Mikuni Carb Repair


I have a Yamaha Wolverine 350cc, year 2000. I have had it bored out with new rings and new valves and a timing chain. After a couple of weeks, it started running bad again and we discovered that the plastic cover for the air cut-off diaphragm for the Micuna [Mikuni] Carburetor is cracked. Glue did not fix the problem.

This part is unavailable to buy. I can not afford to buy a whole new carburetor. [Are] there any remedies to fix this problem? {Ray, IL, USA 2000 Yamaha 350 Wolverine ATV, YFM350FX}


Unfortunately, neither Yamaha nor Mikuni sell this carburetor top separately. You can either try again to repair this piece or find a replacement.

We will start with attempting to repair it. I do not know what type of glue you used previously, but most glues break down in the presence of gasoline and may hold pieces together but do not form a airtight seal, so finding one to work on part of a carburetor can be troublesome.

This carburetor needs to build up vacuum in order to work properly. The best way to achieve a temporary repair is to use black RTV silicone.

I say this is a temporary repair because this will seal it, but it will not last forever. RTV brand silicone is available in different colors that indicate the maximum heat range it will withstand. For your application the black RTV will be best.

Do not use household or bathroom type silicone. It will react with gasoline and oil & breakdown quickly when exposed to engine heat and the elements.

First, wash and thoroughly dry your hands, so you do not contaminate the surface.

Next, put the cap (or top) on the carb & take care not to over tighten the screws.

Using your clean finger, wipe a thin coat of silicone over the entire top of the cap including around the sides where it meets the carburetor body. Let this cure for one to two hours.

After two hours, repeat the same procedure. This time, putting just a little more silicone over the crack. You want to use thin coats, do not just glob it on there.

The silicone should create an airtight seal, allowing a build up of sufficient vacuum to operate. It will not be perfect and will not last forever, but it will be functional.

You should remain on the look out for a used carburetor or carb parts to affect a permanent repair. Some good places to look are , Craigslist.com and local swap meets or ATV clubs.

When you do find one, it will be easy to peel off the silicone and install the new cap.

This Mikuni was not exclusive to the 2000 Wolverine model. It was used on the following models:

  • 1996 – 2000 YFM35FX Wolverine
  • 1996 – 2000 YFM350FX Wolverine 4WD
  • 1999 YFM350FWX Big Bear 4WD

  • The Yamaha OEM part numbers you are looking for are 4KB-14901-10-00, 4KB-14901-20-00, 4KB-14901-11-00 or 4KB-14901-11-00 Carburetor Assembly 1.

    Need more free ATV or motorcycle repair information?

    Q&A:  Leaking Fuel Valve?
    Q&A:  Leaking Gas Valve flooding engine?
    Q&A:  Battery Maintenance
    Q&A:  Battery Types
    Q&A:  Carb Jetting page 1
    Q&A:  Carb Jetting page 2
    Q&A:  Aftermarket Exhaust System
    Q&A:  Carb Float Needle
    Q&A:  Carburetor Identification

    Q&A:  Honda Points
    Q&A:  Rim Bolt Pattern
    Q&A:  CB750F Identification
    Q&A: Broken Speedometer Cable End
    Q&A: Suzuki LT-Z400 QuadSport Tank Removal
    Q&A: Motorcycle Trike Conversion
    Q&A: Honda Rancher Reverse Problem
    Q&A: Kawasaki Z650SR Fuel Mix problem
    Q&A: RM80 Piston Position

    Q&A: LT80 Engine Oil Issues
    Q&A: Clutch Cable Break In period?
    Q&A: Cooling Fan Problem?
    Q&A: 1983 XV920 Virago Oil Change
    Q&A: ATC90 Spark Plug question
    Q&A: Nighthawk 750 Spark Plug Gap
    Q&A: Bike Registration Problem
    Q&A: Lost Hypercharger Instructions
    Q&A: Bourget Charging System

    Q&A: Can Spark Plugs be cleaned?
    Q&A: Wheel Bearing Removal for 1976 CB750K
    Q&A: 1982 YZ490 Kick Start
    Q&A: 1979 GL1000 Goldwing Points Gap
    Q&A: 1982 GS650GLZ Cable Routing Problem
    Q&A:  Ether vs. Carb Clean
    Q&A:  ATV Ignition Trouble
    Q&A:  John Deere backfiring
    Q&A:  Honda Phantom 200 Tire Pressure

    Q&A:  TRX350 Clutch Slip possible causes
    Q&A:  LTF250 Cam Chain Installation & Timing Marks
    Q&A:  Demon X pit bike clutch trouble
    Q&A:  OK to Increase Tire Size?
    Q&A:  RV125 Lost Keys
    Q&A:   1981 GPZ550 flywheel cover
    Q&A:   2000 Yamaha Badger : Hard to start
    Q&A:   1975 CB360T Replacement Tire
    Q&A:   Vintage CB750 Chain Size

    Q&A:  LTA500F Vinson Leaky Fuel Petcock
    Q&A:  TRX350 Rancher Hard Shifting
    Q&A:  Replacement Rectifier
    Q&A:  GS500F Turn Signals
    Q&A:  Suzuki Quad Poor Idle
    Q&A:  Yamaha Wolverine cracked Carb top

    Please support our advertisers.
    They enable WeeksMotorcycle.com to remain a free service!

    Weeks Motorcycle Home

    Website upgrade in progress

    Ask a Repair Question

    Search Our Site
    Custom Search


    Vote for our site on Webbie World!

    Weeks Cycle Salvage
    eBay Store

    Show Off Your Machine!

    Show Off Your Machine

    Weeks Gear
    coming soon!

    Sale Banner at Adventure

    Discount OEM Parts

    Classified Listings

    Review weeksmotorcycle.com on alexa.com

    Site Build It Affiliate Program