Atc 200x upgrade questions

[SasquatchAtc]

Hey all.

I grew up around 2 strokes. And haven't got much experience with 4 strokes besides the regular stock to stock rebuilds. I'm wondering if I need to port the head on my 85 200x if I bump the compression to 10.25:1

Thanks

[oldskool83]

just fly cut the cylinder base to raise compression and throw in a xr200 cam, 200's dont scream unless you dump too much money in them. My way is $200 max

[SasquatchAtc]

My way is $200 max

I like that price lol

[SasquatchAtc]

I heard somewhere that stacking a couple extra cylinder head gaskets gives the same effect as flycutting. Is this correct?

[350for350]

No. That would lower the compression. By stacking head gaskets, you'll be increasing the size of the combustion chamber. That means that the air/fuel mixture won't compress as much.

[207wheelin]

No. That would lower the compression. By stacking head gaskets, you'll be increasing the size of the combustion chamber. That means that the air/fuel mixture won't compress as much.

What piston would you use and how much would you have milled of the cylinder...approximately. Just curious. Thanks
207

[El Camexican]

What is it you’re trying to achieve buddy? If you just plan to toss another piston and rings in to keep your ride running, I wouldn’t touch a thing. You could back a truck full of money and dump it all over that engine and you’re l still not gonna get anywhere near the performance you’re accustomed to from your two strokes.

[ATC King]

You could back a truck full of money and dump it all over that engine and you’re l still not gonna get anywhere near the performance you’re accustomed to from your two strokes.

[SasquatchAtc]

That's exactly what I thought when the guy told me that about the gaskets. What he was saying was contradicting himself, but sometimes you can't explain logic to a crazy person. I'm just looking for a little more power, not a ton. She scoots where she needs too. Just curious on budget upgrades since a stock bore 10.25:1 piston isn't too pricey

[El Camexican]

Rebuild it with that piston, remove any casting flash that doesn’t belong in the ports, don’t mess with decking your cylinder, cutting you head, or different gasket thicknesses unless you plan to get a slotted cam gear and adjust your timing to suit the geometry you’ve changed. The closer you bring the centerline of the crank and cam together, the more you retard your valve timing (typically adds top end at the sacrifice of bottom end). Get your jetting as close as possible and call it done…

or... you could have it ported using a flow bench, put a performance cam in it, bigger carb, high flow exhaust, stroke it, bore it to the max, send it to a tuner for multiple dyno runs and $5,000 later you might be making 5hp more than a stocker.

[Scootertrash]

Rebuild it with that piston, remove any casting flash that doesn’t belong in the ports, Get your jetting as close as possible and call it done…

I would add an XR200 cam and carb as well.

This is exactly what I did with my 84 200S, with the addition of a NOS SuperTrapp I snagged off of ebay. IIRC, I can get 55 mph+/- on the flat straightaway down the road from me on my phone GPS. Maybe one day this summer I'll do a side by side with a vehicle just for comparison

Plenty fast for the machine AFAIC. I leave my buddies on their 185/200's in the dust

[SasquatchAtc]

So you are saying use a stock piston. Or the 10.25 piston.
What year xr200 cams and carbs work on these motors?

Thanks for all your help guys

[350for350]

He was saying to use the 10.25 piston. The XR 200's changed over to a four valve head (I think) and dual carb set up. Parts from those won't work. I think the change was around 1985 or so. I put a XR200 carb on my AutoX in place of the 200X carb. From riding it, I gained a little bit on the top end (it revs higher) and lost a little bit on the bottom end. I doubt very much that anyone but me could have told the differences they were so small. I do have a XR200 cam, but the one that's already in the engine is bigger so I'm saving that for another project.

[207wheelin]

I have one ATC200S with a Wiseco 10.25:1 and a 200x cam. It's a fun machine to ride. I'm currently working on a 200s engine that will have a XR200 cam and the Wiseco 10.25:1 piston. I usually add a better flowing exhaust and a China PZ27 carb.
It makes these machines more fun to ride and hasnt seemed to harm the durability at all.
Take care
207

[Scootertrash]

IIRC the 200X cam is identical to the rest of the 200 series 3 wheelers. "Back in the day" people thought they were different but they aren't.

The XR200 cam pre-4 valve head is the one you want, (XR200R is the 4 valve model) unless they finally standardized a new version that is identical to the normal 200 series cam......

ETA:The part number for the 1983 XR200 cam is: 14101-446-000

https://www.powersportsdiscount.com/...camshaft-valve

Also, be careful not to lose the little rubber plug, #5, and make sure to put it back in on reassembly:

https://www.powersportsdiscount.com/.../cylinder-head

There are old threads pertaining to the cam swap, I'm pretty sure I did a thread when I did my mods. I probably have another XR200 cam or 2 here for future builds, but my garage and storage is a total flustercuck right now and I have no clue where they'd be, so I can't verify part numbers for you......