1991 3.5 hp B&S with Tec carb

Sprocket86

Sprocket86

Active Member
#1
#1
I've always wanted a flat head Briggs with a gravity fed float carb set up. So easy to mount up a Comet Tav2:thumbsup:

I snagged this 1991 3.5 Briggs of Kijiji a few years back and it seem's healthy.

I got a 691922 intake of the Bay and plan on using a Tec carb that has a slightly bigger venturi then a H35 carb. Would this be a wise move for a slight HP gain?

What could I use for a crank breather element on the valve cover? A really small K&N lol. I know I really should be placing my time and efforts on my I/C dual ball bearing B&S I have but the 3.5 hp is nice and compact for the mini bike I have planned to drop this in.

20180429_075824.jpg
 
manchester1

manchester1

#3
#3
Sprocket86

Sprocket86

Active Member
#4
#4
Thanks for the link and suggestion. Unfortunately I'm going a different direction now.

Upon further inspection the end of the crank shaft doesn't have the required end tap to mount up a 30 series comet Tav.

I'm going to switch my efforts to my 5hp B&S dual BB iron cylinder engine. What would be a good size Tec carb for a 5hp briggs?
 
danford1

danford1

#5
#5
That same carb would work. It says it is for HS40 and HS50 engines. That intake has two sharp 90 degree bends and won't flow great even if you put a bigger carb on it. Assuming you were going to use that intake on the 5 hp of course...
JMO Danford1
 
Sprocket86

Sprocket86

Active Member
#6
#6
danford1 said:
That same carb would work. It says it is for HS40 and HS50 engines. That intake has two sharp 90 degree bends and won't flow great even if you put a bigger carb on it. Assuming you were going to use that intake on the 5 hp of course...
JMO Danford1
Click to expand...
I figured it would be sufficient and that H35 intake was just for mock up purposes. I picked up the popular B&S 691922 intake manifold to use on my 5 hp I/C build.

I really should start a 5 hp build thread on here. I still have yet to identify the year of this 5hp metallic blue I/C engine.

The original fan shroud is missing.
 
Sprocket86

Sprocket86

Active Member
#7
#7
This is what I'll be working with and building up. Nothing crazy or even mild for that matter. Unless you OldMiniBikes'ers convince me otherwise lol.
20180503_071726.jpg
 
Sprocket86

Sprocket86

Active Member
#8
#8
The other side. Having the block off plate on the block hints at it being produced in the 1990's and up? The metallic blue paint color doesn't seem right for the era of engine.

20180503_071754.jpg
 
Harquebus

Harquebus

Well-Known Member
#9
#9
Sprocket86 said:
...The metallic blue paint color doesn't seem right for the era of engine.
Click to expand...
The paint color was the choice of the end-user; i.e., applies to whatever appliance the engine was mounted to originally.

I've got one I know was on a Troy-Bilt tiller at one time because it's painted in TB Red...

Black gets boring real quick IMO.

Would love to see a mild build. :thumbsup:
 
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Sprocket86

Sprocket86

Active Member
#10
#10
Harquebus said:
The paint color was the choice of the end-user; i.e., applies to whatever appliance the engine was mounted to originally.

I've got one I know was on a Troy-Bilt tiller at one time because it's painted in TB Red...

Black gets boring real quick IMO.

Would love to see a mild build. :thumbsup:
Click to expand...
I figured this engine was originally on something that had the same blue paint and yes I agree, the black and white engine paint colors are quite boring.

What would be a good starting point for a mild build? I don't want to go the billet route or anything close to that.

What's a good cam that is slightly above the stock lift and duration specs r should I avoid a cam swap all together?
 
Harquebus

Harquebus

Well-Known Member
#11
#11
I think what most people do who are going the ‘mild route’ is a port-and-polish on the exhaust port mainly...
De-burr and smooth the exhaust port and get rid of the casting flash or defects. It is my understanding that the intake port benefits from turbulence created by the casting flash and some of the hard angles inside there, in the interests of swirling the fuel mixture around and mixing it better.

Many others shave the “eyebrow” or the material between the two valves and the piston, e.g. the cylinder wall. Helps increase the flow.

About cams though...hmm. Seems most cams I run across are the high-end stuff designed for racing and methanol. I prefer guzzoline meself so....:shrug:
 
Sprocket86

Sprocket86

Active Member
#12
#12
I'd like the sounds of the "94SS" cam that seems to be quite popular on here with other members.

I'm not sure what other mods this camshaft would require.
 
danford1

danford1

#13
#13
I had/have a 94SS cam. The "problem" with them is they don't have a compression release. You have to make sure you are on the compression stroke when you give the rope a good hard pull. If not, it can and will kick back and that hurts your hand and fingers a lot :)
You are supposed to use new valves also as the base circle is smaller than a stock cam. Stock valves on a 94SS cam will work but not recommended as you will have a lot of valve noise as the lash will be high ( I can attest to that). But. The power difference from stock to a 94SS is very noticeable from my experience. With all of that being said, I took it out and went back to a stock cam. I like to just walk up, yank on the starter rope and go. I couldn't do that with the 94SS unless I wanted to risk having the starter rope pulled out of my hand... special care had to be taken to make sure the piston was where it needed to be. Too much hassle for an old fart like me.
If you can find a performance cam with a compression release, that would be the way to go.
JMO Danford1
 
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Sprocket86

Sprocket86

Active Member
#14
#14
I hear what your saying there big time.

I did a similar mod on one of my Tec HS50 engines. I ground the compression release bump of the intake lobe and this exhibited the same lack of compression release and this required the starting technique as you described.

It's not a major hassle but like you stated, it's nice to be able to walk up and start it.
 
Oldschoolcool

Oldschoolcool

New Member
#15
#15
Sprocket86,

Did you have any issues with the 691922 B&S intake fitting up to the engine? I thought there were issues with the mounting hole spacing?
 
Sprocket86

Sprocket86

Active Member
#16
#16
Oldschoolcool said:
Sprocket86,

Did you have any issues with the 691922 B&S intake fitting up to the engine? I thought there were issues with the mounting hole spacing?
Click to expand...
No not at all. It was a bolt on affair as I was lucky enough to have the 3 bolt hole intake port flange.

When I first found this engine on a rototiller in the scrap yard I had no idea it was a dual ball bearing I/C late model block.

It's my first one I've owned and all I ever had before was a clapped out kool bore plain bearing engine.
 
B

briggsraptor

Member
#17
#17
I have a question regarding that intake 691922. It appears it would angle the carb away from the engine(which I'm looking for) is that correct? I need a new set up because I am unable to attach an air cleaner to my 5hp on my DB frame. I can't find an air cleaner to fit. There is no mounting hole in the bottom of the air horn. And the air horn top is very short to get a clamp to work......
Any ideas I can use or a set up I can try.
 
Sprocket86

Sprocket86

Active Member
#18
#18
briggsraptor said:
I have a question regarding that intake 691922. It appears it would angle the carb away from the engine(which I'm looking for) is that correct? I need a new set up because I am unable to attach an air cleaner to my 5hp on my DB frame. I can't find an air cleaner to fit. There is no mounting hole in the bottom of the air horn. And the air horn top is very short to get a clamp to work......
Any ideas I can use or a set up I can try.
Click to expand...
I'll post some pics of the mocked up intake and carb mounted on the block. Yes the 691922 intake angles the carb away towards the pull starter at about 45 or so degrees.

Post a few pics of what your trying to do and that will always help.
 
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