99cc Harbor Freight Engine

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motorhedfred

motorhedfred

Member
Jul 31, 2009
421
17
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United States
I just purchased the 'lil Predator 99cc and I'm happy to report that the output shaft is dead on .625" on my Starrett dial calipers. The valves are set correctly as well.

Overall, this is a really neat little mill and I'm looking forward to working with it.

MHF
 
silverbear

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
I like mine, too, and think it's a real bargain. I also think the displacement is just right for a motored bike... lots of power, but not too much.
SB
 
D

Drewd

New Member
Jul 25, 2008
425
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Colorado
What are you folks using for a reduction gearbox for this engine? Anybody know if the dax 5:1 reduction box will fit? Thanks!
 
Russell

Russell

Well-Known Member
Apr 19, 2009
1,276
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MA
Drewd said:
What are you folks using for a reduction gearbox for this engine? Anybody know if the dax 5:1 reduction box will fit? Thanks!
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What is the recomended ratio for a HF 99cc and a 26" wheel.
 
azbill

azbill

Active Member
May 18, 2008
3,358
5
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Fountain Hills, Arizona
I am running a variable size pulley set to 3.0" and a 5" rear pulley equiped EZM Q-Matic primary
to a 10tooth - 72 tooth secondary,
26 x 2.0 Tires (Serfas City Drifter) 50psi
my bike weighs approx 120lbs including the 40cal ammo can saddlebags and battery/lighting system
my bike is geared for pulling/cruising, not speed ,,,
I out accellerate most cars across an intersection tho ;) :)
my average speed over 2k miles is 21.4, according to my speedo
(shhh about that last part, the speed limit in AZ is 19.999mph !!! ) laff

I am just offering info to answer a question, this is NOT meant as a sales pitch ;)
 
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beltbuckle

New Member
Aug 22, 2011
81
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Meridian, ID
bought one about 3 weeks ago and it was also 0.625 so they have fixed the shaft diameter problem it seems. that was my only complaint with the preddy. they sure are great engines for the price.
 
silverbear

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
motorhedfred said:
I'm hoping AGK posts some more mods on thier website soon.

MHF
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Me, too. I'd like to get another 99 to sit on the shelf and eventually build it up into a little powerhouse. I suspect a lot can be done with the HF99. I'd also like to see someone make a lighting coil for it. I think we're going to see this engine used a lot on motorbikes. I'm totally happy with mine, but of course if the same little motor can put out more power, then that's good.
SB
 
wayne z

wayne z

Active Member
Dec 5, 2010
1,743
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louisiana
They are easily modified from 3 to to about 5 hp by just removing the govenor and adding a less restrictive exhaust and air filter, and maybe slightly enlarging the main jet.. Both my Preddys can wind up to about 6000 now that they have some time on them to loosen up a little. 5800 seems to be peak power though.
Personaly, I don't see a need for squeezing any more power than this outta this little engine for a bicycle. Allready askin a lot of it, revving so far past 3600. Maybe with the power loss of using a CVT it might help though.
Tradeoffs. Power vs longivity LOL
 
motorhedfred

motorhedfred

Member
Jul 31, 2009
421
17
18
United States
I was very surprised that the valve clearances were correct given how the rockers flop around at TDC on the compression stroke. Also, that baffle plate on the underside of the rocker cover looks like it would be in the way if anyone (AGK ?) made a shaft mount roller setup for it. Billet rod and flywheel...stiffer valve springs...oh yeah !

If this one gets the same developments as the bigger GX clones, it might make closer to 8-10 horsepower. Milled head, porting, more lift and duration...ect.

BTW, what's a lighting coil ?

MHF
 
silverbear

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
Maybe lighting coil isn't the right term. I mean some kind of generator or alternator that is an add on and which produces enough juice for lights. Right now I'm using a sidewall generator to power head and tail light. I could also get a Sturmey Archer front wheel dynamo which would be more reliable, but better yet would be the engine producing the light.

As for more power, for me it is so that I can climb hills with a sidecar and still cruise in the low thirties without winding out the engine and without the need or expense of gears. Power is nice to have even if you don't go real fast. I'm still thinking about your variable speed transmission, Wayne.
SB
 
A

agk

New Member
Oct 2, 2010
151
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Santa Barbara CA
motorhedfred said:
I was very surprised that the valve clearances were correct given how the rockers flop around at TDC on the compression stroke. Also, that baffle plate on the underside of the rocker cover looks like it would be in the way if anyone (AGK ?) made a shaft mount roller setup for it. Billet rod and flywheel...stiffer valve springs...oh yeah !

If this one gets the same developments as the bigger GX clones, it might make closer to 8-10 horsepower. Milled head, porting, more lift and duration...ect.

BTW, what's a lighting coil ?

MHF
Click to expand...
We are working with our vendors to have a billet rod and billet flywheel made for the 99cc Predator. Once we can get those two parts we can transform this engine into a little beast. This process will take a while as the machine shop has some more important products lined up first for more popular engines. Having the rod and flywheel will allow us to spin this engine up into some high rpm. We have access to stainless valves, stiffer springs, retainers/keepers, different cam grinds and some of the other parts that are available for the bigger engines. We are excited about the potential this little engine has.
 
silverbear

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
Wayne,
Looks like a slick setup that can produce a lot of juice. I was thinking of something less powerful similar to what you'd find on a garden tractor or snow blower with a light. Some Briggs and Stratton engines had something that was on the outside of the flywheel shroud and produced electricity as the engine turned. I don't know enough about it to even talk about it, but know that there is such a critter. No belts, no jack shaft and probably a lot less juice, too, but with LED lights you don't need much for decent lighting. It would be nice if there was a simple bolt on solution to producing light with the Predator engines. Way back in the thread archives someone who was formerly a small engine repair guy was talking about such a device on Briggs motors. Good luck finding that thread, though.
SB
 
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