Need a new piston, I'm at a loss?

[SouthRider]

"If I wasn't in the middle of "The American Retro-Cross Over 50 Novice, Air Cool, Non-Linkage WORLD CHAMPIONSHIP" I'd tear the bike apart today."

Garrett - if you don't check out the carb on this bike ASAP you just may DNF soon and kill your points standing completely.

Never EVER EVER sand or polish on internal carburetor parts. you may have caused your own problem here. Adding a little oil to the fuel will not change a thing about the problem that you are having, but it may cause more problems.

A quick look through the carb is not major surgery. Get someone to help you. Go through it carefully & inspect what you have - don't force anything apart or together. Set the float height so that the floats are square to the base of the carb just as the float needle begins to seat. Put it back together slowly & carefully EXACTLY as it was before except the float height. Again, don't force anything.

Now - make a list of the parts that appear to be worn and order them.  Sounds like you will at least need a new needle if you cleaned it with emery cloth.

Go race and have fun. Make new notes of how the bike performs with the float level set correctly.

When the parts come in pull the carb again & replace them. It gets easier every time you do it.

Go ride the bike, make notes, and begin the process again.

Let us know if you need more help.

Good Luck!!


Clark

[garrettccovington]

Right on clark
Somebody earlier mentioned about the float level  I bent the one of the floats when I pulled the carb apart to "clean" it.  I just bent it back, but didn't really check it.  It was "that looks good" ( I know I gonna get it on this one)

After this race, I'm gonna print out these notes and go thru the bike and check everyhting out.

G

72 six-day
79 KTM MC80 250

[tomale]

Good luck Garrett on your race, Several years ago I was having trouble with my bike loading up, it started great and ran fine but if I lugged the bike it would load up.. I rebuilt the Bing carb, which included a new slide, new jet needle and needle jet, all new rubber pieces, and gaskets, wow what a difference!  In my conversation with Bing agency, they suggested that I replace the needle jet and jet needle every year. The reality is that you may not be able to see any wear, but that does not mean it is not there..
As for the pistion, The stock piston will wear like iron.. I still have the stock piston in my 76 mc5  I did replace the rings, If the bike is making alot of noise Ie. piston slap then yea it might take further look, the easy way to do this is to take the piston off carefully remove the rings and slide the piston back in the cylinder. slide a feeler guage between the skirt of the piston and the cylinder wall, check your manual for theses spec.  now the rings are a different matter, first slide the ring back in the cylinder making sure that it is square to cylinder, and check for end gap. again check your manual..  and the last and most important, with the ring still in the cylinder, lift the cylinder up into the light so that you can see through it, what you are looking for is any light that shines between the ring and the cylinder if there is, it is time for a new ring... My Mechanic tells me that it is best that once a year, I pull the top end off, give the cylinder a quick hone and then if everything is fine, replace the rings...  never put new rings into a cylinder that has not been honed, No do not use emery cloth this can cause illregularities in the cylinder wall, a quick cross hatching of the bore is all that is needed, this will keep the barrel fresh and actually prolong the life, because all of the cross hatching will catch oil keeping things moving nicely.
Be thankful you don't have a four stroke, By the way I went nearly a hundred moto's with out a DNF and it still runs great,, These KTM's you can't hardly break them with a sledge hammer...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[garrettccovington]

Race Update.  My main competitor Tom Chavez (AMMEX)was back in action today.  We both have missed the same # of races and I think he has 1 more DNF than me. 2 moto's to my 1.  Anyways, I was thinking about just cruzeing around to get points, but that didn't set well with me.  I psych myself up to run it like I stole it. Go For IT!

1st Moto,  No mamby pamby on the starting line and got the holeshot of all classes, a yz400 ducked underneath me and a Modern open bike went around on the outside after the 1st turn.  I said screw it,  Hold that throttle wide open and took the moto win.  Me and Tom were neck and neck the whole way,  He mis-counted the laps and pulled off and ended up getting 3rd

2nd moto.  I nailed the holeshot again and held onto the lead of all classes until the Yz400 and Modern open bike went past me on the back straight.  Once again me and Tom were racing neck and neck.  I passed the yz400 on the 2nd lap and then the bike started acting like it was running out of gas.  Zoom Tom and the 400 flew by me.  I put it on reserve and just cruized for the overall.

The bottom line I have a month until the next race and am going to tear down the carb and pop off the head.

I pulled the pug after the race and it was 3/4 black 1/4 tan.  Track elevation was 4000 ft.  Fuel mix, still 40 to 1.  I left my oil at the house.

After the Race, Tom stated your bike looks and sounds like its running pretty good me.  I know there is something wrong here.

Again thanks to everybody for pointing me in a direction.

G



72 six-day
79 KTM MC80 250

[dirtbike]

Saw the pictures on facebook Garrett. Tom is #54 I guess? What is he riding? Looks like a CZ. At least the engine.

[garrettccovington]

Tom Chavez is # 54 and is Running a bike he bought as a kid. It is a AMMEX.  It was a bike Designed by Don and Gary Jones, built and assembled in Mexico.  It really is a neat Motorcycle.  Apparently it has Yamaha Components in the Motor and Maico parts in the transmission.  Cylinder castings look kinda like a cross between a CZ and Maico.  I can't believe the story behind that bike and the whole AMMEX story.  Also Tom is friends with the Jones Family and gary helps him keep it running.  Its got a Kawi pipe that Gary told him how to make it work.

Apparently there is only 3 complete bikes known to exist.  2 of them are in collections that very rarely get ridden.

There is a Desert myth out here, that there is a house/garage/warehouse that has 10 of them in crates.  The guys from Texas that "pick" vintage bikes say they know where they are, but won't let on.

I got to admit the guys from Texas do a good job of finding bikes out here.

g  



72 six-day
79 KTM MC80 250

[dirtbike]

Amazing story. I have never heard of that brand. But it isn't so unlikely actually. In Italy there are numerous small brands that are almost unknown to the outside world.

I hope you get your carb right and keep racing your bike.