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Trying to get a pull start Briggs 5hp going.


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#1 NUTNDUN OFFLINE  

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Posted December 27, 2011 - 10:18 AM

Alright gang, this one has me almost stumped. I still need to pull the flywheel off and check to make sure the key and everything is in tact.

This is a pull start 5hp single cylinder Briggs with the flathead. It is an engine that one of my dad's friends brought over to see if he could get running. When we first got it, it didn't have any spark. So we cleaned up the magneto and flywheel and we have good spark.

I pulled the carb off but it is one of those that you can't do much with. It is also a pain in the rear because it sits on top of the gas tank and has a built in fuel pump and it is an extremely long carb.

We tried getting it to fire with carb cleaner and with the carb on it basically wouldn't fire off until after the carb cleaner started evaporating and then it would half run for a pull or two. I am guessing it is because of the length of the carb.

We pulled the carb off for about the 10th time and tried spraying carb cleaner directly into the intake. If you spray it before pulling it just spits it out. If you spray it while you are pulling it would fire off but just doesn't sound right.

So we pulled the head off to make sure the valves were moving like they are supposed to and also decarboned the head. Put a new head gasket on and torqued down the head. The engine owner bought a new carb for it and we put that on. We still can't get it to fire. The carb is definitely pulling gas up into the fuel bowl via the fuel pump but that is about it.

It almost seems like the timing is off which is why I want to check the key. This engine is used for a leaf vacuum and I don't know when or how it quit running. With it's job duty I could very well see something had been sucked up and jammed in the blower housing causing the key to shear and causing it to quit running.

We are going to pull the flywheel off tonight and see what we find, problem now is since the owner bought a new carb for it which was about $90, I feel obligated to get the dang thing running. We did try checking the compression but that is probably pointless since it more then likely has compression release.

#2 MH81 ONLINE  

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Posted December 27, 2011 - 10:37 AM

George, get the model number and check to see if the engine is supposed to have an offset key. I had one several years ago that was.

Also, if you take off the pull starter, is this an engine you can turn backwards by hand? May be able to check compression some that way.
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#3 olcowhand ONLINE  

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Posted December 27, 2011 - 10:42 AM

Kinda sounds like a sheared or partial sheared key. But then there's always those unexplained "no start" engines. Check the key & go from there I'd say.
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#4 JDBrian OFFLINE  

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Posted December 27, 2011 - 11:37 AM

I broke a key on a snowblower a few years back and that's how it acted as well. Good luck getting it sorted.
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#5 NUTNDUN OFFLINE  

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Posted December 27, 2011 - 11:48 AM

I will know more once I get home tonight and try and get the flywheel off. I might be able to spin it backwards and get a compression reading. The cylinder bore didn't look too bad. The engine has definitely been used a good bit and there were maybe three shiny lines in the bore but I couldn't feel any edges with my fingernail. I don't have a bore micrometer which I should get one before too long as it would be nice to have.

#6 DougT ONLINE  

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Posted December 27, 2011 - 11:55 AM

George, the model and code would help. I've never seen a Briggs with an offset key. That was more of a Techumseh thing. Was this originally a points engine or electronic ignition? Some of the point ignition engines' flywheels aren't compatable with the magnetron coil. The compression relief on a Briggs was basically the timing of the intake valve. That's why these seem like they want to blow a little gas back out the carb. Just pulling it over should try to push your finger off the plug hole. If not, i'd suspect a valve not seating.
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#7 NUTNDUN OFFLINE  

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Posted December 27, 2011 - 12:00 PM

George, the model and code would help. I've never seen a Briggs with an offset key. That was more of a Techumseh thing. Was this originally a points engine or electronic ignition? Some of the point ignition engines' flywheels aren't compatable with the magnetron coil. The compression relief on a Briggs was basically the timing of the intake valve. That's why these seem like they want to blow a little gas back out the carb. Just pulling it over should try to push your finger off the plug hole. If not, i'd suspect a valve not seating.


I sent dad an email to see if he could get the model number and post it. If he doesn't get the email or get it posted till I get home I will get it and post it. The engine isn't that old, maybe late 80's or early 90's. It may even be newer then that. It just has the pickup/coil just above the flywheel with the grounding wire running to the throttle position lever. I will get some pictures and post them when I get home as well.

#8 Lauber1 ONLINE  

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Posted December 27, 2011 - 12:01 PM

i have a little system that i use to check out almost any engine. Take off the carb and close overthe hole with a piece of duct tape, take a pencil and poke a hole in the tape. With a 50cc syringe, squirt 20cc of raw gas into the hole, pull the rope, should fire on the second pull. This makes the engine a little rich but tells you if you have enough good parts to run. If it blows back out the hole its probally out of time. Really old briggs engines used a dripper type carb and this makes you a crude one. You should get a spark plug test light if you dont have one already, make checking for spark foolproof. You didnt say what the iggy system is, so im guessing your working with a magnatron, since you said clean the mag and flywheel only. It take more rpms at pulling to get them to start. Make sure theres nothing in the carb linkage that would short out the coil. Sounds like your working with a pulsajet type carb. There a tricky bugger to get to draw up fuel and ussally have to start them with full choke. The flywheel key sounds like a good place to look, and a plug test light will tell you that without having to pull the flywheel off right away.
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#9 DougT ONLINE  

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Posted December 27, 2011 - 12:10 PM

Usually if you pull the nut or recoil piece off the crank you can look at the keyway and tell if its off without pulling the flywheel. They switched from the points in the early 80s so you should have the magnetron flywheel. The first digits of the code will give the year.
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#10 NUTNDUN OFFLINE  

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Posted December 27, 2011 - 04:30 PM

Ok, here is the model number and type:

Model: 135212
Type: 021901
Code: 970109 YB

Edited by NUTNDUN, December 27, 2011 - 04:35 PM.
edited to add the code


#11 MH81 ONLINE  

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Posted December 27, 2011 - 04:58 PM

George, looks like a straight key. May have been aluminum from the factory.

Does it look sheared?

#12 Amigatec OFFLINE  

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Posted December 27, 2011 - 05:33 PM

You might check the valve clearance, I have Briggs hard to start when the valves need adjusted.

#13 DougT ONLINE  

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Posted December 27, 2011 - 05:51 PM

If it worked right, I posted the IPL in the manuals section. It is just the standard key. It should be aluminum and replaced with aluminum. They're made to shear so it doesn't damage the crank or flywheel. Another thought would be to stress the coil and make sure it produces enough spark to fire under compression. It should jump a gap 3/16-1/4 inch outside the cylinder.

Edited by DougT, December 27, 2011 - 05:57 PM.
add info

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#14 NUTNDUN OFFLINE  

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Posted December 27, 2011 - 07:01 PM

Alright, got to work on it a little more tonight when I got home. It definitely isn't the key. So I got to digging around some more and took the head back off. Wanted to check to make sure the valves were seating tightly. The intake valve would seat and I couldn't spin it. The exhaust valve could be spun at all times until it went open. Originally I wrote it off as being the compression release keeping it open but after exhausting (no pun intended LOL) all the other alternatives I decided to pull the carb and gas tank out to get to the valve plate. Took the plate off and low and behold the retainer on the exhaust valve was sitting at the bottom.

We don't have a valve spring compressor yet so if anyone wants to recommend a good one and we will get it. I think we are going to be better off replacing both the valve and the retainer. I don't know which one is worn. I was thinking it also had the split keepers and we were searching for them with the magnet in the crankcase and also drained the oil. Once I got here to the computer though I realized it doesn't have them and it is just the ball stem and retainer.

#15 ducky ONLINE  

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Posted December 27, 2011 - 07:24 PM

That is one you do not see to often. Can not tell you how it happen unless there is a metallurgy problem with the retainer or the valve stem to allow them to wear. Save to replace both = no rework. LOL




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