I agree with you Mark T. I just cross referenced the 71 RT1MX with the GYT kit exhaust part number in the back of the manual and it looks like they are both the same pipe just one has a different finish assuming im decoding the number correctly. 285-14610-10-00 for the 71 RT1MX and 285-14610-10-10 for the GYT pipe. Its going to be hard finding that original pipe. I saw one at mid Ohio but the guy had already sold it for $150.

On a side note i have both LT MX models. The 73 with the GYT pipe and the 72 with the factory down pipe. i have the down pipe for the 73. My 72 needs to be gone through because it doesnt have hardly the guts it should and i know its because the top end isnt MX for starters. Kind of sucks because id like to compare the power difference between the MX and GYT but i have some pretty big fish on my plate right now to fry first.

Still kicking myself for stuffing a very worn chrome bore from a "68 GYT kit cylinder. Dumb B,stard Me, it was worn through the chrome around the ports but still ran as it should albeit rattly. But it sat for years & oneday i thought give it one more go. Not sure what piston i used but think it was the GYT one which had a parralel narrow ring not keystone & was made of something special??. Shuffled all my old rings around & selected something "wrong" that fitted the groove. Stuffed it in 100 yards down the road as wrong ring type ripped the chrome off in strips. Not a happy camper that day. Somebody bought it in Australia to rechrome or maybe they can Nikasil nowdays. That cylinder was Fast & kept its power strong untill the end of the race where the iron cylinder "i have" from the "70-"71 DT1MX fades of a little when hot in comparison. Anyway--i've told that sad story before, so, back in the bad boy corner for me.

Well as sucky as that is at least you didnt throw it in the scrap yard like a lot of people probably would have done. My 68 is probably going to need to be chromed which is ok. I intend to go full out on that one when the time comes.

Im yet to look this up but id be interested in seeing what all came in a GYT kit. I know the pipe, head, cylinder, piston and i believe the carb, reeds and air box all came with it i think. If the bike was reed type that is.

I've only seen the parts sold individually?  I'm no expert by any means but I vaguely remember magazines modifying bikes and having a parts list in the article rather than a "kit" part number?  Yamaha docs I've seen also seem to provide a list of parts rather than a "kit".

If you find something about a "kit", please share!  It's certainly possible they had them!

I seem to recall seeing someone posting a picture of a NOS kit. I think it was in one of the facebook groups and that was around a year ago. I think that one might have been that other kit. Naguchi? does that sound right? i cant remember and me being almost 32 years old means i missed out on the golden era so i have no memory of this stuff. If i find anything ill definitely share it.

I have some service manuals i recently picked up that im going to be uploading on here. HT 90 models both years including the MX, an HT90MX manual, an assembly manual for the 74 DT250&360 and the 72 LT2 service manual. I need to make sure none of these are already uploaded and then get someone over here with a much better camera than mine! This community has always helped me and i try to help when i can but im always so busy. For once it would be nice for me to give something back you know?

Talking DT1 not 360 but when i fitted the GYT kit to the bosses "68 gold tank model it all came all together but i guess my boss could've order the parts separately from the importer.
Was a Chrome bore Cylinder. Piston Kit [with special material ring]. Cylinder Head with center plug. Carburettor & probably the Insulating Block which i think was a gold-ish color.
Chamber Exhaust.
21" front was optional & we just stayed with 19" which might've been a mistake but it worked for us.
Also used a Filtron green element with cage & damn good they were too.

Noguchi did make kits.  That was an aftermarket company.

Yamaha may have listed "kits" too...  I've just only seen the references in manuals and service bulletins that list the individual parts.  That doesn't mean there was never a single kit part number... 

In general, documentation on Yamaha accessory part numbers are sparse... for example part number listings for luggage racks for bikes that didn't come with a factory rack are not always easy to find.  Maybe there's a "GYT kit" catalog out there someplace?

Will just have to keep our eyes and ears open. I usually hear about the GYT stuff from people at the swap meets and once in a while in these groups. Finding the old racers and guys who worked in the dealers is key but theres getting to be less and less of those people sadly. Trying to soak up and collect as much info on this stuff as i can.

They were incredibly fun times. The performance increase was damn scary haha & just wanted to climb to the sky. Hard to keep the front down.

Im glad to see so much is still left. I love my 73 LT MX 100 with the GYT pipe its such a screamer its unreal. I built a rat MX bike using a  74 DT250 motor and frame with a 73 MX carb and gas tank and a 75 MX pipe, that thing rips! so much fun to climb hills with it which im long overdue to do so again.