Briggs Raptor alcohol to gas conversion question

Daniel Coop

Well-Known Member
#1
Hey y'all, I just scooped up a Dover Power Briggs and Stratton Raptor alcohol race engine on eBay and was planning on converting it back to gasoline. I was told that it's just a matter of jets but I figured I would ask. Plan on putting this in either my Easyrider or Sensation
 
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trinik7597

Active Member
#4
You will need a whole new carb ... The circuits are worked on alky carbs it's not just a jet change . And you should check your timing going back to gas . I would crack it open to double check the condition of the internals these engines are run hard and not always properly maintained . You are taking a chance buying a alky motor
 
#6
You will need a whole new carb ... The circuits are worked on alky carbs it's not just a jet change . And you should check your timing going back to gas . I would crack it open to double check the condition of the internals these engines are run hard and not always properly maintained . You are taking a chance buying a alky motor
Agreed ^^^^^^^^ Tim has give you some very good Info here.
 

Daniel Coop

Well-Known Member
#8
I was assured by the seller that the engine had less than 10hrs run time since overhaul and blueprinting in 2015 when it was last used. The seller (Jimmy's go-karts) had a 100℅ feedback score on eBay and guaranteed this was a good running solid motor. I was outbid on a nearly identical engine from the same seller a week before. I found a new reproduction Raptor gasoline carburetor also on eBay for $40, so I will get it and hope for the best. Thanks for the good info though.
 
#9
If the engine was used for racing and depending on how hard it was run (what rpm and especially how hot the engine got), 10 hours on an alcohol-burner COULD be a fair amount of time. Probably not in need of a rebuild yet, but getting there. It is not unusual for racers to perform a "refresh" (hone the cylinder and install new rings) after a weekend of hard racing. Install your new carb and get it running and report back to us.
Michael
 

Daniel Coop

Well-Known Member
#11


HTTP://www.doverpoweronlinestore.com/catalog/item/8223835/8925137.htm

It showed up USPS this evening.
A stock Raptor gasoline carburetor is on its way, but hopefully I can send it back. I am going to attempt to get this running on a Mukini slidedraft carburetor. I have 3 laying around, but first I am going to open it up to inspect it's guts. Hopefully it's already got a usable hot cam and I can maybe just re-ring it. We'll see. Want to fit this in my Roper if possible... Maybe my Trailblazer or Easyrider
 
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Daniel Coop

Well-Known Member
#13
Just saw the OldMiniBikes Forum Build-Off posting and realized that I want to enter with this engine (not sure what bike yet) so I am closing this post. I hope me taking the carb off doesn't disqualify me from using this engine?... Would seem stupid if so, and I can stick it back on. 4 bolts.
 
#14
Just saw the OldMiniBikes Forum Build-Off posting and realized that I want to enter with this engine (not sure what bike yet) so I am closing this post. I hope me taking the carb off doesn't disqualify me from using this engine?... Would seem stupid if so, and I can stick it back on. 4 bolts.
Several of us have engines in pieces or completed for the build-off (me being one). Now, if your bike was underway...you would have an issue.
 

Daniel Coop

Well-Known Member
#15
Nope, got a 3 or 4 options that I haven't touched yet, but they are all complete bikes that I plan on blowing apart and completely redoing with new parts, motor work, paint/powder coating, possible fab work.
 

Daniel Coop

Well-Known Member
#16
Had a surprise waiting inside the motor upon inspection and teardown for refreshing.

Do you see what I see?? Looks great inside so far and already has an ARC billet rod and reinforced lifter area. No stamps on the cam but definitely ain't stock. Next step will be to mount up the dial indicator and check lift, decide whether to change the cam, and get parts ordered.
Also playing with intake manifold options to mount the Mukini. This Tecumseh? Intake manifold looks like it might work with some finesse

Also toying with the idea of using this clean vintage recoil housing for that "sleeper" look. Hard to tell there's a built race Raptor engine under there
 
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Daniel Coop

Well-Known Member
#18
No sir, I am no longer sure it is a true Raptor motor. I have noticed a couple of differences between it and my stock Raptor but it has the dual bearing crank and an ARC billet rod and reinforced lifter area. It's also got the Raptor head. These engines were custom built by Dover Power starting around $1400, so it's every bit as good if not better than a stock Raptor.
 

Daniel Coop

Well-Known Member
#20
Call it what you will, but I guarantee it will spank my stock Raptor at a fraction of the cost for me to build anything like it. And I would venture to say a poor man would buy a $500-$600 Raptor over a $1400+ Dover Power built race motor. For $235 shipped to my door, I'd say I stole it. And the money saved on internals I don't need, I think I might buy a billet flywheel to replace the Raptor unit thats on it now.
 
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