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#1
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It sounds to me like the carb might need a good degunking.
Probably plugged or partially plugged jet/s. Try screwing the needle valves in (gently!) and back out a few time,s then put back to where they were and see if it helps. If not, perhaps something's plugged. You did check for a waterlogged/plugged fuel filter, right? Fuel's getting TO the carb? HTH, PopS wrote in message oups.com... : Hello everyone! I have a Briggs and Stratton 3.5hp engine fitted to a : Hayter rotary mower from the mid 1970s. The Model number is 92982 and : the Type number is 1640-01. It's a 4 cycle, single cylinder, L-head, : air-cooled engine for information. : The problem is I have had it sitting idle for 5 years as the starter : rewind spring broke and lack of time prevented getting it sorted : sooner. Last week I bought a new spring, rope, (approved Champion/B&S) : spark plug and air filter foam element (old one was disintegrating, : saturated new one with oil and squeezed excess out), filled the sump : with fresh oil and put in half a tank of fresh 95RON unleaded. : So far, so good. But pulling the rope and some carburetor needle valve : tweeking got the engine to start eventually, burning off the oil I had : put in throught the spark plug hole. It then splutters and pops (rich : mixture burning within the exhaust?) The spark plug has looks like it's : not running lean (fuel/oil on it). It then cuts out (maximum of about : 15 seconds after starting). Then you can restart straight away. Any : ideas as to the adjustments I need to do (I have found I can start it : and get it to idle very slowly with the throttle lever set to minimum). : Do I need to play with the idle adjustment screw? Is there the : possibility that the carburetor needs new parts too? I've heard B&S do : carburetor kits - how much would I be looking at (UK Pounds) and what : parts do they contain - anyone ever used one? : I know this is a long posting, but i'm not too hot on my knowledge of : getting carbs to work perfectly for a smooth idle. : Thanks in advance. (This email address is invalid because of spammers : so reply on here). : |
#2
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Pop wrote:
It sounds to me like the carb might need a good degunking. Probably plugged or partially plugged jet/s. Try screwing the needle valves in (gently!) and back out a few time,s then put back to where they were and see if it helps. If not, perhaps something's plugged. You did check for a waterlogged/plugged fuel filter, right? Fuel's getting TO the carb? HTH, PopS I'm thinking too that it's gunked somewhere. Fuel _IS_ getting to the carb (if you pull the starter rope gently with the air filter removed you are met by a mist of fuel around the choke valve). Haven't played with any fuel filters. Is there supposed to be some sort of linkage to open the choke plate? It's just that I can't see how it opens on it's own (vacuum effect???) and that would explain richness symptoms on the(new) spark plug and exhaust output popping. |
#3
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wrote in message oups.com... : Pop wrote: : It sounds to me like the carb might need a good degunking. : Probably plugged or partially plugged jet/s. Try screwing the : needle valves in (gently!) and back out a few time,s then put : back to where they were and see if it helps. If not, perhaps : something's plugged. : You did check for a waterlogged/plugged fuel filter, right? : Fuel's getting TO the carb? : : HTH, : : PopS : : I'm thinking too that it's gunked somewhere. Fuel _IS_ getting to the : carb (if you pull the starter rope gently with the air filter removed : you are met by a mist of fuel around the choke valve). Haven't played : with any fuel filters. Is there supposed to be some sort of linkage to : open the choke plate? It's just that I can't see how it opens on it's : own (vacuum effect???) and that would explain richness symptoms on : the(new) spark plug and exhaust output popping. : Well, -something- should open the choke plate, yeah. Is it staying closed or partly closed? If so, that's your problem, or at least one of them. Sometimes it's not obvious what keeps them open so look closely. There could be a spring disconnected that holds it in the open position or something real simple like that. D Matel gave you a great rundown on how to set the idle/hi speed mixtures, BTW, so I'd keep that handy. It's "standard" stuff but not always easy to remember and completely foreign to a lot of people. His method will work 100% if all is right with the carb and engine. A closed or partially closed choke though will certainly make an engine run rough or not at all by starving it for air. I suspect you've come upon the problem if you're relating it correctly. Your original post has been snipped out so I don't recall the original details, but it's fairly UNcommon in my experience for a small engine, esp a B&S, to operate on vacuum. At least I've never seen one; if I'm wrong, someone will be along quickly to correct me, I'm sure g. If there is no seperate cable to close the choke, which there probably isn't on that small an engine, it may be controlled by a centrifugal force wire when the engine is running and the positon of the throttle. I never thought much about it because it's always seemed "obvious" to me when I looked at them, but darned if I can explain it very well right now. Maybe Mr. Martel will come back and explain; something tells me he knows what he's talking about. Or he had a manual handy g. If you don't get anywhere and no one offers furhter assistance, come on back after you study the choke/throttle linkages a bit and I'll go see exactly what my B&S engines do; have three of them. I will say this: When you're assessing the choke plate position, do so while the engine is running (or trying to). I do recall that the choke plate on my push mower is mostly closed when it's at rest, which is fine with me: Keeps the spiders out over the winter! HTH a little at least PopS |
#4
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wrote in message oups.com... Pop wrote: It sounds to me like the carb might need a good degunking. Probably plugged or partially plugged jet/s. Try screwing the needle valves in (gently!) and back out a few time,s then put back to where they were and see if it helps. If not, perhaps something's plugged. You did check for a waterlogged/plugged fuel filter, right? Fuel's getting TO the carb? HTH, PopS I'm thinking too that it's gunked somewhere. Fuel _IS_ getting to the carb (if you pull the starter rope gently with the air filter removed you are met by a mist of fuel around the choke valve). Haven't played with any fuel filters. Is there supposed to be some sort of linkage to open the choke plate? It's just that I can't see how it opens on it's own (vacuum effect???) and that would explain richness symptoms on the(new) spark plug and exhaust output popping. If your carb has a little metal "box" cover on it , then you have an automatic choke. If not, it's a Choke-A-Matic. If you are trying things out with the air cleaner removed, be sure to reinstall the stud... |
#5
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"Rick" wrote in message ink.net... If your carb has a little metal "box" cover on it , then you have an automatic choke. If not, it's a Choke-A-Matic. Let me clarify a little if I can. Off to one side of the carb there will be a rectangular cover that's split on the diagonal if you have an automatic choke... If you are trying things out with the air cleaner removed, be sure to reinstall the stud... |
#6
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Rick wrote:
Let me clarify a little if I can. Off to one side of the carb there will be a rectangular cover that's split on the diagonal if you have an automatic choke... If you are trying things out with the air cleaner removed, be sure to reinstall the stud... The PDF diagram shows a diagonally split cover. I will give it another look tomorrow, maybe check within that cover for movement. Will try running with the air cleaner off temporarily - let's hope the stud (I assume we call it a 'bolt' here) keeps the petrol spray in order. Thanks all. Will keep you informed of progress - let's hope we can fix this for minimal expense. Goodnight. |
#7
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Rick wrote:
"Rick" wrote in message ink.net... If your carb has a little metal "box" cover on it , then you have an automatic choke. If not, it's a Choke-A-Matic. Let me clarify a little if I can. Off to one side of the carb there will be a rectangular cover that's split on the diagonal if you have an automatic choke... If you are trying things out with the air cleaner removed, be sure to reinstall the stud... My hayter from that period has a choke that is closed by moving the throttle past maxiumum rabbit to choke. When the throttle is reduced to top rabbit, the choke has a spring that aligns the plate with the airflow. |
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