Modern Buddy

Ok, I have a Stella 4T with 500 miles on it. I got it in October when it was still pretty warm and it would idle fine in the morning if I used the choke. Now it wont even idle in the morning with the choke on. I haven't wanted to increase the idle speed because the temperature can vary here greatly. It's been about 50 during the day, but it's supposed to be 70 on Thursday, but it has been getting into the mid to low 30s at night. I was thinking that I should increase the idle speed so that it will run a little stronger in the cold air and then when it warms up I can just pull the plug out of the airbox and it will be ok. Does this seem like sound logic? Thanks

Have you had your first service done?

BuddyRaton wrote:Have you had your first service done?

Yes, they have done the first service, but the guy at the authorized Genuine dealer told me that it was the first time he'd done the service on the Stella. So, hard to say if it was done right. Why? What are you thinking?

Can't say what your specific problem is but can tell you what I had to do to get my 4T to idle properly. I am at sea level and found that the Stella was running very lean from the factory but this didn't really show up till the fall when temps dropped. So the first thing I did was to rich en up the mixture by adding a 1/2 turn to the idle mixture screw (anti clockwise) then I put in a hotter plug. At this point it was a little better but the mid and high end was still lifeless and lean. Then I changed the main jet from a #90 (stock) to a #92 and raised the needle with a nylon spacer about a 64th of an inch. All of this got me in the ball park and fine tuning was necessary by balancing out the idle screw and idle mixture screw. Now the scooter runs great through out the full range and idles steady with a snappy throttle response. Hope this will give you a better perspective on resolving your problem. Oh yes I lost about 25mpg as well but it is cold up here averaging 40 deg/F but am still breaking 100mpg.
Cheers

Crew wrote:Can't say what your specific problem is but can tell you what I had to do to get my 4T to idle properly. I am at sea level and found that the Stella was running very lean from the factory but this didn't really show up till the fall when temps dropped. So the first thing I did was to rich en up the mixture by adding a 1/2 turn to the idle mixture screw (anti clockwise) then I put in a hotter plug. At this point it was a little better but the mid and high end was still lifeless and lean. Then I changed the main jet from a #90 (stock) to a #92 and raised the needle with a nylon spacer about a 64th of an inch. All of this got me in the ball park and fine tuning was necessary by balancing out the idle screw and idle mixture screw. Now the scooter runs great through out the full range and idles steady with a snappy throttle response. Hope this will give you a better perspective on resolving your problem. Oh yes I lost about 25mpg as well but it is cold up here averaging 40 deg/F but am still breaking 100mpg.
Cheers

Crew,

Thanks for the feedback. I did read about your whole rejetting in your thread previously and gave it some thought, but I figured that since its so much colder up there, you'd need a richer mixture than me and that rejetting wouldn't really be necessary here. I suppose I should take a look at the plug, but I sort of assumed that the shop would have made adjustments at the first service, but that is probably extremely optimistic. Another thing I have been thinking is to check the choke cable, I know that I saw that Maximus53 was having a problem with his choke cable being too long. I'll look at the plug to get an idea of how it's running too.

But does anyone else see the logic in my initial proposal?

Crew,

Thanks for the feedback. I did read about your whole rejetting in your thread previously and gave it some thought, but I figured that since its so much colder up there, you'd need a richer mixture than me and that rejetting wouldn't really be necessary here. I suppose I should take a look at the plug, but I sort of assumed that the shop would have made adjustments at the first service, but that is probably extremely optimistic. Another thing I have been thinking is to check the choke cable, I know that I saw that Maximus53 was having a problem with his choke cable being too long. I'll look at the plug to get an idea of how it's running too.

But does anyone else see the logic in my initial proposal?

I would invest the 30 seconds and check that your choke is full engaging. A LOT easier than rejetting etc! When you pull the choke there is a little arm that moves, it should move all the way to the stop. if you pull the choke all the way and can still move the arm farther with your finger then the choke is not fully open?/closed?[/quote]

Maximus53 wrote:

Crew,

Thanks for the feedback. I did read about your whole rejetting in your thread previously and gave it some thought, but I figured that since its so much colder up there, you'd need a richer mixture than me and that rejetting wouldn't really be necessary here. I suppose I should take a look at the plug, but I sort of assumed that the shop would have made adjustments at the first service, but that is probably extremely optimistic. Another thing I have been thinking is to check the choke cable, I know that I saw that Maximus53 was having a problem with his choke cable being too long. I'll look at the plug to get an idea of how it's running too.

But does anyone else see the logic in my initial proposal?

I would invest the 30 seconds and check that your choke is full engaging. A LOT easier than rejetting etc! When you pull the choke there is a little arm that moves, it should move all the way to the stop. if you pull the choke all the way and can still move the arm farther with your finger then the choke is not fully open?/closed?

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Yes. And all you need is 1 Phillips screwdriver to make your choke cable right.
Loosen the clamp holding the cable housing at the carb..... Slide the housing out further away from the carb. Then re-tighten the clamp..... 30 seconds.... Your choke should kill the warm motor
at idle when you yank it out...
Good luck

Ok, so I checked the choke and it wasn't fully engaging, but I don't think it was enough to make a difference. I fixed it and then started the bike cold, but it still didn't idle. So, I turned the idle screw 1/4 turn and it didn't make much of a difference, but I didn't want to make any drastic changes. This is a pic of the carb:




The screw on the left with the spring on it is the idle screw. Is the screw next to it a mixture screw? If so, why does mine look like the head got broken off? Does this look right? Finally, while I was poking around, I also looked for the airbox cold weather plug. I didn't see a hole or a plug. Anybody know where it is? Or is this just a 2 stroke thing? Thanks

The 'Cold Weather Plug' is a two stroke thing so don't worry about that.

The angled screw to the right of the idle speed screw is indeed the low speed mixture screw.
For EPA reasons it is supposedly tamper proof but I don't know how they achieved that unless it was modified after assembly......others will have to chime in to determine if that is how they all are. (meaning the screw head).

In your situation, since the idle problem is a recent development, I would suspect the low speed jet is partially obstructed with a bit of debris.
This orifice is tiny with a capital 'T' and anything will disrupt its flow.

This requires removal of the carb, take off the float bowl, remove and clean the jet and then re-assembly.

I would recommend a mixture screw replacement assuming it should have a normal screw head but for the sake of experimentation try to turn what you have 1/2 turn counterclockwise (out) with a needle nose pliers.
I'm speculating the jet may be OK and the incredibly lean EPA setting is just too lean for this engine.

Good luck,
Rob

That is a "D" shaped screw head, Honda uses them on air mixture screws too. The screw may also be loctited in place so you "can't" move them...

Snap-on man has that tool...just sayin'

viney266 wrote:That is a "D" shaped screw head, Honda uses them on air mixture screws too. The screw may also be loctited in place so you "can't" move them...

Snap-on man has that tool...just sayin'

Easy to make a tool for that out of thin-wall brass tubing from the hobby shop as well.

I appreciate everyone's feedback here. I wasn't able to tinker with the idle at all since my last post because the clutch cable snapped. I then had it towed to a dealer since I don't have the cable and I want a second opinion with the front end issues I have been having. They ordered the clutch cable and will be putting it in next week and then tending to the front end. I'll keep everyone posted on the outcome.

magnato1 wrote:I appreciate everyone's feedback here. I wasn't able to tinker with the idle at all since my last post because the clutch cable snapped. I then had it towed to a dealer since I don't have the cable and I want a second opinion with the front end issues I have been having. They ordered the clutch cable and will be putting it in next week and then tending to the front end. I'll keep everyone posted on the outcome.

I suggest you order yourself a second clutch cable to keep on hand if it snaps. I hear it is really easy o replace yourself (I have yet to replace mine, miraculously I have been running on the same one for over 15k miles)

Thanks Lokky,

I had the shop order a spare for me when I dropped it off. I'm so mad because I've been meaning to get the cable for a while as I've heard that they snap, and I just kept putting it off. Live and learn I suppose.

Ok, I am revisiting this thread because after getting the first service done correctly, the bike still doesn't idle when it's cold (it doesn't get that cold in Santa Barbara).

So, I today, I pulled the carb off and took some pictures of what the inside of my carb looks like when the choke is fully closed. The first pic shows this (not fully closed). The second pic shows me closing it fully. Will this affect the bike's ability to idle when cold? I also played with the air screw per the instructions in the 4T manual, but the problem is that I don't have a tach, so I just guessed on when it was at 1,200 rpms. Anyways, I couldn't figure out how to unhook the cable from the choke pull (by the petcock). Anyone know how to adjust this? Anyone have any suggestions? Thanks

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My choke does the same thing, doesn't fully close when you pull the choke plunger out. My shop said they thought it was fine. However, I never need to use the choke. Bike starts on the first kick or first crank of the starter. Even in winter. With out the choke.

Crew wrote:So the first thing I did was to rich en up the mixture by adding a 1/2 turn to the idle mixture screw (anti clockwise)...

I thought that the idle mixture screw on these Keihin carbs was an air screw... so it would lean the mixture by turning it counter-clockwise. Anyone know for sure which it is?

I guess I could turn the screw out until the engine starts sputtering. Then see if the choke makes it better or worse.

Hey - Does anyone know for certain if the mixture screw on the Keihin carb is an air screw or a fuel screw? I've seen it referred to as both, and the 4T shop manual refers to it as the air screw. Of course, that doesn't necessarily mean anything.

I tried adjusting it and seeing how the choke would affect things, but I couldn't determine much by doing that. The engine seems to be running well where I've adjusted it, but it would still be nice to know if turning it counter-clockwise is adding fuel or air to the mix

misterbrackets wrote:Hey - Does anyone know for certain if the mixture screw on the Keihin carb is an air screw or a fuel screw? I've seen it referred to as both, and the 4T shop manual refers to it as the air screw. Of course, that doesn't necessarily mean anything.

I tried adjusting it and seeing how the choke would affect things, but I couldn't determine much by doing that. The engine seems to be running well where I've adjusted it, but it would still be nice to know if turning it counter-clockwise is adding fuel or air to the mix

I don't have a 4t or a 4t manual......However.....If it is a 'Air' screw, upon removal it will have a stabilizing spring.....nothing more....the tapered end will be a bit blunt at the tip.
A 'Mixture' screw upon removal, will have a stabilizing spring, a tiny flat washer below the spring, and a tiny 'O' ring acting as a seal between the screw and the hole it is threaded into. The needle will be extremely fine and end as a point.....like a needle.

Air screws are turned clockwise to enrich the mixture......mixture screws are turned counterclockwise to enrich the mixture.

With any amount of luck your manual will have a detailed drawing or photo.

Regards,
Rob

Thanks for the info, Robbie. I found this video of someone taking a Keihin PB18 carb apart. At 3:09, they remove the mixture screw. Looks like it has a little washer next to the spring, but a blunt tip to the screw. Interesting.....

Edit : I just took a look at the manual and there is a small 'O' ring as well. Ok, so now I am more inclined to think this is a fuel mixture screw. I guess I could just take mine out and see for sure