When I first bought my Yamaha XTZ750 Super Tenere, it was far from running perfectly. One of the biggest issues was the Mikuni BDST38 carburetors, which were in desperate need of a full rebuild. The bike was idling at 4000 RPM when warm, making it impossible to ride properly.
To bring the XTZ750’s carburetors back to life, I used a Mikuni BDST38 carburetor rebuild kit, which includes:
✔ New main jets, pilot jets, and nozzles
✔ O-rings and seals
✔ Vacuum diaphragms
✔ Small diaphragms with shut-off valves
✔ New floats
This same kit is also compatible with Yamaha TDM850, as well as several Ducati SuperSport (600, 750, 900) and Monster models.
Disassembling the Mikuni BDST38 Carburetors
Since my XTZ750 is from 1991, the original carburetors had decades of wear, clogged jets, and cracked rubber seals. The first step was to carefully disassemble both carburetors, making sure to keep track of every component.
During disassembly, I found:
🔧 Gummed-up jets, restricting fuel flow
🔧 Cracked O-rings, causing air leaks
🔧 Worn-out vacuum diaphragms, affecting throttle response
🔧 Aged, brittle fuel lines that needed replacement
Deep Cleaning with Carburetor Cleaner
After taking apart both carburetors, I soaked the metal components in carburetor cleaner to remove built-up deposits. A fine wire and compressed air helped clear the jets and passageways, ensuring unrestricted fuel flow.
Installing the Mikuni BDST38 Rebuild Kit
Once the parts were cleaned and dried, I installed the new jets, O-rings, seals, vacuum diaphragms, and floats from the Mikuni BDST38 rebuild kit. These upgrades restored proper fuel delivery, preventing leaks and ensuring optimal performance.
I also replaced the old, cracked fuel lines to prevent air leaks and fuel starvation—essential for an older bike like mine.
Testing & Adjustments
With everything reassembled, I reinstalled the XTZ750 carburetors, synced them, and adjusted the idle speed and mixture screws. The difference was night and day—the engine finally idled correctly, and throttle response was crisp.
Before & After the Rebuild:
❌ Before: The bike idled at 4000 RPM when warm, ran inconsistently, and had poor throttle response.
✅ After: Smooth idle, steady power delivery, and reliable cold starts.
Final Thoughts: Was It Worth It?
Absolutely! Rebuilding the Mikuni BDST38 carburetors completely transformed my Yamaha XTZ750. If you have an XTZ750, TDM850, or a Ducati SuperSport / Monster, using a high-quality carburetor rebuild kit like this one can breathe new life into your bike.
Looking to restore your own carburetors? Check out the Mikuni BDST38 rebuild kit here:
https://marketstand.net/product/mikuni-bdst38-carburetor-rebuild-kit-yamaha-xtz750-tdm850n-xtz750r/
