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Original: Russ - Cotswolds UK

<div class="postrow has_after_content"><h2 class="title icon">Carburettor Testing (Get it Going)</h2><div class="content"><div id="post_message_2449496"><blockquote class="postcontent restore "><span style="font-size: larger;"> Small Engine Diaphragm Carburettor Tests</span>
QUICK TEST
Prove metering system works . . . .
Put 10psi on fuel inlet and see it hold there, (will creep down slowly) put tube on diaphragm vent hole and blow, watch inlet pressure drop
If it holds and drops that&rsquo;s working

Test Main jet and Check Valve
Screw low Needle in until snug fit (Do Not Over tighten you will damage seat) then remove High Needle, get red nylon tube from WD40 spray can or similar and place in jet hole (takes some fiddling to get a good seal) when you think you are in the jet blow then suck you should feel the valve opening and closing as you do this (easy to blow harder to suck) if your not getting a response try sucking and blowing a little faster, if still not noticeable attach your WD40 and squirt some in (look in chamber and you should see it come out of the main jet, then try the suck blow test again (remember to clean the tube or you will get a mouthful)

Test Low Jets
Remove L needle put tube in and spray with WD40, look in chamber you should see it coming out of both holes.

NB
Using WD40 like this is OK for short periods (Don&rsquo;t leave it in there for to long) I usually flush through with petrol after the test, A Quick blow on the supply tube will prove fuel can get there.
Put both needles back in till snug then back off 1 and &frac14; turns (most working Carb&rsquo;s will start at this setting)

General Notes
Main jet is in the centre of the chamber. Low Jets are each side of the throttle butterfly (Engine end). The H high needle (shorter one) is always closest to the air filter end and the L low needle (Longer one)is always closest to the engine. I made my pressure tester with a bicycle pump that had a gauge or you could use a car tyre pump and make an adaptor with an old valve stem and some fuel line (just remember not to go over 10psi or you might damage the diaphragm)

If it passes all these tests it should start and run now???

Set up the low jet first to get the engine ticking over nicely.
Increase the tick over screw so the engine runs without stalling, now by moving the L Jet in till it starts to die then back &frac14; turn should be ok, now turn the T O screw till the engine runs a nice speed below the clutch cut in speed. Now open throttle and adjust H needle till you get a nice response as the engine speeds up and down (H needle should be set with a hot engine) now this will probly be to lean a mix, with full throttle screw in till engine starts to falter (4 stroke) then turn screw back &frac14; turn. (this should be somewhere handy)
Now I usually run a couple of tanks through just to get everything to stabilise then reset everything again. Just remember to rich it might flood or foul the plug but to lean will kill your engine (so get it right!)

Quick Tip
Most carb faults are caused by storing machines with fuel in, I found if your lucky and its not damaged just clogged up, you can warm it up with an air dryer then flush through with WD40 followed by petrol, found this to work well on a lot of carbs without dismantling anything.

Hope this helps!
Russ&hellip;

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ORIGINAL: Tired Old Man

I'm more interested in what you're growing;)

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