Tdr 125 idles VERY high!

[Tomjoske]

I've tried adjusting the air screw on the carb but it doesn't seem to be doing much... It just seems to idle very high and when you release the clutch you shoot off.. I checked the flap to see if it was getting stuck when I pulled and released throttle and it's fine! Any help guys???

I've only just started getting into bikes and I'm still learning the basics!

 

[Tomjoske]

It also backfires a lot.

 

[my67xr]

there should be an idle speed screw on the side on the carby, they usually have a spring behind it
if turning that out doesn't drop the revs then there could be a vacuum leak

does it just backfire on decelleration, or all the time ?
if only when you back off, the bolts holding the exhaust to the head could be loose ?
or the copper oring/seal has broken or been crushed

 

[Tomjoske]

It will back fire randomly. Ok that's the screw I was messing with so there must be a leak. What do I do now

 

[my67xr]

start the bike and let it idle
then spray some wd40/degreaser/carby cleaner etc on all the joins of the carby/fuel bowl, carby/spacer, spacer/manifold, manifold/head
if the idle changes in any way, then there is your leak.

it could be a warped mounting face that needs filing to make it flat, or it could be a gasket, or o'ring that is leaking

 

[my67xr]

also with the high idle,
check that your throttle adjustment isn't done up too tight.
there will be a rubber boot at the throttle, where the cable joins to the throttle.
slide it back and you should see an adjuster, and locknut.
loosen the nut, and try turning the adjuster back towards the throttle, to give the cable a little slack
then start the bike and see if it has changed it's idle speed

 

[Tomjoske]

also with the high idle,
check that your throttle adjustment isn't done up too tight.
there will be a rubber boot at the throttle, where the cable joins to the throttle.
slide it back and you should see an adjuster, and locknut.
loosen the nut, and try turning the adjuster back towards the throttle, to give the cable a little slack
then start the bike and see if it has changed it's idle speed

ok I sprayed some carby cleaner on the bike while it was idling and it started idling higher.

 

[Tomjoske]

I also noticed the choke flap is quite loose.. it has about 3mm play when the choke is off.. could that be an issue swell?

 

[my67xr]

so did you take notice where you were spraying it when the revs went up ?

the chokes are pretty cheaply made, they can have a bit of play

 

[Tomjoske]

it went up pretty much nomatter where i sprayed it

 

[Tomjoske]

wait up***8230; is that hole meant to be there??

 

[Tomjoske]

I plugged it with my hand and the revs dropped whic hwas good.. but sprayed with the cleaner and the revs sky rocketed again :/

 

[my67xr]

that is the fuel bowl breather hole,
there should be some rubber tubing coming off it and hanging down

 

[my67xr]

that idle speed screw looks like it is wound in too far to me ?

 

[Tomjoske]

that idle speed screw looks like it is wound in too far to me ?

yeah I just screwed out a fair way adjusting the throttle helped heaps too.
it's not revving super high now!
but when I rev the bike, it takes quite a while for it to go back to idle.

 

[my67xr]

that's called rev hang.
it is caused by the mixture screw being set too lean
try turning the mixture screw in 1/2 a turn, and try it again

it sounds like the carby hasn't been tuned yet ?

 

[Tomjoske]

that's called rev hang.
it is caused by the mixture screw being set too lean
try turning the mixture screw in 1/2 a turn, and try it again

it sounds like the carby hasn't been tuned yet ?

I bought the bike 2nd hand off a guy.. he said he had just cleaned out the carby but it had been sitting in his shed for the last 3 months. I've messed around with the mixture screw, no matter what I do it still takes ages for it to go back to idle… could it be the carby not being air tight??

 

[my67xr]

yeah it is possible the carby has an air leak

but,
when the idle speed was set so high, that would make things very hard to try and tune it.
turn the mixture screw all the way in until it bottoms out, don't overtighten it.
then unscrew the screw 1.5 turns and try that for starters

 

[Tomjoske]

yeah it is possible the carby has an air leak

but,
when the idle speed was set so high, that would make things very hard to try and tune it.
turn the mixture screw all the way in until it bottoms out, don't overtighten it.
then unscrew the screw 1.5 turns and try that for starters

alright cool! will try tomorrow morning (don't want to wake up phyco roommate)
if it does have an air leak.. what do I do? do I need to get a new carb

 

[my67xr]

nah, just depends on what is warped.

the fuel bowls warp easily if you overtighten the screws, as the is only 2 holding it on
the front mounting face of the carby could be warped too

you will need a flat sanding block, or flat sided block of wood, or a flat workbench, and a piece of 180 sandpaper, or 320 wet & dry paper.

hold the paper firmly on the flat board/bench, and move the carby mounting face across it, do this a few times, and look at the mounting face

if there are even sandpaper scratches across the face it is flat, and ok.
if it just leaves scratches on either end of the mounting face, then it is warped, it will need another 10 or so passes across the sandpaper to flatten it off.