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17mm Nut: Convenience Versus Leak Concerns
Users frequently praise the K&N KN-138's integrated 17mm nut for simplifying oil filter installation and removal, eliminating the need for special tools. However, this convenience is often contrasted with reports of leaks originating from the nut's seam, leading to safety concerns and track bans.
Track Bans and Reliability Issues with K&N Filters
Several motorcycle forums report that K&N oil filters, including the KN-138, are banned from AMA racing and many track day organizations. This is attributed to a history of leaks from the nut seam, creating dangerous oil slicks, and potentially compromising engine reliability for high-performance use.
K&N Filter Price vs. Performance Debate
While K&N oil filters are recognized for features like their 17mm nut and resin-impregnated media trapping 99% of contaminants, many users find them 'pricey' compared to alternatives like HiFlo Filtro. The debate centers on whether the added convenience and brand premium justify the cost over functionally similar, less expensive options.
Proper Installation Key to Avoiding K&N Filter Leaks
Community discussions suggest that K&N filter failures, particularly leaks from the nut area, often stem from improper installation. While the nut is for removal, using it for overtightening is a common mistake. Adhering to K&N's hand-tighten plus a specified turn method is critical for maintaining seal integrity.
Expert answers based on real user experience
The integrated 17mm hex nut on the K&N KN-138 is a key feature praised by users for significantly easing installation and removal. This design eliminates the need for specialized oil filter wrenches, which can be cumbersome, especially in tight motorcycle engine bays. Users report being able to hand-tighten the filter and then use a standard wrench on the nut for the final quarter-turn, or simply remove it using a wrench, streamlining the maintenance process and potentially reducing the risk of damaging the filter housing during removal.
r/motorcycles
Reports from motorcycle forums indicate K&N filters, including the KN-138, have faced bans from some track day organizations and racing bodies due to concerns over leaks. The primary issue cited is oil escaping from the seam where the 17mm nut is attached to the filter canister. This can create hazardous oil slicks on the track surface, posing a significant safety risk. While not every filter fails, multiple users describe leaks occurring even after proper installation, leading to caution in high-performance or competitive environments.
K&N
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K&N K&N Motorcycle Oil Filter: High Performance, Premium, Designed to be Used with Synthetic or Conventional Oils: Fits Select Suzuki Motorcycles, KN-138. Features: O/E replacement oil filters for most cars, trucks, SUV's, motorcycles, & ATV's. 17 mm exposed nut designed for easy oil filter removal. Heavy duty construction for extreme conditions. Resin-impregnated filter media traps 99% of harmful contaminants. Anti-drainback valve (where applicable) eliminates dry starts, prevents oil f....
| UPC | 024844084217 |
| ASIN | B000E2CVDI |
| Brand Name | K&N |
| Unit Count | 1 Count |
| Thread Size | M20 x 1 mm |
| item-weight | 0.25 Kilograms |
| Manufacturer | K&N Filters |
| Model Number | KN-138 |
| Material Type | Resin |
| Product Grade | Performance Part |
| Item Type Name | Oil Filter |
| Item Dimensions | 7.4 x 7.4 x 8.1 Centimetres |
| Number of Items | 1 |
| mfr-part-number | KN-138 |
| Outside Diameter | 71 Millimeters |
| country-of-origin | Thailand |
K&N
K&N Motorcycle Oil Filter: High Performance, Premium, Designed to be used with Synthetic or Conventional Oils: Fits Select Honda, Kawasaki, Polaris, Yamaha Vehicles, KN-303 ( Packaging May Vary )
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K&N Filters Filter Care Service Kit - Squeeze Red, 8 oz. Squeeze Oil Cleaning Kit-Squeeze
ApriliaForum, r/motorcycles
While K&N filters, like the KN-138, are often perceived as 'pricey' by users compared to alternatives such as HiFlo Filtro, the cost difference is partly attributed to features like the integrated 17mm removal nut and K&N's brand recognition. The filter media is resin-impregnated, designed to trap 99% of contaminants. However, community discussions suggest that for many standard applications, the performance difference between K&N and more economical brands may not be substantial enough to warrant the higher price point for some riders.
r/motorcycles
Proper installation of the K&N KN-138 is crucial, especially regarding tightening. K&N's instructions typically recommend lubricating the gasket with engine oil before installation and then tightening the filter by hand until it contacts the mounting surface, followed by an additional 3/4 to 1 full turn. Crucially, the 17mm nut is designed primarily for removal, not for applying excessive tightening torque. Overtightening, particularly using the nut for leverage, is frequently cited by users as a cause of leaks or filter damage, potentially compromising the seal integrity or the canister's structural bond.
r/motorcycles
While the K&N KN-138's 17mm nut offers installation convenience, community discussions highlight concerns about leaks originating from the nut-to-canister seam, particularly under vibration from rocky trails or high-speed riding. Specific failure reports mention oil spraying from this seam, leading to dangerous situations. Although K&N specifies a heavy-duty construction and resin-impregnated media trapping 99% of contaminants, precise data on the fatigue life of the nut's bond under prolonged vibration (e.g., >10,000 km of varied terrain) or a quantified failure rate is not publicly available from user discussions or manufacturer specifications, leaving a gap in understanding its ultimate resilience compared to filters without this integrated feature.
Product Specifications & User Reports
Users have raised questions about the material integrity of K&N filters, specifically citing leaks from the nut area and concerns about the quality of the o-ring and sealing surfaces. While the KN-138 uses a resin-impregnated filter media for 99% contaminant capture and has a M20 x 1 mm thread, some forum users suggest potential cost-cutting in these sealing components compared to OEM equivalents. Without detailed material analysis or comparative stress testing under thermal cycling (engine operating temperatures varying from cold start to full heat), it remains difficult to definitively quantify the KN-138's long-term sealing performance relative to filters with conventionally constructed seams and potentially more solid o-ring materials.
Product Specifications & User Reports
| Automotive Fit Type |
| Vehicle Specific Fit |
| part-interchange-info | Replacement |
| mirror-housing-included | Oil Filter |
| OEM Equivalent Part Number | KN-138 |
| Compatible with Vehicle Type | Motorcycle |
| Manufacturer Contact Information | RIVERSIDE, CA, 92502 US |
| manufacturer-warranty-description | Limited |
| Global Trade Identification Number | 00024844084217 |
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