Tue May 11, 2021 11:07 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Tue May 11, 2021 11:07 pm linkquote
Hi all,

Trying to tune my set up and changed the MJ from 128 to 120 on advice from another forum, now the scoot wont start.

I am running:
1978 P125x
DR177
SIP2 exhaust
24.24 carb
MJ BE2 with 120
P200 air filter
New spark plug

It appears I am getting fuel to the carb
I am getting a spark
compression strangely feels low on the kick

The last time I rode it 2 weeks ago it was fine and went well, I was just trying to get a bit more out of the set up. Its strange that it now will not start.
Tue May 11, 2021 11:53 pm

Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1719
Location: UK (South East)
 
Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1719
Location: UK (South East)
Tue May 11, 2021 11:53 pm linkquote
Won't be related to the change of MJ size. Is there fuel getting from the carb to the crankcase? Take the air filter off and check for spraying of fuel into the venturi, with and without throttle. Also check that your choke is operating correctly
Wed May 12, 2021 3:04 am

Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1777
Location: Rochester, Minnesota
 
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1777
Location: Rochester, Minnesota
Wed May 12, 2021 3:04 am linkquote
Not running isn't the main jet, you should still start and idle using the choke and idle jet or slow run jet.

My two cents on that huge main jet change, from someone who has soft seized 1 cylinder, and melted a second. Measure cylinder head temperature at the very least and see what your getting now. Don't try to keep going leaner and leaner in the search of power. You'll end up walking home. "Go Lean and Walk Home" Measure cylinder head temperature and see where you're running, slowly step down on main jet sizes, get a variety pack. Try to keep you CHT in the 300°F range.

On the scooter I'm tuning now for example using your 128,

128 Runs CHT max 260°F
125 CHT max 295°F
123 CHT max ? Never found out, saw temperature easily climb above 325°, pulled plug and it was white. Keeping in mind it was black from running rich at 128.

I put the 125 back in and happy so far with plug color and temperature.
Wed May 12, 2021 3:43 am

Hooked
PX
Joined: 28 May 2020
Posts: 156
Location: Bognor Regis
 
Hooked
PX
Joined: 28 May 2020
Posts: 156
Location: Bognor Regis
Wed May 12, 2021 3:43 am linkquote
Re: Changed main jet now wont start
craigyc wrote:
Hi all,

Trying to tune my set up and changed the MJ from 128 to 120 on advice from another forum, now the scoot wont start.

I am running:
1978 P125x
DR177
SIP2 exhaust
24.24 carb
MJ BE2 with 120
P200 air filter
New spark plug

It appears I am getting fuel to the carb
I am getting a spark
compression strangely feels low on the kick

The last time I rode it 2 weeks ago it was fine and went well, I was just trying to get a bit more out of the set up. Its strange that it now will not start.
I have exactly the same rig, i have an AC140 BE5 and 122 MJ and this took quite a while to get right combo thanks to this forum. It runs slightly rich on idle but rather have the wide open throttle running right.
Wed May 12, 2021 7:21 am

Hooked
2005 Stellalossi 177 Fe
Joined: 14 Jun 2020
Posts: 137
Location: MA
 
Hooked
2005 Stellalossi 177 Fe
Joined: 14 Jun 2020
Posts: 137
Location: MA
Wed May 12, 2021 7:21 am linkquote
That BE2/MJ120 combo is way too lean for your setup. The MJ120 is in the ballpark, but needs to be paired with a richer mixer tube like a BE5 or you will blow something up.
Wed May 12, 2021 12:07 pm

Hooked
PX
Joined: 28 May 2020
Posts: 156
Location: Bognor Regis
 
Hooked
PX
Joined: 28 May 2020
Posts: 156
Location: Bognor Regis
Wed May 12, 2021 12:07 pm linkquote
I would Put in the be5 ac140 and a 124 jet to be on safe side but have a 122 to hand. To confirm I have dr177 24mm carb, p2 drilled filter, matched carb box to inlet , road 2.0 which is exactly the same as yours. I run a 7 plug on 20 Mile trips but step to an 8 temperature for long runs. The guys on this forum helped me to get this right so you should be right in the ballpark without the stress of having to experiment.
Thu May 13, 2021 1:44 pm

Addicted
Old douglas ..smallie with polini 115..super with nasco 177
Joined: 07 Nov 2013
Posts: 645
Location: New Zealand
 
Addicted
Old douglas ..smallie with polini 115..super with nasco 177
Joined: 07 Nov 2013
Posts: 645
Location: New Zealand
Thu May 13, 2021 1:44 pm linkquote
95%of carb problems are electrical
Checky your lecky

Points/condensor or CDI depending on what you have is more likely
good luck
Thu May 13, 2021 8:08 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Thu May 13, 2021 8:08 pm linkquote
Cheers
Thanks gents for all the input.

@bluecati, I am getting a spark. Would it still be the condensor? If so where do you start? Any tips?
Thu May 13, 2021 8:10 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Thu May 13, 2021 8:10 pm linkquote
swa45 wrote:
Won't be related to the change of MJ size. Is there fuel getting from the carb to the crankcase? Take the air filter off and check for spraying of fuel into the venturi, with and without throttle. Also check that your choke is operating correctly
It appears I am getting fuel. How do I check the choke? Thanks.
Thu May 13, 2021 8:12 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Thu May 13, 2021 8:12 pm linkquote
Re: Changed main jet now wont start
ferriswolf wrote:
I have exactly the same rig, i have an AC140 BE5 and 122 MJ and this took quite a while to get right combo thanks to this forum. It runs slightly rich on idle but rather have the wide open throttle running right.
Thanks, I'll try that once I can get the thing started!
Fri May 14, 2021 11:56 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Fri May 14, 2021 11:56 pm linkquote
Getting a spark
I am getting a spark. Does this look strong enough? If not where to look next?
Video is here.

Fri May 14, 2021 11:57 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Fri May 14, 2021 11:57 pm linkquote
CDI Looks like this.
Alll good with the CDI?



Sat May 15, 2021 12:00 am

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Sat May 15, 2021 12:00 am linkquote
Getting fuel to carb.
It appears that fuel is getting to the carb. Does this look ok?
Sat May 15, 2021 12:10 am

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Sat May 15, 2021 12:10 am linkquote
Head off
Apart from a little bit of a leak on the cylinder head (I assume lapping and tightening a bit tighter). How does the head look and the inside of the cylinder? Looks OK to me but obvioulsy not an expert.
Why is compression low?
Is this usual?
Is this the problem?
How do I fix it?









Sat May 15, 2021 4:59 am

Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3481
Location: Nashville
 
Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3481
Location: Nashville
Sat May 15, 2021 4:59 am linkquote
I'm going to guess you don't have enough compression for the motor to start and run at this point.

Sadly, you have all kinds of detonation based on those photos of you piston crown and cylinder. The leaky head (the natural state of a DR, btw ) probablyl caused enough damage that you eventually killed it.

Funny thing about killing pistons is that a lot of the time, you don't realize it (I don't, anyway...) until it won't start again, because it had juuuust enough compression to keep running with everything hot, but once it stops, it's dead until you sort things out.

If you can pull the cylinder off entirely, you'll most likely find that the piston has heat damage over the exhaust port area and is preventing the rings from seating properly. Depending on how extensive the damage, you might be able to fix it.

First, free the rings and remove them, then sand/file the piston back into something resembling proper shape.

for the rings and cylinder, they most likely have aluminum smeared on them. Get your hands on some muriatic acid and that will burn the aluminum off, but won't effect the cast iron. Wash it all off good, re-assemble, then fix your jetting before you get back out on the road.

As others have noted, your current jetting is way too lean.
Sat May 15, 2021 6:02 am

Hooked
PX
Joined: 28 May 2020
Posts: 156
Location: Bognor Regis
 
Hooked
PX
Joined: 28 May 2020
Posts: 156
Location: Bognor Regis
Sat May 15, 2021 6:02 am linkquote
chandlerman wrote:
I'm going to guess you don't have enough compression for the motor to start and run at this point.

Sadly, you have all kinds of detonation based on those photos of you piston crown and cylinder. The leaky head (the natural state of a DR, btw ) probablyl caused enough damage that you eventually killed it.

Funny thing about killing pistons is that a lot of the time, you don't realize it (I don't, anyway...) until it won't start again, because it had juuuust enough compression to keep running with everything hot, but once it stops, it's dead until you sort things out.

If you can pull the cylinder off entirely, you'll most likely find that the piston has heat damage over the exhaust port area and is preventing the rings from seating properly. Depending on how extensive the damage, you might be able to fix it.

First, free the rings and remove them, then sand/file the piston back into something resembling proper shape.

for the rings and cylinder, they most likely have aluminum smeared on them. Get your hands on some muriatic acid and that will burn the aluminum off, but won't effect the cast iron. Wash it all off good, re-assemble, then fix your jetting before you get back out on the road.

As others have noted, your current jetting is way too lean.
Not so great news for poster Chandlerman, is there anyway of preventing leaky heads on a DR or is this a question of just checking once in a while that the cylinder head bolts are correctly torqued? I would have assume you would visually see a leaky head?
Sat May 15, 2021 6:17 am

Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1777
Location: Rochester, Minnesota
 
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1777
Location: Rochester, Minnesota
Sat May 15, 2021 6:17 am linkquote
chandlerman wrote:
I'm going to guess you don't have enough compression for the motor to start and run at this point.

Sadly, you have all kinds of detonation based on those photos of you piston crown and cylinder. The leaky head (the natural state of a DR, btw ) probablyl caused enough damage that you eventually killed it.

Funny thing about killing pistons is that a lot of the time, you don't realize it (I don't, anyway...) until it won't start again, because it had juuuust enough compression to keep running with everything hot, but once it stops, it's dead until you sort things out.

If you can pull the cylinder off entirely, you'll most likely find that the piston has heat damage over the exhaust port area and is preventing the rings from seating properly. Depending on how extensive the damage, you might be able to fix it.

First, free the rings and remove them, then sand/file the piston back into something resembling proper shape.

for the rings and cylinder, they most likely have aluminum smeared on them. Get your hands on some muriatic acid and that will burn the aluminum off, but won't effect the cast iron. Wash it all off good, re-assemble, then fix your jetting before you get back out on the road.

As others have noted, your current jetting is way too lean.
Something like this, those long streaks are most likely grooves down the cylinder wall or deposited aluminum. In picture #2 those specks of metal around 12:00 o'clock on your piston are most likely where you were to lean, overheating and detonating and melting aluminum.

While it's apart and your cleaning it up check the squish between the cylinder head and piston. It usually pretty large on these over 2.5mm and you can clean that head up and take some of that squish ring off and it will run better. Something closer to 1mm is good.





Sat May 15, 2021 8:29 am

Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1719
Location: UK (South East)
 
Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1719
Location: UK (South East)
Sat May 15, 2021 8:29 am linkquote
ferriswolf wrote:
Not so great news for poster Chandlerman, is there anyway of preventing leaky heads on a DR or is this a question of just checking once in a while that the cylinder head bolts are correctly torqued? I would have assume you would visually see a leaky head?
My solution was to scrap the DR head. I used a CNC milled VMC head with zero squish, so that I could lift the cylinder with a 1.5mm base packer, thus achieving much better port timings, a tight head/cylinder seal, and a respectable squish. Alternatively, just machine the sealing surfaces or sand them on a piece of fine sandpaper on a sheet of glass, using a figure of eight motion.
Sat May 15, 2021 8:43 am

Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3481
Location: Nashville
 
Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3481
Location: Nashville
Sat May 15, 2021 8:43 am linkquote
swa45 wrote:
Alternatively, just machine the sealing surfaces or sand them on a piece of fine sandpaper on a sheet of glass, using a figure of eight motion.
This is what I used to do. I'd lap both the head and the deck of the cylinder, then use Permatex 80967 when I assembled it.

When you lap them, color the surface with a sharpie so you can track your progress and you'll be amazed at how uneven it is when you first start.

To really get serious, I've done similarly to swa45, only I used a BGM 177 head, which actually sits into the bore, so I had that additional sealing surface, plus it makes it super-easy to get the squish to exactly what you want since it's just a matter of using the correct thickness head packer.
Sat May 15, 2021 8:19 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Sat May 15, 2021 8:19 pm linkquote
Oooh Noooo
Thanks for all the input fellas. Very much appreciated. Although the bad news no so much appreciated!

It all makes sense. I will try and get the head off today and see how it looks and report back.

With regards to detonation issues, does this relate to timing? And if so any advice on setting the timing correctly, specifically for this cylinder and the reduction in squish?
Sat May 15, 2021 10:14 pm

Ossessionato
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 2358
Location: california
 
Ossessionato
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 2358
Location: california
Sat May 15, 2021 10:14 pm linkquote
When you have a leak at the head - it lets air in - and it creates super lean mixture /detonation.

There are lots of ways to address it - as the guys noted above.
I would recommend, start by pulling the cylinder. You are this far, sliding the cylinder off isn't that much more.

If you feel comfortable doing it - take the piston off - and you can examine it nicely on the bench. A sharp razor blade, a small piece of sand paper folded, etc. to reshape the ring grooves if they are melted and holding trapping the rings from expanding - like on Christopoher's picture - will get them back in order.

Often, you can clean up the piston, put new rings on, make sure they float freely and don't bind in their slot, clean up the cylinder walls with the muriatic acid - and get back on the road for not much money.

Of course, you would need to lap the head as the others suggested - to get it nice and flat before you reassemble. If you decide to slide the cylinder off - shoot some pics of the piston and see how it looks. As noted - pay close attention to the area near the exhaust port. It is a common place for them to get trapped.
Sun May 16, 2021 6:11 am

Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1777
Location: Rochester, Minnesota
 
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1777
Location: Rochester, Minnesota
Sun May 16, 2021 6:11 am linkquote
After, cleaned up fairly well, while your cleaning up the head, polish the bowl up and get rid of the casting crap (technical term).

Here is a head that has been cleaned up some, and the squish band removed to almost "0" to get a respectable squish and compression ratio. That's not done being cleaned up but it's what I could find, been a few years. Couldn't do much about the porous casting and air bubbles but did get anything sticking up cleaned off.





Fri May 21, 2021 11:05 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Fri May 21, 2021 11:05 pm linkquote
Christopher_55934 wrote:
After, cleaned up fairly well, while your cleaning up the head, polish the bowl up and get rid of the casting crap (technical term).

Here is a head that has been cleaned up some, and the squish band removed to almost "0" to get a respectable squish and compression ratio. That's not done being cleaned up but it's what I could find, been a few years. Couldn't do much about the porous casting and air bubbles but did get anything sticking up cleaned off.
Great advice. Thanks.
Fri May 21, 2021 11:16 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Fri May 21, 2021 11:16 pm linkquote
Piston and cylinder off
Can this piston be cleaned up? Note what looks like a little hole where the rings are seated.
If I get new rings, any particular type?
If I need a new piston do I replace with a DR. Replace needle bearing as well and circlips?











Fri May 21, 2021 11:45 pm

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2864
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2864
Location: London UK
Fri May 21, 2021 11:45 pm linkquote
Not the worst but certainly your starting issue. It would run again but it's tired and not worth spending money on. Either new rings only or a whole new kit (VMC).
Sat May 22, 2021 12:11 am

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Sat May 22, 2021 12:11 am linkquote
Thanks Jack. Which VMC would you go for?
Sat May 22, 2021 1:16 am

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2864
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2864
Location: London UK
Sat May 22, 2021 1:16 am linkquote
I think the stelvio is competent and would bolt straight on.
https://www.sip-scootershop.com/en/product/racing-cylinder-vmc-stelvio-177-cc_84140100

There are faster and much faster but I don't think that's what you are after.
Sat May 22, 2021 4:40 am

Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1777
Location: Rochester, Minnesota
 
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1777
Location: Rochester, Minnesota
Sat May 22, 2021 4:40 am linkquote
Re: Piston and cylinder off
craigyc wrote:
Can this piston be cleaned up? Note what looks like a little hole where the rings are seated.
If I get new rings, any particular type?
If I need a new piston do I replace with a DR. Replace needle bearing as well and circlips?
It's tired as Jack noted, rings look to be full of carbon from blow by. A new VMC kit sitting on the side would be a good idea. The close up spot looks more like one of the locator pins used to keep the rings from rotating. Don't want the ends to be in a port opening.

With all the above being said, clean it up for the experience. Looks like one ring is stuck in the ring groove. I find the more hands on time I get the more I learn. It would be a good setup to do a little porting on. Check squish clean up the cylinder head etc. If the rings are stuck it will most likely run again after being cleaned up. If your feeling particularly curious and want to learn a bit about honing a cylinder and checking ring end gap. Get new rings.

You can get a replacement set of rings, SIP even has a 1st over piston in stock.

https://www.sip-scootershop.com/en/product/piston-dr-177-cc-1o-s_12190100

https://www.sip-scootershop.com/en/product/piston-ring-set-dr-177-cc_20201000



DR177 Alternative Piston.


Sat May 22, 2021 9:13 am

Addicted
'64 Motovespa 150S (177) , '66 Allstate SF, '65 VBB, '66 180SS
Joined: 27 Mar 2013
Posts: 927
Location: S.Salem, NY
 
Addicted
'64 Motovespa 150S (177) , '66 Allstate SF, '65 VBB, '66 180SS
Joined: 27 Mar 2013
Posts: 927
Location: S.Salem, NY
Sat May 22, 2021 9:13 am linkquote
Almost looks like the protruding ends of the ring broke off and wore away that part of the piston above and below the locating pin.
I once had some 2-stroke Saab pistons that came with weak pin clips that came loose and hammered up and down and wore big ovals in the piston.



Sat May 22, 2021 10:58 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Sat May 22, 2021 10:58 pm linkquote
Thanks for all the input gents. I will look into the VMC. There are a few other things I may have a go at over the summer such as 60mm crank so may split the cases and go fo it.

I do like the idea of cleaning it up and seeing what happens though!

The rings snapped so need new ones.

With regards to honing the cylinder, it doesnt look too bad to my untrained eye. On the photos are there any particular areas where you can advise on what the issue is and why it potentially happened and how to fix it? Just to build my own knowledge.

Thanks for the SIP references and the video. Very much appreciated.
Sun May 23, 2021 12:47 am

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2864
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2864
Location: London UK
Sun May 23, 2021 12:47 am linkquote
If going 60mm crank, there are a whole load more options. Having some idea how much power you want and at what rpm it begins, gets really important when choosing parts.

If still wanting VMC, it will need to be the crono 187 for a 60mm crank.

The top ring on that DR kit has been stuck in for quite a while by the looks of it.
Mon May 24, 2021 2:28 am

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Mon May 24, 2021 2:28 am linkquote
Running lean
To summarise and for my own understanding.
1. It appears there has been some sort of soft seize with the rings getting stuck in the piston and then losing compression?
2. The soft seize is down to an air leak at the cylinder head which is shown by the oil stains?
3. Because of the air leak, this caused the cylinder to run lean and therefore increase the temperature?
4. The cylinder and piston could be reused with some cleaning and new rings. But a VMC would be better?
5. Becasue of the air leak and running lean the performance probably wouldn't have been great. And hence why I have been faffing around with main jets etc?

My way initial way forward:
1. Clean up piston and cylinder and get new rings. Lap faces. Potentially machine the head to the desired squish and put everything back together and tune the carb.

In your view, what would be the likely outcome be with this initial way forward? Worthwhile or not.

Second option:
1. VMC possibly with 60mm crank.

I ride the scooter every other weekend for 100k. Not particularly looking for top end but torque and overtaking would be good to get away from big trucks (plenty here in Dubai).
I want reliability and also dont mind tinkering becasue I like it!

I would really appreciate your views and thanks again, all the help above has taught me a lot.
Mon May 24, 2021 4:06 am

Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1777
Location: Rochester, Minnesota
 
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1777
Location: Rochester, Minnesota
Mon May 24, 2021 4:06 am linkquote
Re: Running lean
craigyc wrote:
To summarise and for my own understanding.
1. It appears there has been some sort of soft seize with the rings getting stuck in the piston and then losing compression?
2. The soft seize is down to an air leak at the cylinder head which is shown by the oil stains?
3. Because of the air leak, this caused the cylinder to run lean and therefore increase the temperature?
4. The cylinder and piston could be reused with some cleaning and new rings. But a VMC would be better?
5. Becasue of the air leak and running lean the performance probably wouldn't have been great. And hence why I have been faffing around with main jets etc?

My way initial way forward:
1. Clean up piston and cylinder and get new rings. Lap faces. Potentially machine the head to the desired squish and put everything back together and tune the carb.

In your view, what would be the likely outcome be with this initial way forward? Worthwhile or not.

Second option:
1. VMC possibly with 60mm crank.

I ride the scooter every other weekend for 100k. Not particularly looking for top end but torque and overtaking would be good to get away from big trucks (plenty here in Dubai).
I want reliability and also dont mind tinkering becasue I like it!

I would really appreciate your views and thanks again, all the help above has taught me a lot.
If you like to tinker I would do option A, not out much money, mostly time tinkering and getting to know your engine.

From what I have been told the VMC is a better performing setup, I have no comparison to know that.

You are thinking correctly about being lean causing a motor to overheat.

Get a cylinder head temperature gauge, like the one linked below. That will let you know if your running hot.

https://www.trailtech.net/en-us/shop/accessories/digital-gauges/tto-mini-gauge/tto-temperature/surface-tto-temperature-black-cylinder-head-sensor-14mm/?pfm=Browse
Fri May 28, 2021 9:55 pm

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Fri May 28, 2021 9:55 pm linkquote
Cylinder
What's the best plan of action for the cylinder?

Muriatic acid was mentioned. Does it need to be rebooted or honed or will a light sanding do it?

Going to get started today so it's either upsizing the piston and rings or stick to the original size. I'll make call on that after I've cleaned up the piston.
Sat May 29, 2021 4:02 am

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Sat May 29, 2021 4:02 am linkquote
Piston, what do you think?
Gents, cleaned up the piston as best I could. Plenty of lines down the exhaust port side and a few evidences of smears in other areas. This is the best I can do. What do think? What effect will these lines have on the engine and how to make sure it doesnt happen again?

New piston or just rings?









Sat May 29, 2021 5:19 am

Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3481
Location: Nashville
 
Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3481
Location: Nashville
Sat May 29, 2021 5:19 am linkquote
so long as you get the aluminum off the inside of the cylinder (that's what the muriatic acid is for...it'll dissolve the aluminum but not affect cast iron on Nicasil) and maybe some new rings, that piston has some life left in it.
Sat May 29, 2021 6:36 am

Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
 
Enthusiast
Vespa P125X
Joined: 30 Aug 2017
Posts: 70
Location: Dubai
Sat May 29, 2021 6:36 am linkquote
Got that Chandlerman. Cylinder has cleaned up well. But no expert obviously. I used industrial toilet cleaner. Best I could get!
  DoubleGood Vespa T-Shirts  

All Content Copyright 2005-2021 by Modern Vespa. All Rights Reserved.

Modern Vespa is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.

Shop on Amazon Smile with Modern Vespa

[ Time: 0.0608s ][ Queries: 28 (0.0403s) ][ Debug on ][ 198 ][ Thing Two ]