Some fun with another Briggs 3hp

#3
Looks like they "adapted" the (larger) 5HP tank/carb to fit! They cut off/shortened the bottom of the tank bracket that bolts to the block...
Michael
 
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Thepaetsguy

Well-Known Member
#6
I'm thinking it may be well ported also? Did you do the work? Or find it this way?
I did it for fun. billet 3hp flywheel with the timing advance the big cam and so fourth. and that is a gen 2 pulsa jet I messed around with after reading jimmy Glenn’s book. No porting but the carburetor has been bored bigger etc.. I have quite a bit of work into that carburetor.
 

Minimichael

Well-Known Member
#9
Wow. Clearanced the crank,huh? Do you have to remove equally from the other side so it's not out of balance? Just curious. I'm also curious about that lobe work on your cam. Do you have to get real mathematical when shaping it after welding?
 

Thepaetsguy

Well-Known Member
#10
Wow. Clearanced the crank,huh? Do you have to remove equally from the other side so it's not out of balance? Just curious. I'm also curious about that lobe work on your cam. Do you have to get real mathematical when shaping it after welding?
You don’t have to true the crank or anything it’s fine for just a junker to mess with. As for shaping the lobes it’s not Important either. I have a big box of polishing stones. I think when said and done getting the lobes more like a glass surface with the stones is probably the most important thing. Next to the valves not touching the head. And the cam not touching anything inside the case. D699A9B9-0513-4485-8D04-BE14E241671E.png
 
#11
Oh My....I always thought it was bad to grind on a crank. How can that be OK to grind on a crank, not rebalance it , and then spin it faster than intended? I have several that I may still be able to do this with.
 

Thepaetsguy

Well-Known Member
#12
Oh My....I always thought it was bad to grind on a crank. How can that be OK to grind on a crank, not rebalance it , and then spin it faster than intended? I have several that I may still be able to do this with.
do not do this unless your buying a billet flywheel.. once that flywheel has been acquired push them as far as you can.. Also to tell you the truth I took a grinder to the crank with zero fear of the outcome. this little 3hp spins up hard. I love snapping it to full throttle with no load. I can’t believe the WOT blasts the thing has already taken. the rod inside this engine is a trooper. Edit: A good 20% of the left crank weight is gone to clearance the lobe.
 

Thepaetsguy

Well-Known Member
#13
here is a 5hp cam I welded up and ran till the rod broke. if the engine is a throw away do whatever you have to to make it work. it’s not ok to grind on a crank and not balance It I understand that. I haven't noticed any difference in vibration before or after the cams though... a lot of stress heating/welding the cam grinding the crank. didn’t seem to bother much of anything. FDF4FE0E-8F5B-4045-9211-C564E74D50A4.jpeg
 

Mr. Pink

Well-Known Member
#17
it would idle fine but after WOT once it would just stall.
I recently had a similar problem with the same type of carb on my old Briggs.
The engine would start on the first pull, idle just fine, but die when the throttle was opened.
After removing the carb, replacing the diaphragm and spraying Gumout throughout, still same symptom.
The fix was taking the wire from a bread tie and cleaning out the port on the right.

Carb Port.jpg
 

Thepaetsguy

Well-Known Member
#18
I recently had a similar problem with the same type of carb on my old Briggs.
The engine would start on the first pull, idle just fine, but die when the throttle was opened.
After removing the carb, replacing the diaphragm and spraying Gumout throughout, still same symptom.
The fix was taking the wire from a bread tie and cleaning out the port on the right.

View attachment 299870
This carburetor had been disassembled completely cleaned and had quite the amount of work done to it. Those ports are what you drill/slot before you screw in the drilled out methanol jet. And I knew to check those before assembly. the only thing that changed was a pump cover swap and new diaphragm from the 5hp. Truing up the pump cover made a world of difference.
 
#19
Hey Man, Have you put a tach on that 3 horse when you ran it wide open with no load? I had a 5 horse with a 3 horse billet flywheel that we welded up the cam and we didn't get the tach hooked up before it threw the rod but it was REALLY screaming fast when that rod let go! I'm glad it was my buddy riding it when it let go. We estimated he was doing about 7000 RPM and 50 MPH when the back wheel locked up and sent him into the grass.
 

Thepaetsguy

Well-Known Member
#20
Hey Man, Have you put a tach on that 3 horse when you ran it wide open with no load? I had a 5 horse with a 3 horse billet flywheel that we welded up the cam and we didn't get the tach hooked up before it threw the rod but it was REALLY screaming fast when that rod let go! I'm glad it was my buddy riding it when it let go. We estimated he was doing about 7000 RPM and 50 MPH when the back wheel locked up and sent him into the grass.
I don’t have a tac to hook to it. I used stiffer valve springs to help with float. i don’t think they will rev to 7k though. I have heard the stock 3hp rods will take a lot more abuse then a 5hp stock rod not sure if that’s true though. if I had to guess it’s in the upper 5k range?
 
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