✓ 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 - `1989-2003 Xl1200 — Harley-Davidson Sportster 1200, Sportster 883, Sportster 883 Hugger (1989-2003)
$222.21
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Dynojet Thunderslide Kit for 1989-2003 Harley Sportster XL1200 carburetors, featuring a custom-engineered slide that extends the needle's range of motion for improved fuel atomization and throttle response. Delivers measurable gains in power output and fuel economy on stock or lightly modified bikes.
Features
- Custom-engineered carburetor slide
- Extended needle range for precise fuel control
- Improved throttle response and fuel atomization
- Not street-legal in California — verify local emissions laws before installation
Specifications
- Brand: Dynojet
- Manufacturer Part #: 8109
- Length: 3.75 in
- Width: 8 in
- Height: 1.3 in
- Weight: 0.4 lbs
Fitment
Fits 1989-2003 Harley-Davidson Sportster XL1200 models with factory carburetor.
Frequently Asked Questions
Is this kit street-legal?
No — Dynojet Thunderslide Kits are not legal for sale or installation in California. Check your state and local emissions regulations before ordering.
Will this fit my 2004+ Sportster?
No — this kit is specific to 1989-2003 XL1200 carbureted Sportsters. Fuel-injected models require a different calibration product.
What performance gains can I expect?
The improved fuel atomization typically yields better throttle response, increased power, and improved fuel economy depending on your setup and riding style.
Do I need a new air filter or tune?
The Thunderslide works with most stock and aftermarket intake setups. Carburetor jetting may need minor adjustment for optimal performance.
| 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
4.6
5 RATINGS
5★
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0
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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!
