For those running hf predator and agk jackshaft

GoldenMotor.com

Mattjb

New Member
Mar 21, 2013
25
0
0
San dimas
Ok I have a bit of a problem here. I'm using a 79cc predator, agk jackshaft for said motor, agk sprocket for attachment to 6 bolt disc brake hub and in this configuration the output sprocket is WAY out of alignment. In fact if I were to center the motor in the bike the chain wouldn't even clear the tire. So I need to move the output sprocket away from center but if I move it as far out as I can (using a .250 spacer so the chain doesn't rub) I would still have to run the motor off center by quite a bit. Is this normal or is the hub (what im pointing to in picture) supposed to smaller? I don't see how this can be a correct setup cause as is the only way for the chain to clear the tire and correct alignment with the sprockets is to move the motor off center by approximately an inch. Any input would be greatly appreciated cause at this point I'm stopping till I find a solution or result to building my own jackshaft which I DO NOT want to do. And I already tried contacting agk. There emails down so if anyone knows whats up share the info cause I don't want to give up and I'm already invested but I'm not going to build a bike with a motor so far off center and I'm not going to invest in machining time.
 

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ocho ninja

Member
Jan 14, 2012
564
2
16
San Jose, CA
I went trough some trouble getting there jack shaft to work, or probaly opt for making my own for another build.

For my chains to line up I had to use some washers between jack shaft and motor.
My engine is also a bit off center.
And the spacer on the shaft between the 9t output sprocket and hub was trimmed down.
 

Mattjb

New Member
Mar 21, 2013
25
0
0
San dimas
Thanks for your reply and input ocho ninga. I was hoping I just got a bad part but it looks like this is just a poorly engineered jackshaft. Ill take your advice and just build my own jackshaft. If I use the parts that came on this jackshaft (mainly sprockets, spacers, collars) it looks like ill only need some bearing hangers, bearings and a longer 5/8 shaft. I'm not finished with my motor mount yet so I can just weld the hangers to that. I was hoping for an easy fix but it looks like all that parts will only cost 20 bucks. Frustrating but whatever. Ill start researching jackshaft designs for ideas and what not.
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,661
240
63
Every install is custom. If standard position is unacceptable, you have three options:

move engine

move or modify jackshaft sprocket

move rear sprocket.

install a second jackshaft.

Since that jackshaft is a "floating" one, the hub has two bearings and needs to be thick to support the strain. Thinning it could weaken the jackshaft. If you choose to modify that support hub, you could install a longer shaft and a supporting jackshaft bearing mounted on the seat post. Shortening/modifying the hub would eliminate its outer bearing, but there's an inner bearing which would support the agk jackshaft.

Even if you don't want to, building a second jackshaft supported by the seatpost permits you to place the engine wherever you desire. It also allows you to lower your gearing (higher numerically) by adding a second sprocket combination.

Good luck. Hope this helped.
 

birdmannn101

New Member
Oct 23, 2011
163
0
0
Indianapolis, IN
That gear right above your finger can come off and be turned around. That 3/4 inch spacer above your finger between the jackshaft and the gear I mentioned is removable and you can either leave it off or replace with 5/8 inch washers.

My ACK jackshaft lined up with my Huffy rear sprocket from my 79cc HF engine.

 

Mattjb

New Member
Mar 21, 2013
25
0
0
San dimas
Thanks for the input y'all. I'm just going to build my own jackshaft, it's the only way to center the motor in the bike and have proper chain alignment. Thanks again
 

Mattjb

New Member
Mar 21, 2013
25
0
0
San dimas
At this point everything I've bought isn't compatible from jackshaft, rear sprocket doesn't clear frame ect ect and requires modification. There's a point where things begin to cost too much and more than the finished product is worth and I'm about there so whatever. Nice knowing y'all and thanks for the help. Peace, matt
 

PAracer

New Member
Sep 14, 2012
284
0
0
Steelton, PA
I just built an HF79/AGK Jackshaft bike. It fit the Micargi Rover just fine right out of the box. However, as 5-7HEAVEN said, every install is custom.

I would make a spacer to fit between the jackshaft plate and the engine block.

Could you shift the rear wheel a bit to the right?
 

CoolCruiser

New Member
Jun 15, 2012
173
0
0
Massachusetts
I removed the 1/2" shaft bushing between the jackshaft hub and the output sprocket and replaced with 3 narrow bushing that are like thin washers. I did have to mount the Predator 99 about 3/16" left of center but it looks and balances fine. The sparkplug lines up right under the cross bar.
 

Mattjb

New Member
Mar 21, 2013
25
0
0
San dimas
I say don't tap out yet Matt, any custom setup requires some type of added work. You have most of the parts already. What clutch did you get?
I have the max torque clutch 3100 rpm engagement from agk. Other than the parts to build a custom jackshaft I have everything, or its coming in the mail including all the stainless so I can build my own exhaust and muffler (not including the gas tank cause well, I wanted to go over the top on that). The jackshaft is one thing and now I have no idea what to do for rear sprocket. I have to do another mockup and measure twice to see what to do about sprocket chain clearance. I could machine the 6bolt flange of the rear hub down about ten to 12 mm and that should get me enough clearance but that only leaves 6mm of thread to clamp the sprocket. I could drill and retap to get me about 12mm but I don't know if that's structurally a good idea. So alot of thinking to do.
 

Mattjb

New Member
Mar 21, 2013
25
0
0
San dimas
Hey ccc, since I'm gonna go down this road of customizing i may as well just go all out, do you know a safe ptv setting for this motor? I understand any damage from advice given or taken is all on me. I currently have .08 intake and .130 exhaust with the lash set at .006. From your experience with these engines could I mill any off the head? Say .030? Any advice would be most appreciated
 

young grease monkey

New Member
Sep 20, 2011
362
0
0
Chicago
agk took off .050 and it worked out for them. I did the same. I also ported, polished the valves so they reflect heat, and polished the combustion chamber. I never actually checked the ptv, but as long as you don't over rev it will be fine.
 

thingswithwelding

New Member
Mar 22, 2016
120
4
0
Long Beach CA
Do you guys know if Bully clutches work with these jackshafts? I am 90 percent done with my 79cc and Im waiting on my Bully clutch. With these jackshafts, the clutches hang off the crank output shaft quite a bit-Im worried my Bully key slot is not going to reach the key slot on the engine shaft.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
7,266
1,797
113
Los Angeles, CA.
Do you guys know if Bully clutches work with these jackshafts? I am 90 percent done with my 79cc and Im waiting on my Bully clutch. With these jackshafts, the clutches hang off the crank output shaft quite a bit-Im worried my Bully key slot is not going to reach the key slot on the engine shaft.
It should work, (but that's a whole lotta clutch for that little engine)!
If it doesn't fit?, let me know & I'll buy it off you. (I'm getting ready to build another 212 bike). ;)
 
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thingswithwelding

New Member
Mar 22, 2016
120
4
0
Long Beach CA
It should work, (but that's a whole lotta clutch for that little engine)!
If it doesn't fit?, let me know & I'll buy it off you. (I'm getting ready to build another 212 bike). ;)
The Bully clutch I purchased is for a 5/8 shaft. Will "not" fit a 212. The whole unit could be a tad smaller. Who knows. If it fits correctly, Im sure its going to be nice. The only other option Id have is to ditch the Jackshaft plate unit. I said the plate was 1/2 inch thick in other post. Actually its 3/8 thick. So, Im hoping that sliding 3/8 away from the engine doesnt hinder the key area too much. I wont know until I get it in my hands. No rush. Im already making a special precision keyed spacer slug that should help. Once its all squared and torqued together, I dont think a 79cc is going to damage it. Bully says, theres supposed to be end play (which will make my slug work better) , But I was reading in the kart forums, that end play damages the keyway from the constant hammering of the loose floating action of the clutch. And I pretty much agree with that to a certain point. I think Zero endplay play is the best result. Im not saying squeeze the clutch either. Im saying where its just on there where the torque of the fastener is more than what the clutch is feeling. I think Bully says that for other reasons. Then in a perfect world with the shaft keyway matching the key matching the clutch key matching the clutch bore it would probably not hammer the output way. Some of these keys I buy are different sizes and need to be hand finished. Go figure. lol. Who knows what kind of tolerances they hold on these engines. They are made for edgers and pressure washers. lol. The rest is up to the builder. Most of this hobby is not turn key. Im aware of it. Didnt mean to hijack the thread. Its related to to the same type AGK unit. That is the only reason I posted it. Thanks for the reply.
 
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