GTS 300 engine replacement.
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Enthusiast
2008 Vespa LX 50, 1964 Vespa 150 VBB
Joined: 03 May 2013
Posts: 96
Location: Brooklyn, NY
Sat Dec 07, 2019 8:45 am quote
Hi Vespa lovers.
I have a project 300 cc GTS with a seized engine, the head is ok, crank is bad. After pricing the replacement crank and all the parts that i will have to replaced I deided to get a salvaged bike with a good motor and do a swap. All the 300s were too expensive to jutify the purchase, so I got my hands on GTS 250. I got the engine out and now i am thinking on putting it back into 300. The only thing i am missing on is the throttle body. I dont have a key for 250 so I have to pay to get it cut and programmed. I will also have to swap the plug from the stator or replace the stator.
Quick question: do you think the throttle body on 250 is different from 300? can i use 300 body on 250 engine?
Thanks

P.S. I figured judging by the part number throttles body are different. What about swapping the top end including cylinder head, piston and keeping the 300cc throttle body. the rest should fit, correct?
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 287
Location: California
Fri Dec 13, 2019 4:23 pm quote
Re: GTS 300 engine replacement.
hvost2000 wrote:
Hi Vespa lovers.
I have a project 300 cc GTS with a seized engine, the head is ok, crank is bad. After pricing the replacement crank and all the parts that i will have to replaced I deided to get a salvaged bike with a good motor and do a swap. All the 300s were too expensive to jutify the purchase, so I got my hands on GTS 250. I got the engine out and now i am thinking on putting it back into 300. The only thing i am missing on is the throttle body. I dont have a key for 250 so I have to pay to get it cut and programmed. I will also have to swap the plug from the stator or replace the stator.
Quick question: do you think the throttle body on 250 is different from 300? can i use 300 body on 250 engine?
Thanks

P.S. I figured judging by the part number throttles body are different. What about swapping the top end including cylinder head, piston and keeping the 300cc throttle body. the rest should fit, correct?
Here's a few pointers:
- The stroke & bore is different between the two motors, and I'm fairly certain that the 300 cylinder/piston will not work with the 250 crank (it would be extremely low on compression)
- The heads should be the same, not much to gain from one over the other, but the camshaft is rumored to be more aggressive in the 300
- The ECU is on the throttle body, and I believe the 250 ECU is incompatible with the 300s wiring. I would suggest using the 300 throttle body on the 250 block. You may have to use the 300s stator also. Tuning may be a bit off, but should actually be better if you have any performance airflow modifications. (intake, exhaust, etc.)
- I would want the 300 ECU anyway, the 250 is not as easily modifiable. It is possible to load new tunes on the 300 ECU for not a lot of money. The 250 ECU isn't as easy. I own a highly modified 250, and have considered buying a 300 throttle body and related wiring just to be able to properly tune it.
Hooked
Vespa GTS 150 3v SUPER. Vespa V100 x 1. Lambretta Li150 x 1. Px 125 x 2. Px 200 x 1 (red bull special) T5 Classic x 1. Vespa Cosa x 2.CF moto 650mt
Joined: 31 May 2015
Posts: 384
Location: Perth Australia
Mon Dec 16, 2019 2:55 am quote
Re: GTS 300 engine replacement.
AnnDee4444 wrote:
hvost2000 wrote:
Hi Vespa lovers.
I have a project 300 cc GTS with a seized engine, the head is ok, crank is bad. After pricing the replacement crank and all the parts that i will have to replaced I deided to get a salvaged bike with a good motor and do a swap. All the 300s were too expensive to jutify the purchase, so I got my hands on GTS 250. I got the engine out and now i am thinking on putting it back into 300. The only thing i am missing on is the throttle body. I dont have a key for 250 so I have to pay to get it cut and programmed. I will also have to swap the plug from the stator or replace the stator.
Quick question: do you think the throttle body on 250 is different from 300? can i use 300 body on 250 engine?
Thanks

P.S. I figured judging by the part number throttles body are different. What about swapping the top end including cylinder head, piston and keeping the 300cc throttle body. the rest should fit, correct?
Here's a few pointers:
- The stroke & bore is different between the two motors, and I'm fairly certain that the 300 cylinder/piston will not work with the 250 crank (it would be extremely low on compression)
- The heads should be the same, not much to gain from one over the other, but the camshaft is rumored to be more aggressive in the 300
- The ECU is on the throttle body, and I believe the 250 ECU is incompatible with the 300s wiring. I would suggest using the 300 throttle body on the 250 block. You may have to use the 300s stator also. Tuning may be a bit off, but should actually be better if you have any performance airflow modifications. (intake, exhaust, etc.)
- I would want the 300 ECU anyway, the 250 is not as easily modifiable. It is possible to load new tunes on the 300 ECU for not a lot of money. The 250 ECU isn't as easy. I own a highly modified 250, and have considered buying a 300 throttle body and related wiring just to be able to properly tune it.
Hi,

It appears from your write up you have some experience with ECUs. A couple of days ago, I placed a discussion on modern vespa re a problem with "ECU OMG what now".
Ive come to the conclusion following on from this topic that my ECU is toast and I need another. I do have a spare one. Its an ECU from a 2014 scooter. It will be going onto a 2008 scooter. Both are 300cc
Firstly, I would like to know if this would be compatible and secondly, is it easy to re program?

Thanks,
Tom.
Hooked
Vespa GTS 150 3v SUPER. Vespa V100 x 1. Lambretta Li150 x 1. Px 125 x 2. Px 200 x 1 (red bull special) T5 Classic x 1. Vespa Cosa x 2.CF moto 650mt
Joined: 31 May 2015
Posts: 384
Location: Perth Australia
Mon Dec 16, 2019 2:57 am quote
Re: GTS 300 engine replacement.
AnnDee4444 wrote:
hvost2000 wrote:
Hi Vespa lovers.
I have a project 300 cc GTS with a seized engine, the head is ok, crank is bad. After pricing the replacement crank and all the parts that i will have to replaced I deided to get a salvaged bike with a good motor and do a swap. All the 300s were too expensive to jutify the purchase, so I got my hands on GTS 250. I got the engine out and now i am thinking on putting it back into 300. The only thing i am missing on is the throttle body. I dont have a key for 250 so I have to pay to get it cut and programmed. I will also have to swap the plug from the stator or replace the stator.
Quick question: do you think the throttle body on 250 is different from 300? can i use 300 body on 250 engine?
Thanks

P.S. I figured judging by the part number throttles body are different. What about swapping the top end including cylinder head, piston and keeping the 300cc throttle body. the rest should fit, correct?
Here's a few pointers:
- The stroke & bore is different between the two motors, and I'm fairly certain that the 300 cylinder/piston will not work with the 250 crank (it would be extremely low on compression)
- The heads should be the same, not much to gain from one over the other, but the camshaft is rumored to be more aggressive in the 300
- The ECU is on the throttle body, and I believe the 250 ECU is incompatible with the 300s wiring. I would suggest using the 300 throttle body on the 250 block. You may have to use the 300s stator also. Tuning may be a bit off, but should actually be better if you have any performance airflow modifications. (intake, exhaust, etc.)
- I would want the 300 ECU anyway, the 250 is not as easily modifiable. It is possible to load new tunes on the 300 ECU for not a lot of money. The 250 ECU isn't as easy. I own a highly modified 250, and have considered buying a 300 throttle body and related wiring just to be able to properly tune it.
Hi,

It appears from your write up you have some experience with ECUs. A couple of days ago, I placed a discussion on modern vespa re a problem with "ECU OMG what now".
Ive come to the conclusion following on from this topic that my ECU is toast and I need another. I do have a spare one. Its an ECU from a 2014 scooter. It will be going onto a 2008 scooter.
Firstly, I would like to know if this would be compatible and secondly, is it easy to re program?

Thanks,
Tom.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 287
Location: California
Mon Dec 16, 2019 7:15 am quote
Re: GTS 300 engine replacement.
tom jones wrote:
AnnDee4444 wrote:
hvost2000 wrote:
Hi Vespa lovers.
I have a project 300 cc GTS with a seized engine, the head is ok, crank is bad. After pricing the replacement crank and all the parts that i will have to replaced I deided to get a salvaged bike with a good motor and do a swap. All the 300s were too expensive to jutify the purchase, so I got my hands on GTS 250. I got the engine out and now i am thinking on putting it back into 300. The only thing i am missing on is the throttle body. I dont have a key for 250 so I have to pay to get it cut and programmed. I will also have to swap the plug from the stator or replace the stator.
Quick question: do you think the throttle body on 250 is different from 300? can i use 300 body on 250 engine?
Thanks

P.S. I figured judging by the part number throttles body are different. What about swapping the top end including cylinder head, piston and keeping the 300cc throttle body. the rest should fit, correct?
Here's a few pointers:
- The stroke & bore is different between the two motors, and I'm fairly certain that the 300 cylinder/piston will not work with the 250 crank (it would be extremely low on compression)
- The heads should be the same, not much to gain from one over the other, but the camshaft is rumored to be more aggressive in the 300
- The ECU is on the throttle body, and I believe the 250 ECU is incompatible with the 300s wiring. I would suggest using the 300 throttle body on the 250 block. You may have to use the 300s stator also. Tuning may be a bit off, but should actually be better if you have any performance airflow modifications. (intake, exhaust, etc.)
- I would want the 300 ECU anyway, the 250 is not as easily modifiable. It is possible to load new tunes on the 300 ECU for not a lot of money. The 250 ECU isn't as easy. I own a highly modified 250, and have considered buying a 300 throttle body and related wiring just to be able to properly tune it.
Hi,

It appears from your write up you have some experience with ECUs. A couple of days ago, I placed a discussion on modern vespa re a problem with "ECU OMG what now".
Ive come to the conclusion following on from this topic that my ECU is toast and I need another. I do have a spare one. Its an ECU from a 2014 scooter. It will be going onto a 2008 scooter.
Firstly, I would like to know if this would be compatible and secondly, is it easy to re program?

Thanks,
Tom.
As long as you have the correct type of ECU, believe everything should work. As far as I know, there are two types that Piaggio used on the GTS: MIU1 & MIU3 (sometimes referred to as MIUG1 or MIUG3). The 2014 is most likely a MIU3, but I am not sure about the 2008 (My 2007 250 is a MIU1). I am not 100% sure what will be needed to get the immobilizer working though, as I don't have any experience with that.

If it they both happen to be a MIU3, but the 2014 ECU is from a 125cc (or anything besides a 300 GTS), the tune could be incorrect for the motor. See this post for how to load tunes on the MIU3 ECU: http://modernvespa.com/forum/topic150992
Hooked
Vespa GTS 150 3v SUPER. Vespa V100 x 1. Lambretta Li150 x 1. Px 125 x 2. Px 200 x 1 (red bull special) T5 Classic x 1. Vespa Cosa x 2.CF moto 650mt
Joined: 31 May 2015
Posts: 384
Location: Perth Australia
Tue Dec 17, 2019 4:31 am quote
Re: GTS 300 engine replacement.
AnnDee4444 wrote:
tom jones wrote:
AnnDee4444 wrote:
hvost2000 wrote:
Hi Vespa lovers.
I have a project 300 cc GTS with a seized engine, the head is ok, crank is bad. After pricing the replacement crank and all the parts that i will have to replaced I deided to get a salvaged bike with a good motor and do a swap. All the 300s were too expensive to jutify the purchase, so I got my hands on GTS 250. I got the engine out and now i am thinking on putting it back into 300. The only thing i am missing on is the throttle body. I dont have a key for 250 so I have to pay to get it cut and programmed. I will also have to swap the plug from the stator or replace the stator.
Quick question: do you think the throttle body on 250 is different from 300? can i use 300 body on 250 engine?
Thanks

P.S. I figured judging by the part number throttles body are different. What about swapping the top end including cylinder head, piston and keeping the 300cc throttle body. the rest should fit, correct?
Tom.

Here's a few pointers:
- The stroke & bore is different between the two motors, and I'm fairly certain that the 300 cylinder/piston will not work with the 250 crank (it would be extremely low on compression)
- The heads should be the same, not much to gain from one over the other, but the camshaft is rumored to be more aggressive in the 300
- The ECU is on the throttle body, and I believe the 250 ECU is incompatible with the 300s wiring. I would suggest using the 300 throttle body on the 250 block. You may have to use the 300s stator also. Tuning may be a bit off, but should actually be better if you have any performance airflow modifications. (intake, exhaust, etc.)
- I would want the 300 ECU anyway, the 250 is not as easily modifiable. It is possible to load new tunes on the 300 ECU for not a lot of money. The 250 ECU isn't as easy. I own a highly modified 250, and have considered buying a 300 throttle body and related wiring just to be able to properly tune it.
Hi,

It appears from your write up you have some experience with ECUs. A couple of days ago, I placed a discussion on modern vespa re a problem with "ECU OMG what now".
Ive come to the conclusion following on from this topic that my ECU is toast and I need another. I do have a spare one. Its an ECU from a 2014 scooter. It will be going onto a 2008 scooter.
Firstly, I would like to know if this would be compatible and secondly, is it easy to re program?

Thanks,
Tom.
As long as you have the correct type of ECU, believe everything should work. As far as I know, there are two types that Piaggio used on the GTS: MIU1 & MIU3 (sometimes referred to as MIUG1 or MIUG3). The 2014 is most likely a MIU3, but I am not sure about the 2008 (My 2007 250 is a MIU1). I am not 100% sure what will be needed to get the immobilizer working though, as I don't have any experience with that.

If it they both happen to be a MIU3, but the 2014 ECU is from a 125cc (or anything besides a 300 GTS), the tune could be incorrect for the motor. See this post for how to load tunes on the MIU3 ECU: http://modernvespa.com/forum/topic150992
Thank you for getting back to me.
Ive done some homework and the 2014 300cc ecu has been cross referenced to the same one as originally fitted to the 2008. Phew. I'll change it out and see how she goes. Thanks and Merry Xmas.
Addicted
2010 gts 300 super. 09 MP3 500 lite
Joined: 02 Apr 2013
Posts: 630
Location: tampa
Tue Dec 17, 2019 6:07 am quote
there isnt gonna be that much difference in ecu mapping between 244cc and 268cc. the ecu operates in closed loop so it will adjust fuel curve as needed. modifying airbox and adding a muffler with no cat would require more ecu remapping than the cc change. or driving from the ocean to 5000ft elevation. I have run my 300 on ecu from 250 no issues. the only real issue here is 26pin ecu and 32pin ecu. the later arrived in 2015 with antilock and traction control. so as long as it plugs into harness you will be okay.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 287
Location: California
Tue Dec 17, 2019 8:28 am quote
jerryd wrote:
there isnt gonna be that much difference in ecu mapping between 244cc and 268cc. the ecu operates in closed loop so it will adjust fuel curve as needed. modifying airbox and adding a muffler with no cat would require more ecu remapping than the cc change. or driving from the ocean to 5000ft elevation. I have run my 300 on ecu from 250 no issues. the only real issue here is 26pin ecu and 32pin ecu. the later arrived in 2015 with antilock and traction control. so as long as it plugs into harness you will be okay.
I was more concerned with the tune differences when using a 125cc ECU on the 250cc.

Any idea if it's possible to run a MIU3 ECU with the 250 wiring & dash? Or does the MIU3 = 32 pin?
Addicted
2010 gts 300 super. 09 MP3 500 lite
Joined: 02 Apr 2013
Posts: 630
Location: tampa
Tue Dec 17, 2019 11:22 am quote
I cant comment on using a 125 ecu on a 250. we didnt get the gts 125 here in usa. so I am not familiar with what parts were even used. I would guess not possible from that much cc change.

the miu3 ecu has more pinouts to communicate with antilock and traction control. there are different wire harnesses for the gts with 26 pin miu1 ecu because of the 250 electronic dash and the again because of the gtv vs gts. but none of that changes the tb/ecu. its 100% not practical to run a 32 pin ecu on a 26 pin harness.
Enthusiast
2008 Vespa LX 50, 1964 Vespa 150 VBB
Joined: 03 May 2013
Posts: 96
Location: Brooklyn, NY
Wed Jan 01, 2020 10:27 am quote
Re: GTS 300 engine replacement.
tom jones wrote:
AnnDee4444 wrote:
hvost2000 wrote:
Hi Vespa lovers.
I have a project 300 cc GTS with a seized engine, the head is ok, crank is bad. After pricing the replacement crank and all the parts that i will have to replaced I deided to get a salvaged bike with a good motor and do a swap. All the 300s were too expensive to jutify the purchase, so I got my hands on GTS 250. I got the engine out and now i am thinking on putting it back into 300. The only thing i am missing on is the throttle body. I dont have a key for 250 so I have to pay to get it cut and programmed. I will also have to swap the plug from the stator or replace the stator.
Quick question: do you think the throttle body on 250 is different from 300? can i use 300 body on 250 engine?
Thanks

P.S. I figured judging by the part number throttles body are different. What about swapping the top end including cylinder head, piston and keeping the 300cc throttle body. the rest should fit, correct?
Here's a few pointers:
- The stroke & bore is different between the two motors, and I'm fairly certain that the 300 cylinder/piston will not work with the 250 crank (it would be extremely low on compression)
- The heads should be the same, not much to gain from one over the other, but the camshaft is rumored to be more aggressive in the 300
- The ECU is on the throttle body, and I believe the 250 ECU is incompatible with the 300s wiring. I would suggest using the 300 throttle body on the 250 block. You may have to use the 300s stator also. Tuning may be a bit off, but should actually be better if you have any performance airflow modifications. (intake, exhaust, etc.)
- I would want the 300 ECU anyway, the 250 is not as easily modifiable. It is possible to load new tunes on the 300 ECU for not a lot of money. The 250 ECU isn't as easy. I own a highly modified 250, and have considered buying a 300 throttle body and related wiring just to be able to properly tune it.
Hi,

It appears from your write up you have some experience with ECUs. A couple of days ago, I placed a discussion on modern vespa re a problem with "ECU OMG what now".
Ive come to the conclusion following on from this topic that my ECU is toast and I need another. I do have a spare one. Its an ECU from a 2014 scooter. It will be going onto a 2008 scooter.
Firstly, I would like to know if this would be compatible and secondly, is it easy to re program?

Thanks,
Tom.
I beleive 2014 did not have ABS. So the swap should be 1 for 1 and you will need a key that will communicate with the other throttle body- they go in pairs.
Enthusiast
2008 Vespa LX 50, 1964 Vespa 150 VBB
Joined: 03 May 2013
Posts: 96
Location: Brooklyn, NY
Wed Jan 01, 2020 10:30 am quote
Just giving you all a quick update. I tried both 250 cc throttle body and 300 throttle body and they both worked fine. i decided to keep the 250 cc throttle body. I also had to swap the stator because of the difference in plugs, that was easy. Also I had to replace/ rewire the O2 sensor on the 250 engine as the plug was different ( 2 pin connector vs 4 pin on 250cc )
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