The Vespa Club of Chicago
Scooter Spark Plug Reference
You may not think about your spark plug often, but it’s always there, igniting a few thousand times per minute to keep your piston chugging back and forth in your cylinder. It’s one of hundreds of parts that must work in unison — flawlessly, for years and years — to keep you and your scooter moving safely through traffic. It’s actually stupefying that scooters or cars, or human bodies for that matter, work at all. Maybe it’s better not to think about it. (closes browser)
Oh, you’re still here? Good. We must take good care of our scooters (and our cars, and our bodies) so they continue to serve us well for many years. So give that poor spark plug the love it needs. Here’s a basic checklist:
The Proper Plug:
Be sure you’re using the right plug. Check your owner’s manual and/or the chart at the bottom of this page. Manuals generally specify a certain brand, and that’s usually the safest bet, but most manufacturers offer suitable equivalents, which can be found online in cross-reference charts, or by comparing specifications. Manufacturers use wildly different naming conventions, but most of them are decipherable with a key, for instance, here are NGK’s naming conventions.
Checking the Plug
Check your plug according to the service intervals specified in your manual. Remove the plug with your plug wrench (in the toolkit) or a suitable rubber-insulated socket (clockwise to tighten, counter-clockwise to remove). Clean the electrodes and insulator with a brush. Check the gap (below) and color (also below) and inspect it for any damage. Plugs are cheap, if in doubt, replace it. When replacing it, it’s best to use a torque wrench set to the torque specified in the manual, but in general, “pretty tight,” is fine—all the way in, then another 2/3 turn or so.
Mind the Gap
The “gap” refers to the space between the plug’s two electrodes, and it’s important that it is set properly. This is easily checked and adjusted with a wide variety of spark-plug gapping tools or feeler gauges. Always carry a tool in your bike.
If the gap is too small, use the tool to gently pry the ground electrode away from the center electrode. If the gap’s too big, gently tap the ground electrode on a hard surface and check again and repeat, until it’s right.
Check the gap of every plug, even if it’s brand new. Some plugs are specially-gapped at the factory, (NGKs are indicated by a dash and a number (in tenths of a millimeter — a BR7HS-10 has a 1mm gap). It’s OK to adjust the gap on these plugs to meet your specs.
Spark Plug color
The color and texture of the electrodes and insulation at the tip of the plug — after it’s been running for a while — can tell you lots about your engine and help diagnose or reveal problems with your engine. The best way to do this is with a reasonably-scientific “plug chop” (which some people take to the extreme of actually cutting up the plug), but on a stock scooter that’s running well, a visual check should suffice.
The plug chop procedure and resulting diagnosis is outside the scope of this article, but If you’re riding a stock scooter, the plug should be a light brown color and not covered in crust or sludge.
The big “R” debate:
In recent years, mostly to reduce electrical interference — your iPhone, electronic components on your bike, your Cardo, etc— spark plug manufacturers have been transitioning to spark plugs with a built-in resistor. In NGK parlance, this adds an “R” as the second letter of the plug model, other manufacturers have different indicators.
NGK and other brands have quietly discontinued most non-resistor plugs in the ranges vintage scooterists want, so non-resistor plugs are getting harder to find — and more expensive — as stock runs out. If you go on scooter and motorcycle forums, you’ll find endless arguments whether it matters or not.
Most actual science-type people argue that it doesn’t. While the resistor may adjust the character of the spark a tiny bit (allegedly a shorter but more focused spark), “R” plugs are designed match the specs of the original versions and shouldn’t cause any problems. If they do cause a problem, buy a non-resistor plug on eBay for twice the price, and convince yourself it’s running better, like you do when you use really expensive 2-stroke oil and “premium” gas. We won’t point out that your fancy NGK plug cap you’ve been running since the nineties has a resistor in it anyway. The 1/4 of a degree your timing is off, your incorrect plug gap, and all the pizza you’ve been eating lately are probably the real issues.
If you have a modern scooter, “R” plugs are spec’ed anyway, so none of this matters. Huzzah!
Feel the Heat
All plugs have a “heat range,” indicating the rate at which heat dissapates to the cylinder.Too “cool” a plug won’t burn off the carbon deposits, and may foul prematurely, leading to misfires and engine stalling. If the plug is too “hot“, the bike can overheat, leading to pre-ignition.
Some scooterists switch to hotter plugs in winter or short trips around town, and cooler plugs in winter or for long-distance trips. Tuned engines may require adjustments. But with a stock scooter, the recommended heat range should give you the best results. If anything more than a step up or down is required to keep your scooter happy, there’s probably a bigger problem that needs to be addressed.
Carrying a spare
Whenever you’re buying a plug, buy two, or better yet a cheaper 4-pack, and keep a spare in your bike (in a hard case that will protect the plug). No-brainer, but you’d be surprised how few people have a spare when they need one.
The Vespa Club of Chicago Spark Plug Cross-Reference Chart
The Vespa Club of Chicago is providing this information as a free resource based on our research and experience, but makes no guarantee regarding the technical or editorial accuracy of the information presented above. Please consult your manuals, dealer, and other sources to make sure you’re using the correct plug and gap, and take into account any modifications or changes made for regional markets.
KEY:
- bold indicates plugs specified in original owner/service manuals
(all other plugs are derived from modern cross-reference charts or recommendations) - † indicates a defunct manufacturer or product
- italic indicates alternate plugs recommended for tuned engines or certain situations
| Model | Gap | NGK | Champion | Denso | Marelli† | Bosch | KLG | AC Delco | Other |
| Vespa (modern/4-stroke) | |||||||||
| ET2 | BR9ES | RN2C | W27ESR | R41CXL | |||||
| most 125/150 models | .7–.8 mm .028–.031″ | CR8E, CR8EB | 8654,8654-2,RG94C | U24ESR-N | UR2CC | Autolite 4302 | |||
| GTS 300 ie | .7–.8 mm .028–.031″ | CR8EKB | RG 4 PHP | ||||||
| 300i HPE | .7–.8 mm .028–.031″ | MR7BI-8 | |||||||
| “M/C – PIAGGIO 2016, VESPA 2011-09” | ER9EHIX | (in NGK book) | |||||||
| Vespa (vintage) | |||||||||
| 1955-1965 Vespa 125 (VN, VNA, VNB, Allstate etc) | .6mm .023″ | B6HS† BR6HS | L82, L82C L85C, L86, L86C, QL86C | W20FS-U, W20FSR-U | CW 225 N-T† or CW230 A-T† | W7A, W225 T1†, 7996 WR7AC+†, W175T1, W175Z1 | F70 or F75 | 43F | Autolite 414, 2655, Motorcraft AV3C |
| 1955-1965 Vespa 150 (VB, VBA, VBB, GL, etc) | .6mm .023″ | B6ES† BR6ES | NA8†, N5C | W20ES-U, W20ESR-U | CW 250 L-T† or CW 240 B or CW 240G† | W240 T2† | FE80 | ||
| 1955-1965 Vespa GS | .6mm .023″ | B6ES† BR6ES | NA8†, N5C | W20ES-U, W20ESR-U | |||||
| GS160 | .6mm .023″ | B6ES† BR6ES | NA8†, N5C | W20ES-U, W20ESR-U | F.E80 | ||||
| Smallframes (50R, etc) | .6mm .023″ | B6HS† BR6HS | L86C, QL86C | W20FS-U, W20FSR-U | CW7N† or SNA7003-8† | W7A, W225 T1†, 7996 WR7AC+†, W175T1, W175Z1 | F75 | 430F | Autolite 414, 2655, Motorcraft AV3C |
| Smallframes (Primavera, | .6mm .023″ | B7HS† BR7HS | L82C, RL82C | W22FS-U, W22FSR | CW7N† | W240 T1† | 445Z | ||
| ET3 | .6mm .023″ | B7HS†BR7HS | L82C, RL82C | W22FS-U, W22FSR | CW7N AT† | W240 T1† | 554Z | ||
| PK 50, 50S, 50S Elestart | .6mm.023″ | B6HS† BR6HS | L86C, QL86C | W20FS-U, W20FSR-U | CW7N† or SNA7003-8† | W7A, W225 T1†, 7996 WR7AC+†, W175T1, W175Z1 | F75 | 430Z | Autolite 414, 2655, Motorcraft AV3C |
| PK 125, 125S | .6mm .023″ | B6HS† BR6HS | L86C, QL86C | W20FS-U, W20FSR-U | CW7N, SNA7003-8† | W7A, W225 T1†, 7996 WR7AC+†, W175T1, WR6BC | F75 | 430F | Autolite 414, 2655, Motorcraft AV3C |
| PK80S automatica, MK125 S automatica | .6mm .023″ | B7HS†BR7HS | L82C, RL82C, 811, 821, 835 | W22FS-U, W22FSR | CW8N† | W4A, W5A | 430Z, M42FF, MC42F | Autolite 413, 2636, 2653, 2654, 4092, 4093 | |
| P-series 150 or 125 (P125X P150X, etc) | .6mm .023″ | B6HS† BR6HS | L86C, QL86C | W20FS-U, W20FSR-U | CW 6N AT†, SNA7003-8 | W7A, W225 T1†, 7996 WR7AC+†, W175T1, WR6BC | 43 F | Autolite 414, 2655, Motorcraft AV3C | |
| P-series 200 (P200E, etc) | .6mm .023″ | B6HS† BR6HS | NA8†,N5C | W20FS-U, W20FSR-U | CW 6N AT†, SNA7003-8 | W7A, W225 T1†, 7996 WR7AC+†, W175T1, W175Z1 | F75 | 43 F | Autolite 414, 2655, Motorcraft AV3C |
| Lambretta | |||||||||
| LD | .6–.7mm .023–.028″ | B6HS† B7HS† B8HS† BR6HS BR7HS BR8HS | L86 L82C L78C | W20FS-U, W20FSR-U | |||||
| Series I,II,III, GP, J, and Luna ranges | B7ES† B8ES† B9ES† BR7ES BR8ES BR9ES | N4 N3 N2 | W22ES-U, W22ESR-U | CW240L† | W225 T2† | Filso AVS 28-6 140 F-01 105†, Filso C12128/1† | |||
| Piaggio | |||||||||
| BV200 | CR8E | 8654, 8654-2, RG94C | U24ESR-N | UR2CC | |||||
| BV250, BV500 | CR7E, CR7EK | U22ESR-N, U22ETR | UR3CC | Autolite 4578 | |||||
| BV500 | CR7E, CR7EK | U22ESR-N, U22ETR | UR3CC | Autolite 4578 | |||||
| Liberty 50 C | RGN2C | ||||||||
| Liberty 125-400 | CR7EB | RG6YC | |||||||
| MP3-250, 400, 500 | CR7E, CR7EK | U22ESR-N, U22ETR | UR3CC | Autolite 4578 | |||||
| Typhoon | BR8ES | W24ESR | |||||||
| X9 | CR7E, CR7EK | U22ESR-N, U22ETR | UR3CC | Autolite 4578 | |||||
| Model | Gap | NGK | Champion | Denso | Marelli† | Bosch | KLG | AC Delco | Other |
| Genuine | |||||||||
| Stella (2-stroke) | .7–.8 mm .028–.031″ | B6ES | RN9YC | WR6DC | |||||
| Stella (4-stroke) | .7–.8 mm .028–.031″ | C8EH9 | RG4HC | UHR3CC | |||||
| Brio 50 | .7–.8 mm .028–.031″ | CR6HSA | |||||||
| Buddy 50 | .6–.7mm.024–.028″ | BPR7HS | |||||||
| Buddy 125, 150, 170i | .6–.7mm.024–.028″ | CR7HSA | U22FSR-U, UR3AC , UR5 | Autolite 4203 | |||||
| Buddy Kick | .7–.8 mm .028–.031″ | CR8E | 8654,8654-2,RG94C | Autolite 4302 | |||||
| Hooligan 170i | .6–.7mm.024–.028″ | CR7HSA | U22FSR-U, UR3AC , UR5 | Autolite 4203 | |||||
| Rattler 50 | .6–.7mm.024–.028″ | BPR7HS | |||||||
| Rattler 125, 200i | .6–.7mm.024–.028″ | CR7HSA | U22FSR-U,UR3AC , UR5 | Autolite 4203 | |||||
| Roughhouse 50 | .6–.7mm.024–.028″ | BPR7HS | |||||||
| Urbano 50 | .7–.8 mm .028–.031″ | CR6HSA | |||||||
| Urbano 125, 200i | .6–.7mm.024–.028″ | CR7HSA | |||||||
| Kymco | |||||||||
| Agility 50 4T, 125 | .6–.7mm.024–.028″ | CR7HSA | U22FSR-U, UR3AC , UR5 | Autolite 4203 | |||||
| AK500 | .7–.8 mm .028–.031″ | CR7E | U22ESR-N | UR3CC | Autolite 4578 | ||||
| Bet&Win 150, 250 | DPR7EA-9 | X22EPR-U9 | |||||||
| Cobra 50/Top Bou | BR6HSA | W20FR-L | |||||||
| CV3 | .7–.8 mm .028–.031″ | CR7E | U22ESR-N | UR3CC | Autolite 4578 | ||||
| Grand Vista | DPR7EA-9 | X22EPR-U9 | |||||||
| Like 50i | .7–.8 mm .028–.031″ | CR8E | 8654, 8654-2, RG94C | U24ESR-N, U20FSR-U | UR2CC | Autolite 4302 | |||
| Like 150i | .7–.8 mm .028–.031″ | CR7HSA, CR6HSA | U22FSR-U, UR3AC , UR5 | ||||||
| People 50 2T | .6–.7mm .024–.028″ | BR8HSA | W24FR-L | ||||||
| People S50, S125, 150, S200 | .6–.7mm .024–.028″ | CR7HSA | RZ96C | U22FSR-U, UR3AC , UR5 | Autolite 4203 | ||||
| People 250, S250 | .8–.9 mm.031–.354″ | DPR7EA-9 | RA8YC | X22EPR-U9 | |||||
| Spade 150 | CR8E | 8654, 8654-2, RG94C | U24ESR-N | UR2CC | Autolite 4302 | ||||
| Autolite 4203 | .6–.7mm .024–.028″ | CR7HSA | U22FSR-U, UR3AC , UR5 | Autolite 4203 | |||||
| Super9 LC, AC | BR6HSA | W20FR-L | |||||||
| Vitality50 4T | CR7HSA | U22FSR-U,UR3AC , UR5 | Autolite 4203 | ||||||
| Venox 250 | CR8E | 8654,8654-2,RG94C | U24ESR-N | UR2CC | Autolite 4302 | ||||
| Xciting 250, 250Ri, 500, 500Ri | .8–.9 mm.031–.354″ | DPR7EA-9 | RA8YC | X22EPR-U9 | |||||
| X-Town 300 | .8–.9 mm.031–.354″ | DPR6EA-9 | RA8YC | X22EPR-U9 | |||||
| ZX50 | BR8HSA | W24FR-L | |||||||
| Royal Alloy | |||||||||
| GT150, GP150, GT150S | .6–.7mm.024–.028″ | CR7HSA | U22FSR-U,UR3AC , UR5 | Autolite 4203 | |||||
| GP300S | .6–.7mm.024–.028″ | CR8EK | |||||||