Doug

I planned to only use the cylinder for added cooling. I picked up a gasgas Randonne 200 last weekend & hope to get the reflex refreshed soon ... I look forward to trying out the Randonne this weekend in Sequatchie, Tennessee !

Congratulations. That's an interesting plot twist, but I was hoping British Columbia "tlrmark" could provide some more ATC information.

 

tlrmark . . . are you out there?

Yes. to answer some of your questions. There are no markings or obvious external differences to identify the big fin cylinder  ATC200X 1983-1985. I can tell the big fin at a glance, the best thing to do is look at photos from the top of the cylinder, if you don't know what a normal small fin looks like look on ebay at a xr200 or xl185 for sale, again from the top  and then go back to ebay listings of the 200x and compare. I have just looked on us ebay and there are 4 or 5 genuine big fin cylinders on there right now. 

    Regarding cyl. heads you don't want the 200X cylinder head for a bunch of reasons, I don't have time to get into. You can use a xr200 or xl185 cylinder head for a big increase in power at midrange and higher. You will lose some off idle power and torque.

   No reason not to use your tlr cam, unless its damaged. If you do want to use the mechanical spark advance setup off the ATC,XL,XR engines you can ( I do) it provides adjustability in timing the tlr setup does not. Your only option in cams if you do is the ATC cam, the XR and XL cam are too much for trials use.

  All this cyl head and cam discussion is not nearly as important as increasing the compression to 10.1 same as xr200 as discussed last year on this thread.

  You do not absolutely need a big fin cylinder, boring a standard cyl for a wiesco piston makes a huge difference.

   Mark

  

Excellent.

Some great information and exactly what I was looking for.

Thanks Mark.

Mark,

Is there a way I can reach you for future modification expertise, like an email address etc.

Thanks,

Doug

dbjamie@msn.com

On 3/24/2015 at 8:03 PM, tlrmark said:

The 1986 and later ATC200X engine is completely different than your xr200/tlr200 engine family. Nothing is in interchangeable from the 1986 and later 200x engine and any tlr/xr engine. You need to look for a 1983-1985 ATC200X cylinder, which will bolt on with no modifications. Be aware if you are looking on American ebay, most 83-85 atc200x cylinders listed are scams by fraudsters and are just regular small fin cylinders. The supply of big fin ATC200X 1983-1985 cylinders has almost dried up because of the great demand and some people are trying to sell anything. I've done many of these swaps over the years.

Hi I am looking for a complete top end from a 83-85 Honda Atc 200X  cylinder and head , if you have anything or can source anything I would be interested

You should be able to find plenty of anything except the cylinders. They have been and are always being sourced.

There was a guy (not long ago) on eBay in the UK selling kits he claimed used "new" cylinders. You are in the UK so I'm not really in a position to help you source parts, but of course you can buy off eBay yourself. Again things come up on the internet, just not as plentifully as years ago. You aren't late to the game, it may just take time for something to surface.

Well . . . here's a post from someone in the US and they claim to ship worldwide.

https://www.ebay.com/itm/83-85-HONDA-ATC-200X-200-X-CYLINDER-PISTON-TOP-END-GASKETS-KIT-REPAIR-/143181538062?_trksid=p2385738.m4383.l4275.c10

Good luck