Fri May 28, 2021 2:54 pm

Enthusiast
'81 Vespa P200e, '85 Vespa PX125e, '70 Vespa 90 basketcase
Joined: 11 Jun 2020
Posts: 96
Location: St. Catharines, Ontario
 
Enthusiast
'81 Vespa P200e, '85 Vespa PX125e, '70 Vespa 90 basketcase
Joined: 11 Jun 2020
Posts: 96
Location: St. Catharines, Ontario
Fri May 28, 2021 2:54 pm linkquote
Hey folks.

I'm planning on taking my px125 on a 300+ km trip this summer. Any suggestions on which spark plug to use?

Since my bike is kitted I run a b7hs for my boots around town.

Let me know your suggestions.
Cheers.
N
Fri May 28, 2021 3:13 pm

Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 3278
Location: Staten Island, NY
 
Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 3278
Location: Staten Island, NY
Fri May 28, 2021 3:13 pm linkquote
B8hs? Little cooler hopefully less chance of heat issues.
Fri May 28, 2021 3:51 pm

Hooked
Rat 2003 Stella 2T; 1979 P125x (in pieces, out for paint)
Joined: 12 Sep 2015
Posts: 313
Location: Madtown
 
Hooked
Rat 2003 Stella 2T; 1979 P125x (in pieces, out for paint)
Joined: 12 Sep 2015
Posts: 313
Location: Madtown
Fri May 28, 2021 3:51 pm linkquote
I don't think a cooler plug does anything for cylinder temp; it only affects the temp of the plug tip. At least that's my experience. Swapping in an 8 for a 7 on long runs does nothing for my running temps, measured by a sensor mounted on the cylinder stud. The material from NGK and the like talks about cooler vs. hotter plugs as all about getting the plug tip hot enough to burn off carbon, but not so hot to cause pre-ignition. See e.g. https://ngksparkplugs.com/en/resources/spark-plug-basics. If you are driving around town all the time you want a hotter plug because the engine doesn't get hot enough to warm the plug past 500 f, which is where the carbon burns off. If your shorter trips are enough to get the engine up to normal operating temps and without causing pre-ignition, I don't think there is any benefit from going to a cooler plug for the 300km trip.

I'd be interested to hear if others noticed different cylinder temps from running cooler plugs.
Fri May 28, 2021 4:16 pm

Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 3278
Location: Staten Island, NY
 
Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 3278
Location: Staten Island, NY
Fri May 28, 2021 4:16 pm linkquote
yackee wrote:
I don't think a cooler plug does anything for cylinder temp; it only affects the temp of the plug tip. At least that's my experience. Swapping in an 8 for a 7 on long runs does nothing for my running temps, measured by a sensor mounted on the cylinder stud. The material from NGK and the like talks about cooler vs. hotter plugs as all about getting the plug tip hot enough to burn off carbon, but not so hot to cause pre-ignition. See e.g. https://ngksparkplugs.com/en/resources/spark-plug-basics. If you are driving around town all the time you want a hotter plug because the engine doesn't get hot enough to warm the plug past 500 f, which is where the carbon burns off. If your shorter trips are enough to get the engine up to normal operating temps and without causing pre-ignition, I don't think there is any benefit from going to a cooler plug for the 300km trip.

I'd be interested to hear if others noticed different cylinder temps from running cooler plugs.
I'm not positive about my suggestion but was actually testing plug heat ranges today and going from a b9 with correct jetting where my cht was steady at 300F to a b8 on same jetting, my cht readings were 310-315F holding steady. Its not that the plug is making the engine run hotter, but the hotter spark point means your jetting needs to be slightly richer to provide the same amount of cooling. This is specifically if you've got your jetting set on the edge of lean for more performance which works fine for shorter rides, but might become an issue on longer rides especially if your timing is not exactly perfect. On my brief experiments today, I came to the conclusion that my jetting needed to be 2-3 points richer on the main when going 1 heat rating hotter. What was good at 125 mj on a b9, after looking at the plug and CHT on a wot run I felt was safer using a 128mj. And I actually got some photo documenting the comparison using the same 125 MJ on b9 and b8, attached below. Butt dyno also felt the b8 plug was a bit more powerful! Maybe I'm imagining things? :shrug:

From the link you provided they even say a too hot plug heat range is a contributor to overheating.. along with wrong timing:
Quote:
CAUSES OF OVERHEATING:
Spark plug heat range too hot
Insufficient tightening torque and/or no gasket
Over-advanced ignition timing
Fuel octane rating too low (knock is present)
Excessively lean air-fuel mixture
Excessive combustion chamber deposits
Continuous driving under excessively heavy load
Insufficient engine cooling or lubrication



120/be3/125 MJ BR9ES plug. 1 mile WOT Run. CHT held steady at 300F


120/be3/125 MJ BR8ES plug. new plug with 5 miles on it then a 1 mi wot run. CHT steady at 310-320F

Fri May 28, 2021 4:40 pm

Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 3278
Location: Staten Island, NY
 
Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 3278
Location: Staten Island, NY
Fri May 28, 2021 4:40 pm linkquote
Malossi instructions also suggest the same based on usage type. Hotter plug standard use, cooler plug extreme use.

300KM high rpm would suggest to me more extreme use than 10 KM city driving.

But again.. I don't think it will make a huge difference if you've got a bone stock setup and its well within safe ranges timing and jetting wise. I'd be happy if someone with more knowledge and experience came along to prove me wrong cause I've been messing with this all day trying to understand it.







Last edited by swiss1939 on Fri May 28, 2021 4:43 pm; edited 1 time in total
Fri May 28, 2021 4:42 pm

Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

 
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2511

Fri May 28, 2021 4:42 pm linkquote
swiss1939 wrote:
I'm not positive about my suggestion but was actually testing plug heat ranges today and going from a b9 with correct jetting where my cht was steady at 300F to a b8 on same jetting, my cht readings were 310-315F holding steady. Its not that the plug is making the engine run hotter, but the hotter spark point means your jetting needs to be slightly richer to provide the same amount of cooling. This is specifically if you've got your jetting set on the edge of lean for more performance which works fine for shorter rides, but might become an issue on longer rides especially if your timing is not exactly perfect. On my brief experiments today, I came to the conclusion that my jetting needed to be 2-3 points richer on the main when going 1 heat rating hotter. What was good at 125 mj on a b9, after looking at the plug and CHT on a wot run I felt was safer using a 128mj. And I actually got some photo documenting the comparison using the same 125 MJ on b9 and b8, attached below. Butt dyno also felt the b8 plug was a bit more powerful! Maybe I'm imagining things? :shrug:

From the link you provided they even say a too hot plug heat range is a contributor to overheating.. along with wrong timing:
That is some real pertinent information, hotter the plug the more fuel need to keep cool, thanks
Fri May 28, 2021 4:52 pm

Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 3278
Location: Staten Island, NY
 
Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 3278
Location: Staten Island, NY
Fri May 28, 2021 4:52 pm linkquote
Here is another link that also has some interesting information on heat range effects, suggesting cooler plugs for higher rpm uses, hotter plugs for lower rpm uses:
Quote:
Cold plugs are ideal for high rpm engines, forced induction applications, and other instances where the engine produces high operating temperatures. Conversely, hot plugs are good for applications that operate mainly at low rpms. Because they have a longer insulator nose length, heat is transferred from the firing tip to the cooling system at slower pace. This keeps the spark plug temperature high, which allows the plug to self clean and prevent fouling.
https://www.enginebuildermag.com/2011/05/understanding-spark-plug-heat-range/#:~:text=Choosing%20the%20right%20heat%20range,%2Dignition%2C%20or%20power%20loss.

I've been suggesting cooler plug on the assumption that his 300+km drive is mostly long stretches of highway riding.
Fri May 28, 2021 5:55 pm

Enthusiast
'81 Vespa P200e, '85 Vespa PX125e, '70 Vespa 90 basketcase
Joined: 11 Jun 2020
Posts: 96
Location: St. Catharines, Ontario
 
Enthusiast
'81 Vespa P200e, '85 Vespa PX125e, '70 Vespa 90 basketcase
Joined: 11 Jun 2020
Posts: 96
Location: St. Catharines, Ontario
Fri May 28, 2021 5:55 pm linkquote
Wow. Great responses. Even better great info up for debate.

The reason for asking is because I will be doing a long trip. In July. Hot humid temps here in Ontario. However the bike will not be wot on freeways. I'll probably be running 70-80 kph on back roads.

Rest stops for gas and engine rest time are unavoidable.

So the question stands: should I put in a cooler plug?

I like running my mixture a bit on the rich side as well to prolong the integrity of the piston and cylinder.

Thanks for all the awesome info folks.
Fri May 28, 2021 6:24 pm

Enthusiast
'81 Vespa P200e, '85 Vespa PX125e, '70 Vespa 90 basketcase
Joined: 11 Jun 2020
Posts: 96
Location: St. Catharines, Ontario
 
Enthusiast
'81 Vespa P200e, '85 Vespa PX125e, '70 Vespa 90 basketcase
Joined: 11 Jun 2020
Posts: 96
Location: St. Catharines, Ontario
Fri May 28, 2021 6:24 pm linkquote
I guess the real question is:

Is the b7 cool enough for the trip?
Fri May 28, 2021 7:38 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 May 28, 2021 7:38 pm linkquote
The only downside to running a cooler plug is possibly fouling. The downside of too hot a plug can be all sorts of damage. For a long distance trip on a kitted scoot I'd definitely go cooler.
Sat May 29, 2021 3:23 am

Hooked
PX150E
Joined: 28 Oct 2018
Posts: 130
Location: Florida, USA
 
Hooked
PX150E
Joined: 28 Oct 2018
Posts: 130
Location: Florida, USA
Sat May 29, 2021 3:23 am linkquote
I know that most of us don't use Champions, and prefer NGK. But if you do, be aware that Champions heat rating is HIGHER with the higher number, unlike all the other brands.

That said, my 1985 bone-stock PX150E has never had any issues, whether using NGK -6, -7, or -8, Denso -20, or Champion N9.
I have measured CHT a couple of times, and never exceeded 250 F.
  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: 0.0452s ][ Queries: 28 (0.0252s) ][ Debug on ][ 201 ][ Thing Two ]