Need help to beat my friend who is running 2 Predators

gearbuilder

New member
Hi, I’m looking for some ideas on how to beat my friend on our backyard track.
He has an old John’s kart with 2 hemi Predators. Both engines have billet flywheels, 0.020” longer billet rods, Dyno 2 cams, header, K&N filter and copper head gaskets. My kart is an old Bob’s kart. I have the same engine modifications except my head is ported and the carb re-jetted.
Our track is about 1/3 mile with 500 and 600 foot straightaways. My kart handles much better so I do better in the turns but he kills me in the straights.
I don’t want to copy his 2 engine setup. It would be great to beat him with a single Predator but I don’t know how to double my H.P.
I’m looking for other ideas like 420 Predator, motorcycle engine, some kind of transmission??????
Let’s hear your ideas.
Thanks Jamie
 

Ted Hamilton

helmet painter and racer
I'm guessing his dual Predator's put out around 15hp each and weight somewhere around 60#.

A single 100cc 2 cycle reed on gas should make around 30hp and should do the job, and weigh only 15-20#.
Keith Freber at Margay has some DAP T85's that should fit the bill for around $500.

If you must stay 4 cycle, I'd try an alky 305 or 390.
 

animal 77

New member
I have a very good 3" bore blockzilla, 0.200 stroker crank big valves making around 30hp ready to race if your interested? or a twin engine snow mobile engine would work :)
 

sCREamnClones

New member
I'm guessing his dual Predator's put out around 15hp each and weight somewhere around 60#.

A single 100cc 2 cycle reed on gas should make around 30hp and should do the job, and weigh only 15-20#.
Keith Freber at Margay has some DAP T85's that should fit the bill for around $500.

If you must stay 4 cycle, I'd try an alky 305 or 390.
You be searching for a long-long time too find a "100cc" 2-smoke that makes '30'! A darn good Yami can only bring 18-20hp.
 

Ted Hamilton

helmet painter and racer
@sCREamnClones -- No offense, but you must not know about real 100cc engines. A good reed ICA puts out mid 30's hp. A formula Super A rotary high 30's. The KT is actually one of the worst in terms of hp, it's just cheap and the most common. Even adding alky to a KT can put it in the 20's.
Real 100cc 2 cycles put out power cheaper per hp, longer relative lifespan, and lighter weight per hp than any 4 cycle. About the only downside is higher fuel consumption. I like 4's and I like 2's and have raced with both on my kart, but if I wanted quick, easy power without adding weight and throwing handling, I'd be looking at a 2 cycle.
 

mikelavite#72

Premium User
Hi, I’m looking for some ideas on how to beat my friend on our backyard track.
He has an old John’s kart with 2 hemi Predators. Both engines have billet flywheels, 0.020” longer billet rods, Dyno 2 cams, header, K&N filter and copper head gaskets. My kart is an old Bob’s kart. I have the same engine modifications except my head is ported and the carb re-jetted.
Our track is about 1/3 mile with 500 and 600 foot straightaways. My kart handles much better so I do better in the turns but he kills me in the straights.
I don’t want to copy his 2 engine setup. It would be great to beat him with a single Predator but I don’t know how to double my H.P.
I’m looking for other ideas like 420 Predator, motorcycle engine, some kind of transmission??????
Let’s hear your ideas.
Thanks Jamie
get you a 420cc and get to work on it . these engines love attention to the head (port work) not necaserally biger valves . cam and carb you will make him scratch his head .
 

gearbuilder

New member
Thanks for all of the suggestions, please keep them coming. I dont know much about 2 strokes or how to improve them. Does that $500 get the expansion chamber? I'm liking the idea of using a big block. Thanks again.

Jamie
 

Flash06

New member
Get you a little cr 125 or equivalent dirt bike motor with a few mods like reeds, pipe, head and jetting. You'll crush him and it will be much more reliable for back yard racing.
 

313boogieman

New member
3inch bore honda 6.5... with 28mm flatslide or 380 tilly carb...with .400+ lift with a isky .310 cam .246 dur..and big valves will do the trick..you are savingg weight, stll have 4stroke small block.... on alky 28-30hp...13.1 comp. I have done it with a kart build and minin drag bike build.
 

sCREamnClones

New member
@sCREamnClones -- No offense, but you must not know about real 100cc engines. A good reed ICA puts out mid 30's hp. A formula Super A rotary high 30's. The KT is actually one of the worst in terms of hp, it's just cheap and the most common. Even adding alky to a KT can put it in the 20's.
Real 100cc 2 cycles put out power cheaper per hp, longer relative lifespan, and lighter weight per hp than any 4 cycle. About the only downside is higher fuel consumption. I like 4's and I like 2's and have raced with both on my kart, but if I wanted quick, easy power without adding weight and throwing handling, I'd be looking at a 2 cycle.
'Touche'! However, my mind-set was locked on 'equal-value' based on the backyard application and not including $5000 motors. :)
 

Flash06

New member
You can find a cr 125 cheap, take motor off and sell everything else off the bike, stock this motor makes around 30hp on gas and I would keep it that way. Qrc makes mount and sprockets. This motor will be cheaper than a big block clone, faster, easier and cheaper to fix, and much lighter. No brainer for me if I was backyard racing I'd be lapping the 4 strokes and laughing when they tore up every few weeks.
 

gearbuilder

New member
Of course this is getting more confusing for me. With the cr125 your going to build a shifter kart, right? I like gears! There are cr125s on craig's list but they are really nice, $1500.00. I'm afraid I would end up riding the bike and not taking it apart. I'll look in the trader paper for one that is damaged. I'm still not sure of the best way to go but, I'm enjoying the research into each of your suggestions.

Thanks, Jamie
 

DLOGAN

New member
When we in this area started racing dirt we had a back yard track . No rules any thing goes.We had duel briggs 5 hp, chain saw engines one guy had a briggs on one side and a 100cc motorcycle on the other .My first race I had a 3 1/2 hp Briggs on . I couldn't keep up on the pace lap . Me and my oldest son had been flat tracking motorcycles . My son's bike was a 77 rmb 250cc suzuki . This bike had 36 hp .stock. When I went through it head, port work Ign.I figure it put out close to 50 hp . So I made my own mount,reworked our down pipe .This kart was a beast .I had to use Dunlop rain tires the only treaded tires made then .1978. I could through up rooster tails down the straights. I finally started getting beat my old kart pushed like a dump truck . Guys started buying new karts and a Comet b-bomb on one started beating me regularly so I went to a comet engine and a factory kart .No one could beat me down the straight. That is the only kart I ever had that I thought I had enough power . The biggest problem with a motorcycle engine is the short power band and one modified very much is really short . I had to shift on any track longer 1/8 mile .
But you could beat all the guy you run with , with any 250cc 2 cycle engine from 1977 up . From 77 to late 80s put out more hp then the newer ones .The air cooled ones .
I remember racing with a bunch of motorcycle engined karts .One guy came in with dual Mac. 101 s . I started last when I got behind him I couldn't hear my engine . "didn't have a tach" So I just shifted up 2 gears and passed him went on to win by 1/2 a lap .
 

animal 77

New member
I also have 2-440cc twin water cooled engines complete with clutch, carbs. and pipes for 500.00 plus shipping for everything, these engines were used in the 80's for formula-1 racing and make close to 60 hp...
 

Flash06

New member
Short power band for sure but when you put a 22-26 rear sprocket on it it's a little diff. Story. There is a guy here on bobs selling a 116 reed jet tha makes 40+ hp for 950. I think it has mount pipe clutch everything. There's also a kx250 kart already race ready for $1500. All this is in the uas/Rwyb sections here on bobs. Any of this stuff I just mentioned will deffinately get the job done and possibly put you in hospital too!jk man but deffinately be careful. A real stiff open clone building it yourself will cost $1500+ that's clutch to carb and the most power you can expect is some where in the 25-30 hp range and it will be a time bomb.
 

Flash06

New member
the 116cc parilla is mine, but it doesn't come with a mount or clutch, but it has everything else :)
See I told you there was one for sale on here and this one will out run the twin preds no problem, you might have better luck in the 2cycle/Rwyb section if you want to find something cheap to out run your friend.
 
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