Fri Jun 19, 2020 1:02 pm

bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: 26 Sep 2013
Posts: 6012
Location: So Cal
 
bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: 26 Sep 2013
Posts: 6012
Location: So Cal
Fri Jun 19, 2020 1:02 pm linkquote
Update:

140AC / BE5 / 118 - 20° timing

Has a couple hours on it now, multiple high speed runs, one full 2-mile uphill WOT torture test. Seems good, runs strong but suspiciously cool ... couldn't get the temp above 248°.



Fri Jun 19, 2020 1:20 pm

Molto Verboso
Vespa
Joined: 19 Jun 2007
Posts: 1320
Location: California
 
Molto Verboso
Vespa
Joined: 19 Jun 2007
Posts: 1320
Location: California
Fri Jun 19, 2020 1:20 pm linkquote
hopefully the burn pattern gets wider. Wonder if lowering the exhaust port to below piston crown might help.
Fri Jun 19, 2020 1:36 pm

Hooked
P Series / Li / LML / Motobi
Joined: 24 Jun 2019
Posts: 458
Location: UK - 3rd Rock From the Sun
 
Hooked
P Series / Li / LML / Motobi
Joined: 24 Jun 2019
Posts: 458
Location: UK - 3rd Rock From the Sun
Fri Jun 19, 2020 1:36 pm linkquote
dropping the exhaust port to meet or sit slightly lower than the piston will in all likelyhood shift your power across the rev range and move it more into the overrun.

seen that done to an older malossi and PM tuning used to do it on there malossi kits..
Sat Jun 20, 2020 5:06 am

Molto Verboso
Vespa
Joined: 19 Jun 2007
Posts: 1320
Location: California
 
Molto Verboso
Vespa
Joined: 19 Jun 2007
Posts: 1320
Location: California
Sat Jun 20, 2020 5:06 am linkquote
Gravelrash2004 wrote:
dropping the exhaust port to meet or sit slightly lower than the piston will in all likelyhood shift your power across the rev range and move it more into the overrun.

seen that done to an older malossi and PM tuning used to do it on there malossi kits..
is that good or bad or possibly both depending on your point of view?
Sat Jun 20, 2020 5:07 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 Jun 20, 2020 5:07 am linkquote
SoCalGuy wrote:
Update:

140AC / BE5 / 118 - 20° timing

Has a couple hours on it now, multiple high speed runs, one full 2-mile uphill WOT torture test. Seems good, runs strong but suspiciously cool ... couldn't get the temp above 248°.
Any chance you had an air leak on the old top end that's now fixed?
Sat Jun 20, 2020 5:13 am

Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

 
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

Sat Jun 20, 2020 5:13 am linkquote
Hopefully current results are good.
Sat Jun 20, 2020 12:12 pm

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2867
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2867
Location: London UK
Sat Jun 20, 2020 12:12 pm linkquote
If the timing is really 20 degrees, then that's plenty. How does the spark plug look at WOT? Main jet might still be a bit big but I wouldn't change it until that piston is fully black.

As it held out uphill, it's not far away.
Wed Jun 24, 2020 7:42 am

bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: 26 Sep 2013
Posts: 6012
Location: So Cal
 
bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: 26 Sep 2013
Posts: 6012
Location: So Cal
Wed Jun 24, 2020 7:42 am linkquote
Plug's too dark. Still sputters 1/2 to WOT.



Wed Jun 24, 2020 7:52 am

bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: 26 Sep 2013
Posts: 6012
Location: So Cal
 
bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: 26 Sep 2013
Posts: 6012
Location: So Cal
Wed Jun 24, 2020 7:52 am linkquote
chandlerman wrote:
Any chance you had an air leak on the old top end that's now fixed?
Possible. But there was literally no sign of a leak at either the base or the head. Engine idled fine, temps were reasonable... no other weird symptoms of a leak.
Wed Jun 24, 2020 11:11 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
Wed Jun 24, 2020 11:11 am linkquote
Weird and frustrating, especially on what you thought was a reliable motor. A loose stud turned into a head leak, turned into a seize at 60mph on my Sprint motor a while back after I *thought* it was reliable. It made me a little paranoid, as I'm sure you can imagine.

The BGM head went in the mail today, so you should have it first part of next week, they said. I'm using one on the Pinasco 177 I'm building for my VBB right now. Assuming I have some time to work, it'll be running on the stand for sure, maybe back in the bike this weekend.
⬆️    About 4 months elapsed between posts    ⬇️
Thu Nov 05, 2020 7:29 am

Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1781
Location: Rochester, Minnesota
 
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1781
Location: Rochester, Minnesota
Thu Nov 05, 2020 7:29 am linkquote
I was looking for EGT information and came across this older thread. Using a 4" x 36" belt sander and very fine grit abrasive has worked twice for me now. I use 1000 grit and it still doesn't take long to do the job. I use my left hand to keep the head centered long ways on the belt and slowly rotate with my right, no down pressure. On an aluminum head it took about 10 seconds to go from 2.12 mm to 1.6 mm. I pulled it after 5 seconds cleaned it up with 1200 wet and dry, wet with water on glass. Measured still to tall, repeated and came up with about 1.6 mm.
Ginch wrote:
charlieman22 wrote:
Looks to me like the Malossi one Ginch posted does the same?
Give's you two good plug and pray options?
🙂

*Edit: think that the BGM one would then move your sealing surface to the top of the cylinder - rather than on the inverted ring - not that that would make it unviable - just a bit different solution if I am understanding them both
Yes CM that's what Christopher says when he first mentioned the idea but I missed it too initially. So you need to make packers to fill the step down, you wouldn't want to leave it empty. Which I think leaves the Pinasco head a nose in front (if you didn't want to invest in the MMW.
I'd use a belt sander (the bench type) to lower that protruding ring, with the 1.75mm gap that's all you should need to touch I think.
⬆️    About 5 months elapsed between posts    ⬇️
Wed Apr 14, 2021 2:42 pm

bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: 26 Sep 2013
Posts: 6012
Location: So Cal
 
bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: 26 Sep 2013
Posts: 6012
Location: So Cal
Wed Apr 14, 2021 2:42 pm linkquote
Update, to wrap up...

After 500 miles or so, advancing the timing from 18° to 20° has made a noticeable difference in piston coloration. See pic below.

I'm calling it resolved. The takeaway: I think the combination of too big squish and too retarded timing at high revs caused too much heat down in the barrel, eventually melting the rings at the exhaust port. Advancing the timing moved combustion up closer to the head, where it dissipates better.

Thx all. Hopefully this piston will last a while longer.



Wed Apr 14, 2021 6:37 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
Wed Apr 14, 2021 6:37 pm linkquote
Nice!
Wed Apr 14, 2021 11:21 pm

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2867
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2867
Location: London UK
Wed Apr 14, 2021 11:21 pm linkquote
Can use this as an example of the perfect piston. Black, gold and nothing else.
Thu Apr 15, 2021 10:23 am

Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

 
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

Thu Apr 15, 2021 10:23 am linkquote
SoCalGuy wrote:
Update, to wrap up...

After 500 miles or so, advancing the timing from 18° to 20° has made a noticeable difference in piston coloration. See pic below.

I'm calling it resolved. The takeaway: I think the combination of too big squish and too retarded timing at high revs caused too much heat down in the barrel, eventually melting the rings at the exhaust port. Advancing the timing moved combustion up closer to the head, where it dissipates better.

Thx all. Hopefully this piston will last a while longer.
Excellent investigative work.
Thu Apr 15, 2021 2:01 pm

El Presidente Del Topo Chico
VNB VSC VBC VSX
Joined: 28 May 2008
Posts: 5115
Location: Hustletown, TX
 
El Presidente Del Topo Chico
VNB VSC VBC VSX
Joined: 28 May 2008
Posts: 5115
Location: Hustletown, TX
Thu Apr 15, 2021 2:01 pm linkquote
Nice to see this sorted.
⬆️    About 1 month elapsed between posts    ⬇️
Mon May 24, 2021 8:57 pm

Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

 
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

Mon May 24, 2021 8:57 pm linkquote
SoCal did end up sticking with the 140AC / BE5 / 118 ? I was also wondering if you lessened the squishy used Chandlermans head or which wau you went there? Last year following along the information wasn't making sense but after doing some reading , lots of reading and coming back and rereading your topic it starts to sink in. I'm attempting to learn this stuff in preparation for my own as I'm following Jacks advice with the 140ac/Be5/118 mj as well. I was also wondering how the bell mouth comes into play with configurations compared to my 20/20 carb?
Tue May 25, 2021 5:06 am

Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1781
Location: Rochester, Minnesota
 
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1781
Location: Rochester, Minnesota
Tue May 25, 2021 5:06 am linkquote
Lynnb wrote:
SoCal did end up sticking with the 140AC / BE5 / 118 ? I was also wondering if you lessened the squishy used Chandlermans head or which wau you went there? Last year following along the information wasn't making sense but after doing some reading , lots of reading and coming back and rereading your topic it starts to sink in. I'm attempting to learn this stuff in preparation for my own as I'm following Jacks advice with the 140ac/Be5/118 mj as well. I was also wondering how the bell mouth comes into play with configurations compared to my 20/20 carb?
When I installed a bell mouth the recommended +10 on the main just to get started wasn't bad.
Tue May 25, 2021 5:27 am

bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: 26 Sep 2013
Posts: 6012
Location: So Cal
 
bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: 26 Sep 2013
Posts: 6012
Location: So Cal
Tue May 25, 2021 5:27 am linkquote
Lynnb wrote:
SoCal did end up sticking with the 140AC / BE5 / 118 ? I was also wondering if you lessened the squishy used Chandlermans head or which wau you went there? Last year following along the information wasn't making sense but after doing some reading , lots of reading and coming back and rereading your topic it starts to sink in. I'm attempting to learn this stuff in preparation for my own as I'm following Jacks advice with the 140ac/Be5/118 mj as well. I was also wondering how the bell mouth comes into play with configurations compared to my 20/20 carb?
That jetting is where I left it. It's a tad rich but reasonable for the riding I do. It could be a jet or two leaner.

The bellmouth in theory increases the velocity of the air flow into the carb. I'm not convinced it really makes that much difference with the top on the carb box, since only so much air can move through that confined space. It's probably like running without the air filter.

Haven't installed the BGM head yet but look forward to doing that. I did shave a bit off the Pinasco head, which tightened up the squish to a little over 1.5mm.
Tue May 25, 2021 6:47 am

Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

 
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

Tue May 25, 2021 6:47 am linkquote
SoCalGuy wrote:
That jetting is where I left it. It's a tad rich but reasonable for the riding I do. It could be a jet or two leaner.

The bellmouth in theory increases the velocity of the air flow into the carb. I'm not convinced it really makes that much difference with the top on the carb box, since only so much air can move through that confined space. It's probably like running without the air filter.

Haven't installed the BGM head yet but look forward to doing that. I did shave a bit off the Pinasco head, which tightened up the squish to a little over 1.5mm.
Not that I would consider doing a bell mouth setup but with these stock si carbs being so complicated I might consider a newer type
Carb like a mikuni which I think I actually have a couple kicking around, but that would be a new chapter.
The way I understand it now the 140/B5 is standard ( JACK stack ) across the pond and basically the main jet needs to be figured according to keeping the temp around 300 degrees , this is what I'm going to aim for and hopefully my piston turns out looking like yours.
As for the Pilot did you simply pick what worked out best according to mixture adjustment results?
After all pilot seems to attribute at a very low gearing only like 1-3rd gear and by 4th your in the upper circuit.
By the way with Jacks suggestion I've been running with no air filter since the beginning so perhaps it is similar to the bell mouth setup, I don't know.
Tue May 25, 2021 6:49 am

Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

 
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

Tue May 25, 2021 6:49 am linkquote
Christopher_55934 wrote:
When I installed a bell mouth the recommended +10 on the main just to get started wasn't bad.
Reading some of your input here and other areas I think my setup may be closest to your engine setup accept for the bell mouth.
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