A forum for owners of Yamaha TTR250 trail and enduro bikes!

jasparach · Senior Member

1996 O.E carburettor

TTRfan · Super Guru

Hi John.

Sounds like frayed throttle cables to me!

Brian

jasparach · Senior Member

Hi Brian,
Not had it apart yet but i am leaning that way myself. I did notice that
the cables were loose on the carburettor as in the nuts had worked loose
but having tightened them it is still the same.

John.

jasparach · Senior Member

Had a chance in the afternoon today to take the cables off the carburettor and
work them as the carb would and on the lower cable in the position that it
would be in if attached to the carb you can feel the catch on it as it slides through
the outer cover, that would be fraying of the cable i guess, time to get another set
of them i reckon. The throttle cables in your shop Brian will fit both models blue

or white am i right in saying?

John.

-- Edited by jasparach on Friday 22nd of May 2015 04:21:33 PM

TTRfan · Super Guru

jasparach wrote:
The throttle cables in your shop Brian will fit both models blue or white am i right in saying?
John.

Yep!

jasparach · Senior Member

Well the cables have been ordered through the new shop, seems to be
working well.

TTRfan · Super Guru

Posted them today John wink

jasparach · Senior Member

I shall await the postman.

jasparach · Senior Member

Looking at the throttle tube where the cables attach to it,
one of the holes seems to be elongated where the nipple fits into
it, is this normal or should it be the the exact size of the nipple. I dont
have one to compare it to and having fitted the new cables it is still
getting caught somewhere and not allowing the throttle to return fully
to the stop so i am wondering is it the tube that may be hindering it,
other than that it may be the carb.
Any input greatly appreciated

John.

TTRfan · Super Guru

Hi John

Yes - one of the holes is elongated so that's normal biggrin

It sometimes helps to take the throttle tube off and clean the handlebar especially if you have the original steel bars fitted. You can get a build up of rust inside.

Make sure the tube moves cleanly on the bars with no resistance and that the grip isn't rubbing on your handguards.

When the cables are off, try pulling them back and forth manually so that you take the throttle tube out of the equation.

Does the carb close all the way to the stop when the cables are off?

Also check that the throttle cables are routed properly with no sharp bends.

Brian

jasparach · Senior Member

Still having trouble with the carb on the 1996 TTR, i have replaced the throttle cables
and the throttle tube and the problem persists and is this, when the throttle is opened
beyond a certain point and and released to close it it seems to stuck and won't return fully
causing the engine to rev, my question is there anything in the carb that i should be looking
for specifically? can the shaft on the throttle wear? would it be something it the carb itself?
Any help greatly appreciated at this stage.

Cheers
John.

Watts · Member

Many of us have had this problem. Search here on the forum for "carb sticking" or "over revving". Now that you've removed the cabling as a variable, I think you are going to take it apart and clean it up. It's not the floats, I think it will be more the throttle slide above the float bowl. You will get good at removing and installing the carb I think. Clean it with iso alcohol I think was suggested on one post, not carb cleaner which was found to be too harsh. Make sure the throttle moves smoothly, and that the needle is properly seated in the throttle. The problem unfortunately has many possible causes, I think mine was just a bit dirty. The brass linkage not being snug is probably #2 reason.
Good luck,
Scott

http://ttr250.activeboard.com/t59996391/engine-revving-on-its-own-wont-return-completley-after-revvi/

ttr250.activeboard.com/t53126627/carb-idle-problems/

jasparach · Senior Member

Thanks Scott, i was wondering about that slide as a cause, i will read the links
you posted and clean the carb through and see what happens but as you said it
can have many causes.

John

jasparach · Senior Member

Should the throttle valve have any movement in it where it slides in the carb?,
side to side movement as it slides up and down, there are some wear marks on
it where its worn through the black coating on it, other than that i can't see much else
up with it. When working the throttle wheel a liitle resistance could be felt as it slid up and down
hard to know though what should be what on it without having a working model to compare it to.

-- Edited by jasparach on Friday 19th of June 2015 04:22:32 PM

jasparach · Senior Member

Well i took it apart,cleaned it, put it back in,fired it up and it was worse
than ever, the dirty bastard. Carburettors i hate the hoors.

leigh · Senior Member

Similar problem for me. I've tried everything and changed lots of parts.

No fix so far. I've just ordered a new slide. Hopefully that fixes it. Mine also looks a little worn. Some of the coating has come off.

Fingers crossed. It's annoying taking the carb out 50 times.

jasparach · Senior Member

At least 50 times, it would drive a body around the bend, If you don't mind me asking how much
is a new slide? I can't see anything wrong with the carb only that.

leigh · Senior Member

$150(au) from the U.S. inc postage to Australia.

$200 locally. As far as I can tell it's the only thing that can be causing the problem. After ruling out lots of other things as suggested on this forum.

Perfect smooth action when the bike is off. Not as smooth when the bike is running. Sometimes gets stuck with 10% throttle open. Never if you let the throttle snap back to position. I think airflow pushes the slide against the throttle body a little and causes it to stick

I only hope the throttle body is not worn as well.

leigh · Senior Member

A test would be to lube the slide. If that fixes it you know the problem.

Lube won't last long I am guessing due the amount of fuel in there going past.

jasparach · Senior Member

Ya thats the same as mine, no problem when the bike is off, it's perfectly smooth. When the
bike is running it's like yours staying at 10% open. wont return fully. At that rate of going
the slide will cost nearly €200 euro here in Ireland which is a lot for what it is. Will have to come
up with some other solution.

locky · Guru

200 euro is a lot ! Think id be on the search for a good used carb or if have a go at fitting something like a Mikuni tm33

petenz · Super Guru

locky wrote:
200 euro is a lot ! Think id be on the search for a good used carb or if have a go at fitting something like a Mikuni tm33

PUMPER FLAT SLIDE CARB

http://www.aliexpress.com/item/32mm-34mm-PWK-Carburetor-with-Power-Jet-Black-Color-Universal-Motorcycle-RACING-Carb-Scooters-dirt-bike/32227603941.html

MAIN JETS

http://www.aliexpress.com/item/New-main-jets-for-Keihin-OKO-KOSO-PE-PWK-carburetor-carb-vergaser-choose-your-size-10/1580288731.html

.

TTRHead · Senior Member

It's not an airleak around the carb rubber is it?

Also cables can be eliminated quickly I disconnect the cables at the carb end and use a flat head screwdriver to push the wheel open to see if it snaps back smooth if it doesn't then you no it's something other than cables. Just my little method.

Clean the carb properly take everything apart. Blow it all through. Clean it all. Take the pilot screw out clean that set it correctly..

Check float height.. Check the slide and check the is no notches inside the carb itself which is stopping the slide from closing.

It shouldn't be worse after you have cleaned it. Send it off and get it ultrasonic cleaned it's not expensive

Gotta clean my carb later... just bought a TTR petrol has been in it a year and it's not a hard job to give it a clean

-- Edited by TTRHead on Saturday 20th of June 2015 12:49:20 PM

jasparach · Senior Member

I have cleaned,rebuilt, fitted and balanced a bank of carbs on my fzr 1000 no bother,
cleaned and balanced the twin carbs on my honda deauville no bother,
cleaned and fitted the carb on my wr 200 no bother
but this one has me bet, i can't get any good from it no matter what i do to it,
it's not the inlet rubber stub, as we spoke about earlier the slide will close
and is smooth out when the bike is stopped, but start it up and rev it, release the throttle
and it will not fully close so i dont know other than the carb fairies must be at it. However
in will keep at it and see what comes of it.

jasparach · Senior Member

I priced it from on the cmsnl.com and €169.50 plus vat plus shipping which would leave
it at €226 euro! From the USA it will be cheaper but add customs charges, vat,shipping and the
kitchen sink, will leave it just as bad. Anybody got a good secondhand carb for sale?

leigh · Senior Member

Damn straight its expensive for what it is. Will let you know what difference it makes once I get it. Some times you've just got to suck it up!

jasparach · Senior Member

That would good Leigh if you could let me know how it works for you,
it would want to work for the cost of it.

Raggis45 · Veteran Member

Is the needle square in the slide body as it rises & falls?? - it may be binding on the needle jet??

Also, with the engine stopped it may not make a difference, but when running and with the differential air pressure on either side of the slide, it may be ****ing & jamming the slide a tiny bit - you mentioned you had some wear marks on the slide, this may give it more clearance than the return spring can deal with.

Not sure if this will help you, as you say you need some spare bits to compare/swap over.

Rob

jasparach · Senior Member

Hi Rob, i stripped it down and moved the slide manually from above and below and there seems
to be a little movement in the bore, as in it can move from side to side so there would seem to
be wear so i reckon that it as you said when it's running with the air pressure it is sticking, i am searching
other yamaha parts numbers for carb slides to see if there is anything the same and maybe pickup a 2nd hand
one, i will see how it goes.

John.