My bikes too slow!!!

[quik_d]

hey i was just reading the 125 engine thread, and it got me thinking. I have a dt125r, F reg with a rebored engine about 6 months ago, so i have a feeling it might have been thrashed before i got it, but the rebore should sorted that.

The engine was run in very carefully by me, and i've put about 2-3000 mileson since so its bedded in fine. The problem is it barely hits 60, flat out top gear which is disappointing i think! Its got a big one silencer on it, and i beleive a matching downpipe.

It gets to 55 ok, but over that sometimes it starts to feel tight and back off too much, could this be its too lean in top revs? In top gear it doesn't rev over 7.5 k, and in general riding i don't take it above 8k (redline at 10k) so im not thrashing it am i?

any suggestions/hints to why it could be doing this? i know i can open it right up by pegging the power valve open but i don't wanna cos i need the bike normal for my test, i just want a bit more speed for the dual carridgeways. I don't wanna minor for being too slow!!!

quik
____________________
LOOK AT DAT M8 WELL LUSH A PARROT INT IT

[JonB]

Is it restricted?
____________________
Be careful whose advice you buy, but, be patient with those who supply it. Advice is a form of nostalgia, dispensing it is a way of fishing the past from the disposal, wiping it off, painting over the ugly parts and recycling it for more than it?s worth.

[quik_d]

well the restrictors for the dt of that yr lie in 2 places as far as i know, firstly the exhaust, which should been fixed by the aftermarket one, and secondly in the power valve, thing is if i peg it open permanently then it will be real sluggish till about 6k then rev its nuts off till redline. I can't be having that for the test, i'll get failed for aggresive riding!! lol i just wondered if theres something i haven't done or something that could cause the lack of top end on my dt125?
____________________
LOOK AT DAT M8 WELL LUSH A PARROT INT IT

[nwbiker]

thats it mate fast as it will go if you dont want to turn the powervalve also if im right remove the pin as well to de-restrict her to full power u already have the exhaust!

it is a DEP exhaust also the front pipe?

my TZR did 70 restricted since i had her rebuilt and fully derestricted does a 10 no problem thats not even red line my mate mate had a K reg DT125R and his did 95 derestricted and a full DEP exhaust.

there is no point changing the sprocket for more speed because it tops out at 7.5Krpm

Take my advice

De-restrict her ull love the powwwwwweeererrrrrrband and ull be wheeling all day and night
____________________
my site
www.nwbikers.co.uk

[quik_d]

yeah i know what ur saying nwbiker, and i was gonna do it ages ago but got the rebore done so had run it in then didn't get round to it etc, and soon as i pass my test im gonna be riding a bros 400 thats waiting in my garage, so no point as it only makes harder to sell.

I haven't got DEP, have a BIG ONE, which also goes by another name, can't remember it now. I really wanted a DEP but never could justify the £150 odd for a kit! think sprokets are standard, i though it sould hit 60mph ok then tail off after that, i miss my old aprilia trailie that was a rocket compared (till someone stole the arrow pipe off it!!)
____________________
LOOK AT DAT M8 WELL LUSH A PARROT INT IT

[stevo as b4]

I didnt think the old pre 96 DT's had much in the way of exhaust restrictions. If its definately got a Big One expansion chamber and silencer, then there should be no problems with the exhaust side of things. Big One pipes are better than std de-restricted for top end, but they are quite peaky without much bottom end, unlike say a DEP. Your problem is likey to be entirely down to having the power valve pegged in the down position, which will not let the motor rev high enough for the pipe to have any effect anyway. try removing and cleaning the valve and turning around into the full open position, and you will probably find your bike goes alot quicker. This will be at the expense of having hardly anything below 6k rpm, so its not the ideal way to ride the bike. The P.V. motor and cables/pulley housing from a later DT should fit ok onto yours, and you'd need to plug the wiring into your CDI. This will give you the best of both worlds and you keep your decent bottom end, but have a top end of about 20bhp at the back wheel. On std gearing the DT can then reach 85mph no problem!

[nwbiker]

Yep get the P.V motor i think i have 1 somewhere with cables and side assebmbly but not the orange bung for the actual powervalve?

thought it would fit my TZR but it didnt so i got another 1!

the motors on their own go for over £50 quid on ebay!
____________________
my site
www.nwbikers.co.uk