What Is Hard To Start For A Four-stroke Dirt Bike Engine? - DIY Moto Fix
Maybe your like
 |
|
what is hard to start for a four-stroke dirt bike engine?12/28/2014 Comments  "Can you define what is hard to start?" This question seems like a simple one at first, but considering all the variables it is tough to answer outright. "Is the bike hot?", "Is the bike cold?", "Has the bike been sitting for several weeks?", "Is it carbureted or fuel injected?", "Was it just tipped over?", or "Was the float bowl just drained?" In my opinion, each scenario I've questioned above invokes a slightly different answer. Combine this subjectivity with one's own personal starting routine and the ease of which the bike will fire up, the bottom line is it's going to be different for every rider. As a rule of thumb, if my bike takes more than five kicks to fire up as time progresses I will begin investigating possible starting issues. "What things might make a bike hard to start but not necessarily mean the engine needs to be torn apart?" On most bikes there are two or three things that adversely affect how well the bike will start. On carbureted bikes the pilot jet circuit controls fuel flow from idle to about 1/4 throttle. The pilot jet has a very small orifice and clogs pretty easily. Once clogged the pilot jet is ineffective in delivering the necessary fuel to the engine and starting the bike becomes extremely difficult. Depending on make and model the bike may or may not be equipped with a decompression system that can be adjusted. For example, on the Honda CRF450 in order for the decompression system to function correctly a certain amount of clearance must be maintained between the decompression adjusting screw and the rocker arm. Occasionally this system needs to be adjusted similar to how valve clearances are checked and adjusted at set intervals. If the system gets out of spec and the correct clearance diminishes, more air escapes each time the decompressor opens the exhaust valve effectively lowering the compression of the engine. Old spark plugs are another culprit which might make a bike hard to start. If the plug is old and worn the spark will be weaker, making it more difficult to ignite the mixture. Keeping fresh plugs in the engine can greatly improve the bikes starting tendencies. Temperature and altitude should also be thrown into the mix here. If for some reason you moved from sea level to 6,000ft, fueling requirements for starting will be different since the air density varies in relation to altitude. As altitude increases the density of air (i.e. the amount of oxygen in the air) decreases thus requiring leaner jetting to make the bike run correctly. Air density also varies with temperature. The warmer the air is - the less dense the air is. So if you have summertime jetting and it's now wintertime and the bike is harder to start, it shouldn't be a surprise. The colder temps require richer jets to be installed for the increased air density. "How do I start a four-stroke dirt bike?" - Another good question that has lots of answers depending on the type of bike, if it is fuel injected, carbureted, hot, or cold. I'm going to assume most of the folks having trouble starting their bikes have carbureted bikes. I will provide my personal starting strategy I use on my CRF450 and if anyone is inclined to outline their strategy or provide alternatives to mine, feel free to leave a comment and share your knowledge. When Cold 1. Fuel petcock turned on 2. Choke turned on 3. Twist throttle to wide open three times 4. Roll engine over with foot until compression stroke is found (on engines with decompression systems typically it will be possible to feel the decompression system working). 5. Kick repeatedly until bike starts (usually 3-5 kicks) When Hot 1. Depress hot-start lever 2. Roll engine over with foot until compression stroke is found (on engines with decompression systems typically it will be possible to feel the decompression system working). 3. Kick repeatedly until bike starts (usually 1-3 kicks) Some of you might be wondering why the throttle is twisted wide open three times and this is a great question if you're unfamiliar with the internals inside a four-stroke carburetor. The majority of dirt bikes produced in the past 10 years come equipped with a Keihin FCR carburetor. The FCR carburetor is equipped with an accelerator pump. An accelerator pump works like a fuel bulb that you might find on the small engine of a power washer or weed wipe. As the bulb is squeezed a splash of fuel is pushed out. The accelerator pump was designed into the carburetors to smooth engine operation from low rpm low load scenarios to transitions to wide throttle. As the throttle is twisted to full-open, a plunger within the carburetor is actuated and forces fuel out of the "fuel bulb" through an orifice into the throat of the carburetor. For starting, the accelerator pump can be used to prime the intake tract with fresh fuel. Does it matter if I find top dead center on the compression stroke? It isn't critical, but this is what I'm used to and what works best for me. I hope you found this write-up helpful! As someone browsing through my repair and rebuild content I think you might like The Four Stroke Dirt Bike Engine Building Handbook. To learn more about the book and pick up your own copy, click here. If any of you want to share your experiences feel free to leave a comment, thanks! Like this blog post and want more like it? Sign up for our eNewsletter! Sign me up for the eNewsletter!I'm ready to take my dirt bike knowledge to the next level. Success! Now be sure to check your email to confirm your subscription. There was an error submitting your subscription. Please try again. Email Address I'd like to receive the free email course. Subscribe Powered by ConvertKit Comments |  Learn More AboutPaul Olesen  Inspirations1. JOHN BRITTEN2. KIM NEWCOMBE3. BURT MUNROE4. FRITS OVERMARS5. JAN THIEL6. WAYNE "WOBBLY" WRIGHTCategoriesAll Buying Used Dirt Bikes Cam Chain Maintenance Changing The Oil Compression Testing Dirt Bike Maintenance Engine Deisgn Fixing Broken Bolts Four Stroke Rebuild Free Motorcycle Films Ice Riding Leak Down Testing Motorcycle Wrenching Tools Replacing Spokes Service Manuals Suspension Two Stroke Two Stroke Rebuild Used Bike Buyer's Guides Wheel Truing Workshop Setup ArchivesNovember 2022 June 2022 January 2022 July 2021 June 2021 May 2021 September 2020 August 2020 July 2020 April 2019 March 2019 October 2018 April 2018 March 2018 January 2018 November 2017 October 2017 September 2017 July 2017 June 2017 April 2017 March 2017 February 2017 January 2017 December 2016 November 2016 October 2016 September 2016 August 2016 July 2016 March 2016 February 2016 January 2016 December 2015 November 2015 October 2015 September 2015 August 2015 July 2015 June 2015 May 2015 April 2015 March 2015 February 2015 January 2015 December 2014 November 2014 October 2014 September 2014 August 2014 Favorite Films1.ONE MAN'S DREAM2. LOVE, SPEED, AND LOSS3. WORLD'S FASTEST INDIAN4. TT3D5. ON ANY SUNDAY |
store | CONTACT US[email protected] | WEBSITE TERMS & CONDITIONS© COPYRIGHT 2022 DIY MOTO FIX LLC |
Tag » How To Start A Dirt Bike
-
How To Kick Start A Dirt Bike: 9 Steps (with Pictures) - WikiHow
-
How To Start A Dirt Bike EASY! Start First Kick Everytime - YouTube
-
How To Kick Start A Dirt Bike! Kickstart Dirt Bike! - YouTube
-
How To Kick Start A Dirt Bike - YouTube
-
How To Kick Start 4 Stroke Dirt Bike, Fuel Injected And Carbureted
-
How To Kick Start 2 Stroke Dirt Bike - Beginners Guide. - YouTube
-
How To Easily Start Any Dirt Bike Hot Or Cold - Motocross Hideout
-
How To Start A Dirt Bike
-
Starting And Shifting A Dirt Bike : 5 Steps - Instructables
-
How A Dirt Bike Kickstarter Works (How To Kick Start My Bike)
-
How To Start A Dirt Bike
-
How To Start A Dirt Bike - SportsRec
-
How To Start A Dirt Bike With A Kick Start - MotoInsanity
-
How To Bump Start A Dirt Bike (4 Easy Steps That Work Every Time)