Should I change my top end before the summer(photos)

[Freedom45]

Hello everyone, I hope you are having a good day!

I bought a kx 100 2007 couples of weeks ago and its running very good. 
The seller told me it was rebuilt from September and it haven't run much since. The bike start on the first kick and is running very smooth. It looks like it has all it's power. Its my first bike so I cant compare. The only down thing is that the compression is fairly low imo. (130 ish) This is why I decided to open up the cylinder head and take a look. I would like your opinion because I know absolutely nothing about  mechanic. I bought this bike so it would force me to try. Can you guys tell me if it looks go or na?

If I need to completely pull off the piston to be 100% sure, ill do it ?

 

Thanks

Here is a video to help you:

https://vimeo.com/user97511199/review/331124432/66ae4d4d07

Edited April 18, 2019 by Freedom45

[KDXGarage]

Sorry, we couldn’t find that page

Make sure you’ve typed the URL correctly, or try searching Vimeo. You could also watch one of the videos below instead.

 

The cylinder head looks very good to me. Most people on here show one that looks like a grenade went off inside the cylinder.

[Freedom45]

Thank you for the quick answer :)! Here is two videos that should work and help you give an opinion !! 
we see some scratch on the piston but I am not sure if it is normal. The two rings looks intact from the pipe view

Thanks again

 

Edited April 18, 2019 by Freedom45

[mlatour]

A wobbly video of the engine spinning doesn't show much at all,

post some clear/in focus still pics of any scratches on the piston and cylinder.

 

If you can feel the scratches in the cylinder with a fingernail, the plating must be addressed.

[Freedom45]

Hello, thank you for the answer. Here is more images!

if I can do anything to make it easier, dont hesitate

have a good day

[mlatour]

The 2 scratches seen on the piston (far right) in the 1st pic look pretty deep,

if it indeed it was somewhat recently replaced / has low hours since, I'd guess :

 

-the air filter isn't sealing properly, letting debris by

-proper care wasn't taken on overall cleanliness during engine work

-engine wasn't warmed up thoroughly before being ridden hard (very mild cold seizure)

 

Your cylinder also shows signs of 'pitting' (3rd pic, left side)

by the time you replace the piston (end of season) the cylinder should also be replated.

 

If you plan on trail/off-roading and not sustained high rpm motocross racing, just replace the head gasket

and run the engine as-is for now, this wear / damage isn't ideal but it's not going the cause of a failure either.

130psi of compression is likely within specs.

Edited April 18, 2019 by mlatour

[Freedom45]

19 hours ago, mlatour said:

The 2 scratches seen on the piston (far right) in the 1st pic look pretty deep,

if it indeed it was somewhat recently replaced / has low hours since, I'd guess :

 

-the air filter isn't sealing properly, letting debris by

-proper care wasn't taken on overall cleanliness during engine work

-engine wasn't warmed up thoroughly before being ridden hard (very mild cold seizure)

 

Your cylinder also shows signs of 'pitting' (3rd pic, left side)

by the time you replace the piston (end of season) the cylinder should also be replated.

 

If you plan on trail/off-roading and not sustained high rpm motocross racing, just replace the head gasket

and run the engine as-is for now, this wear / damage isn't ideal but it's not going the cause of a failure either.

130psi of compression is likely within specs.

Thanks for the answer! Honestly I'm always amazed by you guys who spend so much time giving free advice online. You guys deserve a thumbs up. 
I'm wondering why you say to replace the head gasket. Is it because it looks bad quality ? Do you need to change it each time you open the cylinder head?  

 

Thanks. Also, I just saw a wire that I have no idea where it should go LOL. Can you help me?  Here: 

I also notice that there is a weirdly positioned gasket. I don't know what is the name of this part. Can you help me? Should I change it absolutely? Could it damage something if it isn't well positioned? 

 

Thank you 

 

[zotis777]

 

 

Thanks for the answer! Honestly I'm always amazed by you guys who spend so much time giving free advice online. You guys deserve a thumbs up. 

 

I'm wondering why you say to replace the head gasket. Is it because it looks bad quality ? Do you need to change it each time you open the cylinder head?  

 

 

 

 

 

 

 

Thanks. Also, I just saw a wire that I have no idea where it should go LOL. Can you help me?  Here: 

 

 

 

I also notice that there is a weirdly positioned gasket. I don't know what is the name of this part. Can you help me? Should I change it absolutely? Could it damage something if it isn't well positioned? 

 

 

 

 

 

 

 

Thank you 

 

 

 

 

 

 

 

 

The wire you’re holding in the first pic is not a “wire”, it looks to be a rubber breather hose for the “exhaust valve” or “powervalve” assembly. It has nowhere to be, I imagine it’s normally zip tied or bracketed to the frame

 

 

The gasket for that side of the powervalve is likely fine. Sometimes they don’t fit exactly flush but that shouldn’t cause any harm

[Freedom45]

20 minutes ago, zotis777 said:

 

 

 

 

The wire you’re holding in the first pic is not a “wire”, it looks to be a rubber breather hose for the “exhaust valve” or “powervalve” assembly. It has nowhere to be, I imagine it’s normally zip tied or bracketed to the frame

 

 

The gasket for that side of the powervalve is likely fine. Sometimes they don’t fit exactly flush but that shouldn’t cause any harm

Oh thanks for the info!! I would have search a long time for where to plug the hose lmao!

Anyway idea why mlatour would recommend changing the head gasket? Is it because of the pitting that he was talking about?

[zotis777]

Oh thanks for the info!! I would have search a long time for where to plug the hose lmao!
Anyway idea why mlatour would recommend changing the head gasket? Is it because of the pitting that he was talking about?

The head gasket is made out of metal

Metal head gaskets (many cars and trucks use that style of head gasket as well) are a one time use item. When you initially tighten the head down on a new metal head gasket you “crush” it and that seals everything. Once you disassemble the head gasket may “look” fine but it’s already been flattened and it’s very likely it won’t seal again

[Freedom45]

1 hour ago, zotis777 said:

 

 

 

The head gasket is made out of metal

Metal head gaskets (many cars and trucks use that style of head gasket as well) are a one time use item. When you initially tighten the head down on a new metal head gasket you “crush” it and that seals everything. Once you disassemble the head gasket may “look” fine but it’s already been flattened and it’s very likely it won’t seal again

 

 

 

Makes sense! Thank you. So before I reassemble everything, I should buy this : https://www.ebay.ca/itm/NOS-KAWASAKI-1998-2018-KX100-KX80-KX85-GASKET-SEAL-CYLINDER-BASE-11060-1779/352191219031?hash=item52003b8557:g:3YUAAOSwm3pZ7J0r&vxp=mtr

 

Then after the summer, I can buy a top end kit from ebay. Is it the good gasket ? it seems like it is and it fits my model,year etc.

[zotis777]

Makes sense! Thank you. So before I reassemble everything, I should buy this : https://www.ebay.ca/itm/NOS-KAWASAKI-1998-2018-KX100-KX80-KX85-GASKET-SEAL-CYLINDER-BASE-11060-1779/352191219031?hash=item52003b8557:g:3YUAAOSwm3pZ7J0r&vxp=mtr
 
Then after the summer, I can buy a top end kit from ebay. Is it the good gasket ? it seems like it is and it fits my model,year etc.

No actually that’s a base gasket, that one goes between the bottom of the cylinder and the cases




This is the gasket you want, Kawasaki part number 11004-1214

If you search specifically for the part number you can likely find the part supplied by a number of retailers and order whichever is priced the best


Motosport, RMATVMC, bike bandit, all reputable online stores to order the gasket from



Top end rebuilds are not especially difficult or expensive, it is an excellent idea to do one either at the end of the summer or when your current top end provides any symptoms of significant wear or immanent failure

[Freedom45]

33 minutes ago, zotis777 said:

 

 

 

No actually that’s a base gasket, that one goes between the bottom of the cylinder and the cases




This is the gasket you want, Kawasaki part number 11004-1214

If you search specifically for the part number you can likely find the part supplied by a number of retailers and order whichever is priced the best


Motosport, RMATVMC, bike bandit, all reputable online stores to order the gasket from



Top end rebuilds are not especially difficult or expensive, it is an excellent idea to do one either at the end of the summer or when your current top end provides any symptoms of significant wear or immanent failure

 

 

 

Thank you very much for your help! It is very appreciated. 

[zotis777]

Thank you very much for your help! It is very appreciated. 

Not a problem, best of luck!

[KDXGarage]

Can you catch a fingernail on the lines (scratches?) in the cylinder wall?

 

If you can't catch a fingernail, I would put new rings and head gasket and ride it.

 

Even with video and pictures, it is hard to diagnose without touching the actual parts.

[Freedom45]

18 minutes ago, KDXGarage said:

Can you catch a fingernail on the lines (scratches?) in the cylinder wall?

 

If you can't catch a fingernail, I would put new rings and head gasket and ride it.

 

Even with video and pictures, it is hard to diagnose without touching the actual parts.

You mean directly on the cylinder wall not piston? 

like in this image :

[KDXGarage]

yes, that pic

[Freedom45]

50 minutes ago, KDXGarage said:

yes, that pic

I can't catch a nail at all. It is mostly esthetic. 

When you say: new rings and head gasket. Which rings are you referring to? Can I just put a new head gasket and leave it like that? 

 

Thanks

[KDXGarage]

You could. Would it be as good as replacing the ring or rings on the piston? Not really.

 

Good that the line does not catch a nail.