Overview
Rubber drive coupling plug for the coupler between the engine and the blower. HydraMaster part number 000-106-045, listed as Plug, HD4 Coupling — 1" O.D. × 7/8" Lg., 70 durometer EPDM.
A coupler takes eight plugs. They are a wear item, and they are the part that stands between the engine and the blower.
Specifications
- Outside diameter: 1 inch
- Length: 7/8 inch
- Material: EPDM, 70 durometer
- Coupling type: HD4
- Quantity per coupler: 8
What it fits
- HydraMaster Boxxer 421 — 8 fitted; also listed as a scheduled replacement item in the machine's maintenance schedule
- HydraMaster SpitFire 4.0 — 8 fitted (machine assembly item 22)
- HydraMaster CM402 — 8 fitted
Fitted alongside 5 inch retaining ring 139-022 and washer 174-080 in the coupler assembly.
Why the plugs matter more than they look
The plugs are the flexible element in the drive between the engine and the blower. They absorb the torsional shock of engine firing pulses and take up the small misalignment that exists in every real installation. When they harden and wear, that shock and misalignment go into the blower bearings and the engine crankshaft instead.
They wear gradually and quietly. The first sign is usually a knock or rattle from the coupler at idle or on shutdown, or a machine that has developed a vibration it did not have. By then the plugs have been passing shock through for a while.
HydraMaster treat plug replacement as scheduled maintenance on the Boxxer 421, not as a repair. That is the right way to think about them.
Fitting advice
Replace all eight together. Mixing new and used plugs loads the new ones unevenly and they will not last.
Check coupler alignment while you have it apart. Plugs that have worn unevenly — some flattened, some barely marked — are telling you the coupler is out of alignment, and new plugs will wear the same way if you do not correct it. HydraMaster publish a coupler alignment procedure for exactly this reason.
Check the coupler retaining bolts and the engine and blower mounting bolts at the same time. HydraMaster call this out specifically in the maintenance schedule.
Frequently asked questions
How many do I need?
Eight per coupler. Order eight.
Can I replace just the worn ones?
No. Mixed plugs load unevenly and the new ones fail early.
How often should they be replaced?
HydraMaster list plug replacement on a scheduled interval for the Boxxer 421. Machines doing high hours, or with a history of alignment problems, need them sooner.
My plugs wore unevenly. Is that normal?
No — it is an alignment symptom. Correct the alignment before you fit new plugs or you will be doing the job again.
Is there a different plug for other machines?
HydraMaster list other coupler sleeves and inserts for other drives — for example 152-008 and 152-010. Do not assume the HD4 plug carries across. Send us your machine model and we will check.
Hearing a knock from the coupler? Tell us the machine and the symptom and we will help you sort a plug replacement from an alignment problem before you order.
More HydraMaster parts and equipment, and the full range in Parts & Maintenance.
Related parts
- Sleeve #6 Drive Coupler Spitfire Sidekick (152-008) — #6 drive coupler sleeve
- Coupler Sleeve #7 Drive Coupler (152-009) — #7 drive coupler sleeve
