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View Full Version : Fitting a 26mm Keihin Carburetor to a 1983 ATC 185s.



Bernard3rd
02-11-2017, 05:43 PM
Hello All,

I have recently purchased a 1983 ATC 185 s which is very clean and in overall really nice shape. I want to do some mild mods, and have found a Vintage Supertrapp exhaust and have a K&N air filter. I have picked up a very nice 1982 XR 200 Carb off of Ebay, and intend to use this on the 185s. As the original 185s carb is a 22mm Keihin, and the XR 200 Carb is a 26mm Keihin, I have a few questions about fitting it up that maybe someone who has done this can help answer:

Is the Carburetor insulator from the XR (Honda part #16210-KA2-000) needed to properly fit the XR carb to the ATC? It seems as though the Carburetor insulator from the 1979-1983 HONDA XL185S is the same part?

How does the thumb throttle of the 185s work with the XR carb? Are the cable pull ratios compatible?

I understand that the rubber boot from the airbox lid is able to be stretched over the larger carb, but is there another way of doing this, or is this the best solution? Have any of you who have done this experienced the boot to eventually tear?

Thanks so much for any and all pertinent comments/information.

Bernard

YTZ drew
02-12-2017, 10:35 AM
I'm not sure if the XR intake has the right angle for a 185s. I know it does for a 200x though. The intakes all have the same bolt pattern, but the XR carb gets choked down on any other intake. As for carbs, the XL carb is slightly smaller, it's the same as an original 200x carb except for jetting, and being setup for a cable choke instead of a lever. That's all the info I have at the moment, but if you have any other questions, I have most of the parts in question packed up in the basement, so I can get measurements, pics, etc if you need.

Bernard3rd
02-13-2017, 12:45 AM
YTZ Drew,

Thanks again for your comment. If you happen to have a carburetor insulator from an ATC 185s/200s and a 82 ish XR (Honda part #16210-446-000), it would be cool to eyeball them to see if the angles are similar... I have this pic of the back of the engine which shows the Carburetor insulator fairly well, but it is difficult to know for sure...239733

Also, Scootertrash has said that he's used an XR "intake manifold", and I have reached out to him, but haven't gotten a reply as of yet. Here is the post:

http://www.3wheelerworld.com/showthread.php/140489-Scootertrash-s-85-200S-build?highlight=200S+build

I have found some XR Carburetor insulators on Ebay, and I suppose that spending 40 dollars to find out whether it would fit would not be a terrible thing, and I have seen NOS ones for about 80 bucks, but I'd want to know that it would work at that price.

The rest of my build is to use an XL cam, a port and polish of the head, and maybe stiffer valve springs in case I'd want to drop in a hotter cam down the road though I'm not sure whether the stiffer valve springs would be contraindicated with the XL cam. Seems logical to me that they would just be able to close the valves faster, so would be good overall. I don't want to really go with the largest bore and hottest cam as I fear that the reliability would be compromised and overheating may become and issue on the little air cooled head, but that's only theory. One of the best things about the 185s we had when I was a teenager was that it was rock solid reliable, and as I am now asking this one to haul around about 50 more LBS, I want to have some discretion. I have heard that the clutch can be overwhelmed fairly easily if the motor is modded a fair bit, so I may need to freshen up that with some carbon impregnated clutch plates...

What has been your experience with reliability and/or overheating? What carb are you running?

Thanks again! Here is a pic of my Dad (RIP) and uncles with our original 1983 ATC 185s from about 1986 or 1987.

239734

Bernard3rd
02-13-2017, 08:10 AM
It looks like the first picture I mentioned above did not attach properly, so I'll try again.

239748

Thanks!

PS, It seems to want to post the pic rotated, but you can still see the Carb insulator.

YTZ drew
02-13-2017, 08:17 AM
The XR intake I have is still attached to my 79 xr185, but I'll pull out the other intakes and try to hold them up and check the angles the best I can. I'm curious myself, as I have a few more engines I want to build, in varying configurations. I'll let you know what I find out!

Bernard3rd
02-13-2017, 09:26 AM
As I understand, the 79 XR185 uses a Keihin 26mm (which is the carb that I have), so if the intake on the 79 XR185 looks similar or close to the ATC 185/200s then it seems plausible that it may work...

I'm sure that you have the specs for your XR185, but if not, here is a cool link:

http://www.motorcyclespecs.co.za/model/Honda/honda_xr185%2079.htm