TOPIC:

loudhvx wrote:

Sorry to hear about the seizure. Do you think it was a lemon someone was ditching, or just plain bad luck?<br><br>Post edited by: loudhvx, at: 2007/06/27 11:44

WELL?...that's a tough call,Bud.We've talked to the Seller and His Son,who both have dirtbikes,and who knows...We'll never know.I suppose the possibility is there.My Stepsons's Dad sure seams to think They knew it was a lemon when They sold it to Him.I think it could have been that,plus the Boy was on a paved section of road when it happened,and I also know that MY Son was there too,on His KX250...so maybe the KX100 was trying too hard to keep up to the 250...not letting off the throttle enough.There's a term for that...what is it now?...oh YA...RACING!
Those bikes aren't meant for straight-out racing like that.
I'm not 100% sure that's what went on,BUT...15 years old(young)...first bike...out with Big Brother,and trying to show Him that He can do it too...who knows though,eh?

Yeah I hear ya. Two strokes are hard to call. My friends regularly go through pistons and cranks on those things. Even when everything checks out good, one long WOT on a hot day can melt something.


Anyway, next I want to see an animation of a piston-ported 2-stroke... ie no reed valves.

steell wrote:

The two stroke bike engines that I have worked on had a roller bearing on the con rod. It is possible that the bearing seized and spun on the crank though.

On two stroke bike motors, the oil/fuel mix is drawn through the intake, travels into the crankcase, lubricates the crank and rod bearing(s), then up and through a port in the cylinder wall into the cylinder. The sole reason for mixing oil with the gas is to lubricate the crank and rod bearings.

If the crankcase contains oil, then there would be no reason to mix oil with the gas, ie, two stroke diesels (Detroit and Cummins are two that used to make two stroke truck diesel motors).

Two stroke bike motors are super easy to rebuild

science.howstuffworks.com/two-stroke1.htm

A animated pic of a two stroke.

www.keveney.com/twostroke.html

Do I win? <br><br>Post edited by: steell, at: 2007/06/27 09:33

its been 25 yrs since ive had a 2 stroke,i was thinking it was for keeping rings and cylinder oiled since they forgot to install valves and an oil pump! bottle of doctor tganeks miracle elixer sitting here with your name on it!

Sandy wrote:

Those bikes aren't meant for straight-out racing like that.

small bore 2-stroke

another looker

Pills??? Somebody has pills??? I want some:lol:

While the KX100 is no KX85, it still shouldn't have had the bottom end go like that, and should have been able to see if there was play in the rod last time they did a top end job on it (if ever).

KaZooCruiser wrote:

Sandy wrote:

Those bikes aren't meant for straight-out racing like that.

small bore 2-stroke

another looker

I KNEW Someone would snag Me on that comment,lol.
What I meant was,a "Motocross" bike was not meant(designed) to be raced at WOT on pavement and held there for a long period of time.
Ask Any 2-stroke racer how many pistons and cranks they go through...buy bulk and save,in some cases,I suppose.
The Boy has some lessons to learn,and this will be the hardest one,because now He's going to have to wait til I can reel in all the parts(and Bible) needed for this rebuild.
I remember the days...waiting mostly for snowmobile parts to come in,or waiting for the ol man to get back from working out of town,so He could spend His days off repairing sleds...I frikken HATED it!
Just imagine...12(and 13) years old,living year-round at a lake and NO running toys to play with til the ol man showed up with parts and brains...ya...I sure learned about patience...I learned that I HAD none!
And now I have to pass this all on to MY Kids,and teach THEM...all about having patience...heh heh heh heh heh heh heh:evil:

If the cylinder is ok, you should figure about 300 bucksish for parts (crank,piston,gaskets,bearing,seals)

They're really not too bad and it'll be a good learning tool on 2 strokes (so he knows how to do his future top ends)

KawasakiBob wrote:

While the KX100 is no KX85, it still shouldn't have had the bottom end go like that, and should have been able to see if there was play in the rod last time they did a top end job on it (if ever).

I hear Ya Bob,BUT...had absolutely NO chance to even look the bike over when it was purchased.I was out that day,riding with My Brother(awesome ride,btw),and it was the next day that the Boy took it out.He took it from His Dads place without His Dad knowing(He was napping)so neither one of Us really spent any "Serious" time with it.
As far as any prior work done to it,the Sellers said that They never touched to engine.But They weren't the original owners either,so who knows.
I explained to the Boy how to mix the gas and how important it WAS,to have the mixture done properly...I made sure that He knew HOW to figure out how to mix the ratios in different sized jerry-cans also,and not just one particular size...I showed Him the formula and how to get there,using a calculator if need be,to be 100% exact.
Of course,I give it a quick going-over...checked the chain,cables,throttle for stiffness,clutch-lever,suspension...a quick one in the back alley,knowing that His Dad had already gone over it,but His Dad's not much into the mechanical stuff.
Basically...it was good to go,with nothing jumping out saying,"FIX ME!"

But ya...how do You know if something internal(on a 2-stroke) is about to go?...You don't,unless it's REALLY bad and noisy.

KawasakiBob wrote:

If the cylinder is ok, you should figure about 300 bucksish for parts (crank,piston,gaskets,bearing,seals)

They're really not too bad and it'll be a good learning tool on 2 strokes (so he knows how to do his future top ends)

That's the whole plan,Bob...exactly!

I'm thinking We'll probably end up touching the $400 mark(Canadian),by the time it's all said and done and running again...maybe even more,as I go through it,I may find other..."Things"

Hi Sandy . . . I doubt anyone planted the lemon tree someone picked a lemon off of.

I think you might find that the crankcase seals on the lower end have gone bad.

From the picture of the running two-stroke engine, you can see that the incoming charge is drawn in as the piston moves up in the bore.

A bad seal will allow air to get sucked in, leaning out the mixture, not only diluting the charge, and making the engine run lean, (read HOT) but displacing much needed oil vapor as well.

What was the premix ratio y'all were running?

Did the bike have an oil injection pump?

I think that if it has one, now might be the time to get it operational.

Running full throttle with proper premix shouldn't hurt anything.

A premix only engine loses oil when you chop the throttle. HOT HOT WOT, then no oil when you close the throttle to slow down.

It's a recipe for seized bearings.

An injection pump continues to deliver oil as long as the engine is operational. And usually it is pointed delivery to the bearings.

I don't think you are going to need much more to fix it than an impact driver and the other usual assembly of lawnmower tools.

That and patience.

Sandy when ya figure things out, lemme know.

I may be able to cut ya a good deal on the parts, even shipping to Canada.