul The only way to take it out would be to grind it out around the weld as for performance I am not sure if you will notice any diferance it may give you a bit more top end power at the same time taking a small amount of lower end torqe, this is the same thing as why on most road engines the ex port outlet diam is smaller than the diam of the start of the header pipe it all helps with low to mid range torqe I hope that this has answerd your question Cheers Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 14, 2010 Author Moderator Share Posted January 14, 2010 Paul Mick Abbey has replied to your post about this on the RD forum, in his opinion you will not make a huge difference removing it yes i saw his reply Merv, still going to remove it though, it's part of other changes i'm doing not just something in isolation and i just have a hunch that removing it will help. Other mods are carburation, airbox and reeds. These bikes are in a pretty low state of tune as standard especially the early ones like mine I've had the bike for 27 years now so its long overdue some tinkering ( i know you'll understand ) Link to comment Share on other sites More sharing options...
Moderator mervin Posted January 14, 2010 Moderator Share Posted January 14, 2010 Oh yes i understand Paul recycled teenager !!! merv Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 5, 2010 Author Moderator Share Posted February 5, 2010 Well it's out now Restrictor diameter = 29mm, Header diameter = 35mm This is now a 45% bigger area than when the restrictor was fitted. Link to comment Share on other sites More sharing options...
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