Race Bike Engine Overhaul
Posted: 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!
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.
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.
The flywheel came off easy enough with a Tusk flywheel puller. But what was behind it didn't look any better!
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.
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'
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!
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.
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.
The flywheel came off easy enough with a Tusk flywheel puller. But what was behind it didn't look any better!
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.
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'