Does your BMW G650GS feel jerky and hard to ride when pulling away or at very low speeds? Are you worried about knocking or stalling?
In short, after just 20 km with a BoosterPlug fitted, the bike was noticeably easier to ride when pulling away and at very low speeds. More than a year later, the effect is still there (added October 2026).
Here is my honest review from my own G650GS: changes in low-speed torque and usable rev range, exhaust note and vibration, and the downside of fuel economy.
| Item | Details | Notes |
|---|---|---|
| Bike | BMW G650GS | Single-cylinder 650 cc engine |
| Part tested | BoosterPlug | Plug-in intake air temperature correction device |
| Test ride | About 20 km right after fitting | Feel in town and on ordinary roads |
| Overall | ★★★★★ (very happy) | Worth the price I paid (about 25,000 yen) |
| Long-term use | Over a year | No problems; fuel economy about 8% worse |
In short
- After 20 km, low-speed pulling and pull-away improved a lot and the jerkiness went away
- The comfortable rev range widened from “around 3,000 rpm” to “2,300–4,000 rpm”
- The exhaust note changed from a sharp “bap-bap-bap” to a deeper “bom-bom-bom”, and the vibration became a softer, pleasant “pulse”
- With more low-down torque, I change gear less often and riding in town is much easier
- An honest note: the crankcase breather valve I fitted earlier may be adding to the effect
- Over a year with no problems. Fuel economy about 8% worse (added October 2026)
Verdict after 20 km: is a BoosterPlug worth it on a BMW G650GS?
A BoosterPlug was worth the roughly 25,000 yen I paid. It clearly improved my G650GS’s low-speed rideability, and I recommend it.
Modern fuel-injected bikes run lean to meet strict emissions rules, and on a single-cylinder engine that lean mixture at very low revs can be a real source of stress.
From the moment I rode off with the BoosterPlug fitted, the engine responded to the throttle gently but strongly. Low-speed riding felt very different.
6 things that changed after fitting the BoosterPlug
Over the 20 km test ride, the main changes were stronger pulling at very low speeds and a much wider usable rev range: 2,300–4,000 rpm.
| What I compared | Before (stock) | After (BoosterPlug) |
|---|---|---|
| 1. Low-speed torque when pulling away | Thin torque; I had to be careful pulling away | Strong, steady torque; pulling away is stable |
| 2. Throttle response | Snatchy and jerky when first opening the throttle | Relaxed and smooth, in a good way |
| 3. Exhaust note | A dry “bap-bap-bap-bap” | A deeper “bom-bom-bom-bom” |
| 4. Engine vibration | Hard, sharp mechanical vibration | Softer, a pleasant “pulse” |
| 5. Comfortable rev range | Only a narrow band around 3,000 rpm | Widened to 2,300–4,000 rpm |
| 6. Gear changes | Frequent changes to keep the revs up | Far fewer, as it pulls at low revs |
The biggest benefit is “5. Comfortable rev range”. Before, the bike was jerky unless I kept it around 3,000 rpm. Now it accelerates smoothly from 2,300 rpm up to 4,000 rpm.
This means I no longer need to keep changing down when turning at junctions or speeding up and slowing down in town, and I get less tired on tours. More than a year on, I still think this is the biggest benefit.
The downside: fuel economy gets worse
I have no complaints about how it rides. However, according to the manufacturer it makes the mixture about 6% richer, so real-world fuel economy drops.
The BoosterPlug works by making the intake air temperature sensor reading look colder than it is, so the bike injects more fuel and gets closer to the right air-fuel ratio.
More fuel means worse fuel economy. On my G650GS, my records show fuel economy got about 8% worse after fitting it (added October 2026). Decide whether that is a fair trade for the better rideability.
An honest note: bikes with a crankcase breather valve
The changes I felt are very similar to what I felt after fitting a crankcase breather valve (a pressure-reducing valve, or “reducer”) earlier, so the two may be working together.
My G650GS already had a breather valve that lowers crankcase pressure, and I had already noticed softer engine braking and freer revving.
To be honest, the stronger low-speed pull and softer vibration I felt this time may be partly due to the breather valve as well.
Ideally I would remove the breather valve to test each part on its own, but I am happy with how the combination works, so I have decided to keep riding as it is.
I wrote about the breather valve (T-REV) here (in Japanese): G650GS crankcase breather valve (Japanese)
Compared with a full fuel controller such as a Power Commander (50,000–100,000 yen or more, plus setup costs in Japan), a BoosterPlug or a breather valve costs a fraction of the price and is easy to fit.
Who should (and shouldn’t) fit a BoosterPlug
A BoosterPlug suits riders who spend most of their time at low and mid revs on the road, but not riders looking for more top-end power.
| Riding style | Recommendation | Why |
|---|---|---|
| Town riding and touring | ◎ Highly recommended | The low-speed snatchiness goes away and stop-start riding becomes much easier |
| Enjoying the single-cylinder pulse | ◎ Highly recommended | The harsh edge of the vibration goes, and the pleasant thump gets stronger |
| Chasing top speed | △ Not a good fit | It mainly richens low and mid revs; peak power at high revs doesn’t change |
| Fine-tuning fuel maps | △ Not a good fit | It corrects automatically; if you want your own maps, use a fuel controller |
What I found after more than a year (added October 2026)
It has now been over a year since I fitted it, so here is an update.
- No problems at all. No warning light has ever come on
- The bike passed the Japanese roadworthiness inspection (shaken) with the BoosterPlug fitted
- Fuel economy is about 8% worse, according to my records
- The cable tie holding the ambient temperature sensor hasn’t loosened
- The bike is easier to ride and I get less tired on long rides. I think this is the biggest benefit
BoosterPlug on the G650GS: FAQ
Q1. Do I need to tune the fuelling after fitting it?
No setup is needed: no PC connection and no dials. It is plug-in, and it corrects automatically as soon as you connect it (according to the manufacturer).
Q2. Will it foul the spark plug or turn on the engine warning light?
I have used it for over a year, and the warning light has never come on. I haven’t checked the spark plug for fouling yet. The manufacturer says it adds about 6% fuel.
Q3. Can I fit it myself?
Yes. You just remove the right-hand side panel and plug it into the sensor connector, which takes about 30 minutes. I explain how to unplug the connector and where to put the sensor in a separate article.
Summary: if low-speed riding bothers you, see the installation guide
For about 25,000 yen (what I paid), the BoosterPlug greatly eased the low-speed roughness of my single-cylinder engine. I am very satisfied with it.
If you worry about stalling when pulling away or find the bike jerky at low speeds, I think you are likely to feel the difference.
I explain how to fit it, tips for unplugging the connector and where to put the sensor, with photos, in this article:
Note: This is my personal impression of my own bike. I’m not a qualified mechanic. The “about 6% richer” figure is the manufacturer’s claim. Prices are what I paid in Japan. The product is BoosterPlug for BMW G650GS (BMW-0901).