carb jetting

[too slow]

i have an 02 DT125r (JYADE031) which is absolutely bog standard except i have changed just the end can to an athena end can(rest of the exhaust is standard),it was mentioned to me that i would need to increase the main jet in the carb to compensate for the freer flow that the new end can has given the engine so after reading some of the stuff on this forum and doing some checking on the yamaha spares website, would i be right in thinking that i need to increase the main jet size in my carb from 240 to 260 and do i need to change the pilot jet to something other than 25, the carb that is fitted a flat sided carb. i'm not interested in my dt doing 100mph nor do i want it to sit with an R1 away from a set of lights up to 50mph, i just don't want to burn a hole in the top of the piston OK ???

[Airhead]

I wouldnt go bigger than 250 myself...

[blackhat250]

Aye slowly" how does it run,, main jet affects Wide,Open,Throttle only , how does it pull, and plug colour tell a story,,,

[too slow]

blackhat 250, bike runs perfect, starts really well and easily when cold or hot, when cold and on choke its smokey and when ridden and warmed up runs clear and no smoke, no strange noises, pulls well and i have removed reed switch from under the rev counter/speedo wrapped it in gaffer tape and left in bottom of clock housing just put new plug in(BR9EG) and the previous one(BR8ES) was a little bit black but was nearly 3 years old but still useable.

Airhead, i got the idea of the 260 main jet from some of your posts in another section on here but if your saying dont go more than 250 main jet is there any reason why i can't just make the bike run richer by lifting the needle up 1 or 2 notches ?

[Airhead]

yeah by all means try the needle but that wont have any effect at wide open throttle, chances are it'll be fine with the 240 but just for peace of mind you could stick in a 250, when all said and done without specialist measuring equipment it's all trial and error

Theres no way you'll need to move the needle 2 notches I think it would run rough if you do...maybe 1 maybe none you'll just have to try it

Cant see youll need 260 MJ either just too big a jump...but again, theyre cheap enough so if you want to try 260 and 250 and compare?

[blackhat250]

Why did you go up from a B8 to aB9 that's a colder running plug,? you say its a bit sooty, ,,,

[too slow]

ok airhead i'l get a 250 main jet and leave the needle where it is, took the exhaust off this afternoon and checked the power valve, when the ignition is on, the bore is totally smooth and no lumps or bumps when the little clip thing is in line with the whole underneath the cover if that makes sense. Out of interest any particular places thats good for these jets or are they freely available on ebay and do i just look for jets for a flat sided carb ?

Blackhat 250 the reason for the sparkplug change was simply the one in there is a good couple of years old so changed it as part of the service i done on the bike and also my yamaha owners manual says the spark plug should be BR9ES (NGK), but i only had a BR9EG so changed it for that till i can get a BR9ES

[blackhat250]

I usually take out the jets to see what type they are, then go on ebay ,search mikuni jets, [ size] and compare the types,

Good the plug is standard,,,

[too slow]

since last visit here have turned the carb 90 degrees and removed the bottom of the carb, the jet in the very bottom of the carb that is surrounded by the white plastic piece i take it is the main jet as its got 240 stamped on it so will look through ebay and find some, also does that small black plastic boxey type thing on top of the inlet manifold between the carb and the reed block do anything as well as the one sticking outside the airbox just before the carb ?

[blackhat250]

Are you describing inlet rubbers ? a picy would help ..

[Airhead]

yhe one between the carb and engine is the boost bottle, not sure about the other...the only time I saw emmisions stuff was on a DTRE not a DTR 2002 ?

[too slow]

ok have taken pictures of items but cant find a way of putting them on here from my computer as there doesn't seem to be a way of attaching pictures

[Airhead]

you have to use a hosting site, I use photobucket but there are others, load your pics to there and then copy the img tag to here

[too slow]

nope you've lost me on that one

[too slow]

the best i can come up with is :- go to yamahamotorcyclespares.co.uk then look at DT125R 2002 JYADE031, then look at genuine parts, then look at intake section and its parts 13 air chamber and part 35 air chamber 2

[Airhead]

post the link !

[too slow]

nope don't know how to post a link sorry

[Airhead]

lol just copy and paste the browser from the page you are referring to

like this

[blackhat250]

Run the cursor up to the browse box [top left] left click on it - it will turn blue - then right click - drop down box appears- click copy

then click on your post on here, - right click - drop box -select paste.

Do this with both sites open on different windows

[too slow]

not wishing to look too stupid or ignorant and to give you some idea about my knowledge of computers, in the first line from black hat 250, what is a browse box, i tried to follow your instructions but all that kept happening was i ended up on my home page