OP
@mr-blazer avatar
UTC

Hooked
Primavera 150; SS180
Joined: UTC
Posts: 102
Location: Los Angeles
 
Hooked
@mr-blazer avatar
Primavera 150; SS180
Joined: UTC
Posts: 102
Location: Los Angeles
UTC quote
My motor is a 208cc SS180. My seller recommended a 4% mixture.

I would say it's running 80-90% great, plenty of power while not being lean. However, everything is kind of oily and black, with a lot of black, unburnt residue around the exhaust port and a black spark plug (B8es). So I don't know if it's:

Too rich pre-mix
Too rich jetting
Too cold a plug

Thanks
@birdsnest avatar
UTC

Not So Moderator
VNB VSC 09C VMA VSX - vbc vmb
Joined: UTC
Posts: 8010
Location: Hustletown, TX
 
Not So Moderator
@birdsnest avatar
VNB VSC 09C VMA VSX - vbc vmb
Joined: UTC
Posts: 8010
Location: Hustletown, TX
UTC quote
208cc? How many oversize on the piston?!?

All 2-strokes are sloppy, messy, particulate makers. In my experience piston ported bikes even more so. I run about 3.5% on my SS as modern fuels (and I run ethanol free) are so much better than what they used 50 years ago, but 2% is definitely not enough IMHO. Get a CHT gauge and watch your temps closely.
@oopsclunkthud avatar
UTC

Banned
3:5
Joined: UTC
Posts: 8923
Location: San Francisco
 
Banned
@oopsclunkthud avatar
3:5
Joined: UTC
Posts: 8923
Location: San Francisco
UTC quote
the GS/SS called for 5% when new with old 30Wt oil

in my GS I run 4% Motul 710 or 800RR
OP
@mr-blazer avatar
UTC

Hooked
Primavera 150; SS180
Joined: UTC
Posts: 102
Location: Los Angeles
 
Hooked
@mr-blazer avatar
Primavera 150; SS180
Joined: UTC
Posts: 102
Location: Los Angeles
UTC quote
Birdsnest wrote:
208cc? How many oversize on the piston?!?
Not sure. From the dude's sales pitch: "Piston is a Mark Broadhurst 208 (Lambretta piston)."
UTC

Lurker
Joined: UTC
Posts: 3
 
Lurker
Joined: UTC
Posts: 3
UTC quote
mr-blazer wrote:
Not sure. From the dude's sales pitch: "Piston is a Mark Broadhurst 208 (Lambretta piston)."
It might be worth contacting MB Developments, Mark Broadhurst's business and asking them what they recommend.
UTC

Member
Joined: UTC
Posts: 11
 
Member
Joined: UTC
Posts: 11
UTC quote
I think the biggest issue is the piston ported design. It is harder to lubricate the big end bearing because the charge does not enter directly on it. That is why Piaggio recommended 5% for those models IMO. The cylinder is not a problem if sized and jetted correctly. I have seen many GS160 and SS180 big end bearings wear out from to little oil mix. Stock rotary valve engine cylinders have no problem running 2%. The only difference is the induction method.

I would use a happy medium with modern oils - 3 or 4 %.
UTC

Ossessionato
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: UTC
Posts: 2537
Location: Siam
 
Ossessionato
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: UTC
Posts: 2537
Location: Siam
UTC quote
I've run 3% on both my GS and SS for years without any problems.
@oopsclunkthud avatar
UTC

Banned
3:5
Joined: UTC
Posts: 8923
Location: San Francisco
 
Banned
@oopsclunkthud avatar
3:5
Joined: UTC
Posts: 8923
Location: San Francisco
UTC quote
nomadinsiam wrote:
I've run 3% on both my GS and SS for years without any problems.
I ran my Lambretta TV175 at 2% with no issues for many years. when I started taking it on very long trips I switched to 3% but likely didn't need to.
UTC

Ossessionato
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: UTC
Posts: 2537
Location: Siam
 
Ossessionato
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: UTC
Posts: 2537
Location: Siam
UTC quote
oopsclunkthud wrote:
I ran my Lambretta TV175 at 2% with no issues for many years. when I started taking it on very long trips I switched to 3% but likely didn't need to.
I'm not aware of any data that proves lower ratios of modern oil are sufficient in the old engines, but personal observations have shown me that the lower ratios of modern oils don't seem to do any harm to the old engines.
OP
@mr-blazer avatar
UTC

Hooked
Primavera 150; SS180
Joined: UTC
Posts: 102
Location: Los Angeles
 
Hooked
@mr-blazer avatar
Primavera 150; SS180
Joined: UTC
Posts: 102
Location: Los Angeles
UTC quote
endoftheroad wrote:
I have seen many GS160 and SS180 big end bearings wear out from to little oil mix.
This alone is probably reason enough to just stick with 4%. I'm tired of working on my bikes.
@starreem avatar
UTC

Ossessionato
07 GTS250(RIP), 13 GTS300, Several Lambrettas
Joined: UTC
Posts: 2799
Location: Raleigh, NC
 
Ossessionato
@starreem avatar
07 GTS250(RIP), 13 GTS300, Several Lambrettas
Joined: UTC
Posts: 2799
Location: Raleigh, NC
UTC quote
This reminds me of an magazine article by Gordon Jennings detailing the (somewhat) controlled dyno runs on a Suzuki 250. The gist of the article was that a 15:1 ratio produced the highest BHP with no appreciable carbon build up compared to 20:1 and 30:1

http://www.bridgestonemotorcycle.com/documents/oilpremix6.pdf

I think the salient point that will escape many is the attention to tuning the carb with each iteration of the experiment. It's a sore point of contention with many in the chainsaw world regarding the need to re-tune changes to oil/gas ratios.
OP
@mr-blazer avatar
UTC

Hooked
Primavera 150; SS180
Joined: UTC
Posts: 102
Location: Los Angeles
 
Hooked
@mr-blazer avatar
Primavera 150; SS180
Joined: UTC
Posts: 102
Location: Los Angeles
UTC quote
This is an excellent article. Thanks
DoubleGood Design banner

Modern Vespa is the premier site for modern Vespa and Piaggio scooters. Vespa GTS300, GTS250, GTV, GT200, LX150, LXS, ET4, ET2, MP3, Fuoco, Elettrica and more.

Buy Me A Coffee
 

Shop on Amazon with Modern Vespa

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


All Content Copyright 2005-2024 by Modern Vespa.
All Rights Reserved.


[ Time: 0.0230s ][ Queries: 3 (0.0017s) ][ Debug on ][ 313 ][ Thing One ]