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Discussion Starter #1 (Edited)
i've got 3.5 briggs that i've had for about four years. i've taken very good care of it but now the thing wants to spit, sputter and go up and down in rpm's. Its been good mower. i have changed the plug, checked the coil setting, changed the diaphragm and it has no water in the gas because i,ve changed that and i m going to try carb cleaner so please tell me what can i do beside's that if it doesn't work.




thanks
 
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bugman: install a new high speed needle and snug it in close then back it out 1 1/2 turns and that should solve your problem
 

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Discussion Starter #3
i know it ain't the carb because ive tried a different one of the same model it will run and pop loudly.
 
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bugman: you say that you changed the diaphram.......on a 3.5 briggs....strange...it either has a pulsa jet carb or a vacujet carb so what diaphram are you talking about....your problem has to be fuel related
 

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Discussion Starter #5
its one of those 3.5 classics that use engine vaccum to suck fuel in after you prime it. it was made right before they went to plastic air filter boxes. i just know it couldn't be water do it would have affected my 6.0 horse craftsman.
 
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bugman
what you talking about priming the carb on the 3.5 briggs. it does not have a primer bulb on it. you have a vacujet carb. a craftsman 6.0 runs a tecumseh engine so there is no comparison to the carbs.
 

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Discussion Starter #7 (Edited)
no on the briggs website the model 9d900's is the one i have type 2005 b2 i
see after a while of sitting the gas will disapate and you press the bulb three times to fill the little fuel sump inside there.it a hole with a cross pattern
at the bottom. like an x
the craftsmen is a 6.0 horse (quantum series xrm) briggs. i was just saying water in the gas i keep around would have affected that one. it would have
affected my old murray 8 riding mower. i had another 3.5 briggs same model as the one i have now that i used that carb off of that to check if it was the carb but it still did the same thing as before. i do have one of those 3.5's that are adjustable and was made about 30 some years ago with an all metal carb but the one i'm worried about has no adjustments and is made out of plastic but made before they went to plastic air breather boxes that hold the foam filter.
 

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Discussion Starter #8
i think when the motor gets warm the springs stretch a little. hense spring adjustment. years of use got em worn in guess. for its age the cyl. bore still looks milkish or rather just like new.
 

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I think I have a temporary fix for you.

First off. I'd like to thank you guys for all of your help. I've been searching the web for a knowledgeable forum and this one has the most information of Value to me!!!! I will never buy a Tecumseh ever again !!! hate the float carbs, (fixed a 6.75 craftsman Eager-1). but anyways....

The fix I had for my 3.5 oldschool briggs mower was,... since the engine has slowed all because of the governor spring that has lost some of its tension. My fix to this was, I took a staple out of the stapler and bent inwards it just a little bit. I then attached it to the middle of the long pencil size spring (with a million coils) fitting as many coils inside the staple but not too many, so the center of the coils would not separate. THUS, giving it slightly more spring tension over all.

This resulted in the governor speeding up the engine slightly and cutting my lawn a lot better with less bogdowns from thicker/wet grass. I hope this helps.
 

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Discussion Starter #10
umm actually that was way back when i asked this, basically the engine is highly used and is five years old. it was popping and it was reving up and down. i thought carb at first since i neglected to clean it. well no it wasn't. so i checked the valves, actually the springs were off center so i fixed that and the popping did go away. but when i would go out to use it it would cut off then i wait and it would crank right back up. i changed the coil and havn't had any problems since. oh you should be careful messing with the governor, leads to overheating etc. i was on here to find out other possibilitys due in fact it all led to the carb! but it was the coil. but doing what your saying puts more stress on the rod etc. i actually work on lots of small engines and rebuild carbs and a couple engines etc. it was the magnetron coil is what i mean by coil
 

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overheating.

Yes, very true about the over heating, I didn't think of that. but, I never made the mower go in turbo mode because of my staple fix thing, just got some lost tension back from being old. This 3.5 briggs mower has been my backup and pretty much. A very reliable backup that sometimes was my main one (6.75hp tecumseh Eager-1 on the fritz).

Thanks Bugman. I love your doom1 Icon also hehehe. Take care.
 

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Discussion Starter #12
yeah, they do make replacement springs you know. but well this one has been good but i use it around tight areas now. using syntec in it as well. but the magnetron was my only problem, it was making the same problems as a gummed carb though, it was one of the wierdest things i've seen one do. but yeah, all of my mowers are briggs. and guess what not a problem yet except the 3.5's coil. haha actually a 3.5 could run like that, you know no governor. i did it one time and now that engine is my spare. only problem is it drank gas like nothing, a full tank would last three minutes!!! rod and all is still tight as well. briggs though, try that to a tec and it'll blow, try it on a honda and it'll blow.
 

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:rolleyes: You say that you have a claissic?Hold the phone,I know what it is.I've replaced the diaphragm in those b4 and they would get folded a little and that thing wouldn't do anything but spit an sputter just like it had watter in the fuel.
 

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Discussion Starter #15 (Edited)
actually no, it was the coil, like i said, i replaced the DIAPHRAM and it still did it, i changed the coil and it did it no more, this thread is very old and the problem has been solved, by me. oh yeah forgot to state this, the diaprahm was not folded, matter of fact i made sure of that. i put it on correctly and it still did the same thing, never went back into the carb now, and i just tried another coil because it was spitting and sputtering and then dying like it had no spark. i put another coil on it and it has never done the same thing again, no sputtering or nothing. its a classic, yeah its only 5 years old. i like i stated above was looking for more possibility's to what may be causing a gas problem to it. after putting a new diaprahm and taking the carb apart and rebuilding it, it still did it till i put a magnetron coil on it. i rebuild engines and i rebuild carbs, just it had me stumped because it all led to a gas problem. but it started cutting out like it lost spark before i changed the diaprahm, actually the old diaprahm was still good, i used that on another 3.5 i had and that would still run if i didn't break that crappy plastic carb.
 
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