DT 125 R '88... New project
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@CYBER-NINJA It's werid people say this, A boost bottle and the YIES chamber design from Yamaha never increased horsepower.
All Boost bottles or 'resonance chambers' do is help to smooth out 2stroke induction, which is of most benefit at lower air speeds... Low to Mid RPM running.
@jgr72 The WR200 inlet wont raise the height of the carburettor, but, it will make it clear the Clutch arm and give better clearance around the Shock Absorber.
Also for the love of GOD, do not chop this bike around anymore!!!
I would get rid of my DTR for your 'Endurance Blue' 3DB1 DT125R. They are one of the most desirable models.
See my build thread for carb placement, and note that there is no clean way to upsize carburettor bodies!
EXCEPT. using a (TM30ss) That will just about fit in with the original 125R inlet tract.
https://dt125r.co.uk/topic/77/yamaha-dt125r-01-running-project/73
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@Darty Very interesting, I get the tech behind adding the boost bottle and yes it may never increase HP, which was not it's designed purpose as you have correctly stated. All I can do is speak from experience and shared this. By removing it that must have changed the air-flow and the mixture, as the bike was definitely slower with it off. Yamaha obviously did a lot of testing and choose to run this system for optimum performance. All I can say is that the bike ran better with it on, so I kept it on. The only way to really know for-sure is to test with and without the bottle and pick the set-up which gives the best results for your riding style.
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Ive tried this however the wr200 inlet comes off at a slightly different angle i manage to get it to all go together nice and tight however the carb runs on a angle everytime to open the throttle wide it empties the carb you have to come back off the throttle so it fills back up again, i gave up on the idea of running that carb on a standard dt engine
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@andrewj1680 Modding is like a jigsaw puzzle, finding the right pieces which fit together takes time and experimentation sadly.
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@CYBER-NINJA i know what you mean which is why i have opted to swap everything including the engine and loom to allow me to get the best out of it
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DT have been sitting in my garage for some time... But today, I lift it up and changed the front fork seals that I ordered over 6 months ago... Left side had leaked inside the fork boot allready... I decide to fill it up with 15W fork oil... just to make it a bit stiffer... After that I measured the quantity of oil drained out... there was about 750ml (both sides together)... No wonder why it was a bit soft...
To make sure that there are something to wait for... I just ordered Athena 170cc kit for my DT :smiling_face_with_heart-eyes:
Still need to find new exhaust... Maybe some stainless... Lets see...
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Few days ago, I took the engine in parts... and this is what I found:
Thankfully new parts arrived already:
I tried athena barrel and piston, and it seems that tdc is just as with the earlier barrel & piston.
I will measure both heads and calculate compression ratios just for curiosity...
Still waiting for piston pin bearing to arrive... Old one was just fine, but why not change it to a new one, when it can be done easily...
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@Calum Athena 170cc set fits well into this 3BN engine, there was no problem to install it. Original piston remain about 1-2mm below deck and dome comes just about up to deck hight. Athena piston comes to deck hight and the dome is smaller and comes just over the deck. Athena claims that compression ratio is 13.2 and that is also what I endup by calculating it... combustion chamber is about 13ml and 168cc devided by that is around 13. That's not actually the real CR, since 2T engines start to compress only after the channels in the barrel when piston comes up, damn I didn't measure that part of piston travel...
Next step is to find better solution for TMX30... I ordered from ebay WR200 intake, let's see if it will line the carb better past the rear shock. If not, I may need to build up my own intake... At this point it seems that the DT230 Lanza boot was a waste of money, it does'nt seem to fit in any way... Anyone interested?
I also ordered 170cc version exhaust from Romeu Henriques, let's see how it fits and feels... Silencer will be a gianelli alu silencer...
Anyone have idea, where to start settings of that TMX30? 135 mainjet felt best last autumn... Maybe 140-150 mainjet and needle one step up?
And for all that are oppressing me to keep this as original as possible, that's not happening now... I will store all original parts for later time if I feel to return this original back again...
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@calum said in DT 125 R '88... New project:
Sounds like you caught the tuning bug, very serious this is.
I've had it since 1987
I am surprised you needed a bigger inlet for such a small carb. You can get reducers to fit.
TMX30 will fit quite well to original joint, but the angle is bad... WR200 should have more horisontal angle to avoid rear shock and that joint is originally made for TMX30 carb.
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