Pitbike Engines

[Kurlon]

Two new, never fired pitbike motors up for sale, to fund my transition to Motard. Prices are starting points, shoot me offers.

Motor 1: SDG branded, Lifan sourced 120. 1d3u shift pattern, 52.4mm x 55mm bore and stroke. 27mm x 23mm 'Big Valve' head. Oil cooler taps off the main galley instead of bleeding off the head feed, motor will come with a cast oil cooler. You will need to supply oil lines and banjo bolts. At a minimum, the oil taps on the motor will need to be tied together or you WILL fry the top end by starving it for oil.

I have a 57mm cylinder and a no longer produced Takegawa 57mm slipper piston, which punches this motor out to 140cc. I also have an updated shift star for the transmission. $200 for the package? To complete the setup, you'd need a top end gasket kit ($10), and ideally a wilder cam (TB 300a for $35).

Motor 2: Lifan 150. 4u shift pattern, 56.4mm x 59.5mm bore and stroke, 27mm x 23mm 'Big Valve' head. Daytona style clutch cover with oil filter and oil cooler taps fed directly off the oil pump. Newer style 5 disc clutch pack. I've replaced the head gasket with a thinner unit for more compression. I purchased the motor without a stator plate intending to run my Kitaco IRK setup, but never got around to it, so you'll need a stator plate to make it run. Easiest to just swap over the one from the motor you've been using, that way there's no wiring to convert. $300 for the motor? They are currently $550 retail.

[Doc]

Will the both bolt in the 70 or my Thumpstar?

[Kurlon]

Both will bolt in to either, although on a stock 70 you'll also need a clutch cable and perch. You'll also likely need longer peg bolts and some washers to act as spacers as the bottoms of these motors are wider than a stock Honda 50/70 bottom end.

On your Thumpy, you'll be loosing electric start, otherwise they'll both drop in. I can help with the really simple wiring conversion needed to adapt a Honda harness to an import one.

If you're talking about the 70 you just bought, the Lifan 120 will drop in, you'll need a clutch cable to match the motor though. The Lifan 150 will need a custom rear brake master bracket made up. I mount my brake masters to the motor using clutch cover bolts as 70 frames have no provision for them. The Lifan 150's clutch cover is different enough that my G-Craft and homebrew mounts won't work. I know what needs to be done, I just haven't hacked up a piece of aluminum to do it yet.

[SVRACER01]

how much for the SDG?

[Kurlon]

how much for the SDG?

$200, with the makings of a 140 kit?

Or toss me an offer?

[lopycam]

I have a 1985 ATC 70 three wheeler that had a motor that did not run. I got a crf50 engine with a manual clutch set up that I bolted right in. It works fine but I would like more power. I have a funky pull start lever on the kick start shaft that works great.

So, I already have a manual clutch cable and perch. You seem to know way more than I do about these things. What would I need to do to bolt in either of these? Would I need a different carb? Intake? Exhaust?

Thanks,
Nathan

[Kurlon]

If a CRF50 motor bolts in, the only real impediment you should run into with either of these is going to be space, as they are a touch wider on the bottom than the CRF50, and a bit longer due to taller cylinders.

http://www.dratv.com/itlolimo19at.html

Looking at that conversion, the length may be what holds you back. The Lifan 120 runs a 78mm tall cylinder, the 150 is an 80mm tall unit I believe. Stock Honda 50/70 motors only use a 63mm tall cylinder, so you'll need to make sure you can run a motor that is 17mm+ longer in the front.

Your other option is to hop up that 50 motor, lots and lots and lots of ways to do so, all depends on how fast you want to go... : )

[lopycam]

Lets assume that I have the extra inch of room, which I do not think it will be a problem as I am not running a front fender anyway, could I use the stock 70 exhaust and the stock crf50 carb? What jet would I need and do you know where I can get it?

Thanks,
Nathan

[Kurlon]

Stock exhaust - Yes, as long as you're willing to stretch it a bit... Because of the taller cylinder, the exhaust port on the head is also going to be 17mm further away. I have had good luck on 50's stretching them to fit, as you can get a surprising amount of flex out of the U bend by the motor without distorting the pipe. Just remember that the pipe is tension mounted before you undo any of the bolts lest it snap back and tag you by surprise. The other option is to look at the exhaust's rear mount tab. On most, the tab is big enough that you can drill a new hole that will allow the whole exhaust to shift forward enough to make up the difference. Obviously the stock pipe is going to choke the motor down some...

But not as much as a stock ATC70 carb. You'll be able to use it, and have crazy throttle response, but again you'll be holding these motors back quite a bit. I don't know the specs on the ATC's stock carb, so I can't suggest jetting, but it shouldn't be that big of a change from stock, up a couple on the main, maybe raise the needle a notch? I've run my 70's stock 17mm carb on my 110cc stroker before, killer for short track... if you need any legs, it's not the way to go.

I've got some carbs and intakes that might work, you're going to need a throttle cable made to match the carb to your throttle though. I'll poke through my collection to see what I've got loose at the moment.

[SVRACER01]

$200, with the makings of a 140 kit?

Or toss me an offer?

veeerrry tempting.

[SVixxer]

I am interested in one of the motors since I just snapped the crank in my 125cc Xtreme pit bike. What is the rate HP output of the Lifan 120? Also would you be willing to ship to Enfield Ct?

[Kurlon]

I'm sure if I dig around I can find a retailer claiming 12hp for the Lifan 120... stock form it's more like 8, assuming you're not choking it with your carb and pipe setup. It really depends on what you're pairing it up with.

http://www.x386.net/TTR/tech/dyno.html

It's a little out of date, but that's my old dyno collection when I was really researching these puppies. There is a stock 120 RWHP dyno in there from CHP, along with some built Honda/KLX motors. For comparison, my 151 build put down 15hp, my stroker 110 put down 10hp. Punched out to 140 you're looking at 10hp to 11hp 'bolt up'. With a lil TLC and head work you can get 14+.

The Lifan 150 when allowed to breathe properly is a solid 12hp crate motor.

If I remember correctly, your Xtreme may have a CR3 transmission? If so, I'd put a new crank to it rather than swap the motor, as that's a sweet close ratio setup compared to the typical import gearbox. I've done a couple crank swaps in the past on 120s/125s, not that difficult. I'm going to guess yours let go on the flywheel side?

On shipping, I don't have the original boxes for these motors, so I'd have to get a tupperware container and some packing material. Size plus weight is going to make these pigs spendy to ship, I wanna say $30 to $50 by the time it's packed and hits your door.

[SVixxer]

Good info thanks. I am running a mikuni 25mm carb and a straight through exhaust canister. I actually found a used crank on ebay for $39 and new they are $58 so that is pretty good for price. I do like the gearing in it and the motor goes very well with a top end of 53 mph I like it. I am going to try the crank route first. I hope to get it done before the next TTD so i can tool around on it between sessions.

[Kurlon]

Cool, get a gasket kit too, Dr ATV used to carry them for the imports, if not I can track one down for ya. If you run into trouble/difficultly let me know. Also, what we found was a common culprit for snapping cranks, valve float. Get some better valve springs in that motor, and consider gearing up a touch so you don't hold it at top revs for as long.

[SVixxer]

That makes sense. I brought it to Deals Gap last May and a few of us went ripping through the dragon just before dark. We pretty much ran wide open for along time. I will PM you if I have any issues, thanks.

[Mr. Kurtz]

I am interested in one of the motors since I just snapped the crank in my 125cc Xtreme pit bike. What is the rate HP output of the Lifan 120? Also would you be willing to ship to Enfield Ct?

Matt, if you do end up buying one of Kurlon's motors, and if he would be willing to bring it to a race weekend, I can pick it up from him and drop it off to you on the way home.

[Kurlon]

I have no problems dragging bikes/motors to the track, in fact that makes things much easier for me.

[SVixxer]

I may be there on the 19th for most of the day before Tony's to watch the races. i can swap in the motor that day actually. I will let you know.

[Kurlon]

I'm going to be packing up my truck/trailer starting tonight, so if I'm bringing anything to the track, now is a good time to let me know. : )