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モンキー カブ 12Vライトボアアップ用チューニングヘッド
        

使用パーツ

INポート:Φ20に拡大

EXポート:Φ17に拡大

バルブ摺り合わせ済み

完成後

12V/50cc用純正ヘッド

3°進角用ウッドラフキーが付属します

エンジン諸元表(参考)

  • Product Quantity
    : 1
  • Starting Bid
    :9,800円
  • Highest Bidder
    : bht******** / Rating:80
  • Listing Date
    :2026年01月30日 13時55分
  • Bidding closes on
    :2026年02月03日 21時44分
  • Auction Number
    :l1217846861
  • Condition
    :State it in the description
  • Automatic Extension
    :No
  • Authentication
    :No
  • Early Closing
    :Yes
  • Can I return the product?
    :no
  • Description
  • Q&A ()
  • Cost Estimator
  • Problem Item Response Procedur
Notes
  1. The engine has a problem with residual oil. The product needs to be stored and cleaned separately. An additional charge of 3,000 yen is required for each product. Relevant documents are required for export. If you cannot confirm whether the product contains documents, please ask the seller first. If there are no documents, we will not be able to assist. When you import, after arriving at the Japanese receiving office, it will be forwarded to your designated Japanese address. After pressing Confirm, you can place a bid.
モンキー カブ 12Vライトボアアップ用チューニングヘッド

ホンダ横型エンジンの12Vライトボアアップエンジン(72〜88cc)用チューニングヘッドになります(FIには適合しません)

モンキーやカブのエンジンを,ご自分でボアアップして楽しんでいらっしゃる方は多いと思います.
しかしその性能に満足していない方もまた多いかと思います.

ホンダの横型エンジンは,6Vの時代はバルブ径も大きく馬力もそこそこ出ていましたが,12Vになって馬力より燃費を重視するようになり
キャブ径もポート径も小さくなっていきました.ボアアップの際は,こちらも拡大しないとエンジンの要求する流量には足りません.
このヘッドは,88ccまでのライトボアアップされたエンジンに適合するようポートを拡大,研磨しています.
(充填効率が落ちるので鏡面仕上げはしていません)

性能的には,キタコの75ccライトボアアップキットとキタコのハイカム,PC20キャブで最高速90km/hを確認しました
武川の88cc e-Stageでは以前の出品で100km/h出ていました.

<注意点>
・12Vノーマルヘッド用ボアアップキットに適合します(6V用ボアアップキットには使えません)
・6Vヘッドやレギュラーヘッド用のハイコンプピストンには使えません.キタコのライトボアアップキットや武川のe-Stage等のピストントップ
 が凹んでいるタイプに適合します(フラットトップでも使えますが圧縮比が上がり過ぎる可能性があります→ハイオク仕様になります)
・カムは,リフトが5mm程度のハイカムに適合します.レギュラーヘッド用の6-7mmリフトのカム(武川R10-20など)も使えなくはないですが
 費用対効果でみると勿体無いので,キタコのノーマルヘッド用(4100N-10)や武川のスーパーストリートなどがお勧めです
・ボアアップエンジンでは,ノーマルヘッドから当チューニングヘッドに交換すると馬力が上がります.しかし,クランクが12Vのノーマル50cc
 用Rクランクは,クランクピン径が小さくコンロッド自体も細いので,72cc以上のボアアップで著しく寿命が縮まります.このヘッドを使う際は,
 クランクをC70用(互換品も可)に交換することをお勧めします.(コンロッド大端のニードルベアリングが摩耗すると,金属粉がオイルに混じ
 ってピストンカジリや焼きつきに繋がりオイルポンプも損傷します.最悪ではヘッドやカムまで損傷するので注意が必要です)

<その他>
・諸元表は、同等のチューニングを施した別の12Vヘッドになります
・ポート径はIN側をφ20,EX側はφ17に拡大しました
 → INポートは,拡大しすぎると流速が落ちるため慣性過給効果が弱まり逆効果となります.ライトボアアップではφ20程度が最適かと思います
・バルブスプリングはキタコの強化スプリング(新品)に交換しています
・ステムシールも社外新品に交換済みです
・バルブシート面の摩耗や,燃焼室側バルブシート幅も問題ないものを使用しています
・当然ですがバルブの擦り合わせと圧漏れ検査は実施しています
  → 画像の写りを良くするため光明丹を厚く塗っていますw.実際はもっと薄く塗って確認していますのでご心配なくw
・バルブリテーナーとコッターは馴染ませ済みで,バルブ類の組み付けは完了しています
・プラグ取り付け部とEXスタッドボルト,およびインレットパイプ取り付け部ねじ山(穴)は異常なきこと確認済みです
・マフラー取付用のスタッドボルトは曲がっていたため外しています.替わりにシフトアップの新品(920535)をお付けします
・中古のロッカーアームとシャフトが付属しますがカムは別途ご用意ください.トップ&サイドカバー×2は以前のエンジンから移植してください
・当ヘッドとライトボアアップキットの組み合わせでは,場合によっては圧縮比が上がりハイオク仕様となります.ハイオクGASを使うと点火から
 火炎伝播が始まるまでの時間が遅れ,燃焼完了時期が機械効率が最大となる上死点後16度前後(諸説あり)を外れるためトルクが下がります.
 そのためACGアウター位置決めのウッドラフキーを加工し,レギュラーGASとハイオクGASの燃焼完了時期(最大燃焼圧発生時期)を合わせ
 ているのです.加工済みウッドラフキー(画像⑦)を付属しますので,この違いを確かめてください.
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International Shipping Methods
Proxy bidding and purchasing services are becoming increasingly convenient. However, overseas shopping carries certain risks and issues. To reduce these risks and enhance shopping safety, please be sure to read the following information:

1. International Shipping

   Air Freight: If the item status is not confirmed within two days after the arrival notice, any customer complaints cannot be addressed with the seller.

2. After Receiving the Product

Please confirm and inspect the product as soon as possible to ensure that the product specifications, quantity, accessories, and description are correct

If, unfortunately, there are any issues, you can refer to the following examples on how to report related product problems:
1. Example of missing product information
2. Example of product not matching provided information
3. Example of damaged product information

Important Notes: 1. If the seller is unwilling to ship overseas or is unaware that the product will be shipped overseas, the international shipping cost for returns or exchanges will need to be borne by the member. You may refer to the EMS e-Express fee inquiry from the post office. If it involves alcoholic beverages or items that affect flight safety, the post office cannot be used for shipment, and only DHL can be used to ship back to Japan.
2. During the product complaint handling period, please retain the complete outer packaging of the product (including the shipping label information), and refrain from attempting any repairs or altering the original condition. Any modifications may result in the inability to process the case.

3. After Inspecting the Product

After receiving and inspecting the item, if you have any questions, it is recommended to contact Letao within 2 hours. Here are some reminders:

1. Please do not unpack, use or repair the received item yourself, and be sure to keep the original packaging to facilitate subsequent handling of related matters, so as to avoid changes to the item that may cause the seller to be unwilling to process.

2. You can call customer service, and the customer service will leave a message for you as below. Please provide the following information:
"Hello, we will first help you establish a complaint case for Product ID: _______ .But we need you to 2-3 clear photos of the product issue, including photos of the product problem, product packaging, shipping details slip, and outer box. Send them to service@letao.my and inform us of your desired resolution (failing to provide this may result in an inability to process subsequent matters). After sending the email, notify us in the customer service message. We will confirm with the seller as soon as possible. and if there are any related questions, we will contact you through the customer service message. Thank you for your cooperation."

Please provide:
1. "Product ID"
2. Photo of the "Delivery Note" (if any)
3. Photos of the outer box (including inner and outer packaging)
4. Photos of the product (Please include relevant descriptions to help us confirm with the seller)

Important Notes:
1. Do not include foreign text or other products in the background of the image.
2. Please keep the complete product packaging (including the shipping label information), and refrain from repairing or altering the original condition on your own, as any changes may result in the case being unable to be processed.
3. Please provide the relevant information within 48 hours to avoid missing the golden hour for reflection and causing situations that cannot be handled.
4. Due to 99% of Japanese sellers being unwilling or unaware of shipping goods overseas, if a seller is willing to handle the issue, the goods must be sent back to Japan, and the international shipping costs incurred must be borne by the member. Letao will use postal EMS international express to send the goods back to Japan.
5. As the goods are purchased from overseas, it may take approximately one to two weeks to complete the relevant processing procedures when issues arise with the goods. Please be reminded that you can inquire about the approximate cost through the EMS service at the post office.

4. FAQ

1. Issue of Authenticity: If antique or branded goods are found to be counterfeit upon receipt, clear photos showing the differences between the genuine product and the imitation must be provided as evidence. If unable to provide relevant proof, assistance can be sought to find a third-party reputable organization for a premium authentication service .
2. Leaking Iron Teapot: If an antique iron teapot is leaking, please take clear photos of the leaking area and provide them.
3. Transport Damage: If the goods are damaged during international shipping (to the pickup point), you need to provide photos of the outer packaging of the parcel and clear photos of the damaged goods' outer packaging.

※ Note: Photos provided to sellers should not contain any foreign-related information.
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    Product name: モンキー カブ 12Vライトボアアップ用チューニングヘッド
    Notes:
    Customer service hours:
    • Monday to Friday 10:00-18:00
    Customer service hotline:
    Customer Service Email: service@letao.my