?? Atc 185 engine with Xr185 piston, xr200 cam and carb

[MNhondaguy]

So I have an 81 atc185 engine that needs boring, so I figured lets get creative. I love Hondas dependability, so I am liking the idea of all oe honda parts. I've done some searching but the technicals have me wondering.

My theory is an overbore xr185 piston, with an Xr200 cam and carburetor. The xr piston is domed and 10.1:1 compression. I'm curious if anyone knows if the xr piston and bigger cam will bend valves or is it doable?

Or, if that doesn't work, would a xl185 flat top piston with a xr200 cam and carb.

I'm sure I'll get some weird looks or comments, but I'm curious how "big" I can go with Honda parts. I'm not interested in new topends as my cyl and head are peachy, so just cam and piston.

Does anybody have any pointers or personal experience with these cmbinations?

Thanks for any and all help, info, or pictures.
Cody

[oldskool83]

It's common. It's not gonna be no 350x however. I've been there and done it.

All XR and XL185s and 200s and ATC185/200 series use all the same piston and motor design so it does not matter what bike you pick a piston from. Find you next bore size buy a XR200 carb and cam and put a uni air filter on it and call it a day. It will have a little more snap but will not be a 350x

It's gonna be way harder to pull start, so if you have no decompression lever on that forget about pulling it over. I built one up that really messed a guys arm up...it was the last motor he ever chose to pull over after that...I didn't blame him...I couldn't even start it.

[86125m]

I would go as stock as possible I have found that hopping things up really does nothing but blow up. while mostly stock will last for years and years.

[MNhondaguy]

I have a decomp lever, and am glad to hear a solid response. I'm choosing to stay factory Honda parts in hopes of the everlasting life of these things. I am also rebuilding one To standard specs first, as I need time to accumulate the other parts. And I have a running wheeler.

My plan is to make a descent little trail/woods bomber. 200x frame for some squish with an auto clutch fits my riding style well. And if the wife wants to ride she can.

[loganm]

It's common. It's not gonna be no 350x however. I've been there and done it.

All XR and XL185s and 200s and ATC185/200 series use all the same piston and motor design so it does not matter what bike you pick a piston from. Find you next bore size buy a XR200 carb and cam and put a uni air filter on it and call it a day. It will have a little more snap but will not be a 350x

It's gonna be way harder to pull start, so if you have no decompression lever on that forget about pulling it over. I built one up that really messed a guys arm up...it was the last motor he ever chose to pull over after that...I didn't blame him...I couldn't even start it.

I can see a kicker put how does a pull start hurt someones arm? If anything they can't pull it, it's not gonna kick back. I'd probably end up ripping the rope right off if I couldn't pull it.

[MNhondaguy]

Oh they fight back

[Scootertrash]

I've got an 84 200S Bored 1 over, Wiseco 10:1, XR200 cam and carb, used to have a DG exhaust but now has a SuperTrapp, with the stock airbox.

I love it, have had no problems whatsoever, and would recommend this upgrade to anyone.

[Scootertrash]

I would go as stock as possible I have found that hopping things up really does nothing but blow up. while mostly stock will last for years and years.

Horse hockey. All of my machines have been hopped up to some extent, and I ride 'em like I stole 'em. I haven't blown one up yet.

[oldskool83]

pull start motors pull back...and when your pulling something over with no decompression your arm will get hurt nicely. It's not like pulling over a lawn mower

[83ATC185]

I can see a kicker put how does a pull start hurt someones arm? If anything they can't pull it, it's not gonna kick back. I'd probably end up ripping the rope right off if I couldn't pull it.

I only took a handle to the back of the ear once, ok maybe 3 times, before i started rolling it over before i snatched it.

[greenhuman]

Don't be a Nancy boy. I used to pull start a 310cc ATC90 using a stainless steel pull cord with no problems.

[110 atc]

My 84 200S in modded with a 10:1 wiseco, xl 185 cam and 200X carb. Almost a little bit dangerous but mainly ride like I stole it on frozen rivers. I had to go with a manual decompression lever because the auto mechanism got shredded after the high comp piston was installed.

[Scootertrash]

My auto decomp is still working fine, going on 3 or 4 years now. Increasing the compression doesn't affect the decompressor.

[110 atc]

Wow, I don"t know what exactly went wrong but I suspect after a few bad back kicks the plastic ring got shredded by the metal spring. I found it was easier to bolt in a manual unit.