Idle issues on 2T

The original 2-stroke Genuine scooter and its 4-stroke manual and automatic offspring

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RichF
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Idle issues on 2T

Post by RichF »

Current problem (there's always something!) is stalling and dying while idling. I can get it to start and as long as I am riding and giving it throttle it runs ok, but if I stop it will die within a minute or two unless I am monitoring the sound and give it some gas if it sounds like it is about to die (but sometime it just cuts out too fast). For background I am city driving only (Chicago), so lots of stops signs, constant stop-starts, etc. 2005 Stella 2T with 6,000 miles for which I've had it for four years and 4,000 miles and it seems I always have some type of idling/sputtering issues once or twice every riding season.

I took the carb out and cleaned everything, so I don't think this is a clogged jet. The fuel line was running into the carb so I don't think it's a kinked hose or vapor lock. I checked the spark plug cap and it is on securely. The CDI blue wire into the HT Coil was loose but that is fixed. I just think this is likely an idle speed and idle mix adjustment issue (unless someone has other thoughts) but I can never seem to get the balance between the two right. I've seen some threads on here on how to make these adjustments but it never seems to work and the shop manual is kinda vague on this topic. I'm thinking about getting a digital tach but am still unsure as to what the correct rpm should be.

Also, not sure if this matters, but my MPG has always been poor - about 50 MPG. I know I can increase the idle speed to something very fast to but I hate riding like that - bike too noisy and shaky/vibrating.

Suggestions on how to get this bike reliable again (at least until the next, separate issue pops up)?

Thanks
Last edited by RichF on Thu Jun 27, 2019 4:48 pm, edited 1 time in total.
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Point37
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Post by Point37 »

turn up the idle speed...make sure the gas cap is venting
'10 Triumph Bonneville SE (sold), '00 Yamaha TW200 (sold), '08 Husqvarna SM510R (sold), '05 Honda CBR 600RR (sold), '03 Honda CBR 600RR (sold)
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Stanza
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Post by Stanza »

Did you separate the main jet though? The main jet and jet holder (both brass) come apart, and it's easy to miss the tiny passage in the jet holder. Does your bike smoothly idle down down down and then stall, or is it more of a stumble/hesitation that ends up stalling it out?
RichF
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Post by RichF »

I did not separate the main jet. Whenever I have cleaned this it has always been too tight too separate into parts and I did not want to force it or use any clamps/tools and deform the brass. As far as the stall it usually more of a quick idle down and then die, because sometimes I am able to hear it coming and give it some throttle to keep it going, but I can also say sometimes I can hear a hiccup or break in the idle speed/sound that won't necessarily cause it to die right then but it can signal that it will die soon. When I get home I will see if I can take a video of it idling out. Thanks
RichF
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Post by RichF »

I have some videos if that helps.

The first is starting the bike. It turns over after a couple of tries and runs, but the engine seems to be hunting(?) a bit. I rode it for five minutes or so around the neighborhood. It accelerated fine, went through gears #1-3 fine, but died while in second when I laid off the throttle. https://youtu.be/9RTM9vzpUTE

#2 is trying to restart it after it died. https://youtu.be/LpiZEIkyOk0

#3 is it running again several minutes later, but it's a really weak idle and then it dying. https://youtu.be/WhmmcmeaEu4

#4 is after getting the idle speed much higher (higher than I like to run it) and adjusting the mix screw (brought in in a few half turns). I ran it like this around the blocks and again it dies out within 5 minutes of riding while in 2nd gear and not on the throttle. https://youtu.be/j3QyWOaIceA
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Stanza
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Post by Stanza »

Classic fuel starvation problem. You are still running too lean. I would have another go at the jets, and I would also take out the float/needle to see if the rubber tip of the needle is puffed out. I have seen it before where years worth of additives/ethanol have made the rubber tip of the float needle swell, which slows down and sometimes cuts off the fuel supply even though it's coming out of the line steadily.
RichF
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Post by RichF »

Thanks for the feedback Stanza. I'm going to take the carb out again, rework on the jets (see if I can get the main jet's three parts disassembled) and I ordered a rebuild kit with a new float and needle. I'll post the results.
RichF
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Post by RichF »

Still not working! I recleaned the carb, took apart and soaked all the jets. replaced gaskets, etc. and I'm still having the same issues. For what it's worth when i took the carb apart there was gas in the reserviour under the float (from two days before) and for good measure I put the locking pin holding the seat up back in in case there was an air flow issue.

Video of starting the bike https://youtu.be/dAca6PEonbY,
video of mistiming of idling: https://youtu.be/FxJWK1hX9o8

Again bike strated and rode fine for 5 minutes and then died during idling.

Is this a bad idle screw, air/gas mixture system?
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Stanza
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Post by Stanza »

The way that idle comes up when you disengage the choke is still pointing towards a lean run condition. What size jets do you have in there? Also, have you done any spray testing with wd-40 around the base of the carb to see if you have a base gasket leak?
RichF
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Post by RichF »

Stanza - As far as I know these are stock jets - I have not replaced them in the the four years I've had the bike. I can remove and check them - do they have any markings on them to indicate what the model/size is? I'm not familiar with the gasket leak test - how would I do that? Thanks again.
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tenders
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Post by tenders »

Might not be a jet or mixture adjustment screw problem. Is the air filter cover loose or cracked? Air filter sponge deteriorated or missing? Hose between carb and air cleaner disconnected on either side? How about the diaphragm and needle on the side of the carb opposite the side with the jets, is it cracked or jacked?
RichF
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Post by RichF »

I was out of town so scooter sat for a week. I was going to pull the carb again last night and check the jet sizes per Stanza but decided to take it out for a ride first. It started fine but did die while idling at a stop light about ten minutes in but I was able to start it again within a couple kick starts. It actually ran pretty well. After 15 minutes of going around the neighborhood I pulled in front of my house and just let it idle in neutral to see if it would die (as it had been doing). It ran well at a nice, low, steady idle with out any major hiccupps or stalls for seven or eight minutes. I should mention that I had done this initial riding with the gas cap unscrewed but still in place. I didn't think I had a vapor lock problem but just checking all causes, so after the several minutes idling I screwed the cap back on fully and no difference, same good, steady, low idle. I rode about 15 more minutes venturing a bit farther out and the bike rode fine, including when stopped at a light. Maybe whatever the issue was has resolved itself or maybe after the last carb cleaning something just needed to be flushed out (or maybe whatever the issue was is still there and will hit again soon when I am riding from from home)?

Per Tender's comments I took a look at the air filter. It seems a little dirty but nothing out of the ordinary. However I did notice a crack in the plastic housing it sits in (see attached pics). Also I'm not aware of any sponge in the air filter (as tenders referred to) and don't recall seeing reference to one in the shop manual for the 2T. Is this an issue? Regarding needle and diaphram tenders refers to - is that the needle and float bowl in the reservrour? If so those were both replaced new with the carb cleaning I did last week.

Thanks again
Attachments
Air filter.jpg
Air filter.jpg (57.49 KiB) Viewed 50 times
Air Filter #2.jpg
Air Filter #2.jpg (72.79 KiB) Viewed 50 times
Air filter 3.jpg
Air filter 3.jpg (73.67 KiB) Viewed 50 times
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johnk
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Post by johnk »

I think tenders was talking about the airbox that sits on top of the carburetor, with the filter inside. See this video.

The air filter you took out isn't really crucial, so I don't think you need to worry about that crack. Many people just throw that filter away.
RichF
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Post by RichF »

The airbox with the blue colored cell walls? In that case that was cleaned when the i took out the carb but again I don’t know what the “sponge� being referred to is.
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