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.

https://www.memesmonkey.com/images/memesmonkey/1f/1f4e5470d0bc65dd15ef4105a171f625.jpeg

[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:naughty:

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/oemparts/a/hon/506f7cc8f8700229747b86a4/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/oemparts/a/hon/506f7cc7f8700229747b86a1/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......

[ATC King]

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......


The RFVC (4 valve) XR200R was only made for '84-'85. Previous and subsequent XR200Rs were two valve all the way up to end of production in about 2002. Except for the two year RFVC, the XR200/R from about 1980 to the end uses the same cam.

XR200 versus XR200R is only the difference between the earlier two shock and later mono shock models. It doesn't diferentiate between the RVFC and two valve ones, they used the same model name. Those are just two years of a black sheep.

There's no mistaking the cams as they're wildly different.

I think Honda only made the RFVC in an attempt to compete in a 200cc class race series back then, but it was a flop. I've only seen one being ridden in the wild. They're very rare and probably not a whole lot more powerful than the two valve version, at least where it matters for an enduro type bike. The other thing is the early XR200R had longer travel suspension then the later ones, which turned more into a play bike by the late 80's to early 90's. They did get a full frame though, compared to the earlier open loop frames.

TMI, but I like the little XR200R. They were great learner bikes and with some brake and suspension upgrades, they're still pretty sporty on tight trails with a capable rider while being very low maintenance.

[oldskool83]

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

How does adding metal increase compression, it would lessen it. Key word cutting lol. My local engine builder fly cuts heads and cylinders for $75...its a no brainier every time I build a motor.

if your kick has no slipped you can kiss the kicker gears goodbye, or you will feel it slip. That fix is another machine shop to back cut gears, add a shim normally the thickness taken off by back cutting and adding a stiffer spring. You start throwing money at a 200x for HP you than chase all its weak areas....there's a reason its the most expensive way to go slow.

There is no set number to machine / fly cut. you need to surface it 1st to even get a start, run the numbers and figure out the squish...if your lost like most internet engine builders. Send it to a real shop who does it all the time and knows the squish numbers. Normally you around .010...however you can not assume your cylinder or head has not been cut or decked in the past...you are not the 1st one to be there after lets say...40 years.

If it runs fine let it go...chances are it will be traded or sold for something cooler within 6 months anyway of owner ship. The amount of times ive seen toys i build and sold FS is nuts...and they always are in worse shape each time I see them.