Tune-Up Predator 79cc 4-Stroke

[Frankenstein]

Yeah, Sturmey Archer SX-RK3

The manufacturer was less than helpful. "Our hubs don't work with motors." ...which is a ridiculous response. They should have said, "Our hubs can only tolerate the smallest amount of torque." ...or something like that because the fact that it's hooked to a motor seems irrelevant to me.

Even if I put a fixie hub won't help because that would still need a freewheel connected to the drivechain. That is why I'm thinking a left-side fixed drive might be a better idea.

What is your set up exactly that you use to get right side drive?

 

[Frankenstein]

Just wondering since they do make freewheels for standard threaded hubs, you can get them as a single speed freewheel and that will let you have as least partial working ability. I would suggest never telling a manufacturer or anybody for that matter that you're using a motor when it comes to warranty. They will always tell you that it's not their problem even if it is.

Also saw a read on the web since I felt like researching, apparently a guy uses that hub on e-bikes at 2k watts with no problem, now in horsepower that's just over 2 and a half hp... I don't know for certain but aren't 79cc preds significantly lower than that? Don't see how a guy can abuse his relentlessly (his words, slightly modified) on a electric motor like that without a problem and you doing yours like you did and it somehow be your fault.

 

[ColdCruiser]

Here's my build thread. It has lots of details and pictures of my setup.
http://motoredbikes.com/threads/predator-79-transmission-options.46327/

Here's my FB page:
https://www.facebook.com/MotorizedFatBike/

I was not asking the guy for a warranty replacement or anything, I was just asking for a solution or suggestions. Do they have a better one? Can I fix it? Can I replace only the freewheel? Obviously he was being defensive and probably not wanting to replace it for free like you suggested. It says a lot about a company how they respond to a customer's inquiry. I now have the strong impression that Sturmey Archer makes crap and doesn't care about their customers. Whatever, they have earned no loyalty from me. Might be time to see what Shimano has to offer?

I have seen some pretty heavy-duty looking freewheels for a solid axle hub. Too much actually. Some options are very expensive. It is also probably a rare size hub since it's on a 4" fatbike wheel. Probably needs something special since it has disc brakes too? It would be too bad though to give up the 3 speeds because it is geared nicely to get my loaded trailer going then get up to 30 mph. I have not properly removed the governor so I don't want to put more than 5500 rpms on it.

 

[ColdCruiser]

My motor (Predator 79) has between 3-3.5 hp. It came with ~3 then I added exhaust and intake. I don't think it's a matter of hp though. I don't exactly understand all this but my understanding is there is much less torque up where it is spinning at 2,000 rpms then there is at the pedals at ~16 rpm. So, I don't think there would be any more torque generated by the motor than would be generated by pedaling. No?

If this is the case, would a crappy hub-shifter be less likely to fail if I put it closer to the motor where it is spinning faster with less torque? It would take some serious modifications but theoretically I could put it where my crossover jack-shaft is. I don't know.

Maybe replacing the clutch with a torque converter would prevent the rear-hub from getting spun-out?

The electric motor might not try to spin if there is too much resistance? My gas motor transferred the power all the way to the hub.

 

[Cozmik]

Cozmik, I cleaned everything real good and put new gas in it and now the motor runs fine again.

However, I spun-out the freewheel on the 3-speed hub. I'm not sure how I'm going to resolve that issue. I was thinking about doing a left-side direct drive like you have. How's that working out for you? What gear ratios are you using?

I am running a 44 tooth rear sprocket which should be fine. But I think, because I am a big guy, I need a 50ish tooth rear sprocket to improve take offs. Right now it goes faster than 40 mph, which is fast enough for me.