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Shindaiwa B45 problems

fullchoke

fullchoke

ArboristSite Lurker
Joined
Dec 17, 2010
Messages
18
Location
oregon
The machine is a beast with 140mm line on it, but it won't rev up when the engine gets hot. The engine bogs and won't pull any RPM's. It will drop down to idle and idle indefinitely if you let off the throttle in time. If it's a hot day you might get 10 minutes, a cool morning it can run for hours until the air temp rises. I changed the spark plug, and ignition chip with no change. I took apart the carb and blew it out, but I don't have a kit, and will buy the carb parts if that is the problem. I'm running the carb 1 turn out hi and low. The diaphragm isn't hard and I run non-ethanol gas 25/1. Any ideas? I also have a C35 that is confounding me too, I will start another thread on it.
Thanks
 
fullchoke

fullchoke

ArboristSite Lurker
Joined
Dec 17, 2010
Messages
18
Location
oregon
The machine is a beast with 140mm line on it, but it won't rev up when the engine gets hot. The engine bogs and won't pull any RPM's. It will drop down to idle and idle indefinitely if you let off the throttle in time. If it's a hot day you might get 10 minutes, a cool morning it can run for hours until the air temp rises. I changed the spark plug, and ignition chip with no change. I took apart the carb and blew it out, but I don't have a kit, and will buy the carb parts if that is the problem. I'm running the carb 1 turn out hi and low. The diaphragm isn't hard and I run non-ethanol gas 25/1. Any ideas? I also have a C35 that is confounding me too, I will start another thread on it.
Thanks
I used it again this evening. It started bogging again after some heavy use. I tried running the choke a little with no good result. When I squeezed the primer bulb it came right out of it and worked fine until dark. Is that a sign of a need of a carb rebuild? Diaphragm bad? Definitely fuel related.
Thanks
 

J D

ArboristSite Guru
Joined
Apr 19, 2020
Messages
673
Location
NZ
It's not drawing enough fuel up, could be lines (blocked, collapsing or pinholes), fuel filter (blocked or crap in tank), tank vent (try cracking the cap when problem presents), case leak (causing low impulse), carb (diaphragms, gaskets, air leaks, debris...)
Do you use fuel with ethanol in it?
What type of pump diaphragm does it have?
Carburetor Membranes.JPG
 
fullchoke

fullchoke

ArboristSite Lurker
Joined
Dec 17, 2010
Messages
18
Location
oregon
It's not drawing enough fuel up, could be lines (blocked, collapsing or pinholes), fuel filter (blocked or crap in tank), tank vent (try cracking the cap when problem presents), case leak (causing low impulse), carb (diaphragms, gaskets, air leaks, debris...)
Do you use fuel with ethanol in it?
What type of pump diaphragm does it have?
View attachment 913414
The tank filter looks clean and the primer bulb pumps easily. I use non-ethanol fuel only. It is the rubberized diaphragm. The tank has it's own vent that is clear and you can see it is working.
I'm ready to order a new diaphragm. The main one costs over $20, the ones pictured are less. I have not found a kit yet. Since using the primer bulb when it was acting up made it run again, I know for sure now it is fuel related. It could be the line in the tank too, because when it is low it is more likely to starve for fuel, but it has run it all out in cool weather. The part where it quits when it is hot was the head scratcher. It is always possible there is debris in the carb, or a tiny leak somewhere. I will probably never know for sure what exactly the problem is but I will rebuild the carb next. It starts easy when cold and has excellent compression.
Thanks
 
fullchoke

fullchoke

ArboristSite Lurker
Joined
Dec 17, 2010
Messages
18
Location
oregon
I went out and ran it again this morning when it was cool. I was wrong about the heat causing the bog or contributing to it. Since I was confident I could keep it running with the primer bulb. I lengthened the 140mm string so I get less grass windup on the head and it rips even easier through blackberries, tansy, etc. This makes the trimmer drink more fuel and I'm on the throttle harder. Even if I'm not heavy cutting just pulling a long string makes the engine work hard. Since I was having the bogging episodes before it got hot, just tells me it is due to a lack of fuel. Thought I'd add this to help anyone else with a similar problem to not be mislead by the overheating thought.
 
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