Bike tries to grenade itself.

[BigGreenMachine]

Find yourself a newer KX500 carb which is a Keihin 39mm PWK. Your 83/84 used a Mikuni VM38 which is a large roundslide carb. A nice 38mm Mikuni TMX would also be a good choice.

[Danger4u2]

When I bought my 2004 k5 I asked about parts availability and was told they have to make parts available for 10 years from date of manufacture.  You should be able to find an 04' carb till 2014.

[hughes]

Tuckerocky carries the vm38 Mikuni carb. Part# 42-6025 retail $144.99.

[BDI]

www.sudco.com

[FactoryPhil]

Sudco...yes. Those guys are very very knowledgeable and friendly.  I spoke to one of the guys there the other day and it was the first time in a long while I was able to make one phone call and hang up with the EXACT information I needed. By the way, one of the questions I asked was regarding carb selection, and they said the PWK all the way. I asked about the TMX and the guy said that they were kind of finicky and difficult to jet as compared to the PWK.

[steve1965]

This is a bit late but another thing that can cause the bike to surge is if the fuel tank screen is clogged up. I found out the hard way while crossing the blacktop mine surged and I went off the back and luckaly did not get hurt and the bike wa not hurt to bad. Found the screen had debrie in it. I dont know if this is what happend to your bike. Also a freind of mine had the same thing happen but it was the main jet having something in it.

[booneylander]

Thanks! That's good to know too, I've cleaned and serviced the stock carb as best I can and am planning to put that back in for now, until I can get a PWK, so now I have another thing to check/clean before I put the bike back together to see if I've solved the problem. Thanks again for the input!

On another note, in a very random fashion "one of" the previous owners of the bike got in touch with me recently (he saw a picture of it on facebook oddly enough and said "hey that's my old bike!"). He's an engine builder for one of the factory road-race teams up here in Canada, and has his own dyno/shop here in Ottawa during the winter months.

Well, ANYWAYS, he bought the bike in California and brought it back to Canada and apparently it had "hurt a lot of people" before he got his hands on it, and when he massaged it for himself and tuned it on his dyno, it was at one point putting out 75hp !!!

It's definetely not making that now, but I think he's willing to "massage" it again for me over the course of this winter!

[booneylander]

Just a note to close out the thread.

I took the bike for a spin today and the motor was awesome, I solved the revving issue, and as a bonus unlocked quite a bit more power.

Here's what I did:

-replaced the gaskets on either side of the reeds (one side was just "form-a-gasket" junk - possibly a source of air leaks).
-disassembled the carb and cleaned it.
-smoothed out the slide (had some ridges worn into it).
-set the idle air screw back to about 1.25 turns out (was at ~2.5 for some reason).
-moved the clip on the needle down to the 2nd slot from the bottom.
-smoothed the needle (had some nicks).
-cleaned the reeds, which had some goo on them possibly sticking them shut some times.
-new spark plug.
-cleaned the air filter.
-removed and cleaned the fuel filter on the petcock (has some junk but not too bad).

So now the engine seems to run amazingly well, but about 30 minutes into my ride, a bolt in the rear suspension let go, leaving the top of my shock to just wobble around down there, ending my ride.

Upon closer inspection someone has made some weird suspension setup to use a shock out of something else, and they have a really bad setup that puts way too much strain on a single crappy bolt. So now I've got to re-engineer that setup, but at least the engine is good now