torek, 29. julij 2014

Motorcycle Valve Guides

When repairing cylinder heads, mechanics are often facing the question to replace the valve guides or not.

Before they do it, the valves, valve guides and the valve seats must be inspected thoroughly. Cylinder head must be fully disassembled, to complete the inspection of the various parts. The disassembly includes removing the valves, plugs and seals which should automatically be replaced during a cylinder head service.

If you want to remove the valve guides it is necessary to heat the cylinder head. The aluminum cylinder head will expand twice as fast as a the valve guide, therefore as the head warms the guide will effectively loosen.

The mechanic should place warmed cylinder head onto a wooden support. To initiate removal of the guide, you should use the aluminium drift first -> you can accomplish this with a good hard hit with a hammer. As the valve guide moves out of head, the aluminum drift should be swapped for the steel item to complete the process.

After you remove the valve guides, holes in the head must be cleaned really good with a simple circular brush in an electric drill. Pollished hole will be ready for fitting the new guide. Before the new guides are fitted, head will need to be re-heated and the guides should be placed in a bag, then put into the freezer.

When we reach the appropriate temperatures with the head and guides, the new guides should be drifted into the head with an aluminum drift and the valves should be re-grinded to ensure a good seal. 
valve guide

sreda, 23. julij 2014

Helpful Hints

Helpful Hints

  • Don't ever buy a second hand cylinder at least not without asking for good advice first.
  • You should know that your valve may not be serviced unless it is damaged, in poor condition, which is noticed by the station operator, or you specifically ask for it.
  • If you want your cylinder to be tested and stamped with the next months date, test it at the end of the month due on your test stamp.
  • Don't hesitate to have your cylinders tested annualy, if you have your own compressor.

Condition of the rings, cylinders, and valves can be measured with compression or pressure testing, ususally you'll need a helper to do it. Although you can do it by yourself, it's very difficult, but the biggest problem is, that you can't see how the cylinder pumps up.

pressure testing

Become a wheel repair specialist

You have to educate yourself about the various types of wheels, rims and wheel & rim repair processes. This is very important. Once you become a wheel repair specialist you will encounter two most common types of wheels, which are alloy and steel wheels. A different set of steps for repair will be required for each type.

It's good to know the most common types of damage that can happen' to wheels and to find their repair techniques. If it's possible, find a wheel or rim repair specialist somewhere in your area and ask him if he maybe offers some kind of internships or apprenticeships.

If you can get a position like this, it will give you the opportunity to learn a lot about wheel and rim repair. You'll even get paid for working and will be learning at the same time. Don't be impatient, before you'll become a wheel repair specialist, it will take several months or even years. Learning and practising this skills takes time! Be persistent and dedicated, with consistent practice you'll develop the necessary skills.
rim repair
wheel repair specialist

torek, 22. julij 2014

The valve design

The flow of fuel vapor into the combustion chamber is controled by valves, also the flow of exhaust gases which are leaving the engine. The engine can lose power and fuel efficiency due to pits, cracks or grooves that are caused by faulty or dirty valves which may stick.

You should carefully inspect the valves, when you remove them from the engine. If they are not badly worn and the parts are not damaged, you can tune up the valves and seats so that they seal effectively.

Valves contain a stem, neck, head and face. Each valve stem moves in a valve guide that is machined directly in the cylinder block or in a bushing which is replaceable. It also moves through a valve spring, adjacent to the valve guide, that pushes the valve forward the closed position and holds valve face against the valve seat. Some of the valve assemblies also include a rotator, which is a circular component that turns the valve slightly in each cycle to ensure that wear pattern on valves and seats is symmetrical. 
valve guide

torek, 24. junij 2014

Valve guide knurling

If you roll or cut some patterns onto plastic or metal (or any other material), you're using a method called KNURLING. Typically this procces is used on a lathe, but in some situations we'll use a hand knurling tool instead.

We can often find knurled patterns on knobs, handles and other items where a better gripping surface is needed than the one offered by bare material.
Another use and probably the most popular process is for repairing a worn guide, which can be returned into service. The valve guide is build up and then reamed back to its proper size. When the guide is repaired, we replace the guide seal. 
valve guide

Internal high-pressure testing

When talking about cyclic test mode, pressure is applied to the test item by the controller. On the secondary site volume of oil decreases, witch is caused by the unavoidable leakage (in pressure transformer – the piston creeps towards the secondary side)

The controller stops input of the setpoint value, retracts the piston when a specified limit is reached, thats how he compensates this. When testing this items we must know, that for recognising damage, time period between intervals of oil getting is failure criterion of high precise. If we come across parallel switching, we close the test connection on the distributor and remove the test items.

When the internal high-pressure test is completed, you can draw the dispersion conclusions ( distribution of failures over time) in the test batch. 

Internal high-pressure testing

sreda, 11. junij 2014

Oxidation wheel repair

Alloy wheels can be purchased for cosmetic reasons although the alloys used are not corrosion/oxidation resistant so they will eventually start to corrode (after 3 to 5 years). The good news is that refurbishment is now widely available!

Given sufficient time, a chemical reaction between oxygen and water will cause an alloy wheel oxidation. If this happens to you, we have a few tips/solutions for wheel repair that you should follow:

Don't use any products that contains ammonia or acid for cleaning your wheels. Just use a quality cleaner and wax them, if you want even better protection, use wheel wax because it will cut down on brake dust corrosion. BTW: wheel wax is harmless for your alloy wheels.

Also to prevent rust from starting, keep the underside of your car clean! You can use a simple lawn sprinkler and put it under your car.