So, my 67 kawasaki C2TR last week was being ridden, and out of nowhere, started stalling and then just died. I go tit fired back up on the side of the road but def could hear 'something' in the motor bouncing around. figured for sure a chunk of piston broke off or a ring failed. Nope. pulled top end down, and while this piston had seen better days, there were no immediate failures except obviously SOMETHING got int he crankcases. I rebuilt the crank last year, well, the outer bearings. I have at least 150 miles on it since then, and found this. (see pics). prior it ran absolutely excellent all year. whatever got in there was def metal, and the rod and wristpin bearings were fine as well. so, i had a spare ready to go top-end for it, so flushed out crankcases, looked in there with a borescope, checked the exhaust and the carb and intake area, and found nothing. reassembled with spare top end, and it did the same thing inside of 2 minutes running. :huh: no idea WHATS in there, but def taking the motor out and splitting motor see what the hell is going on. ive never had this happen and not been able to find it, especially on a single. :huh: :bang:
My bike in the past had a crank bearing cage that was letting go over time. Looked very similar to this, pecking the piston and cylinder head.
Im wondering, maybe. the crank bearings are brand new so while possible, unlikely but ive seen weirder things.
Damn
does the rotary valve have any damage?? can't remember if it has needle bearings or not, but whatever caused that was hard metal!!!
nope. i checked the disc thru the window in the crankcase and didnt see any damage. I agree, def metal. Id swear it was a 2-3mm ball bearing by the marks it left, but there's nothing that size in the crankcase or intake. its a fkn mystery as to what it actually is. i mean, i'll find it. one way or another.
My snowmobile had plastic bearing cages and those exploded when I blew it up. Looked like crack all over the place. But, that won't be the case here...
I'd double-check that rotary valve Mark. I had a hole in the middle of mine on my sled once. I mean directly in the middle of the plate. Probably explained the weird sputtering the motor did at low revs. Looked like it wore through somehow. Probably had a bearing going out on the rotary shaft and it had too much play. Or, the 2t oil quit for a while to the plate, plate was warped. Who knows.
beats me. the disc is right on the crank so i doubt thats it, and its a fiber material to boot. its a simple motor so tearing into it is pretty easy. soon, because its bugging the shit out of me. :huh:
i know you have probably looked already, but is all the ceramic still on the plug?? that ceramic is really hard and could cause some issues!!
yes, still there. i thought the ground strap might have come off actually. nope plug ok
Something with the air filter/air box come apart??
Man that sucks!Wrecking 2 top ends hurts. Been there with 2 Moto-villa's in the late 80s. Nice bikes never seen any before or after my 2. It was the Lower rod bearing and cage. Lost a bultaco pursang 175 after but stopped after the first top end.
Ouch, that hurts. That sucks Mark. I'm interested to find out what turns up as the culprit.
I'd speculate that it's a big end cage starting to break up. It could be a main bearing cage failing, but more likely it's a big end.
Quote from: m in sc on January 03, 2024, 04:51:52 PMnope. i checked the disc thru the window in the crankcase and didnt see any damage. I agree, def metal. Id swear it was a 2-3mm ball bearing by the marks it left, but there's nothing that size in the crankcase or intake. its a fkn mystery as to what it actually is. i mean, i'll find it. one way or another.
Are there any check valve balls in a separate lube system?
there is a check valve but it would be impossible for it to get out you can see the nozzle on the intake, in the case, it was in place.
I would lean towards big rod bearing as well, but no sign of it coming apart, the rod play is basically nil beyond stock. as far as a main bearing, not sure, i replaced them in march last year. its possible i had a defective one, but I get the feeling something just got left in the case and eventually got sucked in, maybe via the air filter track?
there also was no abnormal noises leading up to it before the failure, both times. only after whatever is in there was bouncing around.
Im going to pull the motor out in a day or 2 and bring it home, set it on the bench and go thru it soon.
heres when i changed the main bearings 3/23
(https://2strokeworld.net/wp-content/uploads/67-kaw-120/crankbearings-23/336999954_118011497896505_1497564843141412414_n.jpg)
either way, new piston, rings, etc on way wont show up till the end of the month. also going to helicoil the head studs since a few feel 'suspect' when torquing down. (never had a leak but it is 57 years old). this gives me a few weeks to invesitgate and rebuild any crank issues i might find. luckily the rest of the motor is tip top (trans, clutch, etc).
Im kinda surprised you dont have it all stripped down yet.
well, its at work at the moment in the warehouse. I'll pull the motor out in a few days, take the motor home and throw it on the bench. I just ordered a spare crank as well just in-case there's something really wrong w the one in it. I have spare gasket sets already, etc. Ive had this bike 11 years or so, so it's def not going anywhere.
I have to probably pull the head off the GT750 and put that massively oversized spare gasket I have in place of the cometic one since it's leaking again... But its cold in the garage and the house needs work. I will probably wait 'til its good and warm in the spring or summer. Procrastination at its finest.
pulled motor at lunch. going home tonight with the last batch of 2sw shirts (in box) I picked up on way in to work today.
Quote from: rearwheelslider on January 03, 2024, 01:28:50 PMMy bike in the past had a crank bearing cage that was letting go over time. Looked very similar to this, pecking the piston and cylinder head.
we have a winner. rod bearing cage failed and was ejecting rollers.
It is always great when you identify the problem!
I really would like to have a rotary valve single, BTW....
175 to 250 would be perfect.....
i really like the kawi a lot, its a great engine design.
Quote from: m in sc on January 09, 2024, 12:02:18 PMi really like the kawi a lot, its a great engine design.
The only Kawasaki singles I ever worked on, is the KE/ KH100 models from late 70s to mid 80s. The only questionable design feature on those was that the LH end of the clutch shaft, and the RH end of the countershaft ran in Brass bushings, not ball or roller bearings. Is yours the same way?
no, they are all ball bearings. Its interesting, the C2TR and C2SS 67-68-69 IMHO wa s away better motor design than the later ones.
the G3SS for example, was a turd motor design (by comparison). I mean, there's some weird stuff in my motor design wise, but its a solid design.
Oh, I had forgotten that the KE/KH 100 clutches were a little weak as well. Once you had got the engines to run real good, the clutch tended to slip...We were busy playing with porting and cutting the rotary valves back in the early 80s :)
thats one thing they had in common, the 120s clutch is just trash. I actually found out that i could fit aftermarket clutch springs for a grom in mine and it helped, a lot. i have so many nos clutch frictions and steels for it its ridiculous. lol.
pulled the old crank and the replacement ebay one apart as well, and replaced the rod bearing on the 'new' crank. the rod on the ebay one is def a replacement and looked great (left one in 4th pic). got it trued back up home but also brought it to work, to verify on a bigger lathe w 2 live centers. (my small one at home was fine but.. worth a double check)
:clap: That old bearing is toast.
You're lucky to have access to all that equipment (press, lathe, etc.). Sure makes rebuilding a crank easier, faster, and cheaper :thumbs:
thats true. I was going to buy a press but luckily I get to use a friends at work if i need one. its total over kill . but that makes it just right.
the spec is 0.0012" to 0.004, the closest i could get the runout is .002. i'll take it.
i verified the adjustments at work today on the bigger lathe, made setting up the dial indicators easier.
Turns lathe on...
....
(https://2strokeworld.net/wp-content/uploads/MISC-BS/BOOM.gif)
got the lower end together last night, pretty simple as expected. check out this rotary disc I got on ebay though. I bought nos stocker but also this aluminum one which must be a period high performance one. 🤔 I prob won't run that one but I'm going to def check some intake duration numbers.
and the follow up. took the test ride today, did really well. also, note the head nuts. these are M8 nuts for the exhaust on my XR150L, ordered a bunch from partzilla for this, and also should be good for rd chambers as well. 12mm wrench flats and allen key end. while i was in there put on a new RK chain, and did a few other small things not worth mentioning but just small detail stuff. also, i hate the ignition on this thing, the points behind the drum suck. so time consuming to set. :rolleyes:
bike ran great, plug looks right, motor is dead stock except for a 1mm over bore & some tiny port cleanup (which has been there for 10 years). checked compression after the test run, right at 142 PSI.
(https://2strokeworld.net/wp-content/uploads/67-kaw-120/rod-bearing-failure-24/bearing-failure-rebuild-120-2024_28.jpg)
(https://2strokeworld.net/wp-content/uploads/67-kaw-120/rod-bearing-failure-24/bearing-failure-rebuild-120-2024_29-1.jpg)
no shiny bits on the plug. yeah! (no not a plug chop)
(https://2strokeworld.net/wp-content/uploads/67-kaw-120/rod-bearing-failure-24/bearing-failure-rebuild-120-2024_00.jpg)
(https://2strokeworld.net/wp-content/uploads/67-kaw-120/rod-bearing-failure-24/bearing-failure-rebuild-120-2024_30-1.jpg)
:metal: :metal:
Very nice. What a cool little bike. Looks like fun.
I totally agree. A very cool model. The engine looks very similar to the KH/KE 100 models sold in Norway into the mid 80s. I feel a little sceptical about an alloy rotary valve. Aluminum on aluminum does not sound like a happy, friction less "marriage". I believe the composite rotary valves on other Kawasaki models had issues as well?
Don't know which is more surprising, that the bike is already all back together and ripping around or that price for Premium!
Looks great Mark! Small cc FTW! :vroom:
i put in the new NOS fiber one. the aluminum one was just a 'what the hell, i'll get it' thing. it added like 27? degrees on intake duration, it was crazy. most in the beginning of the event, and added like 3 or 4 on the back side of it. lol. the original disc was in good shape, but put in the replacement just because it was cheap.
its very related to the KH/KE motor. ign rotor swaps with them, as does a very few small parts. id love to get a CD unit for one and retrofit this, but they are hard to find. the actual displacement is 115cc.
thanks Russ. it wasn't hard to repair, just waiting on parts and i have not much else going on in the garage right now since the KZ is pretty much done.
You could always mod that aluminum one to run at whatever duration you want by removing material.