top end rebuild "in progess" questions

[kdxepp]

My first time refurbing a top end on an untouched 8 year old KDX 200 engine and had a couple questions for the learned. I am not replacing the piston so I was lightly scraping the carbon out of it's ring grooves and found the top groove to be much tighter than the bottom. To the point where the ring will not fit in the top groove the whole way like it does the bottom. I have scraped out some carbon from both grooves, but the top is still very tight. I am concerned that the new ring won't fit in correctly. Is the top groove purposely meant to be tighter for some reason. Any thoughts?

Second question:
The bore has some scratches that you can feel with your finger. I used a fine scotch bright pad on the entire bore. You can still feel the scratches. This may be hard to answer, but, how do you know when to stop using the sbright pad? How far can you go? I can see the lines from the pad in the bore, but they are not as deep as the original factory hone marks that are still left at the bottom of the cyl bore. It almost seems like I could use a more coarse pad.

Also, FYI, I got the top end gasket kit from Fredette and found that the KIPS rack rod seal isn't included, There goes another week in waiting.

I also found that Permatex gasket remover works even better than oven cleaner at removing carbon build up, and it doesn't corrode the aluminum, fyi.

 

[andrew]

I have also noticed the top ring groove is tighter than the bottom. I always thought the two rings were the same, but I couldn't get one to fit in the top groove. swapped them over and...voila! The manual doesn't mention anything about this, but that has been my experience. There was a forum topic about this some time ago.

As for your bore, like you said, it's hard to say without looking at it but I can tell you they will take a fair bit of wear without adverse effects. If it's not deep enough to catch a fingernail in, I would be inclined to forget about it.

Cheers,

 

[kdxepp]

Thanks for the reply Andrew. I thought the ring question would have many quick replies, not so. After going through dozens of threads on a "piston rings" search I found that post by canyoncarver. I went to the garage and double checked and found that neither ring will fit in the top groove. I am sticking the ring in backwards and many rings are tapered to the inside, not sure about cycle rings, though, I'm a tractor engineer/mechanic. They both have an R on the one side at the break. One ring has a smaller stamped R than the other and is also shinier on the outside edge. I wonder if they are the same or not.

 

[Canadian Dave]

" To the point where the ring will not fit in the top groove the whole way like it does the bottom"

Sounds to me like the piston ring groove is unevenly worn. If the ring doesn't fit perfectly parallel in the ring groove you need to replace the piston. If the top end is 8 years old I'd certainly treat it to a new piston and rings. You should inspect the crank assm. and crank seals while you're at it. 8 years without top end maintenance is a long time.

I think if you check out this the rest of you questions will be answered.

David

 

[daveEX]

i advise doing the botom end too. last year i did the top end on my 91 200 but didnt do the crank or seals. the side play on the rod was ok and no up and down movemment and the seals werent leaking so i left it alone. towards the end of summer i took off the ignition cover and discovered the green gas slime= bad crank seal. now a motor that lasted 10 years before its first rebuild is back apart again :( do the whole thing and youll get a lot more time out of it. also replace any worn bearings or seals in the tranny while th cases are split.its costly but if i wouldve just did it the first time id still be riding.

 

[joe28kdx]

Rin Groove sizes

I swapped out my stock piston for a Pro X and descovered that the top ring in narrower than the bottom. I found this out cuz they sent me 2 bottom rings.
It's only .001 but it makes a difference.
I'd check my piston for sizing or for that matter swapped it out.
Scratches aren't good. If you know a cool dealer show him, expect the worse when you go though. The rings can't seal over a scratch.
There's a letter on you cylinder that tell what size to order a piston, (standard, .001 over size etc..) Maybe they or you can hone the scratches out. Have the dealer look at it. the plating is not thick, but it can be done.
I made a tester to pressurize my bottom end to check my seals,use it all the time,found 2 motors that had seals leaking, adverted a big problem. With an engine that old, it might be smart to do the bottom, bet the $@##$%^ out of a seize later on.
Good luck!
Joe
2001 200
2-TTR 125 Boy "A"s and "B"'s

The older I get the faster I was!

 

[kdxepp]

OK, Just to put us all straight, I called JF today to order the KIPS rack rod seal and maybe a piston. He said that the top ring groove is tapered and the bottom groove square. Therefore the rings ARE different. The shinier of the two is the tapered (cross section) top ring, which can be seen with the naked eye. I mic-ed the piston and bore and both fell exactly at the high edge of the standard limit per the manual, so I'm staying stock original. Remember all of this info is about OEM parts, aftermarket pistons etc. may be different. Thanks to everyone for the input and thanks to Master Fredette.

 

[joe28kdx]

using your head

That's using yopur head now instaed of your credit card later!! Good job. Good luck with the rebuild. You might want to concider buying a shop manual for your scoot. I'm always surprised at the little tips I learn and get mad when they don't have the info I REALLY need!!
Joe

 

[treinsch]

Originally posted by kdxepp
I also found that Permatex gasket remover works even better than oven cleaner at removing carbon build up, and it doesn't corrode the aluminum, fyi.

I have never used oven cleaner but just tried this stuff and it really does work great.

 

[Fuzzy Dice]

Originally posted by treinsch


I have never used oven cleaner but just tried this stuff and it really does work great.

Just make sure none of it dribbles on the painted parts cause it makes a good paint stripper too.I didn't realize this before and found some nice bubbles on my engine paint.

 

[89kdx200rdr]

ok this is confusing. are the 89's diff than the 94's? i have a brand new set of kawasaki rings for standard piston. they both measure .046". last time i did topend i didnt replace rings because they were still well within limit, i took them off cleaned piston and payed no mind to which ring went where. they fit fine.

 

[speedyts49]

I sure have to agree that Permatex gasket remover removes carbon on heads and various other small engine parts aluminum included! On a related note I do not recommend using that last bit of 2stoke gas in your 4stroke lawn mover, not that I would ever do that.
96kdx200
93kdx200
4hp briggs and stratton lawn mover

 

[louis]

My wife cuts the grass