Hard starting 4hp

M

Minnesotajeff

New Member
#1
#1
Hi guys, I'm working on a 1964 Tote Goat for a friend. It has a 4hp Briggs. Went through it all and rebuilt the carb.

Cold starts fine, restarts easily immediately after you shut it down, but if it sits for 5 minutes or more it is a bear to get going again. I've found a very very slim sweet spot on the mixture screw where it will run smooth at WOT and still idle well. Move that mixture 1/8 of a turn either way and you lose either the idle or the WOT rpm.



What can I try to correct this hot restart issue after it sits for a few minutes? Right now, I have to choke it for one pull, then on the next 1 or 2 pulls it might start...... then it needs to be left to idle for a bit otherwise cracking the throttle kills it.

Thanks
 
jackeo21

jackeo21

Member
#2
#2
I'm thinking the problem lies somewhere in the ignition system. Have you checked the spark plug for fowling or to see how the engine is running? Do you know if the motor still has the points and condenser system? It might be wise to clean up the spark plug, clean up the magnets on the flywheel and adjust the points and condenser.

Hopefully someone who has had a similar experience with their motor will chime in!

Ignition is just something to keep in mind. You're on the right track with rebuilding the carb!

Good luck with solving your issue, there are a ton of helpful members here who can help :thumbsup:

-Jack
 
Dr. Shop Teacher

Dr. Shop Teacher

#3
#3
Would be helpful if you posted a pic of the carb. Sounds more like you've got some crud in the pick-up tubes (if so equipped--pulsa jet). If you didn't replace gaskets and needle valve, that'll cause issues, too. The reason I think this is the "sweet spot" you're talking about--if the bowl in the tank is not refilling quickly enough, it'll bog down. Could be pick-ups, diaphragm or gasket leaks.

Updraft carbs are a whole other issue. [MENTION=47323]OND[/MENTION] is one member that I know dealt with one recently.
 
CarPlayLB

CarPlayLB

Well-Known Member
#4
#4
I am with Jackeo on this one. Check the ignition. Of course you have a new plug, but a heat soaked coil or a bad condenser will have this effect!
 
M

Minnesotajeff

New Member
#6
#6
Played around with it some more tonight. New plug, very strong spark both cold and hot. By playing with it more I found that after sitting for a few minutes, if I full choke it for 1 pull, then open the choke it will start on the next pull, but you have to let it idle for 20 seconds before touching the throttle or it will die.

The sweet spot I referenced is strange. If I set the mixture to the best WOT setting, then it stumbles badly off idle. I have to set it rich at WOT in order to have a decent throttle transition from idle. I can't get both set correctly. I rebuilt the carb, it is a Pulsajet, with all new gaskets and needle using a genuine B&S kit. This is the first Pulsajet I've worked on, maybe that is their nature?

The motor is a model 100202
 
H

Havasu Dave

Moderator
#8
#8
Jeff, In addition to Dr. Shop Teacher's excellent write up, This is the best link I have seen to understanding and working on the pulsa jet carb. That particular link covers your 100202.

A helpful tool is the spark tester. It tests the spark in a vacuum where it takes more voltage to gap than laying the plug against a ground. $9 and worth every penny because you don't have to guess if you have a weak magneto or condenser.
 
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Dr. Shop Teacher

Dr. Shop Teacher

#9
#9
^^^^The link Dave references is excellent^^^^ Lots of good information on the site. I used it as a source in my build of the Briggs Cousins when the service manual got spotty.
 
M

Minnesotajeff

New Member
#10
#10
Well, I'm frustrated with this one....

I went through the ignition system, have a strong clean spark, I'm positive that system is good.

I went through the carb again, making certain everything is clean and correct. Both tubes are solid, clean and flow well.

To get it to start I have to open up the mixture screw an extra turn. Then it will start and idle. As soon as I open the throttle it stumbles badly, and as I turn the mixture screw in it clears up and the runs strong. Then it will idle down, but will not come back off idle for anything. Crack the throttle and it dies. The only way to bring it back off idle is to richen up the mixture screw first, then it will come off idle with the throttle, but it's back to stumbling badly because it's so rich.


I've sprayed carb cleaner all over it looking for a vacuum leak but nothing changes.

I'm lost. I'm ready to order a new carb, but it just doesn't make sense..... I'm afraid I'll bolt on a new $125 carb and have the same problem.

The carb number is 299437
 
Dr. Shop Teacher

Dr. Shop Teacher

#11
#11
Two things I'd look at next: 1) gaskets are sealing at the tank (trace leaking fuel) and at the intake port on the block. If it's an old gasket in either place, then they can be an issue. You can easily clean up the mating surfaces if not done already. 2) Flywheel key. If the key is slightly bent or grooved, you can have all the spark you want but the engine won't move from idle to throttle without burping because the timing is off (this takes you back to Jack's and CarPlay's initial thoughts). Old Briggs engines will start and run with stationary throttle controls even if the key is bent/grooved, but they hate variable speed controls when the key is screwed up. The Briggs key, for some reason, is easily damaged.
 
electrathon

electrathon

#12
#12
Poor seating of the exhaust valve. Also possible the the exhaust valve guide is worn. Used to see it a lot. The symptom was starts OK cold, hard to restart after hot, once cool will restart.
 
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