99cc Predator engine upgrade

GoldenMotor.com

azbill

Active Member
May 18, 2008
3,358
5
38
63
Fountain Hills, Arizona
first I stripped the engine of anything not needed
gas tank, exhaust, governer, throttle parts,,,etc


I made a linkage setup similar to Mac's, except,
not having a vice, I used some flat steel and an angle bracket


I used a piece of aluminum, bolted to the top and a spring from the original throttle to move the butterfly lever
 

azbill

Active Member
May 18, 2008
3,358
5
38
63
Fountain Hills, Arizona
next, I cut the weld holding the muffler to the exhaust header,,,
I plan on running my flex-exhaust off of it untill I can get a new header fabbed


more to come as I get further along into this ;)
 
Jul 22, 2008
656
0
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Northglenn,Colorado
There's a Harbor Freight locally from me. It's my favorite store. They may as well call it the Man Store.
I seen that engine there. They have like 10 in stock.
I'm gonna be watching this build!
 

zean

Active Member
Dec 5, 2010
321
216
43
california
Hi. Thankyou azbill for the straight-forward easy-to-understand approach with the throttle and Q-matic details. I'll be checking to see how you beef up the mount on the horizontal bottom tube and if you switch sprockets on the stretch cruiser. I'm really going to be following your updates to this thread when done to see the total mileage you accumulate on the HF 99cc compared to the (I really can't remember) 10,000 plus miles on the HS 49cc. I plan to use this comparison to help determine which company's engine is more reliable and better-built. Thankyou.
 

azbill

Active Member
May 18, 2008
3,358
5
38
63
Fountain Hills, Arizona
zean, I have almost 17,000 miles on the HS !!!
I have nothing but praise for it's reliability (^)
I hope to transplant the 49 into my daughter's Spoiler chopper in the future ;)

so far, I have no plan on changing sprocket size, or the engine mount,,,
I do expect to have a brace from seat tube to the inner bearing carrier of the drive ;)
 

Mac

New Member
Dec 3, 2009
486
1
0
Maine
Bill,
I had the return spring fro the carb. located in the same place you did, the fuel line grommet hold down, popped out several times, suggest a longer spring and either drill a hole in the cover or use one of the throttle mount bolts. Good thing the kill switch worked well!!

Mac
 

wayne z

Active Member
Dec 5, 2010
1,743
5
38
louisiana
Bill,
I had the return spring fro the carb. located in the same place you did, the fuel line grommet hold down, popped out several times, suggest a longer spring and either drill a hole in the cover or use one of the throttle mount bolts. Good thing the kill switch worked well!!

Mac
I think he has the spring hooked in the hole in the shroud along with the fuel line grommet.
 

desertrider

New Member
Nov 7, 2011
5
0
0
phoenix az
Howdy bill, I have a Question how you going to get around the under 50cc law over here??? or do you know something I don't know? because I to was looking hard at the 99cc predator engine. I really don't think the 4 stroke lawnmotor looking kit for $350.00 is not worth it. the only thing is stopping be from buying the Predator engine is the under 50cc law here in az.


Desertrider
 

wayne z

Active Member
Dec 5, 2010
1,743
5
38
louisiana
Thats a cheapo HT engine filter I got off ebay. I had to alter the heck out of the adaptor plate to make it work
 

Mac

New Member
Dec 3, 2009
486
1
0
Maine
Bill,
As for gearing, I'm not into speed that much, lot's of hills here. I used the 68T, did change the front pulley to 2.5" AX belt, GREAT power, top end was acceptable too, I used GPS at first, I bought a mini tach and can tell the speed from the rpm. I put a 56T on just for giggles, still pulls up the big hill in front of my house, top end is about 43mph(too fast for me) but cruise with the 56T rear is really sweet and quiet. When I had the 68T on the back, it would actually pull the front up if I leaned back a bit! I bet your 72T rear and the extra length of you bike will be a sweet combo. Good luck and keep the Pix coming.

R/Mac
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
Wayne, it may be cheapo, but it sure looks good.

Mac, that's good to hear about the gearing I'm running a 64 tooth in back, so it should be fine with the predator.

SB
 

Mac

New Member
Dec 3, 2009
486
1
0
Maine
AZBILL,
I just installed a AGK overbore carb. and a header with the flange, I didn't care for the stock exhaust manifold design and the immediate turn off the head, after header and carb install, I'm getting 4150rpm vice 3600rpm up the hill in front of my house, good improvement, top end about the same 6100(valve float), didn't play with jetting, too cold to do repeated runs, I'll wait a couple months for that, I'll attempt to post a Pix tomorrow, welded a large 1" thread hotdog muffler to the end of the pipe, nice deep tone.

R/mac