Planet Minis

Darren S90

Hello all,

Im a new member here in search of help. I dont know if this is the right place to post this, so forgive me if its not, im still trying to find a good forum.

I just got a 1967 honda s 90. I got it running and it starts right up and idles perfect but its a real dog with me on it (220 lbs). It would barely do 40mph. What I am thinking of doing is swapping in a new Lifan 140cc motor. I think this would boost overall performance? Whats the best tranny option for street applications, 1up 3 down or the 4 down?

Has anyone here done this swap? From what little I have gathered, its NOT a direct bolt up. Something to do with 2 motor mounts verses 3 mounts.

Can some one fill me in or point me to another website that may be more helpful?

Thank you very much
Darren
Colorado Springs, CO

fatcaaat

Darren,

I think a YX motor would be your best bet given the amount of space availble due to the larger heaver motor it would be replacing. You are going to have to do a little bit of fabrication work too because the mounting for the motor will be different. Also you will need the lighting coil on the bike, so ask who every you buy from to make sure it comes with that.

So, if you can tackle the mounting issue and get yourself a different exhaust pipe, you'll be halfway there.

Next you are going to have to rewire it for a CDI pulse so you'll need to get a short harness. If you don't know your electrical, you are going to be in trouble. All the new motors are 12v, so a simple swap in and plug is not going to work. So, you will need a wiring diagram, a rectivier, 12v battery, 12v blinker, and new 12v bulbs.

For a novice this is going to be a real challenge. I've been doing this for quite some time and it will end up being a nightmare I can tell you. I've done a Honda s65 in the past and it was just quicker to take the old harness out and make my own from scratch.

So, instead of going this route, maybe you could go this route:

Get an ATC125M crankshaft and swap it in there for a 54mm stroke (pretty sure they are compatible). Then, get a bore up kit to 54mm and you'll have a 125, honda based motor that will provide ample speed and torque for that bike. Get some HD clutchs springs while you are at it. If you want to go really fast, go to webcamshafts.com, get a mid range cam and pop on a 26mm mikuni VM26 carb.

Darren S90

Thanks for the quick reply, What is a YX motor? Im a novice with this bike but I have restored cars and boats, so I think I can do just about anything. I guess Im just looking for instructions. Do the Lifan motors come with good wiring instructions? As far as mounting the motor, has anyone made any drawings for adapters or mounts or anything?

These lifan motors are so cheap, it just seams easier to fab one of these in , opposed to messing with the 40 yr old stocker. I see deals on the 140cc lifan for around $300 with all the electrics and carb

Thanks
Darren

XNachoX

YX150 motor:
sgr-usa.com

Darren S90

Is the yxmotor better than the Lifan 140cc? Here is a pic of my bike, not bad for $400

MySpace

GTWORKS

So what did you end up doing Darren... I'm in the same boat as you

I'm going to upgrqade the motor in my S90 too

T Bolt USA

we have the yx160cc motors NEW type
100% Good to date / 0 failures on this newest version
TBolt USA, LLC » Engines » Piranha Engines » .Piranha 160 Engine
same this with yx150 and its so trick looking
TBolt USA, LLC » Engines » Piranha Engines » .Piranha 150cc (Daytona Type) Engine

guys have done it but unlike ct70 xr50 its not a bolt in job
i hear 1 bolt goes right in so that would be a big help

__________________
T Bolt USA
ALL top Pitbikes ,Engines and Parts for Pitbikes & Minis
Website
Contact THECRKID@TBOLTUSA.COM or Call 215-630-3554

topr

You can make the motor that's in it a "runner" and have no worries of fitment issues. Drop Firepower a PM and see what ideas he has. It may also give you a good idea of what it would cost.

Dan_Lorenze

Honestly, I think a good ole Lifan 125 would be the ticket.. YX's are a good option when you want to build an engine up with lots of aftermarket parts to choose from.. The smaller Lifan's slip right in and are a little narrower so that the stock peg mounts fit, they also come with a lighting coil. I owned two Lifans a YX and a Zonger... From a "Dropship crate motor" stand point I think the Lifans are hard to beat.. I orded a Lifan 125 off of ebay and slipped it right in on of my CTs, even looks stock.. That 125 ran like a sewing machine for years, smooth and quiet...

nielspbr

S90(=OT90) like OT cub90 will never be a drop in, different mounting points.

For shift pattern, go for the 4 up versions. 1 down 3 up boxes are always a pain to get in neutral.

T Bolt USA

correct !!

__________________
T Bolt USA
ALL top Pitbikes ,Engines and Parts for Pitbikes & Minis
Website
Contact THECRKID@TBOLTUSA.COM or Call 215-630-3554