ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Guide To Four Stroke Motorcycle Engines, Part 6

Updated on December 31, 2009

Four Stroke Engine Service & Repair

The first step in any repair job should be to identify the real existing problem and its cause. Spend a few dollars for the specific shop manual for your machine. The specifications and the procedural information it contains will speed the repair process considerably. The successful repair is one that not only fixes the damage, but lessens the likelihood of its recurrence. Therefore, the good mechanic begins his task with a thorough diagnosis.

The question that immediately presents itself along with the machine is: "Will it run?" If not, then are the ignition and fuel systems operating properly? Is the valve adjustment correct? Is the fuel fresh? If all of these check out, then it's time for a compression test to determine the basic engine condition.

Compression Test

A simple compression test is performed when you try to start the engine with the kick starter. If you notice that there is virtually no compression resistance to kick through, especially when you already suspect a compression problem, there's a good chance your gauge readings will be low.

Remove the spark plug and insert the gauge into the plug, hole being careful not to damage the soft aluminum spark plug threads. With the gauge in place, open the throttle and kick the engine through about five times, or engage the electric starter for a 2- to 3-second burst.

If the engine shows less than 90 to 100 psi compression pressure, you should look further into the upper end for your troubles. Begin by squirting about a teaspoonful of clean engine oil into the cylinder and rotating the engine several times to distribute the oil around the rings. Now you're ready to take another compression reading with the rings temporarily sealed.

If your readings jump up to 120 to 190 psi, you know a re-ring job is in order. If the reading remains extremely low, however, you know that compression is probably escaping through the head gasket or valves. In either case, if you have taken a careful compression test, with the valves adjusted properly and throttle open and you still get low readings, you know the top end should be disassembled and repaired.

Cylinder Leakage Tester

Another type of compression test employs the cylinder leakage tester. This device pumps air into the cylinder and isolates the problem by tracing down the escaping air. Note: Never use any sort of leakage tester on a two stroke engine as the crankshaft end seals will surely blow out.


Sometimes the compression readings are good, but the engine is noisy. Often these noises come from cam chains, primary chains, rattling clutch hubs, or loose valve adjustments. Eliminate these areas of potential noise by inspection and adjustment before dismantling your machine for an upper-end overhaul.

The tone of the noise is usually a hint of what is causing the problem. Ticking and light tapping noises indicate that the offending part is small, perhaps a rocker arm or a valve. Heavy slapping and clunking suggest heavier parts, such as pistons, rods, crankshafts, and clutch assemblies, as the offenders.

These heavy slapping noises may also come from cam or primary chains slapping against engine cases. Constant grinding or "whirring" noises indicate the problem is occurring at a rotating shaft rather than a reciprocating part. Hissing or puffing sounds suggest compression loss through leaking gaskets. Such leaks must be caught early and corrected before the sealing surface is damaged by blow-by, which mean re-machining or replacement.

Continued in Guide To Four Stroke Motorcycle Engines, Part 7

Back To Start


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)