Hawk locking up

[Sir kayakalot]

Great job tearing it down. You'll be an expert on these engines when this is all said and done. How many miles did you have on the bike when this happened? I wonder what caused those gear teeth to break off, cheap metal or something get in there that wasn't supposed to be in there?

[Lit Hawk]

Thanks, I am beginning to feel like an expert. After replacing the piston and rings on my sons 125cc and it running better than ever now(no more white smoke) I feel like I’m getting there. Now to just replace these broken gears. I found nothing foreign in the engine just one more tooth, that makes 5 total. I also found half a clip of something not sure where it came from, I’m sure it’s from the engine though. I have about 5k miles on it, the only thing I can really think of that caused the teeth to break is I started using synthetic oil. I went from changing my oil every two weeks with Rotella 15w40 to synthetic rotella and I was probably 3 weeks in when it broke. I doubt it was the oil change but I’m never using synthetic again just to be safe. Here’s a pic of the last tooth and something else I found in there. Also does anyone know why my pics don’t come out with better resolution when I post them on here?

[Megadan]

Likely just a casting or manufacturing defect. It happens even with US, Euro, and Japanese vehicles, one visually good part sneaks through from time to time.

I would not blame this on the synthetic. I have been running T6 in my bike the last 700 miles and have not had one problem.

Once a gear loses one tooth, generally you end up with a cascade effect and more teeth follow. Either due to stress introduced from the missing gear, or the loose teeth themselves getting where they shouldn't be and causing more damage.

[2LZ]

Originally Posted by Megadan

Likely just a casting or manufacturing defect.

I'm with Dan on this. These things can normally take a ton of thrashing.

[Ariel Red Hunter]

Originally Posted by Lit Hawk

Thanks, I am beginning to feel like an expert. After replacing the piston and rings on my sons 125cc and it running better than ever now(no more white smoke) I feel like I’m getting there. Now to just replace these broken gears. I found nothing foreign in the engine just one more tooth, that makes 5 total. I also found half a clip of something not sure where it came from, I’m sure it’s from the engine though. I have about 5k miles on it, the only thing I can really think of that caused the teeth to break is I started using synthetic oil. I went from changing my oil every two weeks with Rotella 15w40 to synthetic rotella and I was probably 3 weeks in when it broke. I doubt it was the oil change but I’m never using synthetic again just to be safe. Here’s a pic of the last tooth and something else I found in there. Also does anyone know why my pics don’t come out with better resolution when I post them on here?

I don't know what caused this (my WAG is an improperly heat treated spring broke and went through the gear train), but I know what did NOT cause it. Synthetic oil.....ARH

[Lit Hawk]

Ok ok it wasn’t synthetic oil just saying that is the only thing I’ve done different on a perfectly fine running bike. Just saying I’ve never used synthetic oil and when I drained it it did seem thinner than regular oil and had broken teeth in it. So do you think the half c clip thingy is from a broken spring. Should I keep searching for the rest of the broken piece. It’s pretty thin Doesnt look like it’s from a spring looks more like the circle piece that holds the piston in place but mine were still good. Also I’m gonna cut out the cat from exhaust and put zerk fittings
On the bike. Also gonna try to fabricate my own skid plate. Put heavy duty tubes on my Shinko 244’s that I just ordered before she broke and really clean her up. I like the idea of painting the silver on it also. Maybe customizing her a little more visual wise, while she’s down. Any ideas anyone on what else I can do to improve while engines torn apart. Can’t wait to get back on the road!!

[Ariel Red Hunter]

Originally Posted by Lit Hawk

Ok ok it wasn’t synthetic oil just saying that is the only thing I’ve done different on a perfectly fine running bike. Just saying I’ve never used synthetic oil and when I drained it it did seem thinner than regular oil and had broken teeth in it. So do you think the half c clip thingy is from a broken spring. Should I keep searching for the rest of the broken piece. It’s pretty thin Doesnt look like it’s from a spring looks more like the circle piece that holds the piston in place but mine were still good. Also I’m gonna cut out the cat from exhaust and put zerk fittings
On the bike. Also gonna try to fabricate my own skid plate. Put heavy duty tubes on my Shinko 244’s that I just ordered before she broke and really clean her up. I like the idea of painting the silver on it also. Maybe customizing her a little more visual wise, while she’s down. Any ideas anyone on what else I can do to improve while engines torn apart. Can’t wait to get back on the road!!

Normally if it is a problem of a gear shucking a tooth, that's all you find in the bottom of the transmission. No, I don't think the broken c-clip came from a spring. I couldn't tell it was a broken c-clip from the pics. I'm fighting off pnuemonia at the moment, and my vision is not as good as usual. My apologies. You are going to have to figure out where that broken piece came from, and figure out if it was a bad c-clip groove, or a brittle c-clip...ARH

[Lit Hawk]

Yup it’s a c clip. Like in the pic now to figure out where it went

[Ariel Red Hunter]

Originally Posted by Lit Hawk

Yup it’s a c clip. Like in the pic now to figure out where it went

Yes. Now the real problem is to figure where it came from. I'm guessing it came from inside the transmission. Maybe either the shifting forks, or the shifting cam shaft...ARH

[Lit Hawk]

Found it! Turns out it’s the c clip between 3rd and 4th gear. Still waiting to hear back from company I bought it from. Usually they respond right away to my email but I haven’t heard anything back since yesterday morning.

[Ariel Red Hunter]

Originally Posted by Lit Hawk

Found it! Turns out it’s the c clip between 3rd and 4th gear. Still waiting to hear back from company I bought it from. Usually they respond right away to my email but I haven’t heard anything back since yesterday morning.

Great job!...ARH

[Lit Hawk]

Finally got back on the road about a week ago. Y’all were right these engines are easy to work on. Last year I had no idea how to work on a bike and barely new how to ride one. Now I can pretty much rebuild this engine myself. Thanks everyone for the confidence to get it done. I got the gears from cscmotorcycles about $25 cheap fix. I was still having some problems with my carb, engine revving down when I stopped at a light. Yesterday I could top out at 68mph. This morning adjusted my carb I think perfectly. 115 main 3 turns out, now my top speed 75mph

[JerryHawk250]

Originally Posted by Lit Hawk

Finally got back on the road about a week ago. Y’all were right these engines are easy to work on. Last year I had no idea how to work on a bike and barely new how to ride one. Now I can pretty much rebuild this engine myself. Thanks everyone for the confidence to get it done. I got the gears from cscmotorcycles about $25 cheap fix. I was still having some problems with my carb, engine revving down when I stopped at a light. Yesterday I could top out at 68mph. This morning adjusted my carb I think perfectly. 115 main 3 turns out, now my top speed 75mph

Glad to here you got it fixed. Yeah, these little engines are so simple.

[Lit Hawk]

Almost died tonight!! Geez I have no idea what happened all of a sudden it locked up busted open the engine. My front sprocket is jammed into the chain guard like my engine is crooked. Any ideas what happened PLEASE HELP!!! The gears inside the engine are rubbing against the case. Where can I get another engine case I dont think csc has the same kind because the gaskets didn’t match.

[Merlin]

Did the engine shift?