I was at the track today and rode for about 4 hours. On my last lap of the day on the SX track, I came up short on a double and heard a pretty loud crack...I quickly gave it gas to clear the next double (of a 3 double rhythm section) and nothing happened but a high rev. I nearly went over the bars on the second double because I came up so short, but the suspension soaked it up pretty good and I rode it out. Well, the chain broke.....effectively taking out the case guard, plastic sprocket guard and the entire bottom of the compartment that holds the clutch arm. It completely tore the portion of the case that the bolts holding the case guard on out....you can't even screw a bolt into the spaces left....the bolts didn't break mind you, the case broke around the bolts. The hole under the clutch arm is bad enough that I'm fairly positive it's not fixable. It didn't blow oil out, but it seeped a couple tablespoons. I've got some pictures if anyone is interested in hosting them so everyone can get a peek. Looks like ServiceHonda can get me a replacement Left Case for $180...not bad considering I was guessing at least $250. Looks like I'll be splitting the cases myself (no way is the local Honda dealer getting my business). Question: anything in particular I should look into replacing while I've got this engine torn down? I know the valves have been troublesome to some, but thus far I've had no problems. The bike has probably 60 hours or so on it and I'm not hard on it, so there shouldn't be any excess wear on anything. Are there any special tools I'll need? I've got a friend that did a complete top and bottom end rebuild on his 99 YZ426 over the spring, that's going to help....so the process shouldn't be excessively difficult.
Well, I'm going to go sulk now. Thanks for listening....
Oh yeah, what I think happened. The track was pretty muddy today and I stopped to clean mud out of the case cover twice in that four hour period...it would pack in there pretty bad. I just adjusted the chain last night because I put on a new sprocket...so I know it wasn't too tight. Anyway, I also noticed a tooth broken off my new sprocket. So I'm guessing a rock got lodged in-between a link and once it hit the sprocket it pulled the chain too tight (breaking a tooth in the process). Well, I came up short on that jump and I think the combination of the two broke the chain. I found the masterlink (it's what broke) and it was twisted really bad and the riveted side is what broke. The retaining clip was still attached to the pins.
:(
Well, I'm going to go sulk now. Thanks for listening....
Oh yeah, what I think happened. The track was pretty muddy today and I stopped to clean mud out of the case cover twice in that four hour period...it would pack in there pretty bad. I just adjusted the chain last night because I put on a new sprocket...so I know it wasn't too tight. Anyway, I also noticed a tooth broken off my new sprocket. So I'm guessing a rock got lodged in-between a link and once it hit the sprocket it pulled the chain too tight (breaking a tooth in the process). Well, I came up short on that jump and I think the combination of the two broke the chain. I found the masterlink (it's what broke) and it was twisted really bad and the riveted side is what broke. The retaining clip was still attached to the pins.
:(