Free 97cc engine

[vdubbles24]

I'm getting this engine free tomorrow. It's the flathead style.

I'm having a hard time find info on modifications. Any leads would be appreciated.

Thanks
Brandon

 

[vdubbles24]

I say flathead but pics look like OHV. I'm waiting on a pic of said engine.

 

[maniac57]

All the modern powerplants are OHV these days.
I have not seen a flathead in quite a few years on anything new.

 

[vdubbles24]

Here it is.

 

[cannonball2]

Thats a Lifan. Its one of the better small engines to come from the land of the Panda. It is a flat head(properly called a side valve). I have run 4 of them with excellent results. Smooth and torquey. You got a good "deal" there!

 

[vdubbles24]

What kind of performance mods can be done to this engine?

 

[cannonball2]

Never really modded mine save remove the governor on a couple and run a straight exhaust. They will reliably turn close to 5k stock(with the better exhaust), but will blow oil out of the crankcase breather unless you add a medium like scothbrite, chore boy, etc.
Any mods made to the B&S flatties will apply. Milling the head, trenching, port work, advancing the ignition timing carb increase etc. If you are wanting serious mods check out some of the kart forums.

 

[FFV8]

A bigger carb helps a lot:

.

 

[vdubbles24]

Awesome guys thank ya.

Is that a mikuni carb?

 

[maniac57]

Yup. Sure is a flathead! Never seen one like it before, but then again, I'm not into four strokes these days. It looks nice though...
All the usual hop up mods like pipes, carbs, bigger valves, porting etc. work just as well on these engines as they do on a blown hemi.
One of my all time favorite mods for the 5hp briggs flattie was to bolt on a XR75 Honda carb on a homemade manifold. MUCH better throttle response and ease of hooking a throttle TO it!
Also find an electronic points replacement conversion if it does not already have one.

 

[Davezilla]

Bigger carb and open up the exhaust will make a big difference, gotta remove the governor too.
I did that with a 5Hp Tecumseh on a baja go kart when I was 16 and that thing would easily hit 55 to 60mph (confirmed by having someone follow me in their car and they were surprized asking if I knew how fast I was going, I just guessed around 45 or so and then they told me over 55)on the flat straightaways using 18" tall rear tires and a Comet Torque a verter, governor removed and a Honda Twinstar 185 carb. The exhaust was also just a straight pipe. I should have got a better piston rod tho because it eventually broke the rod, but it did run reliably for 3 years before the rod broke, back then there really weren't any billet rods easily available like they are now, but I'd strongly recommend a billet rod if you can get one... cheap insurance.

 

[cannonball2]

I believe this engine is a clone of the 100cc(or so) Honda flattie which hasn't been produced for a while. I have never seen any speed parts for the Lifan, but then I have never looked very much either. If its a true clone maybe there are parts available for the Honda. I have turned mine in the high 4k range for miles with no issues using jut the stock parts. I built a 5hp Briggs for a friend that ran a kart in the gas class. No mods were allowed(every body cheated) except the engine could be brought into manufactures specs. by swapping stock parts. These engines turned easily over 6k reliably. I expect the Lifan might too.

 

[curtisfox]

Intresting as i have a G100 Honda that needs a carb,how big do i dear go with the carb?.........Curt

 

[Davezilla]

I can't remember right off hand the size of that Twinstar carb, but I remember it bolted right on and connecting the throttle cable to the carb was also dead easy to do, I used to sneak the carb off this bike to put on the kart fairly often when I was a kid and never even massed with the jetting or adjustments other than idle speed, mainly beacuse I needed to sneak it back onto the bike before my dad noticed it was on the kart or off the bike...
For that year model, the Twinstar 185 only made about 10hp and used a single carb so I'd guess it was around 20 to maybe 22mm and it definitely made a difference on the Tecumseh engine. Too bad we didn't have easy access to billet rods back then...

As far as carb size selection I'd say keep it around 22mm and you should be ok, you could probably go up to 24mm just fine. If you can find a CV carb between 22 and 26mm, that would work really well since it'll only open up to what the engine can use to prevent bogging and they accelerate very smoothly, even if you snap the throttle to full from idle.

 

[curtisfox]

THANKS
I will see what i can find. ........Curt

 

[Dan]

Never really modded mine save remove the governor on a couple and run a straight exhaust. They will reliably turn close to 5k stock(with the better exhaust), but will blow oil out of the crankcase breather unless you add a medium like scothbrite, chore boy, etc.
Any mods made to the B&S flatties will apply. Milling the head, trenching, port work, advancing the ignition timing carb increase etc. If you are wanting serious mods check out some of the kart forums.

CB, what is "trenching"? I looked it up but didn't find any thing.

 

[vdubbles24]

So would the mikuni blow through carb work if I make adapter?

 

[vdubbles24]

What is "TRENCHING"

 

[Mongrel1]

I got a ported 80cc china girl with a fred head and 80kx racer expansion chamber. I'm currently running the stock NT 14mm carb with the choke 3/4 open and want to know, how much larger should I go with the carb. I was thinking at least 18mm maybe even 19mm. I see some sweet deals on the mikuni's lately. Any thoughts on this anyone?