✓ VERIFIED
Jun 12, 2019
Will 6/12/19 I installed this kit on my 97 FLT after problems of fowling of spark plugs and the kit cured it and got better throttle response and a smoother engine at speed
DYNOJET
SKU: 133-4012
Dynojet Thunderslide Kit - XL1200 Carbureted - Harley Sportster
$222.21
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About Dynojet
Dynojet builds the dynamometers most performance shops tune on, along with the Power Vision and Power Commander tuning hardware riders use to actually take advantage of an intake and exhaust upgrade. Nothing else in this catalog does more to turn bolt-on parts into measurable horsepower.
The Dynojet Thunderslide Kit for 1989-2003 Harley Sportster XL1200 carburetors is engineered to significantly improve your bike's performance. This kit features a custom-designed slide that extends the needle's range of motion, leading to superior fuel atomization and a more direct throttle response. Experience measurable gains in both power output and fuel economy.
Why riders pick this
- Custom-engineered carburetor slide
- Extended needle range for precise fuel control
- Improved throttle response
- Enhanced fuel atomization
- Measurable gains in power and fuel economy
Unleash the hidden potential of your carbureted Sportster XL1200 with the Dynojet Thunderslide Kit. By optimizing the fuel delivery and air-fuel mixture, this kit ensures a more efficient burn, which translates directly into a more powerful and responsive ride. It's a key upgrade for riders looking to get more out of their stock or lightly modified Sportster.
Enhanced Sportster Performance
- Custom-engineered carburetor slide for precise control
- Extended needle range improves fuel atomization
- Delivers sharper throttle response
- Increases power output and fuel economy
- Specifically designed for 1989-2003 Sportster XL1200 models
Upgrade Your Carbureted Sportster
This Thunderslide kit is a straightforward yet impactful upgrade for your Sportster, transforming its rideability with improved power and efficiency. It's an excellent choice for riders who want better performance without complex overhauls. Always check local emissions regulations before installation, as this product is not street-legal in all areas.
Specifications
- Brand: Dynojet
- Manufacturer Part #: 8109
- Length: 3.75 in
- Width: 8 in
- Height: 1.3 in
- Weight: 0.4 lbs
Common questions
Will this Thunderslide kit fit my 2004 or newer Sportster?
No, this kit is specific to 1989-2003 carbureted Sportster XL1200 models. Fuel-injected Sportsters or later model years require different calibration products.
Is this product legal for street use in California?
No, Dynojet Thunderslide Kits are not legal for sale or installation in California. Always check your state and local emissions regulations before ordering.
What can I expect in terms of performance after installation?
You can expect improved fuel atomization, a more responsive throttle, and measurable gains in both power output and fuel economy on compatible Sportster XL1200 models.
Ordering from Vtwinbikers
- Brand new, sourced through authorized US distribution — never used, never grey-market.
- Not sure it fits? Use Shop by Bike to filter by your year and model, or email us and we will confirm before you order.
- Harley-Davidson and Indian Motorcycle is all we do, so you are talking to people who ride what you ride.
| BRAND | Dynojet |
| TYPE | Intake/Carb/Fuel System |
| SKU | 133-4012 |
| WEIGHT | 0.4 lb |
Please contact us to confirm fitment for your specific motorcycle, or check the product title for compatibility notes.
CUSTOMER REVIEWS
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✓ VERIFIED
Oct 3, 2025
A Good Jet Kit
Overall, a good kit for the price. My '96 FXSTC was lacking power and struggled sometimes with the stock CV carb, so I figured I would try this to see if it helped. The install was relatively easy, and the instructions helped out a lot. The hardest part for me was fine-tuning the carb after the jets were installed, as the bike idled super high and would die randomly. Eventually, I figured out the problem was a vacuum leak, and once I fixed that, the bike ran great. Now my bike sounds healthier and has much better power and throttle response.
✓ VERIFIED
Jun 28, 2023
Bike runs fucking great??
My only complaint? spring was way too big, radius, and length, used stock spring. Bottom line? Bike runs fucking great??
✓ VERIFIED
Sep 23, 2019
Dynojet Jet Kit delivers
This kit is awesome. I've never taken a CV carb apart but the directions included made this a super simple upgrade. If your carb is older, be very careful with the brass screws, and when drilling through the air/fuel mixture.
✓ VERIFIED
Sep 28, 2006
As expected it was great!
