# need help b&s 18.5 h.p carb problem



## spider123 (Nov 9, 2009)

hello
18.5 h.p b&s 42a707 1238-01 . took my carb off today,removed the fuel line,choke cable,vacume hose and small link on left side of carb. removed nut on right side of carb,lots of dirt . removed that little jet inside,cleaned that out. put carb back on and engine just cranks but wont fire,put some gas in carb nothing,pulled spark plugs dry.i was looking at the screw on the left side of carb,low idle adjustment ?.anyways when i hook up the link that goes to the throttle plate rod it pulls the flat part away from the screw. i think it should be up against the screw when the throttle lever is in the low position. i removed the carb and reinstalled it again and it still does the same thing. there is a bolt that screws into the intake manifold that has 2 small arms the link i removed hooks on one arm and then hooks on the throttle rod it seems to be spring loaded, it pulls the little tab on the end of the throttle rod away from the adjuster screw, is that correct? is there any were i could find a picture of that linkage. 
thanks you


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## 30yearTech (Sep 14, 2006)

spider123 said:


> the link i removed hooks on one arm and then hooks on the throttle rod it seems to be spring loaded, it pulls the little tab on the end of the throttle rod away from the adjuster screw, is that correct? is there any were i could find a picture of that linkage.
> thanks you


Yes, that is correct. The governor spring, even in the lowest setting will pull the throttle open when the engine is not running. Once the engine starts then the governer will apply pressure against the spring and pull the throttle back.

Did you split the carburetor and clean out inside?

It sounds like either no fuel is getting into the float bowl, or if fuel is getting in, then it's not being metered out.


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## spider123 (Nov 9, 2009)

so its ok for the flap to be pulled away from the adjuter screw.i did not take the carb apart just removed that big nut on the right and cleaned out some dirt, i did unscrew the little brass jet and sprayed some cleaner inside the carb and cleaned the jet. before i took this apart engine would start and run ok if you keep the choke on about 1/3 of the way closed then after 15 to 20 min it would die. its strange it just cranks no spit no sputter ,i even put some gas in the carb still nothing, i though maybe it was flooded but when i pulled the plugs they were dry. there was fuel pooled in the intake i could see it. the only other thing i did was change the starter solenoid , but if anything it seems to make it crank over better than before. i check the wires on the solenoid. pos and neg ,also a ground wire were it bolted to the tractor and a smal push on wire just those 4 are all clean and tight.


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## 30yearTech (Sep 14, 2006)

You may want to test for spark, just to be sure this is not a problem. You could also try priming the engine with a little fuel and see if it will fire off that way. I think that there is something blocking off the fuel through the main jet.


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## spider123 (Nov 9, 2009)

could i have caused a problem by tipping the carb on its side ?.and i may of tipped it upside down while i was spraying out that jet passageway. im going to get a kit and take it apart. anything special i should do or look for ?. 
thanks


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## 30yearTech (Sep 14, 2006)

Tipping the carburetor should not cause any issues, unless it's full of dirt and or varnish. If that's the case, then it needs to be taken apart and cleaned good.


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## spider123 (Nov 9, 2009)

thanks for all the info. i will let you know what gets it fixed .thanks again :wave:


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## spider123 (Nov 9, 2009)

rebuilt carb and fuel pump today (sat) still will not fire up. engine would always start but would not run well unless you kept choke 1/4 on . i decided to remove carb and clean, all i did was remove the big nut on the right side and clean some dirt out of the jet, put nut back on and reinstalled carb then engine would not start.before and since i rebuilt the carb i have pulled both plugs they looked dry,put fuel in cylinders still no start,checked the plugs for spark, can see spark jumping the gap.put fuel in carb still no start.i feel i must of done something when i removed carb the first time because it would always start,today when i took the carb apart there was fuel in itand no dirt to speak of.what else can i try??
thanks


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## 30yearTech (Sep 14, 2006)

If it will not start and run off a prime, then there is some other issue. While the carburetor may still be a problem, the engine should fire off a prime. 

Is the throttle plate open in the carburetor when you try to start the engine?


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## spider123 (Nov 9, 2009)

yes it is open,i checked the key way thats fine, whats the best type of tester to test the spark. i did pull the plug and i could see the spark,after i primed the cylinders it shoud of at least tried to start (spit- sputter). its just hard to understand what happened, it always started fine.could you tell me how to check compression, do you just hook the gauge up and crank ?. what should it be?
thanks for all the info


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## 30yearTech (Sep 14, 2006)

Use a standard automotive compression tester, I would look for 75lbs + for engine to start and run. 

An inline gap type spark tester is what you should use to test the spark such as this one: 

http://www.toolfetch.com/Category/Automotive/Spark_Testers/LIS50850.htm


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## spider123 (Nov 9, 2009)

*service repair manual 42a707 18.5 hp b&s*

does any one no were i can down load a service repair manual for this engine
thanks:confused


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## 30yearTech (Sep 14, 2006)

spider123 said:


> does any one no were i can down load a service repair manual for this engine
> thanks:confused


http://www.mymowerparts.com/pdf/Bri...er L-Head repair manual BRIGGS & STRATTON.pdf


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