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

OkieRider · Member

High or sticking idle??

ttboof · Super Guru

I would have gone with a leaking inlet stub but if your sure it's ok

Are the cable freecplays set correctly might be a case of the cables not letting the carb close correctly

As it been opened up it may need the next size up on the pilot jet and set the mixture adjuster and idle again

-- Edited by ttboof on Sunday 30th of October 2016 06:55:12 AM

JOHNYBOY · Super Guru

i would say the same as above air leak but if you are certain this is ok why not take both cables off the carb & try that by slowly do revs by hand in different positions if not it can only be the slide thats sticking & not going to its stop position

petenz · Super Guru

worn needle & or emultion tube...

....

TTRfan · Super Guru

Sorry to hear of the problem David!

You are not alone on this one. I had a very low mileage 2004 TTR with the same symptoms and, after a lot of head scratching, a strip of the carb showed the throttle linkage securing screw to be loose. Worth a check!

With regard to Thumper Talk, I think you will find that most TTR owners have migrated over to this forum wink

Brian

Inside top of carb.jpg

OkieRider · Member

I will check for any air leaks again, but I'm like 95% sure there isn't one. I've literally sprayed everything down and I can't get anything to happen.

I'll also check the needle and emulsion tube. I was actually thinking about that last night after I posted. That could definitely cause this.

TTRfan, I've never looked at that. I'll definitely check it out today when I pull it off again!

Thanks.

OkieRider · Member

I pulled it apart again. Totally forgot to spray it down with brake cleaner looking for airleaks, but I did check the screw TTRfan told me to check. It's tight, and everything else in there is tight too.

I was going to check the needle to see if it was worn out... But this bike is almost new. It still had the stock tires on it when I purchased it. It's only got 1000 miles on it. It wouldn't be worn out that quick would it?

OkieRider · Member

I sprayed every single hole in this carb with carb cleaner today. Re assembled it with a size bigger pilot and main jet (52.5 pilot amd 140 main) The hanging idle thing appears to be gone (but it's also "dissappeared" before and then come back) Thinking maybe there was something I just missed clogging one something up.

Now the problem is, there is a bog if you open the throttle up all the way from idle. I know my accelerator pump is working, because I tested it. Do I need to raise or lower the pilot jet size? I'm honestly not sure. The air fuel screw doesn't seem to do much at all.

leigh · Senior Member

Hey Okie, mine had similar symptoms, did as you did and as Brian suggested and checked everything a million times. For me it was the carby slide being worn. It has some sort of coating on it and wears over time and when the motor is running, vacuum causes the slide the push against the throttle body and stick a little.

Mine had 20,000k on it and was doing it on and off from about 12k and gradually got worse.

Someone mentioned carby cleaner can damage the surface of the slide. I don't know, but I wont use carby cleaner on the slide anymore just in case as they cost more than Donald Trump's hairpiece. I cleaned the old slide and the throttle body where the slide moves up and down with alcohol like Metholated spirits instead and that actually helped a little. The cloth was pretty dirty after "polishing" the carby neck. Anyway a new slide in the end fixed it for me. Not unusual to see people write about this symptom.

1000 miles is nothing, but I wonder if something or carby cleaner has damaged the slide?

Leigh

Assuming its not a cable sticking or throttle tube issue.

-- Edited by leigh on Wednesday 2nd of November 2016 11:12:22 PM

OkieRider · Member

Definitely isn't a sticking cable.

The slide looks brand new, so I doubt it is that... But when I pull it apart again I'll look it over and see if anything appears to be wrong with it.

Greenson · Newbie

Hi folks , just my two penneth for what's it's worth , I have also become versed in removing the carb quite frequently to try and get here to run without , bogging down , misfiring , not starting etc etc etc and eventually changed all jets ,the emulsion tube , the needle , all the o rings and diaphragms , checked float level using the clear pipe on the outside of the carb method connected to the float drain , fitted a new inlet mount and checked the whole lot for air leaks , but was not satisfied until ..... I had one final check ... Dropped needle one click to slightly richen the mixture which helped but my success really came when I decided to brave removing the float pin and replace the float valve , and tucked up inside where it fits is a very small dome filter on top of the float valve and it was coated in crap which I removed and replaced with new parts .... Bingo one perfect TTR, worth a try and I may be wrong so forgive me if I am , but it's not mentioned in any of the already excellent guides on the forum for carb servicing etc and it sorted me out ... Happy days and good luck

JOHNYBOY · Super Guru

have you got a picture of this filter never seen one on my carb strip is it a std carb off a ttr

TTRfan · Super Guru

I haven't got a good picture - this is the best I have.

This is where the float valve filter is located:

Location of float valve filter.jpg

I will look back at the carb articles and add some info about it but, yes, it is surprising what debris can gather on it bearing in mind how fine the filters are on the fuel tap confuse

I did post a message when I found a particularly dirty filter - see http://ttr250.activeboard.com/t45797183/petrol-filter-above-float-needle/

Brian

OkieRider · Member

I'll check that out. thanks

OkieRider · Member

I still haven't checked that filter out. I'm about to do that. (Taking it apart now)
I did pull the spark plug, and it looks totally fine.. Maybe even a tad rich. That confuses me.

I'll update you guys when I get this filter checked out.

OkieRider · Member

The small filter TTRFAN talked about is spotless.

OkieRider · Member

I'm not sure what else to do. I've cleaned the entire carb (that I can tell) checked every screw, nothing. Everything is as it should. I'm about ready to give up and toss the bike off into a nearby lake. Atleast there it won't give anyone else problems.

ANY ideas??

Moo · Senior Member

Have you tried returning everything to stock? As in using an airbox with a full snorkel and no air holes, stock jetting etc and see how it runs?

I've always been tempted to try the airbox mod in the hunt for more power, but my TTR pulls flawlessly throughout the rev range, even when it's just about to stall out greenlaning, the throttle picks up with no bogs or hesitation. So I've never been able to justify changing it.

ttr steve · Super Guru

Good to put it back to original and see if that works. I take it the inlet stub was fine?

OkieRider · Member

By inlet stub, do you mean the rubber hose (for lack of a better word) that goes from the carb to the engine? If so... No. It is not leaking. I have sprayed the entire thing down with starting fluid about 10 times. Nothing idle change, anywhere. It also still rubbery and bends (not dry and cracked)

I've put it back to stock jets, and put the air box snorkel back on. That doesn't change anything. Right now it has a 140 main, and 52.5 pilot. Im not even see where those are compared to stock, I forget what they come with.

I'm stumped.

OkieRider · Member

I guess I should also say that it runs great, pulls good with no flat spots or drop in power, no bog. It's jetted perfect. If only it would idle.

JOHNYBOY · Super Guru

have you sprayed wd40 ali around carb to inlet on tickover if it races up slightly its drawing air thats what it sounds like to me also does slide go up/down free without spring on

OkieRider · Member

I've sprayed everything down, idle doesn't change.

I will check the slide when I get home. I did notice when you pull the rottle lever by hand (not hooked to cables) you can feel a drag almost. But it appears the slide goes all the way back down everytime.

ttr steve · Super Guru

Hi David

So now the only thing is the idle speed?

I take it you have tried altering the idler speed? Interesting thread about it here http://ttr250.activeboard.com/t54555922/idle-speed-screw/

Steve

Edited bit, also if you have a bit off sticking, I found it can also be up at the throttle, sometimes just tacking the throttle and checking the throttle tube and putting back together helps.,

Please don't throw it in the lake, sure we will get to the bottom of it.

-- Edited by ttr steve on Saturday 4th of February 2017 05:54:54 PM

JOHNYBOY · Super Guru

if you have done the wd40 bit take carb off couple up cables work throttle look down at the slide from inlet or outlet you must be able to see its not releasing it could be one cable fighting against another adjust cables to suit hope this helps

OkieRider · Member

Cables are adjusted fine, already checked that.

Ttr steve, that was a helpful post. I've always had the same problem with it not wanting to back out. I filed it like he did and it works great now!
That still doesn't fix my problem. But it was nice. Lol.

I re installed it today, it seems better now but it still idles high sometimes. I'm about ready to just give up and ride it. Maybe it'll fix itself.

OkieRider · Member

A few days back, I found a little brass piece laying in the floor. I had remembered seeing it a loooong time ago, inside the carb. Did a little looking and it was the "check valve". I don't think it does anything at idle, but it's back in there now. Bike has run fine everywhere else so I'm not sure what that does.

TT-R250M · Super Guru

Hey OkieRider,

Given that you have checked the cables and the slide is not sticking, I would suggest that you are using a #52.5 that is too rich for the bike to handle with your set-up. Try using the stock Teikei (US) #50 and see if that is the problem. If you have used a different brand of jets other than stock Teikei or 6 Sigma this could be your problem too. Different brands have jet sizes that does not correlate to others so keep that in mind.

In regards to the accelerator pump it does not effect the idle at at, it comes on from about 1/3rd throttle, it helps to regulate the accelerator response by shooting a squirt of fuel when the throttle is rolled on. This is the reason why I would not change the stock carb personally, it helps to stop the lean condition (less accelerator response) that other carb's have that do not have this feature.

I personally would not recommend to take the snorkel out, I would be enlarging the inlet. Search 'air-box modifications' and you will see how I did it. Edit: Just remember you might need to use the #52.5 pilot jet

Let me know how it goes for you.

Jarrah

-- Edited by TT-R250M on Saturday 11th of February 2017 03:11:03 AM

OkieRider · Member

Stock pilot didn't help any when I tried it.

It seems like it is running better now, so until something else happens... I'm gonna leave it alone.

Jumpn · Veteran Member

i'm having the same problem. new bike to me, 2004 ttr 250. I haven't seen this carb before. is the slide that everyone is talking about part #14 in the diagrams, called "valve, throttle 1"?

http://www.partzilla.com/parts/search/Yamaha/Motorcycle/1999/TTR250+-+TTR250L/CARBURETOR/parts.html

TTRfan · Super Guru

Yep - weird name Yamaha have given it eh?

Jumpn · Veteran Member

I dug into my problem today. Here's a youtube link of what mine was doing.

www.youtube.com/watch

I took the carb out, thank you to all who have posted instructions here!! It went pretty well, hardest part was getting one of the throttle cable out of it's clip. The intake tube from the airbox was loose, and I think that was one source of my issues. It basically fell off, and I could see an indention in the rubber that it didn't appear to be seated properly. I didn't even have the unscrew the clamp, so that's my clue there. I went ahead and cleaned the outside, then dove into the guts. I removed the to piece, and peered inside. It appears clean, and I didn't feel comfortable with removing the needle.

I replaced the gasket, and removed the bowl. Removed the jets, and they were clean. I replaced with Mikuni 52.5 and 140 jets. I removed another portion with the nickel sized gasket, and replaced it. The bowl gasket was flat and brittle too. I couldn't get the float needle pin to budge, and since everything else looked good inside, i decided against possible breaking those pin mounts, and left it alone. Lastly, I removed the cover for the accelerator pump diaphragm. this piece was stuck to the outer cover, and was brittle with tears in it. I think that was a problem too. That piece has been ordered, so I hoping all will be resolved later this week.

With the rebuild kit I received, it had a single small o ring. I used it on the new fuel screw, as it didn't have one on it from the kit, but the old did have an o ring, however it looked flattened out. All the gaskets were flattened or brittle, by the way.

A huge thank you to all who have traveled and documented this road before me. I truly appreciate it. Cheers!! I will figure out how to load photos later tonight.

This is as far as the jets went in. The stock ones were in further. Is this correct?

-- Edited by Jumpn on Monday 20th of March 2017 02:06:43 AM

-- Edited by Jumpn on Monday 20th of March 2017 02:10:13 AM

-- Edited by Jumpn on Monday 20th of March 2017 02:12:32 AM

-- Edited by Jumpn on Monday 20th of March 2017 02:16:49 AM

Jumpn · Veteran Member

Here is how it was running before.
www.youtube.com/watch

Notice how the rpm's stay elevated after the rev, lack of responsiveness. the throttle return snaps back fine, and the choke is off. It dies by itself.

Here's a video of my carb after cleaning. I'm awaiting a new accelerator diaphragm assembly before it goes back on the bike.

https://www.youtube.com/watch?v=VZzlHaWUsYQ

-- Edited by Jumpn on Monday 20th of March 2017 02:31:41 AM

TTRfan · Super Guru

Thank you for documenting the carb rebuild so well especially with the photos and videos biggrin

I think you have done an excellent job on the carb and it all looks squeaky clean.

As the carb was working before the strip down then it is more than likely that the float needle is free and working properly.

My suggestion is to put the carb back on when you get the diaphragm and see how it runs. It could be that the slide was a bit sticky from not being use for a while. Maybe running it for a few miles will sort your problem out. If not, we will need to give it some more thought but at least you will have a running TTR to get out on and enjoy riding wink

Brian

Jumpn · Veteran Member

Thank you. I hope that it all comes together. I will report back when the diaphragm assembly is in and the bike is (fingers crossed) running well.
The diaphragm should not have been stuck to the cover, should it? Or does it keep suction there all the time? It was very dry and cracked though.

PlumasDude · Senior Member

Lots of posts on this thread!

If you said you were also having problems keeping a good even low idle I'd type "pilot jet" in all caps, but I think you're saying it will idle nice and low but then jumps after you hit the accelerator and won't go back to a nice low idle? I still say pilot jet but in lower case letters.

Just to be sure, you tried the STOCK (Teikei?) #50 pilot? Not the Mikuni. And it was a NEW stock #50 pilot? They can't be cleaned. I swear its this bike's Achilles heel (the pilot jet that is).

Those Mikunis drove me crazy. I found the #140 main jet too big, even with the airbox opened, went back to #137 (stock!) and leaned the needle from there.

I have a 2003 US model.

BTW what ever Jarrah ttr250.activeboard.com/m1686051/profile says about the carb is probably right.

PlumasDude · Senior Member

Jumpn wrote:
Here is how it was running before.
www.youtube.com/watch

Notice how the rpm's stay elevated after the rev, lack of responsiveness. the throttle return snaps back fine, and the choke is off. It dies by itself.

Here's a video of my carb after cleaning. I'm awaiting a new accelerator diaphragm assembly before it goes back on the bike.

https://www.youtube.com/watch?v=VZzlHaWUsYQ

-- Edited by Jumpn on Monday 20th of March 2017 02:31:41 AM

Jumpn Dude! I just watched your video. PILOT JET (new, stock). If I'm wrong I'll buy you a beer. I will now change my handle to "pilot jet."

Jumpn · Veteran Member

Well, I hope you are right. I replaced with the larger jets, but do have new stock jets if it seems to need them.
I decided now is a good time to clean. Bathroom scrubbing bubbles do a great job!

I cleaned up the airbox. and noted a crack in the rubber piece between the intake tube and the black "box" thing on top. Guessing I should silicone seal this up? It looks like previous owner already tried. What does that box do?

Along with this conical piece, what is it's function?

TTRfan · Super Guru

Some information on the "black box" here - http://ttr250.activeboard.com/t51169250/yamaha-energy-induction-system-yeis-boost-bottle-air-chamber/

The conical device is an emulsifier and pulls most of the oil mist out of what gets pumped from the crankcase breather pipe to the airbox. Needs emptying regularly.

I would assume all the parts and connections should be airtight for them to work effectively wink

Brian

Jumpn · Veteran Member

OK, so the emulsifier is like an oil catch-can thing. thank you. I will empty it prior to re-install. From what I gather, the air chamber is a separate piece, and isn't "molded" into the rubber boot as I originally thought. I didn't want to go prying things off. Thank you

Jumpn · Veteran Member

My new accelerator pump diaphragm and o-rings came today. I put them in the carb, now it's going to be time to re-install the carb. Anything I need to look out for on reinstall?

PlumasDude · Senior Member

Just about everything you could want is in the carb stuff pages: ttr250.activeboard.com/f611253/carb-stuff/

I've found these two particularly helpful: ttr250.activeboard.com/t55374798/rebuilding-a-ttr250-teikei-y30p-carburettor/; ttr250.activeboard.com/t47674647/carburettor-pictorial-guide-to-stripping-and-checking-a-carb/

And don't forget the NEW STOCK #50 pilot jet and while you're at it might as well install a new, STOCK #137 main.

Once you get it dailed in you'll know it, the set up is pretty bullet proof with basic maintenance.

PlumasDude · Senior Member

Another great one on jets and needles: ttr250.activeboard.com/t49951533/carb-jetting-information/

Jumpn · Veteran Member

www.youtube.com/watch

It lives!! It took a little while to get fuel to her I think, but with a blip of throttle while hitting the start button, she lives!! So much easier to ride with a good idle. Thank you to all here on board!!

Jumpn · Veteran Member

I adjusted the air screw just a tad, now it fires with just a press of the magic button. No cranking at all, just BAM, and she hits. so nice.

TTRfan · Super Guru

Good job!

z1g · Senior Member

Sorry not to to rehash OLD post. GREAT POST BTW.
So replacing the acc pump diahpram solved you're high idle when riding issue?
your problem seems similar to mine, except mine idles fine, no need to use throttle to start, will idle all day long.
I took mine off to clean, and perhaps i damaged it.
Will be taking carb apart and check this.
sorry to be lazy, but what kit did you buy to replace the item? Is it in the full carb rebuild kit, or is it something else that is bought for this particular problem.

Z.

DTRAL · Member

RESURRECTING OLD POST:
I have read the info above and I think some of it may help me, but I will ask my questions here anyways...

'01 US -spec, original carb- At start, with choke or no choke, the bike immediately RIPS. I'd say 2-3k RPM from the get-go w/ zero throttle. It stays in this extremely fast idle (no slowing down after warming up or whatever) and will not back down to a lower idle after throttle blips, W/O, anything. Header pipe is glowing red within five minutes (typically indicates lean, correct? Too much air?)

I have backed OUT the adjustment screw on the bottom of the carb as far as it will go, but not tried cranking it all the way IN. Now that I think on that, was I going in the wrong direction?

Recent changes:
All Balls carb kit - all new internals & gaskets (followed B. Sussex rebuild guide).
-I believe there is a 50 jet in there now.
-Needle clipped one notch higher than middle setting (attempted to enrich mix... did I move the needle the wrong way?).
-New diaphragm pump and o-rings.
-New "boot" from carb to engine, old one was toast. Clamp is tight, no leak.

Notable:
-Airbox appears to still have 'snorkel'... 90-degree curved plastic intake at top of box assembly by the electronic box, yes?
-Airbox does not have a foam filter. I have one on order (ETA 6/2/23). I have had other vehicles experience minor performance shifts w/ open air boxes or no filter, but this seems extreme...
-Clamp from airbox tube to carb is tight, no leak.
-FMF Megamax exhaust. Recently disassembled, cleaned, and re-packed. Installed 8 of the 11 external baffle rings and the spark arrestor plate. (Internets say 8 is 'base' setting).
-Prior owner deleted "yamaha-energy-induction-system-yeis-boost-bottle"

-Also, I think the All Balls kit lacked the air screw rubber o-ring, and I want to say I went with a hardware store replacement that may or may not be correctly sized. If this o-ring is too small, is it possibly allowing excess air into the mix at idle?

-Also, also... I replaced the throttle cables and the new one is not a great fit... too loose. However, the high idle at start is present even when I manually move the throttle cable connection all the way to the close limit with my hand. I have twisted it to the stop using my fingers and there is no difference to the extra-fast idle.

Any advice, guidance or suggestions appreciated. Heck, I'd even appreciate some ridicule. TYIA!
Al

-- Edited by DTRAL on Saturday 13th of May 2023 02:06:35 AM

-- Edited by DTRAL on Saturday 13th of May 2023 02:58:12 AM

mossproof · Super Guru

Certainly sounds lean. Having no air filter will make a difference. Removal of the YEIS should not make a notable difference unless the hole where it was fitted is unplugged. You have the external part of the airbox snorkel. Does it extend 3 or 4 inches into the box or has the PO cut it off?

Screwing the fuel screw out SHOULD enrich the mixture, but don't discount the possibility that a hole is blocked. In fact this counts for the whole rebuild - it is possible to dislodge some crud from one spot, only for it to relocate somewhere else! If air is leaking past the o ring it could be the problem. Temporarily "seal" the thread with some grease to see if it makes a difference.

Putting the needle clip higher up (towards the "blunt" end) drops the needle further into it's seat, restricting fuel flow and making it leaner. For richer setting, move the clip towards the pointy end.

Removing baffles from the end can will probably make the bike leaner.

As long as there is some slack in the throttle cables that should not be your issue. I think the pilot circuit in your carb is the most likely, since it happens with no throttle input. Pilot jet and fuel screw.

Was the bike running at all before you started?

Carbs can be very frustrating. Hang in there! Good luck!

-- Edited by mossproof on Saturday 13th of May 2023 11:03:47 AM

DTRAL · Member

Was the bike running at all before you started?

-- Edited by mossproof on Saturday 13th of May 2023 11:03:47 AM

It ran briefly (poorly) on this rebuild, BUT that was prior to the most recent removal and addition of the boot from the engine to the carb.

Oddly enough it ran better with the torn boot in place. That doesn't make a ton of sense... torn boot = extra air = leaner = higher idle.

The deleted YEIS has been capped. Thanks for that insight, glad I can eliminate that now.

Sounds like my action plan is:

-Remove carb and re-clean pilot circuit;

-Determine if the air screw o-ring is a factor, find correct size o-ring if necessary;

-Move needle clip closer to point of needle while carb is off;

-Note whether snorkel is chopped off INSIDE air box.

-Adding additional baffles will follow all the carb tinkering, since that is all external and easy to do.

After posting last night I located my old carb parts from before the All Balls re-build kit went in. Once I have the carb out and apart I'll have to determine if the newly-installed pilot jet is different apperature size than the prior part.