Yam DT125x power hike???
Discussion
Hi there, another newcomer here.. I am an experienced rider with full licence, a few years and a few spills under my belt, I have a couple of bikes, but latest one is a dt125x, bought to learn to mess around for more control, wheelies, stoppies, that kind of thing! It's really good too, excellent for stoppies due to a mental front brake!! Wheelies tho' more difficult, it is a tad underpowered, almost held-back, feeling.. I had a NSR125 a few yrs back as a novice, and if I remember that would hit 90.. This bike just gets 70 and it's a bit lacking in acceleration - I only weigh 65 kilos so it's poss the bike is restricted in some way, for legal reasons. It's a proper UK bike and only has 800 miles on it.. Any advice on improving the grunt (no smart comments pls.. you know why I bought it!!!) Bless y'all!
If it's just a stunt toy do you really need a 70mph top end? Or a 90mph top end??
The modern DT has a restrictor in the front pipe of the exhaust - easily removed with a dremel on the welds or with a hammer and chisel if you're a bit pikey.
You will also need the powervalve motor from a Yamaha dealer, he'll want to see your full licence before he orders it.
With these 2 mods it should hit 95mph on standard gearing.
Quickest and cheapest method of making wheelies easier though is to buy a new front sprocket 2 teeth bigger for about £12. It will knock about 10mph off your current top end but it should wheelie off the throttle in 1st and 2nd.
The modern DT has a restrictor in the front pipe of the exhaust - easily removed with a dremel on the welds or with a hammer and chisel if you're a bit pikey.
You will also need the powervalve motor from a Yamaha dealer, he'll want to see your full licence before he orders it.
With these 2 mods it should hit 95mph on standard gearing.
Quickest and cheapest method of making wheelies easier though is to buy a new front sprocket 2 teeth bigger for about £12. It will knock about 10mph off your current top end but it should wheelie off the throttle in 1st and 2nd.
stu 9-5 said:
Quickest and cheapest method of making wheelies easier though is to buy a new front sprocket 2 teeth bigger for about £12. It will knock about 10mph off your current top end but it should wheelie off the throttle in 1st and 2nd.
Shouldn't that be 2 or more teeth bigger on the 'rear' or a 'smaller' sprocket on the front??
To get the best advantage of the derestricted exhaust, the powervalve motor is required. I can't remember how much they are but probably about £100 for the whole kit including push/pull cables and the wiring harness.
http://erekiteru.ld.infoseek.co.jp/bike/mente/DT125_piston/YPVS2.jpg
Without the powervalve motor the powervalve chamber is blanked off, giving the engine plenty of low down 'power'.
When you buy a powervalve motor, the chamber is blanked at lower revs - but when the revs rise to 7000ish the motor turns the blanking grub, opening the chamber and changing the characteristics of the exhaust port, giving the bike better top end 'power'.
You can manually rotate the blanking grub for more top end and sacrifice the bottom end - but that's less stunt bike compliant.
It's on the left side of the engine and looks like this,
http://www10.plala.or.jp/satoyan/satoyansp016009%5B1%5D.jpg
I used to race a TZR 125 up in Wigan years ago in the ministock 125 class. Same engine virtually, I used to use a DT125 bottom end as it had a 7 plate clutch, better than the TZR 6 plate but undetectable to the scrutineers, better gear ratios too for the tight and twisty 3 sisters circuit.
http://erekiteru.ld.infoseek.co.jp/bike/mente/DT125_piston/YPVS2.jpg
Without the powervalve motor the powervalve chamber is blanked off, giving the engine plenty of low down 'power'.
When you buy a powervalve motor, the chamber is blanked at lower revs - but when the revs rise to 7000ish the motor turns the blanking grub, opening the chamber and changing the characteristics of the exhaust port, giving the bike better top end 'power'.
You can manually rotate the blanking grub for more top end and sacrifice the bottom end - but that's less stunt bike compliant.
It's on the left side of the engine and looks like this,
http://www10.plala.or.jp/satoyan/satoyansp016009%5B1%5D.jpg
I used to race a TZR 125 up in Wigan years ago in the ministock 125 class. Same engine virtually, I used to use a DT125 bottom end as it had a 7 plate clutch, better than the TZR 6 plate but undetectable to the scrutineers, better gear ratios too for the tight and twisty 3 sisters circuit.
Thanks for all the info, I'm very grateful, being new to 2-strokes..
My other main interest is custom bikes, at the moment I'm just completing a project- it's a 1958 Triumph pre-unit rigid period chopper, or bobber to be more precise. It's a "hot rod" type bike, as done by the yanks in the 50's and early 60's before they started extending the forks and raking out the frame headstocks. I will be assembling it over the next 3-4 weeks having taken the frame and tank etc to the painter today. All the chrome and the motor and tranny are due back with me over the next week or so, it's a busy time for me! I have high hopes for this bike and plan to show it next year as well as riding it as much as possible.
I will post some pics soon as it's done..
My other main interest is custom bikes, at the moment I'm just completing a project- it's a 1958 Triumph pre-unit rigid period chopper, or bobber to be more precise. It's a "hot rod" type bike, as done by the yanks in the 50's and early 60's before they started extending the forks and raking out the frame headstocks. I will be assembling it over the next 3-4 weeks having taken the frame and tank etc to the painter today. All the chrome and the motor and tranny are due back with me over the next week or so, it's a busy time for me! I have high hopes for this bike and plan to show it next year as well as riding it as much as possible.
I will post some pics soon as it's done..
Just had a thought, the powervalve pic looks very familiar (thanks for that).. That whole unit is there on the side of my dt engine, does that mean my engine has the powervalve? Or is it just the casing there ready for it.. The two cables are there coming from the circular housing as per the pic too. Any way to tell without removing anything? Maybe I just need the exhaust mod in reality..
You can tell if the motor is fitted by switching on the ignition. You will hear a soft whirr as the motor sends the valve through it's cycle to clean off any carbon.
Your engine may have the valve fitted, but if it's UK restricted spec it will defitely have the restrictor in the top of the exhaust. Simply remove the whole of the front pipe and you'll be able to see a big daft 'reducer' to the bore of the front pipe, maybe 2" in.
Be very aware that any adjustments to the exhaust tuning will need to be matched on the inlet side of the engine, usually by changing carburettor jets. 2 strokes are quite fickle to running lean and can nip up or heat seize if not being fuelled/exhausted correctly.
Your engine may have the valve fitted, but if it's UK restricted spec it will defitely have the restrictor in the top of the exhaust. Simply remove the whole of the front pipe and you'll be able to see a big daft 'reducer' to the bore of the front pipe, maybe 2" in.
Be very aware that any adjustments to the exhaust tuning will need to be matched on the inlet side of the engine, usually by changing carburettor jets. 2 strokes are quite fickle to running lean and can nip up or heat seize if not being fuelled/exhausted correctly.
Ummmmmmmmmm.. I just checked out my exhaust front section.. no nasty thingys in there as far as I can see! Re: the powervalve too, yes there is a faint whirring when one turns on the ignition.. Doh! Is mine a de-restricted model? Am I just simply too used to the grunt of an R6?? I don't think it's that tho' in reality, there is just no "get up and go" after about 65 mph in top (keeping in the powerband).. certainly no chance of 85 mph - of that I'm dead certain! Any more ideas? Still great for stoppies tho'
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