ATC 90 questions

[ATC Lover]

I got a ATC 90 that I am dieing to fix up, although about the only thing stopping me is the fact that I'm a fat but and I'm sure it would haul me around very good at all. So I was thinking of what I could do to hop up the performance a little, to really get her to spit out some power you know?

Well here are some questions!
--Would the ATC 110 cylinder fit onto the 90?
--What about the 125m, of course early years.
--The standard big bore on a 90 is boring it out to 54mm?
--Would this cylinder fit? Click! (http://cgi.ebay.com/ebaymotors/54mm-Cylinder-Body-125cc-ATV-Dirt-Pit-Bike-Go-Kart-Cart_W0QQcmdZViewItemQQhashZitem414b6ea86dQQitemZ280438417517QQptZMotorcyclesQ5fPartsQ5fAccessories)
--What else could I do to get this machine really putting out some power? How would I go about making the intake bigger?

[atctim]

You will find that in stock form is should haul you around OK. I am over 250 pounds and mine hauls me OK. It is no powerhouse - but I can trail ride it.

One easy cheap way to boost your power is a Lifan 125cc pitbike motor. they can be had new for roughly $250. search ebay for one. they bolt right in - but you will need to do some work for the reverse kicker for the starter and the exhaust and intake.

Buy one with an electric start and your kick start woes are all gone!

[ATC Lover]

Well if I was to restore it, I would want the original engine look, not that the engine has to be stock at all, but look stock. If you know what I mean.

[atctim]

I do see what you are saying - but they really don't look that much different than stock. You can make your current engine aggressive, but be ready to shell out alot of clams!

[ATC Lover]

I think I would most likely split even if I rebuilt the engine with performance in mind. We will just have to see. But I still would like some questions answered if anybody knows. Thanks atctim.

[Vealmonkey]

The lifan will not bolt right in. The atc90 and the atc70/z50 blocks are different sizes.
There are lots of things you can do with a 90. A cheap 90 hop up was to use a 110 intake and carb. Also a good idea would be to use an aftermarket exhaust and a nice free flowing filter.
Looking for more bang. Find a stock cam from a cl or sl90, that will give you some added boost and not bust the budget too much. Early performance cams were based on the trike based cams as they had better cam profiles than the atc cams did.
Now if you want to go Bigger. Of course you can still find piston kits that will take you out around 110 or 124. These are the biggest you can find easily. Bigger piston will start to mean you will have to sleeve the cylinder. These pistons often come in a higher compression ratio which is a help. You need to find a bigger aftermarket intake and a larger carb. The aftermarket intakes are out there and you can contact several board members who have such parts and they might have some for sale. You definitely need an aftermarket filter and exhaust. A DG exhaust is better than a cobra. Also start shopping for a nice used aftermarket pipe, it will help alot. If you're really lucky and want to pony up, you may find some interesting aftermarket exhaust.
Stroking your crank would be the next big step. Look at Powroll for such things. They don't stroke them as large as they once did since most of the parts are used 25 years old or older.
Next step is using a motorcyle piston and a custom sleeve. CB750 piston is about the biggest I've been involved with in conjuction with a stroked crank and puts you out around 183 ccs' or so. Large cams usuallyl come into play here as well as hi test/ racing gas like cam2/ or alcohol if the builder is so inclined. Each fuel has it's own seperate set of circumstances. At this stage you need to seriously vent your head and engine cases to relieve excess pressure as you will be revving these engines out pretty well. Custom headwork is a must and very few people are modding old atc90 heads anymore. A larger intake valve is very recommended. I always left the exhaust valve alone, forced spent gasses out much faster, but lots of porting and polishing. I never did work like this myself. Best left to a professional as I've seen many a 4 stroke head trashed quite quickly. There are also other to go larger as I'm just so recently learning, but they involve alot of aluminum welding and hi tech machining of vital parts. Both expensive if you don't have access to the equipment and the knowledge to do such things. I now know of a atc90 that displaces over 300cc, but with alot of exotic work.
It all depends on how crazy you want to or can afford to get. But you have to remember, once you go so far, they will become not near as reliable as they were. Also, these kinds of things cost big money and some of the parts are very hard to find. But the possibilities are there for the foolhardy! LOL

[ATC Lover]

Wow. I'm not looking to build a death trap. HAHA

[BigTBones]

Wow. I'm not looking to build a death trap. HAHA

I'm sorry, I do believe the word "death trap" is a forebidden word used around trikes! :nono:

[harryredtrike]

your stock 90 should move you around decent