Hi, I'm in the process of restoring a 1986 ATC200X. I will be using a .040 high compression wiseco piston (12-1), mild cam from "web cam", new DG exhaust system, high flow air filter and ported air box lid. Does anyone have any suggestions on a carburetor/intake combination to take advantage of the mods? Thanks.

Chris

 

I am doing the same mods to an 85 200x, totally different motor then 86. But yeah 40 over 12to1 wiseco piston, web hi rev cam, DG pipe, new valves, heavy duty springs, cam chain, adjustable timing cam gear, and would also like to know of any carb mods that can be done, and also if anyone would know what i can do on intake and exhaust porting.

 

I decided to go with a Mikuni 28mm (TM-28-418) flat slide carb. Main reason? I got one along with a bunch of parts I just bought! It should work pretty well. I going to have to make some adapters for the carb to fit though. It has a spigot type end instead of a flange on the motor side, and the airbox side end is to big to fit in the stock intake boot. I will probably make them out of aluminum and then epoxy or jb weld them to the carb permanently. Not sure on jetting yet, maybe 25 pilot jet and 180-200 main? That may be a little lean, I don't know. I'm leaving the stock 5DP39 needle in with the clip on the 3rd groove. It won't take long to see if the jetting is way off. I wouldn't be surprised if I have to switch to a 300 main or so. I already have drawings for the adapters. If for some reason you use the TM-28-418 carb let me know, and I will get you copies. I also have heard that Mikuni made a smooth bore 29mm carb that was stock on alot of street bikes that used the same size of flange as the 200x carb; bolts right on. Might pay off to call local motorcycle shops.

 

If you go with a 12-1 piston it kinda sucks getting race gas every time you go ride. I put a 12-1 in my 350 and hadnt had problems yet but I have been using 118 octane. What did wiseco recommend you to run in your x with a 12-1. They told me no less than 112. That sucks.There is only one person here that sells race fuel and it is 5 bucks a gallon. I was told not to use octane booster from someone at wiseco.

 

Wiseco recommended 100-102 to me. If I were you I would try the GT100 from Sunoco. It is a race fuel with 100 octane rating. I think its been running a little over 3 bucks a gallon. I would try it, if you get no ill effects, pinging, etc. It should work fine. You may find that the extra octane in the 112 has not been necessary. At worst you may have to use the gt100 with a little octane booster. I am lucky in that I have a sunoco station close by that has a pump for the gt100. Check out sunoco's web site and it will show you the stations in your area that carry it.

 

Hey thanks for the ideas, if I try anything different and it works good i'll let you know. I live in NJ but we do most of our riding in PA, near lake wallenpaupack, there is a Mobil station with cam2 racing fuel (108 octane). Klotz has an octane booster which brings it up ten points. I used in my 250R when it was bored, ported and polished took care of the detonation I was having when it got hot. Still have to get my motor together and in the bike.

 

Hi, wanted to let you know that when I received the wiseco piston kit, it had a note enclosed that stated that no lower than 102 octane was to be used with the 12-1 compression ratio piston. I will probably start out with the GT100 and use enough octane booster to make up the additional 2 octane points. I'm not sure but I would assume that the 350 hi-comp pistons would have the same requirement. I wouldn't think that the larger diameter bore would require more octane to prevent pre-det. I would think that since the comp ratio is the same, the octane requirement would be the same. You might want to check with wiseco to be sure. Better safe than sorry. Pre-det can destore an engine. Happy riding!