Dennis Country

Dennis Country

Welcome to my blog ...

Please send me an email if you wish to leave a comment. My website includes sections on the environment, green woodworking and some industrial history photos from Gwent, UK.

Decarbonising a Small 2-Stroke Engine (Decoke)

ToolsPosted by Dennis Hopkins Sat, January 06, 2018 02:50PM

An old brushcutter engine had carbon deposits in the top of the cylinder and piston, and in the exhaust port. It was decided to try to remove this because any dislodged pieces might damage the engine. For this I used some carburettor cleaner which slightly softened the carbon, a perspex scraper and fibreglass tip "pen". Of course it's essential not to damage the cylinder or piston, so using any tools harder than the cylinder/piston metal isn't recommended. The perspex is quite hard, part of an off-cut, and can be cut to shape with a hacksaw. The fibreglass "pen" is usually used to clean circuit boards etc., but worked well as a second stage tool here (the fibres are a health hazard to skin, eyes).

After a couple of hours most of the carbon was removed, except for some very hard material at the top of the cylinder, some of which was embedded in pit-damaged areas which will have to stay as it is. Some 1200 grade emery paper was used to lightly polish the piston (after photo was taken).

Of course this is also a good time to check the condition of the crankshaft, bearings, and wear on the cylinder, piston and rings, also that the ring(s) can move freely in their groove(s).

The engine seemed to run more smoothly after doing this, but it could be my imagination ... at least it ran.

The main tools used, plus carburettor cleaner

Small Carbs 2 - Ryobi fails to start

ToolsPosted by Dennis Hopkins Fri, November 29, 2013 11:44PM
I've uploaded this in case it helps anyone with a garden machine tool having a Ruixing H142R carburettor, fitted to some Ryobi models (and other "cheap" makes such as Homelite and Sanli use Ruixing carbs). The brushcutter was difficult to start when warm, and after several hours use it ran too slowly to be usable. On searching the internet it seems that many other people have the same problem - I believe the fuel/air mixture is preset too lean.

On this machine the idle (marked L), and fast running (marked H), mixture adjustment screws require a special tool known as a "pacman" style adjuster - obtainable for about £15. However, it is possible to cut slots in the adjustment screws to adjust them with a flat screwdriver. I did this using a mini cutter disc fitted to an electric drill, having removed the carb. from the machine. I adjusted first the L, and then the H mixture screws, and although not perfect the machine now starts better, and runs at a usable speed. Instructions on how to adjust the mixture on 2 stroke engines are commonly available. It may be illegal for users to tamper with this adjustment in some countries.

Having adjusted the mixture the engine does usually work acceptably most of the time.
I should say to please take care if you're working on engines - there is a risk of a fuel fire, and other precautions should include wearing safety spectacles. It's important to get both the petrol/oil and the fuel/air mixtures correct to the manufacturer's specification, otherwise the engine may be seriously damaged.


Update August 2016:
The engine of this machine stopped working while using the hedge trimmer. On stripping it down I found that the bolts holding the cylinder onto the crankcase were loose, the piston was badly scored, the crankshaft bearing had disintegrated - in effect a disaster. I suspect the cylinder bolts may have worked loose some time ago, which would give poor starting and running performance.

My Conclusions:

1. In the case of poor starting and running check compression is near 100psi, and
plug, spark, fuel and air filters etc. are OK. Also check crankcase sealing - black oil covering engine may indicate a gasket, seal or fixing bolts problem.

2. Don't purchase "cheap" machines made by Ryobi, McCulloch, Sanli etc. unless they are intended for very light or practically no use!


Extending Handle Repair on Pruning Lopper

ToolsPosted by Dennis Hopkins Sun, November 10, 2013 09:27AM
The catch had broken on the extending handle of a pruning lopper (see photos below). On dismantling I found that a locating lug had broken (it was made of a cast metal). It was the second one to go on this tool, and I repeated the last repair which used a cut and filed down 4 inch nail to replace the broken part. Otherwise this is a good pruner, so spending about 30 minutes on it was well worthwhile. Luckily the catch is held together with removable pins, other designs may not be so easy to work on. A vice and good files are pretty essential for this repair. There is a video slide show here.




Small Carbs

ToolsPosted by Dennis Hopkins Wed, February 27, 2013 12:46AM
An older brush cutter was not revving fast enough. After checked things like air filter, fuel tank and filter, spark plug, thoughts turned to the carburettor - is there dirt inside, are parts worn? It's also worth checking the adjustment of the fuel mixture. Some other problem areas are carbon debris in exhaust port, a leaking crankcase gasket or seal (engine may have external oil residue), and worn piston ring/cylinder.

It looked like a carb. problem, and because it was an old machine I thought I'd start by fitting a rebuild kit (pump diaphragm, gaskets etc.). Having found the make and part number (stamped on the carb. usually), I found some information about it on the internet and located a source for the kit - on Ebay in this case.

This is the the carb. partly dismantled, a kit of new parts (usually costing around £5 - £10), and the "exploded diagram" - useful not essential. A couple of links to carb. manufacturers are here: WALBRO | ZAMA - much information on these websites. Another web page, "Basic Small Engine Repair", appears to have useful information including photographs on this type of carburettor.

With the metering and pump parts removed, I used carb. cleaner and air from a foot pump to flush the fuel pathways within the carb. body. I have seen advice not to use carb. cleaner on this type of carburettor, also only to use low pressure air for flushing. The the cleaning fluid was only present for a short time in this case. I had also removed the idle and power mixture screws, which were reset to their factory setting (final adjustments made with the engine running). Moving the mixture screws (if fitted) should not be necessary on newish machines. However it seems that some Ryobi models, and others using Ruixing carburettors, do not start and run well with the manufacturer's setting.

After several hours of use, the engine cut out at high speed and over-revved or hunted at idle. Luckily this was easy to fix - a blocked petrol cap breather hole resulted in intermittent fuel starvation. It was possible to dismantle and clean the cap components. Other causes could include a collapsing fuel line, or an air leak in the fuel line or carburettor seals.

Please take care if you're working on machinery like this - there is a risk of a fuel fire, and other precautions should include wearing safety spectacles. It's important to get both the petrol/oil and the fuel/air mixtures correct to the manufacturer's specification, otherwise the engine may be seriously damaged.


Update, 2018: What's under a Welch plug?
There may be one or more of these soft metal caps in a carburettor. They seal areas which have been drilled and/or machined. They can be removed for inspection of hidden areas, but a new one is needed since the old one is normally damaged in removal. They are a press/distortion fit, and a suitably shaped punch is needed to install a new one. This is easy with a circular shape, but a wooden "punch" can easily be made for other shapes. The photo below shows the area under the Welch plug of a Walbro WT249 carb (above centre):
This plug covers the low speed fuel pathway. Light can be seen through three small holes which go into the carb. barrel. These are for the idle fuel "jet" (top), and two lower holes (progression), which carry fuel as the throttle is opened from idle. Fuel is sourced from a fourth hole via a one way valve (brass insert with hole, see below). This valve feeds both the low and high speed fuel paths in this carb, others may have a separate one-way valve for the high speed circuit.

The fuel flow is constricted by the "L" mixture adjustment screw (lower right). It's only necessary to remove Welch plugs if it's though a jet hole is blocked or that there may be debris underneath it.

One Way Valves
There may be one or two one-way valves in carburettors like this. They let fuel flow one way and exclude air flow into the fuel paths. They are delicate, and a reason why only very low air pressure should be used to clean the carb.. The valve(s) can get stuck open or shut or be intermittent, in which case the engine may be impossible to start and/or power up from idle. Sometimes new valves are available, but if not a new carburettor is probably needed.


Wooden Frame Saws

ToolsPosted by Dennis Hopkins Sat, June 23, 2012 08:58PM
I recently made up several wooden framed saws as an experiment - with a practical use perhaps. In the photo, the top two use standard 21ins bow saw blades, the bottom two use "emergency" or "survival" saw wires (approx 24ins, £2 each). Click photo for larger image in new window
These designs go back many hundreds if not thousands of years. The hardest part is of course making the blade, which I left to someone else! The ash frame (top left) took a while to make, but should be quite durable. This one, and the frame saws made of (willow) sticks, are best made of seasoned wood. Willow makes a light weight stick frame, but what type of willow you may ask. I used crack willow (I think), but it's cheap to experiment.

The bow (bottom right) is the simplest and probably oldest design, and it can also function as a walking stick amongst other things. It needs to be made of wood which has some spring in it - as in a bow and arrow! It can be fitted with a conventional blade, or in this case a "survival" saw wire. The wire bladed frames can be used as improvised fret saws for cutting intricate shapes, naturally the shorter the wire the more accurate the cut is likely to be. See also: www.dchopkins.co.uk/wood which includes a video slide show of making the ash-framed saw.

Hand Saw Sharpening

ToolsPosted by Dennis Hopkins Thu, May 24, 2012 10:42PM
I had a go at sharpening and setting some of my carpentry saws - but needed some kit to start with, see below:
Some of the main requirements are: a vice to hold the saw blade firmly, a saw set (I bought this one for £2 in a car boot sale, needed some cleaning), triangular file (smooth, £1.50). I also found a hands-free magnifier with light useful (£11).

Modern "hard point" saws cannot be sharpened
with normal files, but they can still be set. So you may get more life out of them if you can check and adjust the set angle of the teeth. I won't try to explain how to set/sharpen saws - it's covered elsewhere. For example, the article on this web page: http://www.vintagesaws.com/library/primer/sharp.html , gives very useful information on saws, and sharpening/setting techniques.
The photo above shows the result of converting a cheap cross-cut saw to rip saw (more or less), by filing. A rip saw tooth "chisel edge" should be at a 90 degrees angle to the blade length. I nearly took this cheap saw to the recycling centre because it had never worked (kept on binding), but with filing and setting it now does a useful job.

Notes:
1) A cross cut saw is designed to efficiently cut across the wood grain (the teeth act like knives), whereas a rip saw is designed to cut along the wood grain (the teeth act like chisels).
2) The set angle of the teeth shown in the photo above is greater than might normally be used. This results in the cut wood edges being "rougher" than normal, and the cut not so accurate, but the saw has less tendency to bind.
3) If a saw tends to steer away from its intended cut line it could be that the set angles of some teeth are generally greater on one side of the blade than the other (and the blade tension may be too low on a bow saw).
I used the above mentioned "rip saw" to cut down a piece of tongue and groove plank to make a bow saw blade guard. A deeper groove was cut (arrow) to house the teeth.



Stock Fencing Accessories

ToolsPosted by Dennis Hopkins Fri, December 30, 2011 11:55PM
In addition to fencing pliers, I found these items useful when working with stock fencing / barbed wire:
Left: the punch is useful for starting to remove staples.
Middle: this "wire twister" is a thin bar with 5mm hole, useful for splicing wires
Right: another "wire twister" - this one leaves a shorter sprig, and is made from a hasp (but it's possible to buy ready made ones). A piece of the hasp hinge was cut away to allow wire to be slotted in as shown, and two recesses were filed to guide the wire being twisted.

Both of these wire twisters are mild steel, and will cause some damage to the wire plating. I don't have a solution to that yet, other than using a softer metal such as aluminium ...

September 2013: a bucket and belt full of tools -
The wire twister and punch are still going strong. This selection of smaller tools was used for stock fencing with rails and electric fence - iron bar and post basher not shown. For larger jobs it could look like a truckload of tools - spade, tamper, shoveholer, chain saw, wire tensioners, winch etc..