How To Check Valves on A Dirt Bike – Beginners Guide

A dirt bike rider can be in trouble when he faces the problem of valve clearance adjustment and that is why it is necessary to understand how to check valve on a dirt bike in the sense of many terms which includes clearance also. You may have knowledge about what is the importance of bikes valves clearance.

What is the necessity for that to be maintained? If you are not aware of this you can go first read it out and understand the importance of dirt Bike valve adjustment. What if being a rider you go to a service centre then you ask for valve adjustment cost and that will make you realize you should also do it yourself.

What is the correct time for valve adjustment is really a necessary thing which should be understood by every Rider. And I am sure you are also one of them who is really serious about your bike and you love riding. This is why you are going through this post and want to gain some knowledge regarding this.

I want to ensure you that after reading this post you will also become a good mechanic for your dirt bike, don’t take it as other but we are talking about for your bike only because a rider should have all the knowledge regarding a bike so that if he is riding in a place where no one is there to help then you alone can tackle these problems. So now without wasting your time let’s start and understand how to check dirt bike valves?

How To Check Valves on A Dirt Bike – Beginners Guide

It is always considered to be checking and adjusting valves on a regular basis and make it a habit of a routine inspection. There should be a daily routine that should be maintained on high-performance engines that are used regularly on a track.

Inspections of valve clearance are not that much hard to be performed and most of the dirt bike owners have the capability to perform it in an effective way. However, there are many tricks and tips shared by the experts that can make this job here goes smoother and that will give the result it satisfies.

If you have a dirt bike, street bike or any bike which is consists of the four-stroke engine then you must have received your owner’s manual through which you get a perfect guide for engine valve clearance inspection. And every rider should understand the symptoms of tight Valves of dirt bike or a Motorcycle.

According to the use of it, the inspection interval can be different from the brand to a brand that can be in point of particular hours and can be based according to distance.

All bike owners have to check the clearance in a particular specified interval as it is important to be sure the engine continues to perform with good efficiency that will be running longer.

Tools Required for the Inspection of Dirt Bike Valve

  • Feeler gauges
  • Clean rags or towels
  • Screwdrivers
  • Vernier Caliper
  • Metric wrenches
  • Metric sockets

Other additional tools which are Required:

  • Owners manual
  • Allen keys
  • Tie-wire
  • Magnet

Feeler gauges

How To Check Valves on A Dirt Bike

A feeler gauge is a measuring instrument that can be used with hands for measurement of the gaps between two objects. It is consists of a number of folding metal strips which are also called leaves or blade that have different specified thickness levels.

The unit of measurement is taken in millimetres or it can be in inches also which is grouped in the centre of its every strip. It is a minimum of 0.02 mm so it can fit into the smallest gap between two sheets or two metals for any objects which have this much gap.

Feeler gauge has the capability to measure the minimum dimension of 0.02 mm that is called 0.0008 inches and maximum it can measure up to 5.08 mm which is 0. 2 inches. When you buy this measurement gauge and instrument you will get measurements and Specs rate and on the strip of 8 and also you will have manual for this.

A filler gauge is a little bit different from other measuring devices as you can visually see the gap and insert the metal strips of feeler gauges until it completely fills the gap. If it has filled the complete you get the exact gap between any dimension.

Clean rags

Cleaning rags are considered to be part of any cleaning routine. It is one of the most environment-friendly if you to use it in a correct way. You don’t have to leave lint after cleaning.

While using it you have to take care of this because if not used correctly then it can become a gross smelly mess. During the valve checking for cleaning purposes, we can use cleaning rags.

Screwdrivers

A screwdriver is defined as a tool that is operated by the hands turning motion which is a specially designed tip that can be inserted in the screws head. There are different types of tip designs for special applications that are used for the application of assembly.

But the most common screwdrivers are standard that is also called flat straight or shared tips. The screwdriver has made of plastic or wooden handle.

Many screwdrivers today coming with rubberized cover for perfect grip. During the inspection and maintenance of the valve, a screwdriver is always a tool for use.

Vernier Caliper

measuring valve clearnaces

The Vernier calliper is one of the most precise measuring instruments. It has a tolerance of 0.02 mm and the reading error is 1/20 mm that is equal to 0.05 mm.

This instrument is used to take an accurate measurement reading between two graduated markings on a linear scale by the implementation of mechanical interpolation.

vernier caliper

This instrument is used for making accurate linear measurements and the scientist behind this invention was Pierre Vernier. He was a French citizen.

In vernier scale, there are to graduated scales first one is the main scale that is similar to a ruler and the second one is the vernier scale that slides parallel to the main scale and it enables reading to be made to a fraction of division on the main scale. Vernier callipers are widely used in the scientific laboratory and also in manufacturing for Quality Control and Quality analysis.

Metric wrenches

Fastener tools are really very important such as a metric wrench. Almost every house needs wrenches to fix there different types of machines.

Most of the people used a wrench to adjust fastener such as nuts and bolts of their home appliances vehicles for bikes. Being a bike rider you must have a wrench.  The wrench comes in different sizes and shapes.

Metric sockets

Metric socket wrenches fit fasteners where that nominal length is a round number of millimetres like 8 mm, 10 mm or 15 mm. By using this metric socket a number of ranges can be measured exactly at the nominal dimension. Clearances and tolerances are very important in manufacturing industries.

How To Check Valves on A Dirt Bike – Complete Step by Step Method

For the inspection of the valve, we need to uncover the engine partially. As for the inspection you need to open the engine so it will be good if it is completely clean.

There is a chance of dirt and debris to be entered inside the engine so before going further steps you should clean it thoroughly. First of all, you need to clean the cylinder and its surrounding area.

Remove cylinder head-cover

Now you have to remove that cylinder head cover after its cleaning. For cleaning, you can use clean racks as we have already mentioned above.

You need to remove your seat, fuel tank, and other components after this. It can be done by following your service manual which is consists of sufficient guidance for the removal of the parts or components you need to uncover your engine.

There is one thing you need to note down that is when you are removing the cylinder head cover you have to be extremely careful and aware of not to fall anything inside the cylinder head.

Position the Valvetrain

Next step you have to position the valve train so that clearances can be inspected. In service manuals, there is a specified setting method of the valve train and given that the piston is at TDC that means the top dead centre on the compression stroke.

When you set the valve train at the specified position then it ensures that the cam is at a circle and in that position intake and exhaust valves are not open. The circular motion of the cam is the base circle of it that does not play any role in the valve lift.

If you are not comfortable with the user manuals which is the most recommended for setting the piston position and engine stroke when the engine is being assembled then it is not necessary especially when you are working on the engine that is being rebuilt.

You can complete the inspection of valve clearance with the cylinder head removed from the engine and positioning the cam lobe opposite to the lifter brackets and it will ensure that the clearance measurements are taken with the cam on its base circle.

The service manual that comes with the manufacturing company has enough guidance to set the engine on its compression stroke at TDC. Engines also provide meeting alignment signature on the crankshaft and engine case as well as cylinder head and cam gear.

It is necessary that you should know and understand how to utilize this reference point’s as a mark because these are used to set the cam timing correctly after any valve clearance adjustment had been made successfully.

Measure the Clearance 

When you have correctly positioned the cam valve, clearance can be measured using feeler gauges. Feeler gauge measurements are really necessary as it requires a skilled person as it has narrow surrounding geometry and a person who is not experienced can get variations in his measurements.

measuring valve clearnaces

To get the accurate and perfect measurement data it is necessary that the gauge should be inserted between the lifter bucket and cam as close to parallel as possible. To maintain the parallel entry you have to bend the feeler gauge as it required so that their tip can easily put inside between the cam and lifter bucket.

measuring valve clearnaces

It is considered that gauge measurements are subjective because they are based on the hand measurements which is like a feel. The most accurate and valve clearance measurements can be obtained when the feeler gauges pass between the lifter bucket and the cam with slide drag.

When the feeler engages passes through easily or it must be forced through should be considered to thin to thick respectively. When this happens other gauges should be tried also if you are between sizes the average of the two should be used as the valve clearance.

Compare the Recorded Clearances with Standard Specification

After cmpleting the measurement of intake and exhaust valve clearance their reading should be compared with the standard specification mention on the user’s manual.

If the valve clearances fall within the manufacturer’s recommended specification there is no further work that should be done and it is not required. If clearances are above the specification mentioned on the user’s manual then you have to determine what adjustment needs to be made in the next step.

To complete this you should get the measurements of current valve shim thickness and you need to disassemble the cylinder head so that shims can be removed and measured.

Remove the Cam Cap, Cams and Lifter jackets

Now you have to follow the user’s manual for the further steps to slacken the cam chain, remove the camp cap, cams, and lifter jackets.

When you are removing cam cap you have to be sure to follow any sequence mention in the user’s manual for removal or tensioning. The cam chain is free to use a piece of wire to secure it to the cylinder head if anyhow it falls in the chaincase you can use a pain magnet to lift it.

tie wire on chain

For removing the lifter bucket pen magnet or a valve lapping tool can be used. When you are taking out the lifter bucket from the valve you have to be careful.

While removing the lifter bucket you need to be careful with valve shim to be the stick. Underneath the lifter buckets makes sticking shims common.

When the engine is in operation the lifter bucket mate to their respective bores. Most of the people are familiar with disassembly but assembling it on its own position can be hard. To make it easier you can draw a diagram for disturbing and you can keep it in sequence and when you are again and assembly would this it will help you a lot.

Remove the Valve shims

Now from the cylinder head remove the remaining valve shims. When you remove the valves shims measure the shim thickness and diameter of the shims.

removed shim and bucket

Find the required shim thickness

For determining the shim thickness there is the formula:

Req. Shim Thickness = Measured Clearance - Specified Clearance + Old Clearance

Now where you have to calculate the required Shim thickness for adjusting the valve. Which of the international companies have valves Shims available but the shim kits that come with different sizes are also available from the aftermarket.

Before buying the shim you need to measure the diameter of the shim you required. Because there are different sizes of diameters available by different companies.

Valve Shim Diameters

  • KTM – 8.90
  • KTM – 10.00
  • Japanese – 7.48
  • Japanese – 9.48

When you are going to find out the required shim thickness then you should set up in your mind that you have to move on the upper end of the prescribed clearance range.

Adjust valve by Inserting the required shim

This is always advised by experts because valve clearance is usually diminished over time. 0.02 mm and above diameter show the Shims that can be useful will also make an impact on the new clearances that can be achieved. Finally when you are having the correct shim thickness then valve train reassembly can be started.

valve shim

Lubricate and install the valve shim

You have to lubricate the valve shims and carefully install them so you can use engine oil. You have to lubricate the lifter brackets also before its installation when you are inserting the lifter bucket into their respective bores you need to be sure that buckets bottom on the shims and properly adjusted.

If so happened that the bucket comes back up during the installation occasionally the shim will stick to it and become displaced. If the shim is not properly fitted then the engine can be damaged severely between the valve and lifter bucket.

Set the cam valve and its timing

Now set the cam and cam timing and place the crankshaft at the exact correct position.  Now pull the chain and tighten it from the crankshaft. Check the orientation of cam gear is correctly placed and the chain should be wrapped around it. Check the alignment of all components and parts and cam bearing should be properly lubricated.

While installing the cam cap follow the user’s manual and maintain the torque specifications and all sequences. There should not be any deviation that can bring a fitment issue which causes wear of cam.

After securing cams use the feeler gauges and confirm whether the clearance is under tolerance. Deviation should be maintained if anything is not in specification then the error should be rectified before going further steps.

Tension the cam chain

Now you have to proceed to tensioned the cam chain. Follow the manual’s guide to complete this. When the tension is perfect then rotate the engine at least 5-6 full revolutions. This will correct the chain position. That will also confirm the engine has been timed correctly. Fix the position of the piston on the compression stroke and check the timings feature on the crank and cam remaining in the specification.

Finally, finish the process by reinstalling the cylinder head cover carefully.  And in specification tighten the bolt. Hurray, now you are ready to ride.

Conclusion

How to check valves on a dirt bike can be a tough question to be asked from a beginner Rider but for the older one, it can be a daily routine like him. Inspection of valves on a dirt bike is like and habit if it is really serious about the riding.

That’s why maintaining the performance of a bike to get greater efficiency is a really necessary task. Hence in this post, we have talked about Dirt Bike valve inspection so that you can also be a master in this activity.

Sources: Thumper talk (how to check and adjust valve clearance), How stuff works Screwdriver

LEAVE A REPLY

Please enter your comment!
Please enter your name here