Flatheads Forever (Briggs mostly)

Mini Bike & Go-Kart Parts

#1
New to the forum, I live and breath flathead briggs. Still learning everyday and it's awesome. If you have any questions regarding these engines chances are I have an answer. Especially if it makes to have more power. Ask away. Thanks Don.
 
#4
hello, I have a question regarding the twisted metal piece in the end of the pulsa-jet carb. Would it increase flow to remove that?
If I were you I would remove it and toss it in the nearest trash can. Any obstruction will hurt it. Remember they were designed for 3600 rpm rarely full throttle. I bet you are full throttle quite often right?
 
#6
If I were you I would remove it and toss it in the nearest trash can. Any obstruction will hurt it. Remember they were designed for 3600 rpm rarely full throttle. I bet you are full throttle quite often right?
I wouldn't suggest it on a mostly stock engine. I would agree on a modifed engine that runs WOT or the power band has been moved up due to camshaft/port and head modifications. However in mostly stock form, off idle and part throttle cruise response is defitely compromised...
 

SAS289

Well-Known Member
#8
Isn't 3600 the max governed speed of these engines? Factory specs, of course.
The 3600 is a standard but isn't important for lawn mowers and mini bikes. Where it is important is running a generator. You can govern your lawn mower or mini bike to 3800 but you won't get 120 VAC and 60 HZ at that RPM running a generator. For a generator you need closer to 3600 with the governor maintaining that RPM at various loads.
 
#9
I wouldn't suggest it on a mostly stock engine. I would agree on a modifed engine that runs WOT or the power band has been moved up due to camshaft/port and head modifications. However in mostly stock form, off idle and part throttle cruise response is defitely compromised...
In my experiences a bone stock briggs flathead 2,3,or 5 horse will run quite well up to 6800 rpm. The 4 horse model 11 is differnt though because it's piston is so large and stroke is small. It has a piston quite a bit larger than a 5 horse. I was surprized. That said , I have not personally had a lot of seat time with the model 11 but the other "small blocks" I certainly have.
 
#10
Isn't 3600 the max governed speed of these engines? Factory specs, of course.
Yes at least every briggs I have ever seen anyway. The twist piece is a waste of space for our application simply because we have a throttle and not a governed set speed/rpm. It is helpful at steady 3600 but what I have seen on my flowbench is just another usless restriction. Already have the flow killing size of carb, obscure right angle at the air horn ect ect not to mention the inefficient valve port. So I guess if u want to keep it in there have at it. One more wall to block the air won't hurt. Right? Lol. These engines designs flat out suck. But once you get everything in harmony it is surprisingly satisfying to say the least. I think of them as a wild animal that you have to tame out, get to know and spend constant attention to. It really is.
 
#12
funky ole is 100% correct for a stock or (mildly) performance-built engine. Now, if you are building an engine for high performance- Yes, it could make a difference.
Michael
 
#13
New to the forum, I live and breath flathead briggs. Still learning everyday and it's awesome. If you have any questions regarding these engines chances are I have an answer. Especially if it makes to have more power. Ask away. Thanks Don.
I've got a question regarding cams. This came with a 5hp that was torn down when I got it. How can I tell if it is just a stock cam? What does the number on the side represent if anything and it looks like someone engraved a pair of 9's on the end would this have been the factory? 20210817_170615.jpg 20210817_170454.jpg
 
#14
I've got a question regarding cams. This came with a 5hp that was torn down when I got it. How can I tell if it is just a stock cam? What does the number on the side represent if anything and it looks like someone engraved a pair of 9's on the end would this have been the factory? View attachment 283356 View attachment 283357
this cam is a "bluepprint cam" from a known manufacture. which manufacture is difficult to know. its a slapper cam.
 

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