Race Bike Engine Overhaul

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doakley
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Race Bike Engine Overhaul

Post by doakley » 06:13 pm Aug 06 2019

Hi, Guys (and gals). If you've followed me to this thread from the "KDX in National Enduro Series" topic, you already know I had a serious engine problem in the Rattlesnake Enduro. For those of you who just stumbled on this thread or were looking for info on engine rebuilds, here's a little background.

Basically, I'm competing in the 65+ class on my 1999 (decidedly not stock) KDX220 in the 2019 NEPG National Enduro series. Ten events for the season and, at the time of this writing, we are through event #5. Unfortunately during one of the tests, I think test 3 or 5 (C riders and old riders skipped test 4) I fell just right and managed to knock out that little glass window in the side of the clutch cover. You know, the one that lets you check the oil level supposedly (although I always run the engine well overfilled with ATF. Of course I lost all of the fluid and of course, did not know this until somewhere in test 5 when the bike began to act erratically and sounded like it was tearing its guts out. Obviously some bearings were beginning to fail. End of the race day for me!

After some very brief dreams of buying a new bike, I decided the smart thing to do was to bite the bullet and split the cases. There was some talk of filling it back up with fresh ATF, after plugging the hole where the window used to be, and giving her a try. But the rear wheel had temporarily locked up on me riding back to the race start and really, it sounded like all hell was breaking loose inside my engine. I wasn't sure if the autoclutch was coming apart or the transmission or what. If I was going to have any trust in this bike to run the second half of the season I needed to bite the bullet and tear down the engine. I'm only a fair mechanic, meaning I can follow a manual but I lack the wisdom of experience. I've done a lot of work on bikes, but I've never split the cases before. This would be new to me. I'll try to document as best I can as I go along and I'll try to add what my thinking was on the decisions I'll have to make in the process. So here we go!
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It hurts to see my girl looking like this but you have to remove the engine so get over it! Follow the manual (including some tips on this site) and engine removal is no more hassle than removing the suspension linkage and bearings, actually less.

I'm pretty comfortable removing the rt side items since I installed the autoclutch. Let me just summarize what I found was the autoclutch appeared to be fine. The fiber plates even measured at the upper end of spec for thickness, which was a real surprise! But when I turned the clutch shaft by hand, the noise coming from inside was horrible! On to the case splitting.

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An early step is to remove the magneto stuff. When I took off the cover this is what I found. Ugh! Obviously this cover wasn't sealed well. This will now be an item added to my routine race maintenance list.
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The flywheel came off easy enough with a Tusk flywheel puller. But what was behind it didn't look any better!
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Hardest part was getting the stator plate mounting screws removed after being corroded in place like this. One cam out with an impact driver, one required vise grip pliers and the third had to be carefully drilled out. Keep that damn cover sealed and check it often! Also I note the manual says to use red Loctite putting these back in. I refuse to use red Loctite on anything that EVER has to be removed again. It will get blue!

Splitting the cases with the Tusk case splitter was easy. I highly recommend watching the video on this on Rocky Mtn ATV. Watch it twice! Go slow, take your time and pay attention that the cases come apart evenly.
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So this is where we are right now. The engine is apart. There was NO major damage evident. I thought the bearings felt good but this is where experience counts. I took the cases with bearings intact along with the transmission to a mechanic who I really respect for his opinion. He was surprised at the minimal wear but did find two ball bearings he recommended replacing and of course ALL the engine seals. When I started removing bearings they came out so easily I decided to remove and replace them all. The total parts cost for replacing everything was about $200. It wasn't worth it to me to try and save a few bucks since the engine was already apart anyway. So she get all new bearings and seals.

One comment is to look at all that case sealant slopped all inside this engine! It makes me wonder if someone else has split these cases before? I mean would the factory be so sloppy with sealant? Nothing like working on an old bike!

My mechanic pronounced the crank to be in excellent condition so it goes back in with new case bearings and seals, but we will not rebuild the crank. Remember, it is lubricated by the premix so loss of transmission oil is not an issue.

So right now I'm waiting for all the parts to arrive and hopefully I'll be wrenching then riding again very soon!

Y'all keep braaapppping!

Old guy Racin'

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Re: Race Bike Engine Overhaul

Post by kdxsully » 06:57 pm Aug 06 2019

Very nice. What bearings did your mechanic buddy say needed replacing? That sealant looks kinda crusty as well as sloppy. No transmission wear??
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Re: Race Bike Engine Overhaul

Post by SS109 » 07:06 pm Aug 06 2019

Sorry to hear about the engine failure.

Good to hear you're replacing all the bearings. My philosophy is to replace every bearing, bushing, thrust washer, and seal that would require splitting the cases if it failed. I don't like having to split an engine unless I've actually planned on it.
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Re: Race Bike Engine Overhaul

Post by bufftester » 09:06 pm Aug 06 2019

Thats about how mine looked when I opened it the first time, and I've had mine since mile one. Good call to replace it all while in there. Before you reassemble, make sure the case halves are nice and burr free and flat. I used a piece of plate glass and some rubbing compound and lightly sanded the face seal before reassembly. No gasket so you want to make sure its nice and flat.

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Re: Race Bike Engine Overhaul

Post by doakley » 12:45 am Aug 07 2019

Thanks for the tips. What I decided too, replace anything requiring a case split while it is down. Good idea on checking the cases and no, the transmission showed no wear. Everything seems to be fine.

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Re: Race Bike Engine Overhaul

Post by KDXGarage » 01:00 am Aug 07 2019

You are off to a great start! Good call to just go ahead and replace all the bearings and such.

I thought for a minute that the front half of that case had a paper gasket on it. :-)
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Re: Race Bike Engine Overhaul

Post by kdx633 » 08:15 am Aug 07 2019

Did you remove the small needle bearing in the top center of the case?If so how did you get it out?

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Re: Race Bike Engine Overhaul

Post by SS109 » 10:29 am Aug 07 2019

kdx633 wrote:
08:15 am Aug 07 2019
Did you remove the small needle bearing in the top center of the case?If so how did you get it out?
You use a blind hole puller and, IME, use a little heat.
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Re: Race Bike Engine Overhaul

Post by doakley » 10:19 pm Aug 07 2019

Exactly as SS109 said. Did not need heat though. I am expecting to use a heat gun on the case and freezing the new bearings to reinstall. They were delivered today so hopefully I can start the reassembly tomorrow.

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Re: Race Bike Engine Overhaul

Post by kdxsully » 11:00 pm Aug 07 2019

Another tool to buy. :doh:
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Re: Race Bike Engine Overhaul

Post by doakley » 04:06 pm Aug 16 2019

Just a quick follow up. The last part I ordered came in today so I can finish the engine reassembly. I’ll take a few photos tonight. So far so good. I guess it depends on what I screwed up or didn’t do correctly! Should know tomorrow.

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Re: Race Bike Engine Overhaul

Post by bufftester » 04:25 pm Aug 16 2019

Take your time, double check everything, especially when reassembling the tranny/shift forks/shift tubes. It's a bit of a PITA getting all that stuff lined up, but when you do it should slide together easily. I would do it once dry to make sure everything operates correctly, then apply your sealant and do it for real

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Re: Race Bike Engine Overhaul

Post by doakley » 11:15 pm Aug 16 2019

Lord, I wish I had read that before I reassembled everything! Got it together and checked the trans before finishing out the rt side clutch cover, etc. Trans would only shift through three gears. Obviously I put something together wrong! Pulled it back out of the frame stripped it and ready to split the cases again. This time I will do a dry assembly without the crank until I know I got the transmission correct. Damn!

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Re: Race Bike Engine Overhaul

Post by doakley » 07:07 pm Aug 17 2019

This is soooo frustrating. So I split thecases(again) this afternoon. I carefully compared my transmission to the photos in my service manual (I use Cyclepedia.com). I wasn't certain but thought just maybe I didn't have the shift drum installed correctly. So I took it all out and reassembled carefully, double checking everything. Put the cases back together and the transmission rotated easily. All looked good.

I started putting the right side components back together, primary drivegear, water pump gear, nut, kick start mechanism then the shift mechanism. After inserting the shifter shaft I slipped theshiftlever over the otherend and tried to shiftthetransmission through its gears. No go! So here's my question: with the engine on the work bench, the trans and ALL shift mechanism parts installed, shouldn't I be able to shift through the gears or does the bike have to be running?

I'm stumped because I can't see anything I've done wrong. Any suggestions?

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Re: Race Bike Engine Overhaul

Post by Vossman » 07:53 pm Aug 17 2019

tranny should be rotating, by hand should be more than enough.

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Re: Race Bike Engine Overhaul

Post by SS109 » 08:06 pm Aug 17 2019

Yeah, you'll need to rotate either the input or output shafts to get the trans to shift. Shift gear, rotate input or output shaft till you hear a clunk, then it should shift again.
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Re: Race Bike Engine Overhaul

Post by doakley » 08:30 pm Aug 17 2019

Thanks for the benefit of y’all’s knowledge. I’ll try it again!

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Re: Race Bike Engine Overhaul

Post by Vossman » 03:27 pm Aug 18 2019

Did you get it to shift?

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Re: Race Bike Engine Overhaul

Post by bufftester » 04:58 pm Aug 18 2019

Yes, the transmission will only shift while in motion, should spin easily by hand, then manually run through the gears. You can verify by watching the speed the output shaft rotates at compared to the input shaft. Most likely you had it together right the first time, and you can get a couple gears but then you have to spin the motor. Bet if you did that it would have shifted the other gears as well. But as they say, a hard earned lesson is a hardly forgotten one lol.

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Re: Race Bike Engine Overhaul

Post by doakley » 10:18 pm Aug 18 2019

Yes, a hard earned lesson indeed! I think I'm a reasonably decent mechanic, for someone who doesn't make his living at it. At least I can follow a manual reasonably well. But sometimes I come up short on the experience curve.
I'm putting stuff back together now and hopefully will have it ready to race this weekend. Leaving Friday afternoon and the last part I ordered won't arrive until Wednesday afternoon or more likely, Thursday. While I'm waiting for the part, the little spring on the shift mechanism, I'll finish up getting the KTM ready just in case. Maybe I can get them both done in time to go for a short ride on each before Friday.

Thanks for everyone's input and for not making me feel like a total idiot!

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