Big bore kits for atc 70

[Macs]

I was scanning through beatrice cycles and buying some parts i needed for the atc70 restore. When i was there i saw an 88 cc kit. It comes with carb, head, cylinder, piston, intake and all gaskets. I know sooner or later i am going to need a top end, plus i have been lloking at buying a new carb ( the one i have is really pitiful ) So with the price of the carb, piston and bore i could have bought this kit. I wander how much extra power it gives. Has anyone used these.

http://www.dratv.com/attr88topend.html

[Tri-ZNate]

looks like a cheap enough price. Powroll.com wants $160 for an 82cc big bore kit http://www.powroll.com/P_HONDA_ATC-CL-SL-TRX70.htm

[gravelord]

atc70 engines are the same as XR50 engines except for the bore, you have two better options in my opinion. go with a chinese 125 engine which you can get for around 300-400 bucks, bolts right in, has 4 speed, and has a kick starter, but the kicker will hit the fender so you have to cut a hole in the fender, or take them off every time you want to start it, also, besides that, all the XR50 big bores bolt right up to the atc70 engine. the atc70 engine is going to be tired, think about all the work that crank did, and how the internals really are.... replace the whole engine its cheap enough to do, if you dont wanna go with chinese parts, find your self a XR50 engine and start working that up, you can take that thing apart and convert it to a pull start too if you really prefer to have a pull start. they also make electric start kits for them as well, but thats going to cost you a extra penny :) well, good luck, i modded up a XR50 REAL good one time... let me tell you, a big bore really does wonders, but you need a "super oil pump".... then youll realize you need a bigger carb, then a bigger exhaust, then etc etc... it just never ends... go with the 300-400 chinese engine.

[MisterFurious]

Gravelord, where's the best place to pick up one of the Chinese 125's?

[Macs]

you can get them off of ebay. I have a couple of questions. will the head hit the front tire or the front fender? how much of a power increase is it, this 70 is going to be ridden by mainly little kids. i was looking at the 84cc cause i didnt think it nwould make much of a diffrence bit a 125 would. i dont want nothing that is going to be uncontrollable for the wee ones

[TrikeKid]

eBay and Dr ATV you can get a 110 chinese engine (Lifan) with electric start and a 4 speed, that's what I'd do if I didn't already have a 90 engine. Gravelord, depending on the year of his ATC, he may already have a 4 speed, only pre 81 engines are just a bored XR50 engine. Barry, I've seen the Lifans run, they haul the mail with an adult on board. Theres a vid somewhere of treshombre from glamisdunes.com anihalating a 125 pit bike with his, and he's a good sized dude.

[Macs]

there is currently a 4 speed in it.

[TrikeKid]

Here's the vid of tres stomping the pitbike with his 70
http://video.google.com/videoplay?docid=-7617365135637177778&q=atc+70
Here's a thread about how the bore kits and lifans compare http://www.glamisdunes.com/invision/index.php?showtopic=91211&hl=lifan

[Vealmonkey]

Barryman, the 88cc kit only increases power by 2 or 3 hp. You would have to add bigger cam and oil cooler to help push power more. You can get the 110 kit with bigger cam, but I have heard complaints they are a bear to start. At best, you are putting a new top end on a 20 year old plus engine, no telling what part will let go next with all that new power. For around $300 or so, you get all brand new and ready to bolt in. You can convert a kick start to 4 sp and you can get manual or auto shift or even electric start if you want. You can get anywhere from 50cc to 138cc now, and they have a big bore kit to put you out around 146. If your worried to much about power for the kids, keep it stock. If you want a trike for you, buy the lifan. Look for an atc70 with a trashed engine, an bolt in some fun. You will usually have to change a couple electrical connectors, and maybe add something if you want the electric start but, they are well worth it.

[Rex Karz]

Here's KASEY on his "70" (Chineese 125cc)

http://www.youtube.com/watch?v=87_Ilkni2o4

[TravEX]

When it's time, I will buy a Lifan motor. A brand new drop in complete motor for under $300 is too easy to pass up.

I wonder too about the front fender and 90/110 motors in a 70 frame.

[TrikeKid]

The engine will hit with a Honda 90/110 motor, I don't know if the Lifan does.

[blue27]

If you get the Lifan 110/125 motors they will not hit the fender, they are the same dimensions as a 70, but a Honda ATC 90 or 125 engine is larger and will rub the fender.

[gravelord]

doing a big-bore on a atc70 engine is going to give you MAJOR torque, that means EXTREME wheelie power.... touch the throttle too hard , your on your butt. my XR50 that had a cam, bigger carb, 88cc big bore... ive put people on it, that had riding experience, and they ALWAYS fell off the back almost immediately, they had no idea what they were in for. its mostly because of the gearing. lots of power + stock gearing ='s too much torque. basically if your big boreing, go with aftermarket sprockets. if you buy a lifan 125 engine or something, the tranny inside the engine is MEANT for that bore. and i dont think it will be quite as crazy, even though the sprockets your using still does mean alot. best place to get these engines is either ebay, or find a website. make sure though that when you get the engine you buy a kit that comes with wiring, comes with a carb, and maybe even a exhaust if you can. if you get the full kit expect to pay between 300-400, and thats definately more worth it then buying a bolt in engine that uses the stock carb etc, for 200-300... it will be way under-carburated using the stock atc70 carb, also, bigger carb will give you more top/mid and a smaller carb is just going to give you way more of that wheelie ripping bottom end that you probably dont want for your kids. and one last thing, if your using a thumb throttle, switch over to a LT80 style one or something, if you can figure it out, because then you can put a govern it.