Whats your fantasy open motor build like???

496 BB

New member
Figured Id start a new thread for this since other one is about side cover gasket.

Just wanted to get some input on an open motor build I will be doing this winter. So far I want to keep it s/a on the outside. BUT have not decided on carb yet. You see alot of rules motors on here but not much in the way of open. Im sure there are several reasons for that and I wont dive into why. So why not all of us chime in on this one to maybe help someone out in the future on new Bobs.

This is strictly for a super small track (dirt) and am currently not seeing over 7000rpms. Like to see built on race gas first. Then may go to alky.

Anyways heres what Im thinking so far:

Mike Clements Big Bore 2.815" w/ 3.303" billet h beam rod
Max stroke crank to give .010" in hole (with 3.303" rod)
Honda or Wiseco flat top piston (Which one?) Want it in the hole .010" and Honda will do that
14 cc head - possibly shaved .030" and maybe smoothed and worked a bit (gasket size depends)
Dover carb - s/a
Arc 930 ceramic coated pipe
Champion shaft mount rockers 1:1 ratio
Cam - Nr between 274-0207 or 280-0611 or 285-02 (Cant decide...have BP2 2 now with 1.3 ratio)
Billet side cover w/ cometic gasket
Head stud kit
Side cover stud kit
Enlarge oil galley
Springs - 26lbs or TBD depending on cam
Billet locks and retainers
SS valves
Arc adjustable flywheel
Portable starter to start

Am I on the right page for a good open build? Just for fun as of now but was wondering if I ever do run at a sanctioned event if this would be competitive on alky. Want to keep it on race fuel now for various stupid reasons.

Im basically going with a little more than what I got now but with added reliability with studs and sidecover and all. I know your not going to get reliability like a Volvo or something in one of these but you know what I mean.

Fire away.
 

rookieracer75

New member
i am gonna do a small open build 14 cc stock valves dual spring isky .330 or .350 cam with 246* duration. i am thinking wiesco long rod combo with a 2.776 piston pvl flywheel with 8* advanve timing 304 tilly on alky seks 2 pipe. should do all right on small track
 
Twin motors not in a freight train but side by side some how welded
or butted together to make it look like one.this way would not
need a jack shaft setup.it would look like a 600 cc bike motor.
a v twin is to big and would want to do it with the small blocks.
one can always dream lol.not sure how you would do the crankshaft.
 

Flash06

New member
On that small track I would run the 18cc honda head with 27/32 valves, Isky adj 310 with 1.2 rockers (champion or arc), 37-52lb springs, 2.79 bore, arc stroker crank, large ports polished on both sides, 304 blue printed from ec. Turn it about 8200-8400max and let it rip tater chip, and I would deffinately go with alky over gas no matter what! This motor would be a beast on that small track, with the right tires and setup with a good 3 disk mod bully would destroy comp.! Oh yeah go ahead and put it on mode kill about 32-35 degrees timing( I suggest light flywheel w/adj timing brkt from raceng instead of the heavy adj flywheel)! This motor should be great on power and very quick reving , yet still reliable for an open clone! Oh yeah billet side cover too!
 

clone king

New member
Mine Stays locked up in the Dungeon under constant Guard, becsuse it's Power is so Awesome !!! , If it was ever unleashed, Everyone in the. Kingdoms would all Die from it's Awesomeness, and leave me here all Alone.
 

sCREamnClones

New member
Figured Id start a new thread for this since other one is about side cover gasket.

Just wanted to get some input on an open motor build I will be doing this winter. So far I want to keep it s/a on the outside. BUT have not decided on carb yet. You see alot of rules motors on here but not much in the way of open. Im sure there are several reasons for that and I wont dive into why. So why not all of us chime in on this one to maybe help someone out in the future on new Bobs.

This is strictly for a super small track (dirt) and am currently not seeing over 7000rpms. Like to see built on race gas first. Then may go to alky.

Anyways heres what Im thinking so far:

Mike Clements Big Bore 2.815" w/ 3.303" billet h beam rod
Max stroke crank to give .010" in hole (with 3.303" rod)
Honda or Wiseco flat top piston (Which one?) Want it in the hole .010" and Honda will do that
14 cc head - possibly shaved .030" and maybe smoothed and worked a bit (gasket size depends)
Dover carb - s/a
Arc 930 ceramic coated pipe
Champion shaft mount rockers 1:1 ratio
Cam - Nr between 274-0207 or 280-0611 or 285-02 (Cant decide...have BP2 2 now with 1.3 ratio)
Billet side cover w/ cometic gasket
Head stud kit
Side cover stud kit
Enlarge oil galley
Springs - 26lbs or TBD depending on cam
Billet locks and retainers
SS valves
Arc adjustable flywheel
Portable starter to start

Am I on the right page for a good open build? Just for fun as of now but was wondering if I ever do run at a sanctioned event if this would be competitive on alky. Want to keep it on race fuel now for various stupid reasons.

Im basically going with a little more than what I got now but with added reliability with studs and sidecover and all. I know your not going to get reliability like a Volvo or something in one of these but you know what I mean.

Fire away.
That'll work, but....put (at least) a '275' cam in it w/ 35-36* on Alky and you will have abt 1500rpm in reserve. (Note....ALWAYS go w/the l-o-n-g-e-s-t rod possible!) BTW....'reliability' should be no problem!
 

Racer14sl

New member
What size valves are you thinking about putting in that 14cc head? I wouldn't go larger than 27/25mm. If your not seeing over 7000 rpm, I would go with the 285-02 cam and 26# springs.
 

496 BB

New member
That'll work, but....put (at least) a '275' cam in it w/ 35-36* on Alky and you will have abt 1500rpm in reserve. (Note....ALWAYS go w/the l-o-n-g-e-s-t rod possible!) BTW....'reliability' should be no problem!
What happens when I go longer rod and say .010 oversize and Im only say .002 in the hole or popped out even? Then if I shave the head as well Id have to run a huge head gasket right?

What would this be with race gas? What octane?

Im thinking a nice mild 16-18 race fuel open would be what Im looking for. Then on alky it will be 20 possibly. Itd be nice to add something to alky to make it smell like cam 2...lol. Not cherries.
 

496 BB

New member
Do you think this would be too much for a Dover s/a carb? Maybe have to goto a Mikuni or Tilly? Ive never messed with them and from what I read they sound daunting.
 
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