Tdr 125 idles VERY high!

[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

Followed what you said, it's definitely better now! Idles at a good speed and the rev hang seems to be heaps better! Will take for a ride tomorrow and see how it goes. Thanks mate!

 

[my67xr]

yeah give it a few runs on the same track section
even adjust it 1/8 turn more or less and see what it suits it best
do the same section each time you adjust it

idealy you want a long straight slight incline to load the engine up a little, do it in 3rd or 4th gear

 

[Tomjoske]

yeah give it a few runs on the same track section
even adjust it 1/8 turn more or less and see what it suits it best
do the same section each time you adjust it

idealy you want a long straight slight incline to load the engine up a little, do it in 3rd or 4th gear

Hey there, Took the bike for a big ride today. I played around with the air mixture screw and it seemed to idol very nicely with no rev hang, there was a bit of backfire when I accelerated but that was about it. It rode good for about 10 minutes and it started revving high again and lots of backfiring. I kept having to lean the mixture screw each time it would do this. Any thoughts?

 

[my67xr]

ok,
where is the idle speed screw set to now ?
if you take note which way the slot is, then wind it in counting how many full turns it takes to reach the end of the adjustment
let us know.



but, t sounds like there could possibly be a vacuum leak somewhere
if it idles ok,
go back to post #5 and use the method i described to check for leaks


if you can rule that out, then it may be a blockage in your pilot jet circuit ?
if you blip rev the engine once, does it hesitate at all ?

 

[Tomjoske]

ok,
where is the idle speed screw set to now ?
if you take note which way the slot is, then wind it in counting how many full turns it takes to reach the end of the adjustment
let us know.



but, t sounds like there could possibly be a vacuum leak somewhere
if it idles ok,
go back to post #5 and use the method i described to check for leaks


if you can rule that out, then it may be a blockage in your pilot jet circuit ?
if you blip rev the engine once, does it hesitate at all ?

When I sprayed on the air mixture screw area that's where it would start revving high. If you look at post 11 you can see. And by blip rev do you mean Erving the bike while it's idling?? If so the bike will sorta die so I have to release and rev again and then it will backfire

 

[my67xr]

there is no mixture screw in post 11, but there is an idle speed screw (with the spring on it) ?

sounds like the front/manifold mounting face of the carby could be warped ?

 

[my67xr]

check that your 2x 10mm headed exhaust nuts are tight/firm too, underneath the head at the front
either side of the exhaust pipe where it comes out the head

don't overtighten them though, they can break the studs

 

[Tomjoske]

there is no mixture screw in post 11, but there is an idle speed screw (with the spring on it) ?

sounds like the front/manifold mounting face of the carby could be warped ?

Ah yes that's what I meant!! Haha sorry. Ok so what should I do?

 

[Tomjoske]

check that your 2x 10mm headed exhaust nuts are tight/firm too, underneath the head at the front
either side of the exhaust pipe where it comes out the head

don't overtighten them though, they can break the studs

I did them up as tight as I could. There was a metal thingy (I'm hopeless with all the terminology) like a big washer which on my other pit bike screws up flush with the engine.. On this bike I couldn't. Also, the rivets on the muffler we're loose and there was a little bit of play like 2mm

 

[my67xr]

this carby is basically the same as yours,
but if you look towards the manifold end you can see the mixture screw,
it's the brass one with the flat head screw slot

is your mixture screw on the opposite side of the carby ?

 

[my67xr]

if your exhaust gasket is missing, or crushed too much, it will cause backfireing on decelleration
they are cheap to buy-
http://www.ebay.com.au/itm/Exhaust-..._Parts_Accessories&hash=item4ace9a682a&_uhb=1



and if you want, drill out your pop rivets in the muffler,
and fit some new ones, make sure they are about 20mm long minimum

 

[my67xr]

if you need more help with checking the mounting faces for squareness, let me know.
i have a couple of those style carbys here, i can take some pics to help explain it

it could be the fuel bowl that is warped too
when you sprayed wd40 or whatever over the idle speed screw, it would have run down the carny and over the join where the fuel bowl meets the carby base

 

[Tomjoske]

Ah yes the flat head screw is on the opposite side. I'll definitely look into that exhaust gasket aswell! Should I worry about those rivets? Will that little bit of play hinder the performance in any way???

 

[Tomjoske]

Do I need to adjust that screw as we'll?

 

[my67xr]

the rivets will eventually fall out, then you could lose your muffler or tip ?

the mixture screw could help it run better,
try undoing it half a turn, then take it for a ride,

 

[Tomjoske]

I sprayed it with wd-40 this time nothing happened the revs stayed the same. It's also 4 turns anti clockwise to get the bike to idle normally

 

[my67xr]

ok, sounds like there might not be any leaks



i think you might need to reset your mixtures, with the mixture screw being that far out.

turn the mixture screw back in 2 full turns, so it is about 2 turns out


start the bike up and let it run for a minute or so,

turn the idle speed screw inwards to raise the idle speed a bit, up to somewhere 1800 rpm, not too high

now the mixture screw on the other side of the carby can be adjusted.
turn the screw out a quarter of a turn.
listen to the engine carefully,
if the rpms drop, then the mixture screw needs to be turned in a 1/4 of a turn.
the rpms should increase to what they were,
now try tuning the mixture screw another 1/4 of a turn in
if the rpms increase again, then try another 1/4 of a turn in.
if at any stage the rpms drop, or it starts running funny, then turn the mixture screw back out a 1/4 of a turn

adjust the mixture screw, until the engine is revving at it's highest/smoothest point
when you are happy it is close to perfect, then you can unscrew the idle speed screw (with the big spring) until the rpms drop back down to a decent idle speed.



see how it runs like that., and post up your results

if the mixture screw still needs to be 4 turns out, then i would say there is a blockage somewhere in the Pilot jet circuit.
i will have to guide you through cleaning it out.

 

[Tomjoske]

Sorry the idle screw is 4 turns out not the mixture screw. The mixture screw is screwed in as far as it an go

 

[Tomjoske]

And when I engage the choke it doesn't idle higher??

 

[my67xr]

Sorry the idle screw is 4 turns out not the mixture screw. The mixture screw is screwed in as far as it an go

ok,
so use what i wrote in post #37 to set the mixtures right

And when I engage the choke it doesn't idle higher??

with the mixture screw screwed right in, it is set as rich as you can get at idle,
so the choke isn't really going to do much.