A little concerned

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Jul 30, 2003
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#1
Hey. I am buying a KX 100 in about two months here for a slightly early christmas gift.

Thats the good part.

I am now having many concerns with the maintinance of these 2-stroke dirtbikes. I am coming off a Honda XR, where all I really had to do is fill it up with gasoline and change the oil. Now with these 2-strokes, I am a bit concerned with all of these confusing maintinance issues.

I am not very knowledgeble when it comes to these mechanic type deals. Jetting, Rebuilding top end, etc..I see all of these issues here on these boards and elsewhere about things like jetting, rebuilding, flood levels, fouling plugs, pilots, mixture ratios etc.. I know nothing about any of these things..

Will a 2-stroke motocross bike still be good for me if I am not completely knowledgable about them? None of my friends who have 2-strokes really know much about them, and they seem to have all sorts of problems fouling plugs and breaking things. Then again, my friend only cleans his air filter once a month ;)

I am completely willing to learn and to really maintain this bike as best as I can. I will be getting this thing and riding in the winter, so I am concerned that I might have to jet the bike for colder weather, right? Is this something hard to do for someone who really doesent know all that much about these things? And again, I am completely willing to learn and everything but what I am asking is if these 2-stroke maintinace issues are going to have me in too deep.

Thanks in advance!

-Tiylu
 

CJG

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#2
Tiylu,
Don't let the maintenance concern you too much, most of it is really easy. Basically the only difference maintenance-wise between a two-stroke and your XR is that you have to mix your gas and oil and you will need to replace the top-end more frequently(about once per year depending on how much you ride). Jetting is an issue with both two and four strokes, so that shouldn't concern you too much. You might need to rejet for winter riding(It's really easy, you would probably just need to go with a slightly richer main and pilot), but it may not be absolutely necessary depending on your conditions.
You will probably never find a bike more bulletproof than an XR, but two-strokes are not as high-maintenance as you might think(I personally think they're easier to maintain than modern high-performance four-strokes). Plus, if you need help with something you can always just come here and ask.
Good Luck.
P.S.- If your friends are fouling plugs then they probably just need to rejet(if the plug is wet and black, they're running too rich and need to lean out the jetting a bit). If they're breaking things then they either need to quit wrecking so much or take care of their bikes better. ;)
 
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#3
Yeah, thanks alot for the advice. I am fully willing to take great care of this bike, its just that I really don't know how to. Should I pick up a Service Manual as well with the bike?

Thanks, any other input is greatly, greatly appriciated.
 

Chili

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#4
If your buying new the bike will come with a service manual. I would also suggest Eric Gorr's book as required reading.
 

gwcrim

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#5
You didn't mention how old you are but at the ripe old age of 15 I was rebuilding the top end on my old CR125. Of course that was before watercooling but still sometime after the invention of the wheel.

Get a good set of tools and a repair manual and spend this winter studying. You'll develop skills that will last you a lifetime and save you countless dollars. For me, spinning wrenches is a great way to relax.

I doubt that you'll find a 4 stroke in the size of a KX100 that will provide quite the same adrenalin rush. :thumb:
 

Y2Z

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#6
You will be suprised once you get it how little maint. there really is. I have never owned a 4 stroke in my life and every 2 stroke i have had at most i have needed to do 1 top end, and they were all used and old. Keep that air filter clean, grease bearings, tighten your chain, change your oil, and a few other things im missing are the main things, these things are all found in the manual and are very easy to do. Depending on how hard you ride you will probably need a new top end in about 100 hours or so, but when it comes time its cheap and eric gorr has a tape that you can buy to help you along the way. Keep that bike running strong and you will LOVE it!
 
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#7
Wow, thanks alot for the enlightment guys! I deffinetly feel a bit better about the purchase!

Im just a little concerned when sitting on my friends RM and looking around at all these different things with different liquids and all these parts I don't understand. But I guess I will figure it out.

And also, you can really feel when a top end and a low end needs to be redone, correct? I was riding my friends CR80 which is about 3 years old without a rebuild ever, and when starting it up, you can feel it really bogging out really down low when trying to accelerate at times, and when topping it out, the top end just seems to die. Should I try to persuade him to rebuild? And is this is what rebulding is referring to?

Thanks for the enlightment guys!
 
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#8
Top end usually refers to changing te piston, rings, the wrist pin and the bearing that rides between the wrist pin and connecting rod.

lower end usually refers to the crank shaft and main bearings and seals.

when you do a top end job, don't forget to get new gaskets for the cylinder and head. Also, clean out the power valves. All this sounds complicated, but you really can't get much simpler than a 2 stroke. Plus, the owners mannual, shop mannual, clymer repair mannual and Eric Gorr's book all do a great job of explaining things. I recommend getting all of these books(of course the owners mannual comes with the bike when new.)

The symptoms that you described(on your freinds bike) could be due to improper jetting. But after 3 years, he's definitly due for a new top end.