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Judson Briggs and Stratton

OliverT

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i have a judson lazer it has a 27 hp liquid cooled B.S. motor. the motor is skiping and backfireing at slow speed but not at full speed. i think its the carb i sprayed cleaner in it and let sit. it still runs the same. i think the carb needs to be taken off? i will have to use the backup machine tomorrow!! what do u guys think? Oliver
 

OliverT

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that sounds right the carb must be pluged up or something? that would mess the fuel/air mix i guess?
 

Gnu

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your intake manifold is leaking. as higher rates of air pass through it "the intake" the vacuum from the engine actually pulls the manifold tight. thus no backfireing at high speeds. and as lower speeds go less vacuum is in there and allows it to leak air and when the air/fuel mix is ready to ignite the flash goes upto the leak. if you have a vacuum gauge for vehicles. attach it to the manifold if possible.

if it has less than 13 hg at idle its leaking. but just tighten the bolts and inspect them.
 
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OliverT

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thank u pat i will look at it tomorrow. i will let u know how it goes. thanks again
 

Ara Klujian

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your intake manifold is leaking. as higher rates of air pass through it "the intake" the vacuum from the engine actually pulls the manifold tight. thus no backfireing at high speeds. and as lower speeds go less vacuum is in there and allows it to leak air and when the air/fuel mix is ready to ignite the flash goes upto the leak. if you have a vacuum gauge for vehicles. attach it to the manifold if possible.

if it has less than 13 hg at idle its leaking. but just tighten the bolts and inspect them.
Engine vacuum at idle is going to be higher than vacuum at higher rpm. The reason for this is because the throttle plate is closed at idle, creating more vacuum at lower rpm. When the throttle plate begins to open more air is passing through and the engine is breathing better with less resistance or less hg lift. Although your thinking as far as diagnostics with a leaky intake manifold may be correct. Often times just reading a vacuum gauge for specic number is not enough. Proper diagnostics are met with readings as to what the needle is doing because vacuum reading varry from engine to engine. A leaky manifold is good diagnosis but other factors can contribute as well. ie. valve issues. Also, I do not recommend tightening down the intake because it can warp and make problems worse for you. Always check the specs on the intake because they are actually low in newton meters and ft pounds of tork.
 

OliverT

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yeah i am waiting for him to call back theres no rush i have a backup machine. i will let u no
 

OliverT

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thanks for the info. i was talking to a guy a the local machine and parts store. he said it also could be the carb. not even sure if its gonna get fixed if its gonna cost more that a 1000 i might as well buy a new one!! i was thinking valves to. do u think it could be as simple as adjusting the valves? i was also thinking about ethonal issues? thanks for the info
 

OliverT

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Had my machine fixed along time ago forgot to post what the problem was. It turned out to be a fuel solenoid at bottom of carb. I had a B&S mechanic fix it. As soon as the mechanic heard it running badly he said its carb fuel issue. Glad to have a mechanic close by. The problem was probably from the ethanol in our fuel. The seals in the solenoid where ERODED. Machine was bought new and didnt get used much when we first got it mainly because I was using my diesel machine which was only 2 years old. guess from all the fuel sitting in the carb caused this problem. I started machine ran for 15 20 minutes every month when its was sitting for 8 months. It ran great for 2.5 years before i had a problem

If u have backup equipment that sits I would recommend draining fuel from engine or add fuel additive. I think draining fuel is the best option

Machine has been running great since the fix. 2553 hours and purring like a kitten...... O yeah i change my oil a lot every 20 to 30 hours