250-500cc 2006 WR250 Engine noise (Help requested)

I have a 2006 WR250 that I picked up from a friend not long ago. Bike had been barely used, and until this issue, I'd only put approx. 10 hours on the thing. Long story short, while riding today, I got on the gas to pass a friend I was riding with. As soon as the bike began to hook up, I heard from the engine what sounded similar to the chain slipping on the sprockets, or really loud valves on a 4T (ratchety type sound, consistent with engine RPM). I killed the engine immediately, and pushed back to my truck.

Tonight I got the engine pulled and torn down. I'm a bit perplexed. Top end looks brand new (though I'll grab some calipers tomorrow & bore gauge to verify). I checked the side to side play on the connecting rod (at crank side), which measured 0.029-0.030" (wear limit is something like 0.035"). Here is a video:



Like I said, I'm rather unsure of what the exact issue is. The bike had been running just spot on up until this point. Only mod to the thing is that I installed a Rekluse Core exp 2.0.

Possibly a bearing, or something in the trans? I can't feel any "vertical" play on the connecting rod bearing, but it will tilt side if you hold it extended from by the piston end. I appreciate any input. Hate for first post being issue related, but what can yah do!

Thanks,
Andrew

Pulled off side cover, and pretty sure I found the problem:


Noticed that the crank had a dead spot while spinning it.

Andrew

Woah!
That'll do it! Those gears aren't super cheap from HVA (here in Aussie anyway) but at least it's a pretty simple/easy job to replace.
Make sure you find the rest of that missing tooth, you don't want that doing further damage in the engine.

I found all of the missing tooth, and when I went to remove the clutch basket, I found the culprit:


On the left, is a screw head. It's the lone flat head screw holding the shifter mechanism in location. Apparently it backed out and found it's way into the primary. Thankfully I also found the body of the screw as well, though it isn't quite shaped how it was. haha. Couple parts & I should be rolling. I'll call up Halls today, see if they have one, otherwise I've found one on ebay.

Thanks,
Andrew

My 125 started making the same sound last week in the garage. I pulled the top end and noticed nothing abnormal. I haven't pulled the side cover yet. You've given me hope that it's something simple. I really don't want to have to split the cases.

It seems that the only way I can buy the part I need through Husky, is if I purchase the clutch basket set with it. Annoying, but I understand why it's packaged this way. If the one gear busted, you'd figure the other did too. Time to do some calling around to see if anyone happens to have one sitting on a shelf for some reason.

Andrew

I have an extra bottom end. You want me too look?

I pulled my side cover today, similar problem, different gear.


My shift mechanism retaining bolt was right where it should be, so I'm not sure what caused the tooth to break.

How does the gear on the back of the clutch look ?

Not sure about andrewgore's, but my clutch gear looks fine. No other gears were missing teeth and the only foreign debris in the bottom of the case was the one missing tooth.

My clutch gear was in good shape. I'll double check it again, but I inspected it best I could and saw nothing wrong with it.

Andrew

Try Central Jersey Cycles Bob wallace. 609 758 1887

I have one in my parts box.

I think I have that idler gear too.

In fact I have a whole bottom end if someone wants one.

Got the bike back together last night. Got to go test run it here. Still got the same\similar noise. Thoughts\Ideas?



Andrew

Sounds like a rod knock to me.....

Get a big screwdriver.Put the tip of it against various areas of the engine and put your ear against the handle of the screwdriver.Figure out where it is the loudest to pinpoint where it is coming from..

You don't think that the knock sounds too slow to be a rod knock?

I'm pretty sure I sourced where the noise is coming from. I wanted to isolate the 3 main areas noise could be coming from:
1. Crank\Top End
2. Transmission
3. Clutch area

I pulled the plug, and spun the crank by hand (via flywheel). I noticed along the way that there was a tight spot in the rotation. Next step was the remove the clutch\basket\etc. I removed the clutch basket, and noted that the crank (with no clutch basket in) spun freely and smoothly. I then spun the transmission input shaft by hand, which spun very freely and smoothly. No issues there. At this point I looked as close as I could to the clutch basket. Upon further inspection I found where the pesky screw made contact with the clutch basket. If you look at the picture here:


I noted what I believe to be the culprit. That tooth there is kinked over to the side. It's rather minute, but I believe to be the cause. It seems to make sense with the noise coming from the bike. Note that the sound doesn't appear to be on every revolution of the crank. This coincides with the tightness I felt in the crank, and probably explains why I didn't initially feel the tight spot upon reassembly. I must have installed the basket orientated so that I didn't run over the bad portion of the basket.

It's apparent that the basket will need to be replaced one way or another. I'm going to see if I can massage the gear at all (I'm a machinist....have no fear. haha), and see if I can get the tight spot to go away. I'll still look into replacing the thing, but in the meantime, it should save me from splitting the cases prematurely.

Andrew

Victory. Tossed the bike back together. 2 kicks and it was purring like a kitten. Rich, let me know what you'd want for a clutch basket if you have it. This is why husky only sells the primary with the clutch basket. If one is messed up the other probably is too. I'll test the bike more tomorrow. Didn't want so piss off the neighbors too much tonight.

Andrew.

Test rode the bike today. Looking like we're good to race on this thing. I'm stoked.

Andrew