Bike stalls when coming to a stop.

[Serf27]

Hey all, one question and problem I have, my 1980 yamaha tt250 stalls when I am coming to a stop. I have to hold the clutch in and shift to neutral or hold the clutch in and give the bike some gas when coming to a stop.

It's pretty annoying. Can't really stop comfortably while riding without the fear of the bike dying and dealing with kicking it back on.

I have:
cleaned the carb
Set air needle on carb all the way in till snug, back out 1 and 3/4 turns.
Adjusted the clutch cable
Adjust throttle cable
Cleaned the spark plug, the plug was more on the black side when I pulled it out.

When started cold the bike will idle most of the time.
When turning it back on after it stalls when stopping, sometimes it idles alone, other times needs some fuel.

What do you guys think it might be?
I read might be loose/dirty ground on the coil?

Thanks in advance.

[CaNsA]

up the idle a little.

[Serf27]

[jaffa90]

Does it have the correct air filter fitted?
Did you check the float and needle valve shut off position.

[Suntan Sid]

[Copycat73]

[WD Forte]

Had a similar problem with the old CX
It would start and tick over fine but when warmed up, often cut out at junctions causing me to up the tick over and rev it to keep going which was a PITA.
I tried many things but eventually found the exhaust header seals were loose/leaking and tightening them up solved the problem.
Checking yours may help
____________________
bikers smell of wee

[Glover]

I've got the same problem at the moment, i've tried all sorts. mine is only while the lights are on though, causes the revs to drop and cut out. so question, is it when your lights are on, does it idle ok with the lights off?

I ran mine with the regulator disconnected on the weekend and it was fine so new one on order and should be problem solved.

[chris-red]

Sounds like clutch sticking to me. If it doesn't stall in neutral that would be my first look.
____________________
Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.

[Serf27]

Thank you for the replies everyone!

Got some time to work on it and here's what I did.

CaNsA, I turned the idle screw up all the way, it helped some, but still experiencing it dying sometimes when stopping.

Jaffa90, I am using an aftermarket pod filter, it does not have the original air filter box, the filter is brand new, got it today.
Could this be an issue since it's not the stock filter?
I checked the float needle position when I first cleaned the carb, but did not adjust it or anything. I couldn't find the spec for it on this bike online, I will need a manual to adjust the height.
The float needle is good though.
The bowl is getting plenty of fuel though, when I loosened the bowl drain screw, fuel did come out of it for a few seconds.

Suntan Sid, I did sand the ends of the coil(pack?)where it mounts to the frame to clean metal, also sanded a small ground wire that bolts with it, also sanded the actual frame where the coil is bolted onto. Not sure if it helped a little but problem still occurs.

Copycat73, I bought a new plug and put it in, stalling still occurs.

WD Forte, I did not check the exhaust seals, I will check those possibly tommorow and tighten the exhaust if it's loose.

Glover, my bike doesn't have lights, but thanks for the input.

Chris-red, I adjusted the clutch cable the other day but I think I may have adjusted it too tight, as the clutch lever does not have enough play I have seen when people on YouTube asjust theirs. I will remove the case cover and clean the clutch discs possibly tommorow

Here's what I have done and bike still stalls.

-Idle screw that holds the throttle cables on the carb, turned all the way up for highest idle.

-Cleaned the carb and jets, twice.

-Installed new spark plug.

-Bought new air filter, guy at the bike shop said the pilot jet was dirty and causing this, I did not find the pilot jet on the carb diagram but assume it was one of the jets I cleaned since I cleaned the carb up and down, side to side.

-Rode the bike with the idle air screw set at these different settings, all started with air screw tightened till snug.
•Turn screw out 1 turn.
•Turn screw out 1 1/2 turns.
•Turn screw out 2 turns.
•Turn screw out 2 1/2 turns.
Should I try 3 turns out?

The bike will start fine when cold, usually less than 5 kicks.
Once started cold, it will idle fine.
It drives fine and is a fun and semi fast bike for trails and just fast enough for my experience.

When coming to a stop though, I have to give it gas a little and keep the throttle open just a tiny bit to keep it on.
On RARE occasions, when I stop, I can release the throttle slowly to keep it on, but 95% of the time releasing the theottle slowly it will just start to bog and die.

I can't remember how it idles when I start it warm.

I will clean the clutch pack to see if they are sticking, like Chris-red said, I think I have seen this symptom online once before with someone else with the same issue.

I will also check the exhaust seals as WD forte suggested.

Other than that I am out of ideas, besides tightening the throttle cable more to open the throttle more, since the screw for it is holding the throttle as far open as it can.

Thanks again all for the replies and help, any more help is greatly appreciated!

[Dimerz]

If your idle isnt stable on the rev counter check your air flow screw (should be by the idle screw), turn it clockwise to let less air through and anti clockwise for more air to mix in. I had this problem with mine, set my idle to a steady 1.5k.

[Serf27]

Thanks Dimerz, I have already tried the idle air screw at 1-1.5-2-2.5 times out. No luck.
I will try .5 turns out and 3 turns out tomorow.

Someone confirm this please, when people say turn the idle air screw out 1.5 turns, they mean 1 full 360 degree turn then another 180 degree turn correct. ?

[ADSrox0r]

Checked inlet manifold rubber for cracks?
____________________
Current bikes: '08 VFR 800 VTEC(yo) , '07 ZZR1400 Winter hack: '95 Aprilia 650 Pegaso Currently lusting after: RC30

[Serf27]

Thanks for the reply ADSrox0r.
The inlet boot for the carb to head is in good shape.
What I forgot to do was to replace the gasket that connects it to the head. I will replace the gasket and see if it helps.
Thecarb slides into the booth nicely and made sure the boot and carb ends were clean, forgot to replace the gasket.

[ADSrox0r]

That's most likely to be your culprit then. Air getting into the fuel mix will cause the exact symptoms you're describing.
____________________
Current bikes: '08 VFR 800 VTEC(yo) , '07 ZZR1400 Winter hack: '95 Aprilia 650 Pegaso Currently lusting after: RC30

[Serf27]

[Serf27]

To add, are you suppose to be able to see through each jet?

Each jet has holes at the tip which are clean and able to see through them.

One jet had clear holes at the bottom I could not see through the inside of it from top to bottom.
I blew plenty of carb cleaner through it.
I used a thin wire from a wire wheel and either the wire was hitting the inside of the jet because the wire was too thick, or the jet is sealed in the middle.
Any thoughts.
I don't know what jet it was though.

[jaffa90]

You have a pilot jet, main jet and a choke/ starter plunger jet .
A jet has a hole going in and a hole coming out. Some jets have a one hole entrance and a few holes coming out.

https://www.boats.net/parts/search/Yamaha/Motorcycle/1980/TT250G/CARBURETOR/parts.html

[Serf27]

Thanks, I think the pilot jet is seriously clogged up. I couldn't see light through there today, I will clean it out again tomorrow using a thinner wire to see if it clears up.

[Serf27]

I put a new gasket between the carb boot and head.

I got a new jet, which is way bigger, but thought it would work.
The old,pilot jet was a 17.5, the new jet was a 37.5.
Still didn't idle. Seemed harder to start, but it was cold and raining outside.

The old 17.5 pilot jet was clogged bad, couldn't see light through it, probed it with a thinner wire this time for a while and nothing budged or came out.

The new 37.5 pilot jet was clear.

Could the size difference not make the bike idle either? Or should it still idle even with a much bigger jet?
Help please.

I am about to push the bike off a cliff.

[Serf27]

Update: I cleaned the carb a 4th time. Took it down to the bare carb body, and had it soda blasted at a shop for safe measure.

The carb has a pod filter, I got these new pieces:
Pilot jet size 20. stock jet is 17.5
Main jet 170. Stock main jet is 155-165.
And some o rings.

Good news is the bike would bog like crazy with the air filter on, and run good without the filter, the main jet was too big! It had a 180 main jet, I dropped to a 170 and it's much better with the air filter now.

Semi good/bad news, the bike will stay on most of the time coming to a stop if the choke is on, but the choke always moves it self to "off" and I have to reach down, put the choke on when stopping.

Bad news is it won't idle without choke on will die coming to a stop.
And if it doesn't die, it will BARELY stay on, like will bog badly and as soon as it sees throttle, it dies.

The choke on this bike is an enrichment choke I believe, do I need to get a bigger size pilot jet since it only idles when the choke is open/on giving it more fuel?

[Serf27]

Finally!
The idle screw on the bike was the wrong one and was too short so it would bottom out before it would start to increase the idle.
I got a longer screw and was able to open the throttle slide a bit more and now it idles fine with no choke and I can come to a stop comfortably!
Thanks everyone for the help.

[ADSrox0r]

All's well that ends well.
____________________
Current bikes: '08 VFR 800 VTEC(yo) , '07 ZZR1400 Winter hack: '95 Aprilia 650 Pegaso Currently lusting after: RC30

[Serf27]

[jaffa90]

Remember your first reply from CaNsA.