KX Top-end Q's

[mischi_punk]

Okay, so I just got home from riding at my buddies track. Well, short story- My bike won't start anymore. First I'll give a little backround for those who don't know my "current situation."

I got my bike this summer. It had its piston replaced right when I bought it. I rode it all summer, no problems... Until about Jan-ish. It was making a funny sound when I rode. I still haven't figured out the problem. It sounds like a whirring type of noise, I think it is in the exhaust. Last week when I rode my friend said that he could see smoke coming out of the pipe, around where there is a re-weld. Mid-way through our 'riding session' my bike began to pop a little more than usual, it seemed like I was running reg. gas, not premium.

So today I went riding and at first there wasn't anything too unusual, the popping that started last week, and the 'whirring sound,' which I had assumed to be a hole in the exhaust. Again, mid-way through our 'ridding session' it started acting up. It started loosing power and sorta bogging. Then it died! So, I tried starting it about an f-ing million times, no luck. So I took the spark plug out to see if it was black. It was, and I tried to sand it. It didn't work.... STILL!! But when I put the plug back in and tried to start the dang bike it felt like there was NO compression AT ALL. (could that be the spark plug not in all the way? or not seated right?)

My friends dad (who has raced 2t 4wheelers and mini-sprints; co-owns truckrepair shop) said he thinks that I blew the top-end. I really want to know what I need to get if this is the case. So if someone posts the rebiuld kit that would be great. Also, please say what spark plug to get.

So I am REALLY wondering WHAT is going on!!!! AHH. Someone please help me! Is it just the plug and the exhaust? Do I need to re-jet it? New Gaskets? New piston seals? Any ideas?? Please help! And when you answer the more detail you give the better! I'd rather you treat me like an idot (which I sorta am. lol) than a genius.

Oh yeah, I forgot to mention this, but After I changed the plug it made a loud *POP* and right about then was when I began to notice the lack of compression. Also, the plug was an NGK R and the name/code thing started with a b and ended with a g, so not to sure about that. I have 2 topend rebiuld and 1 bottom end rebuild kit. Is that what I need?

Thanks for any replies!
~Mike

 

[SirHilton17]

well... if yur bike is makeing some weird noise... dont keep riding it...

pull apart the engine... just the cyl, and head for now...
and if it is messed replace it...

its a simple matter..

these bikes dont last forever

 

[njrealtor55]

take the spark plug out. put your finger over the hole, and kick the bike... you will feel compression if there is any.

sounds like the top end went. I would personally use this as a good time to rebuild the entire engine. But in reality, you may just need a top end rebuild.

I have a great MX race shop by me that only charges $300 + parts for an entire engine rebuild. For that price, you can bet my engine will be there next winter for a complete rebuild.

Since you need instruction, I'd take the bike to a reputable shop and have them rebuild the engine.

No matter what anyone says on these forums, you need to have a good knowledge of what clearances need to be checked (ring end gap, piston clearance etc..) and also a general knowledge of how to dis-assemble and re-assemble the engine. If you have all this knowledge, then go for it.. if not, then let a shop do it because if you mess up it will cost 2x's as much as getting it done right the 1st time.

 

[mischi_punk]

Well, my friends dad said he would help me rebuild the top-end(as I said before, he has lots of expierience in this area) since I'm assuming that is the problem. What all am I going to need to rebuild the engine? I already have 2 sets of gaskets. I will need a new piston and rings right? Would it be easiest to order thes off the internet, I don't think that the 2 dirtbike shops here would carry pistons, but I could check. Anyways, if anyone know what piston or has a link that would be great.
Thanks
Mike

 

[SirHilton17]

Well, to do a top end your gonna need at least gaskets, and piston kit(piston, rings,and pin, sometime sm. end needle bearing) if your piston does not come with the needle bearing, pick one up... they are around 12 bucks.
Here is a piston for your bike
click
you have to figure out if your bike has a A, or a B cylinder... a A or a B will be stamped on the cyl somewhere.
and here is your needle bearing... click

The dirtbike shops around ur place should have pistons... maybe not in stock, but they can alwasy order them...

Be sure to break it in nice when you get it running