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 (Holts) which slightly softened the carbon, a perspex scraper and fibreglass tip "pen". Of course it's essential not to damage the cylinder or piston (especially sides), so using any tools harder than aluminium 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 3000 grade emery paper was used to lightly polish the piston (after photo was taken). The engine seemed to run smoother after doing this, but it could be my imagination ... at least it ran.

The main tools used

Making a Long Handled Grabber from Telescopic Pole Pruner

ToolsPosted by Dennis Hopkins Thu, March 31, 2016 09:27PM
I needed to grab some litter out of a pond, and for a cheap solution I adapted a low cost telescopic pole pruner to do the job (click photo for a bigger image). It's quite heavy when fully extended, fitting a shoulder harness may help with handling.

There is no permanent modification to this pruner, I just removed and replaced two nuts (1 and 2 in photo), so it can be easily reverted to normal use. For this conversion I used some old metal bits I had saved - a (rusty) metal "T" bracket (A), with holes enlarged and fixed to the existing pruner nut/bolt (1). A section was cut off the T bracket which formed a jaw of the grabber (A2). I used a strip of metal (B) to hold part (A) in place with existing pruner nut/bolt (2), and additional nut/bolt (3).
Note: here the pruner blade is still in place and may cut grabbed objects

I also fixed a piece of strong wire (C) with a hooked end to the pruner using duct tape. So litter etc. can be held in 3 ways: 1:with this wire, 2: the "grabber" jaw, and 3: between the cord and the pruner mechanism. With a little more thought I'm sure the design could be improved, for example to shield the blade - otherwise grabbing electric cables, fish etc. not recommended!

Thorny Problem

ToolsPosted by Dennis Hopkins Fri, October 24, 2014 11:57AM
This not-too-thrilling entry was inspired by reading that people were getting stung by nettles and scratched by brambles while clearing vegetation. I've found that thick, closely woven clothing gives some protection. As for gloves, a good compromise might be all leather, lined types. Those made with fairly thin, supple leather allow use of tools while providing some protection against thorns. Even with careful handling, thorns may go through the leather, but the lining should reduce the probability of injury. Puncture wounds could become infected by bacteria etc. present on the thorns, possibly a serious health risk. Heavier duty clothing and gloves are probably advisable for handling hawthorn/blackthorn and the like.
Lined leather gardening gloves can be bought for around £10 in a store or a bit less online (left). So called "Driver's Gloves" provide similar limited protection - available for around £6 (right).

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 March 2016:
The Ryobi tool has worked to some extent for a couple of years, but has been very reluctant to start, or sometimes impossible. On two occasions I've found that a piece of debris has located or "grown" in the spark plug gap - see photo below (I couldn't determine what it was):
I've stripped down the caburetter again, more fully this time - finding what looked like a piece of brush hair in the H (high speed) mixture valve. Maybe it'll run faster with that removed. There was also a sticky, wax like substance in the centre of the metering section "bowl", which I removed. I have probably left fuel standing in the tool for too long on some occasions.

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. If poor starting and running can't be fixed by working on the carburettor (and the plug, spark, fuel and air filters etc. are OK) - check the cylinder to crankcase
fixing bolts and gaskets (check them regularly anyway).

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. Other problem areas include a clogged exhaust, carbon debris in exhaust port, and a leaking crankcase gasket or seal (engine may have external oil residue).

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. It didn't harm this equipment, but the cleaning fluid was only present for a short time. 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.

[Note 8/2016: I suggest that if poor starting and running can't be fixed by working on the carburettor (and plug, spark, fuel and air filters etc. are OK) - check the cylinder and crankcase fixing bolts and gaskets. I've seen 2 machines with loose cylinder fixing bolts recently, and an engine with a displaced crankshaft seal (photo)]

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.

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: 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: , 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.

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.

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