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Top Picks for You
Turbook C9588 Rocker Box Gasket Kit for Harley-Davidson Twin Cam 1999-2017
The most complete box on this page, with a catch: it is an unbranded copy of the Cometic C9588, so buy it for the parts list, not the brand.
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Vertex-Winderosa 817851 Valve Cover Gasket for Honda TRX450R 2004-2005
OEM-fit gasket-only part for the TRX450R, the right fix when the rest of the seal stack is still healthy.
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Caltric Head and Valve Cover Gasket for Honda Rancher 350 TRX350 2000-2006
The cheapest route here, with published part numbers you can verify before you order and aftermarket QC worth inspecting.
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4-Pc Valve Cover Gasket O-Ring Seal Set for Yamaha XVS 1100/650, XT600, SRX600, TT600
Targets the hardened o-ring seals that cause “new gasket, still leaks” on Yamaha cruisers and dual-sports.
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2-Set Valve Cover with Gasket and Bolts Kit for Can-Am Outlander/Commander/Maverick 330-1000
The only kit here that replaces the cover itself, the answer when a gasket swap failed because the cover is the problem.
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The Turbook C9588 is the most complete box in this list, but the genuine Cometic C9588 it copies is the one I would buy for a Harley. For every other bike here, match the kit to the wear: a gasket-only kit works while the tube seals and bolt grommets stay soft, and fails when they harden.
I have opened enough valve covers to know the leak is rarely the gasket. Bolt grommets harden, half-moon seals shrink, and tube seals let oil pool around the plugs.
Too many kits ship two of those parts and skip the rest, so the missing piece arrives a week later. Here is what the five kits ship with. If oil shows up where it should not, our guide to a motorcycle leaking or burning oil confirms whether the valve cover is the source.
Here is the part this guide is built around: what ships in the box for each of the five picks. “Complete kit” means different things to different sellers, so check the columns that matter for your engine: tube seals and bolt grommets are the parts most listings skip.
| Kit | Molded gasket | Tube seals | Bolt grommets / washers | Half-moon seals | Cover | Bolts |
|---|---|---|---|---|---|---|
| Turbook C9588 (Harley Twin Cam) | Yes | Yes | Yes (washers) | Not listed | No | No |
| Vertex-Winderosa 817851 (Honda TRX450R) | Yes | No | No | No | No | No |
| Caltric (Honda Rancher 350) | Yes | No | No | No | No | No |
| Yamaha 4-pc o-ring set | No (o-rings only) | No | Yes (o-rings) | No | No | No |
| Can-Am 2-set | Yes | No | No | No | Yes | Yes |
Which Kit Covers a Full Harley Twin Cam Rocker Box Reseal?
Key Features
- Copies the Cometic C9588 spec, the industry-standard Twin Cam rocker box kit
- Listing fitment note covers 1999-2005 Twin Cams, not the full 1999-2017 title range
- Gaskets, seals, washers, and o-rings ship together in one order
- Genuine Cometic C9588 runs about $43 at V-twin shops for riders who want brand QC
The listing calls it a fit for Cometic C9588, and that phrasing is the tell: the seller is Turbook, not Cometic. This is an unbranded copy of the Cometic C9588, the industry-standard Twin Cam rocker box kit that sells for about $43 at V-twin shops. If brand backing and consistent QC matter to you (and on a Harley top end they should), buy the genuine Cometic instead.
What this box does offer is the parts list. Gaskets, seals, washers, and o-rings for both rocker boxes ship together, so you are not running to the dealer mid-job for one missing seal. Harley OEM seals bought one at a time cost far more.
The trade is QC: forum riders report knockoff gaskets arriving warped or needing a trim, and this listing’s own fitment note says 1999-2005 while the title claims 1999-2017.
Check your year against the note, not the title. A rocker box weep sits high on the common oil leak sources list for Twin Cams, so getting the full seal stack in one order matters here more than on most bikes.
Pros: one box covers both rocker boxes with no mid-job parts run; far cheaper than Harley OEM seals bought piecemeal. Cons: unbranded seller with unknown QC; vague fitment notes that disagree with the title.
Best for: Harley Twin Cam owners doing a full rocker box reseal who want everything in one box on a budget.
The tradeoff: you are gambling on an unbranded copy of the industry-standard kit. If the copy wins, you saved real money. If it arrives warped, you learn why the genuine Cometic costs $43.
Can a Gasket-Only Kit Fix a Weeping TRX450R Valve Cover?
Key Features
- Part number 817851 matches the Honda OEM spec for direct fit
- Fits Honda TRX450R, 2004-2005 model years only, with no universal-fit risk
- Genuine Winderosa/Vertex hardware from a decades-long powersports supplier
- Single-gasket shipment: budget for fresh bolt grommets on 15+ year-old machines
Sometimes the gasket is the whole problem. If your TRX450R cover weeps and the tube seals and bolt grommets still feel soft, this Winderosa/Vertex part, genuine stock part 817851, drops in with no fitment guesswork. Winderosa has supplied the powersports world for decades, so the mold and the material are known quantities.
The box holds one gasket and nothing else. That is fine for a quick reseal on a quad whose seal stack is healthy. It is not fine on a 20-year-old machine where the bolt grommets have turned to plastic. I have seen riders swap this gasket, ride one weekend, then watch oil creep back down the head because the hardened grommets never let the cover seat.
Pair it with fresh grommets on anything with 15-plus years on it. And if the smoke is blue and follows the throttle, read our piece on motorcycle burning oil and blue smoke: that points at rings or valve seals, not the cover gasket.
Pros: OEM-fit part number, no fitment guesswork; Winderosa’s decades-long powersports reputation; a cheap fix for a known-weeping cover. Cons: gasket only: hardened bolt grommets will bring the leak back.
Best for: dirt bike and quad owners doing a simple reseal, not a rebuild.
The tradeoff: this solves the gasket and ignores the rest of the seal stack. That is a fair trade on a young bike and a trap on an old one.
What’s the Cheapest Kit That Still Lists Real Part Numbers?
Key Features
- Lists Honda OEM part numbers 12251-HN5-671 and 12315-HN5-671 on the listing
- Fits Honda Rancher 350 TRX350, model years 2000-2006
- Ships as a pair: head gasket plus valve cover gasket in one order
- Published dimensions let you check the new gasket against the old one on the bench
At ten to fifteen dollars this is the cheapest way to do the job, and Caltric earns that spot with paperwork: the listing publishes exact OEM part numbers and dimensions, so you can measure the new gasket against the old one before the cover goes back on. Fitment lists are thorough for the Rancher 350 TRX350 from 2000 to 2006.
The catch is the aftermarket QC lottery. Pieces can arrive warped or a touch off-shape, and thin packaging sometimes lets a gasket bend in transit. None of that is fatal. It just means you inspect every piece against the old gasket on the bench before installation.
Lay the new gasket over the old one; if the bolt holes or the perimeter drift, send it back. Before you order, make sure the oil loss is a cover leak and not valve seal or piston ring wear: no gasket fixes oil that burns past the rings.
Pros: the cheapest way to do the job; published part numbers and dimensions let you verify fit before buying; thorough fitment lists. Cons: aftermarket QC lottery: pieces can arrive warped or off-shape; thin packaging can let gaskets arrive bent.
Best for: budget-focused owners of older utility ATVs who check fitment carefully.
The tradeoff: price against consistency. For the cost of a pizza you get a workable gasket set, as long as you do the QC the factory skipped.
Which Kit Suits Yamaha Covers That Seal with O-Rings?
Key Features
- Cross-references Yamaha part 93210-62446-00
- Four o-ring seals in one order (bolt seals, with spares in hand)
- Fits XVS1100, XVS650, XT600, SRX600, and TT600 valve covers
- No material spec published, so inspect the rubber before installation
These Yamahas seal their valve covers with o-rings, and the o-rings are the part everyone forgets. A fresh molded gasket over hardened bolt-seal o-rings will weep within a month.
I have watched riders do the job twice before they learn the o-rings were the leak all along. This four-piece set targets that wear part and nothing else for the XVS1100, XVS650, XT600, SRX600, and TT600, and it cross-references the Yamaha part number.
The seller is generic and unbranded, and no material spec is published, so you are trusting an unknown rubber compound. Cheap rubber hardens fastest. That is the whole risk in one line.
Pros: targets the forgotten wear part: hardened o-ring and bolt seals are the top cause of “new gasket, still leaks” on these Yamahas; avoids buying a full kit you do not need. Cons: generic brand with no material spec published; cheap rubber compound fails fastest.
Best for: Yamaha cruiser and dual-sport owners whose covers seal with o-rings rather than molded gaskets.
The tradeoff: the smallest, cheapest kit here buys you the right parts with the least brand confidence. Keep the old seals as backup until the new ones prove out.
What If the Valve Cover Itself Is Warped or Cracked?
Key Features
- Cross-references Can-Am part numbers 420610393 and 420630260
- Fits Outlander, Commander, and Maverick models from 330 through 1000
- Two covers, gaskets, and bolts ship together; the only pick here replacing the cover
- Set each cover on glass and check for flatness before installation
When a gasket swap fails twice, the cover is the problem more often than not. Cast aluminum covers warp from heat cycles, crack around bolt bosses, and lose threads when someone before you cranked the bolts too hard.
This is the only kit here that replaces the cover itself: two valve covers, gaskets, and bolts for Can-Am Outlander, Commander, and Maverick machines from 330 to 1000, cross-referencing the Can-Am part numbers.
The brand is unknown and the fitment range is broad (330 to 1000 covers a lot of engines), so the listing’s warning to verify your exact engine model and part number is not boilerplate. Read it as a requirement. When the parts arrive, set each cover on a sheet of glass and check for rock or daylight under the flange before you touch a bolt.
Pros: solves what other kits cannot: warped, cracked, or thread-damaged covers; bolts included means no fighting seized hardware. Cons: unknown casting quality; broad fitment is risky, so verify exact engine model and part number.
Best for: Can-Am owners whose leak survived a gasket swap because the cover is compromised.
The tradeoff: the most complete “kit” here from the least trustworthy brand. The glass test takes two minutes and answers the only question that matters.
Should You Buy a Gasket-Only Kit or a Complete Kit?
Buy the gasket-only kit when you are doing a quick reseal and the rest of the seal stack tests good: tube seals still soft, bolt grommets still springy, no oil around the half-moons. That is the TRX450R scenario above: a known weep, young rubber, one afternoon.
Buy the complete kit when the cover comes off for real work. A valve-clearance check is the classic moment: the cover is off anyway, the bike has real miles on it, and the extra cost of tube seals and grommets is small next to doing the job twice. Full top-end refreshes fall in this camp too.
Athena’s catalog shows how wide the single-gasket market runs: Athena’s motorcycle engine gasket range covers individual gaskets for most popular engines, but a catalog of single gaskets is not the same as a kit.
Count the seal stack on your engine before you order: gasket, tube seals, bolt grommets, half-moons. If your kit covers fewer than the ones that are worn, you have not saved money.
How Much Torque Do Valve Cover Bolts Take?
Less than your wrist wants to give them. Typical M6 valve cover hardware calls for about 88 in-lb (about 10 Nm), and silicone gaskets can call for as little as 10 to 15 in-lb.
Go past that and the gasket cuts, the cover warps, and the aluminum threads strip. None of those failures announce themselves; you find out at the next oil change.
The bolt grommets deserve the same attention as the torque figure. Hardened grommets stop compressing long before they look bad, and a fresh gasket over dead grommets seeps within weeks. That is the “new gasket, still leaks” story from the Yamaha section, and it repeats on every brand.
Half-moon seals get a dab of RTV at the corners, never a full bead. ThreeBond’s tech data for TB1207B, the silicone liquid gasket riders use on those spots, is explicit: tighten to the specified torque with no retorque. A full bead squeezes into the head and hardens where oil flows.
A motorcycle torque wrench that reads in inch-pounds is the tool for this job: most Nm wrenches cannot resolve 10 Nm with any honesty. And always check the service manual: the figures above are typical, not universal.
Why Does Fitment Beat Brand on Valve Cover Kits?
No valve cover kit is universal, and the ones that pretend otherwise are the ones that leak. Match year, model, and engine code, above all on vintage Hondas and Harleys, where one casting change across model years breaks “close enough” fitment.
Brand still counts for something, and forums are blunt about which names hold up. Vesrah is the name that comes up for vintage Hondas: a Japanese maker with OEM-supplier roots (Vesrah’s history page covers the manufacturing background), and riders treat it as the safe aftermarket pick where Honda OEM no longer exists.
That last point is not academic: Honda discontinued OEM valve cover gaskets for the DOHC CB750s, so Vesrah or Athena is the only option for those bikes, not an upgrade.
On the Harley side, James Gaskets gets the forum praise for consistent Twin Cam seals, and Real Gasket’s reusable silicone covers (realgaskets.com) have a loyal following among BMW airhead and Guzzi owners who pull covers often.
Fitment first, brand second, price third. In that order.
Frequently Asked Questions
Why is my valve cover still leaking after replacing the gasket?
Four usual suspects. A warped cover that no gasket can seal. Check it on glass. A blocked crankcase breather building pressure behind the seal. A silicone gasket that was over-torqued and cut. Or hardened bolt grommets that never got replaced, the most common cause of all. An oil stop leak additive will not fix any of these: it cannot unwarp a cover or soften a dead grommet. Work through the four in that order before you buy a second gasket.