Dont Touch Idle Screw - GTS 250
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Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Sun Jan 12, 2020 9:55 am quote
Does anybody have any experience with the "dont touch" idle screw having been "adjusted"? And how it affects the running of the scooter? I recently got a 2009 GTS that only very reluctantly starts if you give it full throttle and most of the time not even then. It will idle fairly well after it warms up but does have a faint back fire thru the exhaust coming to a stop. I have replaced the fuel pump, fuel injector, has new battery, a hot spark and good compression. Everything is there for it to start, but it doesnt. Everything else works - instrument lights, headlight, tail/brake lights. Only thing I can think of is that the PO messed with the idle screw. Does that reasoning make sense? Anybody have spare ecm/throttle body?
Hooked
S150, Beo 500ie
Joined: 14 Aug 2019
Posts: 352
Location: Bermuda
Sun Jan 12, 2020 10:10 am quote
Mess with the screw if you want, just make sure you know which direction richens, donít leave it too lean for long, and put it back if it doesnít help.

But these symptoms sound to me more like valves in need of adjustment than an idle mixture issue.
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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Location: Pleasant Hill, CA
Sun Jan 12, 2020 10:11 am quote
Have you cleaned the idle bypass passage yet?
Hooked
50cc Beo, BigBeo
Joined: 30 May 2015
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Location: Chelyabinsk, Russia
Sun Jan 12, 2020 11:09 am quote
I'd say it needs TPS reset. Mixture is incorrect for current "zero" position of butterfly valve.
And yep, idle bypass should be cleaned and checked.
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Sun Jan 12, 2020 12:52 pm quote
jimc wrote:
Have you cleaned the idle bypass passage yet?
I will do that and see what happens. Only has 1750 miles so would not think it would clog so soon, but will do it just to be sure. Spray with carb cleaner? Thanks for the help.
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Sun Jan 12, 2020 1:04 pm quote
Jah wrote:
I'd say it needs TPS reset. Mixture is incorrect for current "zero" position of butterfly valve.
And yep, idle bypass should be cleaned and checked.
Does the TPS reset require a dealer service? Is that what the idle screw changes? Can the idle bypass be cleaned with the throttle body in place or does it have to be removed? Thanks for your help.
Hooked
S150, Beo 500ie
Joined: 14 Aug 2019
Posts: 352
Location: Bermuda
Sun Jan 12, 2020 2:12 pm quote
stevdmo wrote:
jimc wrote:
Have you cleaned the idle bypass passage yet?
I will do that and see what happens. Only has 1750 miles so would not think it would clog so soon, but will do it just to be sure. Spray with carb cleaner? Thanks for the help.
If itís going to clog, it will be due to fuel age, not mileage.
Hooked
2009 250
Joined: 13 Oct 2019
Posts: 155
Location: Canada
Sun Jan 12, 2020 3:31 pm quote
Juan_ORhea wrote:
stevdmo wrote:
jimc wrote:
Have you cleaned the idle bypass passage yet?
I will do that and see what happens. Only has 1750 miles so would not think it would clog so soon, but will do it just to be sure. Spray with carb cleaner? Thanks for the help.
If itís going to clog, it will be due to fuel age, not mileage.
I don't think fuel passes thru the idle bypass passage. Only air from the air cleaner, which, if oiled incorrectly or with the wrong oil could clog the passage, maybe?
Hooked
2009 250
Joined: 13 Oct 2019
Posts: 155
Location: Canada
Sun Jan 12, 2020 3:49 pm quote
stevdmo wrote:
I have replaced the fuel pump, fuel injector, has new battery, a hot spark and good compression.
Did you clean and oil the air cleaner while you were doing these other things?

Last edited by S.Ro on Sun Jan 12, 2020 4:03 pm; edited 1 time in total
Hooked
2009 250
Joined: 13 Oct 2019
Posts: 155
Location: Canada
Sun Jan 12, 2020 4:02 pm quote
stevdmo wrote:
Only has 1750 miles.
With such low mileage I don't think it's a valve lash problem.
Hooked
2009 250
Joined: 13 Oct 2019
Posts: 155
Location: Canada
Sun Jan 12, 2020 4:10 pm quote
stevdmo wrote:
Anybody have spare ecm/throttle body?
I think you would need their keys also.
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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Posts: 38896
Location: Pleasant Hill, CA
Sun Jan 12, 2020 4:30 pm quote
stevdmo wrote:
Jah wrote:
I'd say it needs TPS reset. Mixture is incorrect for current "zero" position of butterfly valve.
And yep, idle bypass should be cleaned and checked.
Does the TPS reset require a dealer service? Is that what the idle screw changes? Can the idle bypass be cleaned with the throttle body in place or does it have to be removed? Thanks for your help.
Did you read the Cheekythomas article I linked to in your other thread?
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Sun Jan 12, 2020 4:53 pm quote
jimc wrote:
stevdmo wrote:
Jah wrote:
I'd say it needs TPS reset. Mixture is incorrect for current "zero" position of butterfly valve.
And yep, idle bypass should be cleaned and checked.
Does the TPS reset require a dealer service? Is that what the idle screw changes? Can the idle bypass be cleaned with the throttle body in place or does it have to be removed? Thanks for your help.
Did you read the Cheekythomas article I linked to in your other thread?
I did read the article (thanks for that) and will reread before I do the cleaning. Maybe it explains in the article if I have access to the port without pulling the throttle body, in any case I will figure it out.
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Sun Jan 12, 2020 5:11 pm quote
S.Ro wrote:
Juan_ORhea wrote:
stevdmo wrote:
jimc wrote:
Have you cleaned the idle bypass passage yet?
I will do that and see what happens. Only has 1750 miles so would not think it would clog so soon, but will do it just to be sure. Spray with carb cleaner? Thanks for the help.
If itís going to clog, it will be due to fuel age, not mileage.
I don't think fuel passes thru the idle bypass passage. Only air from the air cleaner, which, if oiled incorrectly or with the wrong oil could clog the passage, maybe?
Yes, maybe! I removed the air cleaner cover and the sponge filter was very dry with some signs of red oil. Paperwork I got with the scooter showed that air filter oil had been purchased. Maybe filter was over oiled in the past.
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Sun Jan 12, 2020 5:14 pm quote
Juan_ORhea wrote:
stevdmo wrote:
jimc wrote:
Have you cleaned the idle bypass passage yet?
I will do that and see what happens. Only has 1750 miles so would not think it would clog so soon, but will do it just to be sure. Spray with carb cleaner? Thanks for the help.
If itís going to clog, it will be due to fuel age, not mileage.
I did sit for a long time with old ethanol gas in the tank. Gas tank had to be cleaned out.
Hooked
2009 250
Joined: 13 Oct 2019
Posts: 155
Location: Canada
Sun Jan 12, 2020 6:09 pm quote
stevdmo wrote:
Paperwork I got with the scooter showed that air filter oil had been purchased. Maybe filter was over oiled in the past.
Hopefully!

Best way to oil the air cleaner is with a 50-50 mix of gas and engine oil in a ziplock bag. Squeeze excess out and let air dry.
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Granturismo 218
Joined: 04 Feb 2013
Posts: 6290
Location: NWAOK
Sun Jan 12, 2020 11:15 pm quote
A lot of ECUs have been replaced over the years because people are told not to adjust the screw. Think about it for a moment. Can you turn a screw and adjust the voltage output on your voltage regulator?
o, because there's nothing on it to adjust. So if they make something that never needs to be adjusted, do you think they would have put an adjustment screw on it?
If you know where it is, and you turn it and nothing good happens, you can turn it back where it is when you are done messing with it. Out of tens of thousands of these that come out of the factory, what are the odds that one or two wasn't adjusted perfectly at the time of assembly?
The odds are that once you run a few tanks of gas through this thing, without seafoam or any other snake oil, the bike will start running right, and if the idle is too high, you can then turn it back to where it was.
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2966
Location: East Anglia, a dryer region of the UK than Israel
Mon Jan 13, 2020 4:55 am quote
Seafoam is not snake oil!
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2966
Location: East Anglia, a dryer region of the UK than Israel
Mon Jan 13, 2020 4:58 am quote
S.Ro wrote:
stevdmo wrote:
Paperwork I got with the scooter showed that air filter oil had been purchased. Maybe filter was over oiled in the past.
Hopefully!

Best way to oil the air cleaner is with a 50-50 mix of gas and engine oil in a ziplock bag. Squeeze excess out and let air dry.
This /\ /\.

Don't oil Vespa GTS foam filters with oil from spray cans. It isn't good for the sponge material and can cause the sponge filter to start breaking up after a year or so. It can react with the sponge. Only use petrol and oil mix, or better still, buy a new filter because they cost peanuts. Over this side of the pond they cost £5.20 for the original Piaggio/Vespa part and it comes already oiled with the correct oil.
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2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni
Joined: 13 Oct 2012
Posts: 8627
Location: Ashburn, Va. Home to the Internet
Mon Jan 13, 2020 6:06 am quote
Stromrider wrote:
Seafoam is not snake oil!
Just really weak cleaner.
If you're going to use a cleaner use a good one that doesn't have to be used so often, like BG44K.
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Tue Jan 14, 2020 3:06 pm quote
Well, I think I am going from bad to worse. My first question: Will the 250 GTS not start if the oil pressure is too low? My last entry had me pushing the scooter home after it died at a stop sign and would not restart after a short ride. Checked the oil today and it only showed about 1/8" on the dipstick. Is there a safety that prevented it from starting? So today - I knew there is a good size oil leak because there was a oil puddle on the garage floor. I could see that the hose from the engine breather was cracked. I cleaned up the oil in the engine compartment with Dawn and hot water and blew it dry, getting ready to pull the throttle body/ecu to clean the idle bypass. First I pulled the breather hose and found a large slit, but it bothered me that all that oil could be lost thru a breather hose. So I took off the air filter cover and about 4-5 ounces of oil drained out!!!! What-In-The-World is going on here?? Only thing I can think of right now is blow-by forcing oil past the rings, but it never smoked and seemed to have pretty good power for a 250 scooter when it ran. Am I going to have to rebuild a 1750 mile Vespa? I am getting more and more stumped.
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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Tue Jan 14, 2020 4:09 pm quote
stevdmo wrote:
Well, I think I am going from bad to worse. My first question: Will the 250 GTS not start if the oil pressure is too low?
No, there is no such mechanism.
Quote:
My last entry had me pushing the scooter home after it died at a stop sign and would not restart after a short ride. Checked the oil today and it only showed about 1/8" on the dipstick. Is there a safety that prevented it from starting? So today - I knew there is a good size oil leak because there was a oil puddle on the garage floor. I could see that the hose from the engine breather was cracked. I cleaned up the oil in the engine compartment with Dawn and hot water and blew it dry, getting ready to pull the throttle body/ecu to clean the idle bypass. First I pulled the breather hose and found a large slit, but it bothered me that all that oil could be lost thru a breather hose. So I took off the air filter cover and about 4-5 ounces of oil drained out!!!! What-In-The-World is going on here?? Only thing I can think of right now is blow-by forcing oil past the rings, but it never smoked and seemed to have pretty good power for a 250 scooter when it ran. Am I going to have to rebuild a 1750 mile Vespa? I am getting more and more stumped.
It's not unusual to have quite a bit of oil disappear into the breather tube. Either as a mist when the oil level is slightly high and the engine is maxed out, or as a result of being on its left side with the engine running for even a second.

It's why there are those 'bubbles' underneath the air filter, so you know when there's been a bit of oil escaping.
Hooked
2009 250
Joined: 13 Oct 2019
Posts: 155
Location: Canada
Tue Jan 14, 2020 4:31 pm quote
stevdmo wrote:
Checked the oil today and it only showed about 1/8" on the dipstick.
You screwed the dipstick all the way in, right?
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Tue Jan 14, 2020 5:41 pm quote
S.Ro wrote:
stevdmo wrote:
Checked the oil today and it only showed about 1/8" on the dipstick.
You screwed the dipstick all the way in, right?
Right, twice to make sure.
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Tue Jan 14, 2020 5:59 pm quote
jimc wrote:
stevdmo wrote:
Well, I think I am going from bad to worse. My first question: Will the 250 GTS not start if the oil pressure is too low?
No, there is no such mechanism.
Quote:
My last entry had me pushing the scooter home after it died at a stop sign and would not restart after a short ride. Checked the oil today and it only showed about 1/8" on the dipstick. Is there a safety that prevented it from starting? So today - I knew there is a good size oil leak because there was a oil puddle on the garage floor. I could see that the hose from the engine breather was cracked. I cleaned up the oil in the engine compartment with Dawn and hot water and blew it dry, getting ready to pull the throttle body/ecu to clean the idle bypass. First I pulled the breather hose and found a large slit, but it bothered me that all that oil could be lost thru a breather hose. So I took off the air filter cover and about 4-5 ounces of oil drained out!!!! What-In-The-World is going on here?? Only thing I can think of right now is blow-by forcing oil past the rings, but it never smoked and seemed to have pretty good power for a 250 scooter when it ran. Am I going to have to rebuild a 1750 mile Vespa? I am getting more and more stumped.
It's not unusual to have quite a bit of oil disappear into the breather tube. Either as a mist when the oil level is slightly high and the engine is maxed out, or as a result of being on its left side with the engine running for even a second.

It's why there are those 'bubbles' underneath the air filter, so you know when there's been a bit of oil escaping.
Thought maybe it didnt start at the stop sign because of the low oil level. Guess it is just the same hard starting issue. Kind of glad I pushed it home with the oil level being that low. Never ran the bike hard. About 8 - 10 miles around the neighborhood at 20 -30 mph and then about 3 - 4 miles at 45 -55 and 6000 rpm when it died coming to a stop. Never been on its side. Tomorrow I am going to replace the breather hose, clean out the air box and filter, and pull/clean the throttle body. Thanks again for your continuing help.
Hooked
2009 250
Joined: 13 Oct 2019
Posts: 155
Location: Canada
Tue Jan 14, 2020 6:16 pm quote
Sounds like a good time to clean and oil the air filter with engine oil.
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Tue Jan 14, 2020 6:50 pm quote
S.Ro wrote:
Sounds like a good time to clean and oil the air filter with engine oil.
I am thinking the same thing.
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2966
Location: East Anglia, a dryer region of the UK than Israel
Thu Jan 16, 2020 3:18 pm quote
WEB-Tech wrote:
Stromrider wrote:
Seafoam is not snake oil!
Just really weak cleaner.
If you're going to use a cleaner use a good one that doesn't have to be used so often, like BG44K.
Yes, BG is fine and is more powerful (and expensive) but usually not needed. Seafoam or an equivalent works fine on most fuel related issues and if used once a year will prevent sticky fuel deposits in the fuel system and on the injector tip. Shouldn't need using more than that. Not sure a fuel system cleaner of any kind is going to help the OP on this occasion. Worth a try though!
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Granturismo 218
Joined: 04 Feb 2013
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Location: NWAOK
Thu Jan 16, 2020 4:35 pm quote
Stromrider wrote:
Seafoam is not snake oil!
You do know that 28.329% of the active ingredients of Seafoam is actual snakes, in a tincture of diluted mermaid tears? So technically, while it's not pure, unadulterated snake oil, that is one of the principal ingredients, second only to hokum internetium, which is some sort of herb that is also used in the making of suppositories that cure just about everything and, interestingly enough, kills snakes.
You can make homeopathic seafoam by diluting it to 2-whatever number you want to make up ppb in a gallon of gasoline, and it works even better. While not trying to hijack this thread, I've been looking for information about all inclusives in Benidorm and I thought you might be the person to ask. Is there one you would recommend? Reviewers say there are scooters everywhere. Are there a lot of Vespas?
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2966
Location: East Anglia, a dryer region of the UK than Israel
Sat Jan 18, 2020 7:09 am quote
Motovista wrote:
Stromrider wrote:
Seafoam is not snake oil!
You do know that 28.329% of the active ingredients of Seafoam is actual snakes, in a tincture of diluted mermaid tears? So technically, while it's not pure, unadulterated snake oil, that is one of the principal ingredients, second only to hokum internetium, which is some sort of herb that is also used in the making of suppositories that cure just about everything and, interestingly enough, kills snakes.
You can make homeopathic seafoam by diluting it to 2-whatever number you want to make up ppb in a gallon of gasoline, and it works even better. While not trying to hijack this thread, I've been looking for information about all inclusives in Benidorm and I thought you might be the person to ask. Is there one you would recommend? Reviewers say there are scooters everywhere. Are there a lot of Vespas?
Huh, you haven't realised that Mermaid tears were deleted from the mix some 2 years ago. There were complaints from the Mermaid society that they were being abused by using their tears. Someone had to 'poke' them with a stick to make them cry! This is clearly an abuse. So they upped the snake oil a bit instead, but not so you'd notice. It now contains more bean juice too and Thunderfly oil so if anything it's Thunder bean fly oil, NOT snake oil! Even a novice can see that!

Regarding all inclusives, yes there are loads, and lots of Vespa's too. I'd recommend asking Donald Trump as he seems to know everything!! And yes, I'm the one to ask about almost anything..lol.
Hooked
S150, Beo 500ie
Joined: 14 Aug 2019
Posts: 352
Location: Bermuda
Sat Jan 18, 2020 8:46 am quote
All this time I had been doing it all wrong. I had thought Seafoam was oil FOR snakes, not oil FROM snakes. No wonder itís been so ineffective.

And those poor mermaids. In civilized countries the tears are harvested by showing them Hallmark Christmas movies and serving them sushi. The sticks leave scars that reduce the yield when the leather is harvested.
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2966
Location: East Anglia, a dryer region of the UK than Israel
Sat Jan 18, 2020 8:48 am quote
Juan_ORhea wrote:
All this time I had been doing it all wrong. I had thought Seafoam was oil FOR snakes, not oil FROM snakes. No wonder itís been so ineffective.

And those poor mermaids. In civilized countries the tears are harvested by showing them Hallmark Christmas movies and serving them sushi. The sticks leave scars that reduce the yield when the leather is harvested.
Arrrh! I see.
Ossessionato
Yamaha Tricity 155 Urban 2019 - MV Agusta 125 RS 1956 - Yamaha Majesty 250 DX 1998
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Posts: 3938
Location: Latina (Italy)
Sat Jan 18, 2020 9:05 am quote
Stromrider wrote:
Juan_ORhea wrote:
All this time I had been doing it all wrong. I had thought Seafoam was oil FOR snakes, not oil FROM snakes. No wonder itís been so ineffective.

And those poor mermaids. In civilized countries the tears are harvested by showing them Hallmark Christmas movies and serving them sushi. The sticks leave scars that reduce the yield when the leather is harvested.
Arrrh! I see.
Veni, Vidi, Posti
Lx 50 4T, GTS 250, S 150 (Missing in KS), Something Chinese, GT 200 (sold)
Joined: 21 Feb 2011
Posts: 8760
Location: KS USA
Sat Jan 18, 2020 8:16 pm quote
Too late the husband has already touched that.

I wasn't looking...
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Sat Apr 11, 2020 10:23 am quote
I thought I would post a conclusion to the hard starting problem I was having.

After pushing the scooter home I pulled the sparkplug and found it covered in oil and also a catch can connected to the breather hose had several ounces of oil. I knew then the only solution to this was somewhere inside the engine, regardless of the hard starting issue.

I pulled the engine, and removed the head and cylinder. Everything looked normal until I noticed that the top and middle piston ring end gaps were in line, and the compression ring gap was at about 2 oclock from them! Found it! The piston rings were not properly staggered. I removed the piston and rings, I found the piston was cracked between the second and third ring lands. The PO said the Vespa set for several years because of a bad fuel pump, which I had replaced under recall. Now I can see that he went inside the engine, for some reason, and obviously didnt know what he was doing. He was supposed to be an engineer.

I ordered the piston set from Scooterpartsco (Thanks Motovista) and reassembled the engine easily enough. When installing the piston into the cylinder without a ring compressor, the first and second rings went in easily but the compression ring took a little "technique" to get it to slide in, and I can see the knucklehead PO instead of lightly tapping, kept hitting harder and harder until the piston cracked before finally going into the cylinder.

Anyway, after I got the engine back in the scooter, the second push of the starter button the engine fired. Closed throttle, steady idle. The hard starting was caused by a lack of compresion. So I dont have to worry about the "dont touch idle screw" having been "adjusted." I have about 500 miles on my new old Vespa GTS 250. The rings are seating well, no loss of oil at all, and I am amazed at the performance of this little 250. I had a Honda XL 250 back in the day, and this little scooter would run rings around it. Bought a tall windshield and cut it down to the perfect height, probably get a top box and better shock absorbers. Really liking this little scoot.
Hooked
S150, Beo 500ie
Joined: 14 Aug 2019
Posts: 352
Location: Bermuda
Sat Apr 11, 2020 10:34 am quote
Thanks for following up. Good story. I don't have a Piaggio piston handy but I'm looking at an outboard engine piston, and all three of the ring grooves have little dots cast in them so that it's utterly clear where the ring gap is supposed to go. It's hardly subtle. Did you piston have those markings too?
Member
2009 Vespa GTS 250
Joined: 15 Nov 2019
Posts: 26
Location: Charlotte NC
Sun Apr 12, 2020 3:57 am quote
Juan_ORhea wrote:
Thanks for following up. Good story. I don't have a Piaggio piston handy but I'm looking at an outboard engine piston, and all three of the ring grooves have little dots cast in them so that it's utterly clear where the ring gap is supposed to go. It's hardly subtle. Did you piston have those markings too?
No, there were no markings on the piston. I just used the standard 120 degree separation between ring gaps.
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