Thoughts about using an 80cc kx motor on a kart

[jdub198425]

I'm already looking for the next way I can upgrade my kart! LOL
I'm thinking I'd like to use a dirtbike engine. I currently have a 5.5 horse honda on my kart (which is fun BUT I want more.....imagine that). Is an 80cc 2 stroke going to offer that much of a noticeable difference in performance? I have a line on a rebuilt older kx80 that is owned by a mechanic friend....or I could try to find a 125cc from someone and not know what I'm getting. I just want to be sure that performance wise it'll be worth the work involved with it!

 

[landuse]

An 80cc 2 stroke should be a lot better than your 5.5HP. Have you got the skills to fab up mounts etc to get it installed?

 

[GregMartin]

Is an 80cc 2 stroke going to offer that much of a noticeable difference in performance?

Yep

You could use a Honda CT110 (postie bike) engine. They have a four speed gearbox and a centrifugal clutch (you can also get manual clutch kits for them). There are Lifan 140cc replacement engines on ebay for about $250. Of course you will need to fabricate a different engine mount.

 

[jdub198425]

I can fab up a mount. I have the tools, know how and a few local friends brains I can pick if I get stumped with something along the way. I know that the kx80 that I have in mind has been gone through completely. I'd be able to pull out everything that I need and not have any concerns about having to rebuild anything. He's got it up for 450 for the complete bike. I might be able to walk away with it for around 400

 

[GregMartin]

Yeah could be the way to go.
Those Lifan engines are new but they don't come with a carby or header pipe so there's a little bit to get.
Anyway good luck with the upgrade.

 

[rlcj_racing]

I've been riding with my buddy all weekend. he has an 80cc 2 stroke 4spd. on his kart & I've been riding my sons kart w/6.5hp clone motor & I've been beating him terribley. My sons kart is a bit lighter & geared better.
He's rally gonna be upset when I finish MY kart, lol.
IMO an 80cc is a bit small for a kart, in stock form. I do have to admit tho; it is fun dropping the clutch & shifting gears!

 

[anderkart]

I'm already looking for the next way I can upgrade my kart! LOL
I'm thinking I'd like to use a dirtbike engine. I currently have a 5.5 horse honda on my kart (which is fun BUT I want more.....imagine that). Is an 80cc 2 stroke going to offer that much of a noticeable difference in performance? I have a line on a rebuilt older kx80 that is owned by a mechanic friend....or I could try to find a 125cc from someone and not know what I'm getting. I just want to be sure that performance wise it'll be worth the work involved with it!

I'm not sure what type of kart you have, but this video shows what you could expect riding a KX80 powered shifter racekart to be like:

(his kart is powered by a CR80, but a KX80 would be very similar)

http://www.youtube.com/watch?v=CczJCdnSCgM&feature=related

 

[r97]

I've been riding with my buddy all weekend. he has an 80cc 2 stroke 4spd. on his kart & I've been riding my sons kart w/6.5hp clone motor & I've been beating him terribley. My sons kart is a bit lighter & geared better.
He's rally gonna be upset when I finish MY kart, lol.
IMO an 80cc is a bit small for a kart, in stock form. I do have to admit tho; it is fun dropping the clutch & shifting gears!

Is your buddy's 80cc air or liquid cooled? Around when was it made? Judging by the fact that it is a 4spd, I would guess it is relatively low tech. An engine from a new-ish moto-cross bike like a KX80 will have significantly more power than an 80cc trail bike engine. The video that Anderkart posted is proof of what an engine like the KX80 can do, but remember that you need to put it on a correctly sized vehicle.

 

[rlcj_racing]

I agree w/that, New mx eng.s make more power than old ones. They are still the "little" dirtbike in the lineup.
My friends r eng. Is air cooled & nothing "fancy". Their kart is heavier than mine & could use a better sized rear sprocket. The shame of it all is that the perfectly good m/c they butchered for the eng. ran great, pulled 1st,2nd & gear wheelies & best of all could jump.
Sorry for those who took it as a blanket statement that 80's suck. Consideringthe price it's pretty impressive with what you do with a 6.5 for so little. But some say their too small also.

 

[Kaptain Krunch]

I agree w/that, New mx eng.s make more power than old ones. They are still the "little" dirtbike in the lineup.
My friends r eng. Is air cooled & nothing "fancy". Their kart is heavier than mine & could use a better sized rear sprocket. The shame of it all is that the perfectly good m/c they butchered for the eng. ran great, pulled 1st,2nd & gear wheelies & best of all could jump.
Sorry for those who took it as a blanket statement that 80's suck. Consideringthe price it's pretty impressive with what you do with a 6.5 for so little. But some say their too small also.

A stock kx80 motor will outrun any 6.5 clone, no matter the mods, as long as they are on similar karts.

I would much rather have a kx 80 motor than a lifan 4 stroke or similar. Cant beat the acceleration and top end of a liquid mx 2 stroke.

 

[jdub198425]

It's funny cuz I hadnt even mentioned my thoughts of buying the KX to my friend who owns it. The other day I had him on the phone and he suggested that I buy it and put the engine on my cart.... I replied well ACTUALLY.....lol....

 

[anderkart]

Researching my RM80 engine has resulted in a few surprise findings. First, engine output for mine is rated around 28-30hp, which is more than enough for a yard kart, provided you gear it correctly to avoid loading it up and burning out the rings. Second, is that since the RM80 is a 'Race' bike, it has a six speed transmission, which means lotsa go fast, and that I can gear it lower than I originally planned to keep it in its power band. Third, the RM80 is liquid cooled, meaning I will have to come up with a radiator mount and run hoses to and fro, but it shouldn't be any set back.

I do plan on using a live axle(duh) and utilize the bike's hydraulic rear brake and rotor on the axle, which should be enough to sling me up against the steering wheel if really stepped on, lol. Still brainstorming some sort of shift mechanism, and leaning towards an air shifter with buttons placed on the steering wheel, which means a small battery, compressor, and air tank will need to fabbed and mounted as well, and that brings me to the clutch. How has everyone done theirs? I have seen some cable levers attached to the steering column, I have seen some with a side handle mounted near the side of the seat, and some just rigged and dangerous no clutch systems like some shifter karts.

You'd get much better advice if you started your own build thread, instead of asking for specific advice like this on someone else's... When you start your thread, be sure to post some pics of your kart & engine, and we'll help you all we can