Alky to gas

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davidlamb78

Member
#1
#1
I picked up a kart with a flathead on it, but I swapped for a clone because I know a lot more about them. I also had no interest in running alky. I am now in need of a motor for a project that I'm starting, and this thing is calling my name. I don't know all of the mods, but I do know it has a bigger cam, longer rod, and the cylinder will close the gap if I don't index the plug.
My question is, can I just reject this thing, or does it need a different carb? If I can re jet it, any body know what numbers I should start with? It's got the normal breather and an open exhaust header. I also have an RLV pipe and muffler I can use.
I'd love to do away with the whole "carb on top of the tank" setup. Anybody know of a good cheap carb that is a gravity feed? Help me, guys. I'm new to flatheads!
 
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davidlamb78

Member
#2
#2
And what is the difference between a flathead and a raptor? Is one specific to racing? Is any flatty that is modded for racing a raptor? I think mines a raptor. Has the yellow fan shroud and says something about Briggs racing on it.
 
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davidlamb78

Member
#3
#3
Anybody ever stick a clone carb on a raptor? I'm assuming a manifold would need to be built. I've got one that is stock off of a hemi I could use.
 
CarPlayLB

CarPlayLB

Well-Known Member
#4
#4
Lotsa questions David!

A good gravity feed carb is the Tecumseh style carb. I bought a China copy for less than $30 on eBay...works great! (and I have a manifold that will bolt right up!)

A Raptor is the racing version of the 5HP I/C motor...still a flathead...and it has the iron bore instead of aluminum...the yellow shroud is normally found on Raptors, but it also can be put on a scrap yard 5HP to make a "poor mans raptor"...yours probably is a Raptor as it has all the goodies. A Raptor will not have provisions for a governor.

I don't know about rejetting the carb...have to wait for someone that knows to chime in

You could put the clone carb on if you have fab skills...I don't believe that carb has a standard round flange that would easily bolt up. This manifold here will fit the Tec carb, a non pumper Tilly, or a PZ22 Animal type carb


good luck!
 
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davidlamb78

Member
#5
#5
Awesome! I think I'll try the clone carb. Ill jet it up a little and try it. My buddy is the lead fab guy at his shop. He'll help with the manifold. My welds look like I did them with my feet. The motor used to be his. I know it's legit. Did you buy that manifold?
 
CarPlayLB

CarPlayLB

Well-Known Member
#6
#6
Yuup. That is the manifold i bought, but the wife bought me a billet one for Xmas. I personally think a clone carb conversion is too much work for what its worth. Just my .02
 
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davidlamb78

Member
#9
#9
outlaw17 said:
clone carb will kill performance of then engine. i do have quite a few billet intakes if anyone is looking.
Click to expand...
@ outlaw- I'm looking for a good affordable carb combo. If it involves a billet manifold, I'm certainly interested.
@ carplay- I'd be willing to run one of those Tecumseh knock offs. Can you send me a link? I found a bunch on eBay. Which one would be best? I don't know which part numbers work best with the raptor.
 
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davidlamb78

Member
#11
#11
keithcar72 said:
You can put a gas jet back in the stock carb and it will do ok. it will not run as good as one that hasen
Click to expand...
I've heard this would happen. Has the carb had work done to it to set it up for alky other than the jetting? Would I be better off buying a used gas briggs carb and jetting it for what I have? What about the Tecumseh that was mentioned? Would that be similar to the clone carb? I'm not looking to go stupid fast on this. I'm only using this motor because I want to build this bike on a very low budget. I'm much more comfortable with clones, but I'm not spending that much on this bike...yet.
 
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outlaw17

New Member
#12
#12
a good inexpensive route is probly the tecumseh carb. a tillotson would be better for performance but alot more expensive. clone carb is way too small and lean. carb could be richened but still way to small. ideally a carb with a 1" throttle bore and 3/4-7/8" venturi will be the all around best. any other questions or need an intake just let me know
 
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davidlamb78

Member
#13
#13
Well, I got an old stock 5hp carb, and I think I'll need to get a new pickup tube for it. I took it apart and checked it out, and I have a couple questions.
First off, I found the jet that is behind the needle, but is there another one? Also, will the diaphragm be okay as long as it's not torn or full of holes? I'll need to hit this with some carb cleaner and a toothbrush, but I think it will be a usable carb.
Secondly, since this is going on a raptor, will I need to open up the jet at all? I'm sure it's the stock jet that came in the carb. My raptor is currently running a straight pipe with no muffler, but I'm hoping to put an RLV muffler on a curved header and run it soon. I figured I'd have to open the stock jet up to compensate for the open header. If so, does anybody know about how big the jet should be? I've got a pen vise and small bit set, but I'm also not above picking up a few jets and testing them. I just don't know where to begin.
 
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