Briggs 5HP I/C build ...I need some guidance!

#21
That is absolutely gorgeous!!!!!!! I know that was a lot of work, and I wouldn't even try to guess how many hours of work you have in it, but that Flat Head is going to be a real head turner! Amazing!:thumbsup:

Matt
 

CarPlayLB

Well-Known Member
#22
I too just bought a I/C dual bearing block and will be doing a build with it, I already have all the parts just have to do the work. I built one for my build off bike and used a kool bore block I had lying there and ended up seizing the crank to the block. I will be using a .300 lift cam, billet lifters, arc rod, 22mm Mikuni, 3hp flywheel and coil, ss valves, dual springs (only outers), copper head gasket. With that setup I had to cut the lifter bores for the billet lifters, didn't have any problem with it breaking and there was no welding. The motor I seized got rode hard and just couldn't take the heat with the bushing block. With my gearing it would push my bike about 50.
I am considering using a 22 Mikuni on this. What are you using for a manifold?
 

CarPlayLB

Well-Known Member
#23
That is absolutely gorgeous!!!!!!! I know that was a lot of work, and I wouldn't even try to guess how many hours of work you have in it, but that Flat Head is going to be a real head turner! Amazing!:thumbsup:

Matt
I can actually steal this from myself and not get caught! I have no fingerprints left! They will never catch me!
Lotsa work ...but I like my shiny things! Thanks for the compliment

Please call my wife and tell her I am not insane!
 
#24
I am considering using a 22 Mikuni on this. What are you using for a manifold?
I'm using a 22mm Mikuni on my current flat head build as well. I built my own manifold, but I did see a place offering Briggs Mikuni manifolds called the Haddock. I'll post a link below, as well as a link to the my thread showing how I made mine. I really do look forward to watching this build progress.

INTAKE MANIFOLDS

http://www.oldminibikes.com/forum/b...s/80440-briggs-high-rpm-poor-boy-special.html

Matt
 

MB165

Active Member
#25
you can use a PZ22 carb from your briggs dealer, its what is being used on the animal right now, jet kits parts etc all from dlr. EC birt has manifolds to match to the newer wide bolt (or three hole) flange.
If this is the I/c block im thinkiing of the exhaust seat is stellite, very hard, a neway cutter will have trouble making the seat round if its warped. you may have to have a auto machine shop grind on it. looks nice there.........guys these things run good with the internal your discussing

get a new set of valves and billet lifters, mock then up youl need to grind to set clearance.
raptor parts interchange, I used a 03sscam, 3hp flywheel, and a arc head, copper gasket, the compression is very high and its hard to pull over, gotta get it right or it yanks back....mill the deck after you shave (Trenching) the eyebrows. if you dont get a good head, a thinner gasket and the milling will help. I dont believe lifter bore welding is neccessary if you use the "ss" cams i think they are the limit. thats my .02, have fun guys


i forgot to add...i used the h-d springs minus the inner spring too,
I have a spring pocket counterbore, maybe I can send it to you guys. just a small cut, with a hand drill really helps keep the springs centered up. pm me if intereseted.
 
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CarPlayLB

Well-Known Member
#26
Thanks for the input MB!
I am not going for an all out motor...I want it to be reliable and be able to rev it up a bit, but nothing too radical.
I have an Animal on another mini that I have and I really like the Walbro carb...but they are just too damned expensive!. I am still conflicted about that. I see the Mikuni and Keihin carbs on eBay pretty cheap. I think I'd rather have a new one of those versus the Walbro that someone else has messed with! I dunno yet...but I have time to figure it out.
 

CarPlayLB

Well-Known Member
#28
OK...been a while since I posted. I am buying parts as I get money. Here are my latest toys! The Edelbrock head is for the Blockzilla, but can be modified to fit the flat head. I will take that to my guy next week and have him get started. The holes line up except for the 3 closest to the carb/exhaust. The rear most bolt hole will need to be filled and redrilled...but I got the guys to do it!



 
#31
Man the block is unreal looking . Did you polish it or have it done ? There is flat head info on Bobs 4 cycle forum in the tech section about building your motor up , very good info there .:thumbsup:
 

CarPlayLB

Well-Known Member
#32
Thanks for the comps guys!

I polished this myself...cheap F'er that I am, I was tired paying big money to have my stuff polished. Bought the bigger Harbor Freight polishing motor and did some internet learnin'. It is not great, but it's about a 6 footer (looks good at 6 feet away!)

As much as I am getting invested in this, I may have someone build it for me. I dunno enough about them to have the confidence. I would be OK building a stocker, I have those skills, but the risk vs. reward factor is getting too high!
 
#33
Hello CarPlayLB,

Very cool build, I have been wanting to get billet flywheel and rod, not because my stock engine needs it, just think would be cool.

Only comment I have is carb. I don't have personal experience with Tillotson carbs, but have been around them over the years. I have a lot of experience with Walbro WB3 carbs on Yamaha KT-100 engines and others, a similar pumper carb to Tillotson, only smaller.

I also currently run Animals so have experience with that carb. Easy to start with choke, idles nice, runs great.

I would go with Animal carb, very good carb. Tillotson is great racing carb, but for just riding around I don't know. May have problems starting without electric starter, and maybe won't idle. Just my thoughts based upon my experience.
 

CarPlayLB

Well-Known Member
#34
My collection of parts is growing for the flathead! I was able to get an Edelbrock head for the Briggs...that was the good news...bad news is that it only fit the Raptor 2 or 3 (I forget which)...but not to be deterred, I motored on!
Here is the head on the motor as I received it. Notice that the three head bolts nearest the intake/exhaust are missing...those are the ones that do not line up.


So that got me thinkin...I could machine aluminum rod, heat the head, freeze the rod, press fit and plug weld top and bottom...but wait, I'm not a machinist and I cannot weld...how about red neck engineering? I bought some 6061 aluminum thread rod, tapped the old holes, cut thread rod so it would leave a space on both sides of the head, take to the welder and just pay for plug welds,,,yuup, that's the ticket! Here is the finished product...polished of course!


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I sanded it flat on a piece of glass...old school style...I think it came out OK...what say you guys?
 

CarPlayLB

Well-Known Member
#37
Awesome work Eric :thumbsup:
So you decided to go with a tilly after all ?


Vic
I dunno Vic...I just bought 2 Walbro Animal carbs off eBay. I need to see if they will fit with the manifolds I have. I bought the Tilly on a package deal...nice little carb from EC..brand new...I guess I will just collect a sh*&^%load of parts until I decide what I am going to do.

I am getting kinda anxious to get this motor done as I have one of the manual clutches for it
 
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