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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK

15 Feb 2020 01:06
MR.MONTERO
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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK #1
Hi guys. I have a 72 LT2 that has a stuck kick crank. Opened her up and the piston and cylinder are fine. This piston just won’t move up or down. This kick crank is stuck and skips. I haven’t opened the crank case to look inside due to rusty bolts. Just wanted to hit the thread first to see if anyone had any insight on what might be happening. Let me know if anyone can help. Thanks!

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15 Feb 2020 02:14
RT325
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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK #2
Hello & welcome. Sounds like what you're saying really, is the crank wont turn. Not kick tart but the crank the conrod is connected to. Need a bit more information or further investigating by you before we can give an educated guess. By opening up do you mean the cylinder is 'off' & if so is the conrod free to move as in rocking back & forth but crank flywheels are stuck. If you grab the magneto flywheel will it turn. Lots of questions. Have you lust bought it. Has it sat for years unused. Was it sitting out in the rain with spark plug out--things like that. Thanks.
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15 Feb 2020 11:46
MR.MONTERO
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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK #3
Hi there! Thanks so much for the quick reply. I bought the bike last year. I tried cleaning the carb and did a rebuild on it due to not idling or starting. I got it started and rode it around for a bit until I blew the piston. I tried cleaning out all the debris but don’t know if I got all of it out. I just recently rebored the cylinder and replaced with new piston and clips. I kicked it over 2x and on the second kick the kick crank got stuck half way. I took the cylinder off to examine the piston. The piston is fine and so is the cylinder. I just twisted the magneto counter clockwise and the connecting rod stops going up and down / back and forth on the 2nd turn. I reversed it a couple turns clockwise and turned it counter clockwise again to move freely until it stops again... Seems like there’s more debris down there? The connecting rod with piston goes up and down but then stops. I haven’t opened up the right side where the kick crank is. I have to figure out how to open it due to rusty bolts. Do you think i have to split the case? Also if so. What should i be replacing? Seals and bear rings?Please let me know what you think. Thanks so much again!

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15 Feb 2020 15:05
RT325
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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK #4
Sorry, not much help from half a world away but in a similar situation i've turned my Ag100 upsidedown & put the water blaster up in there & spun it over. Only thing in my case it ended up with the left main bearing cage had broken & locking it up when turning by hand. I don't know--to prove a point take piston off then hook a stretchy cord to the conrod eye & up to the frame or something, then turn it over & when it locks then feel if its the rod or in the crank main bearings. Slight possibility its in the primary gears, or something come adrift in the magneto, but considering you melted a piston--'or did' piston break up?, think the problem is likely due to that. Can get bits of alloy into the bigend but wouldn't lock it solid from turning. Conrods with longways slots are more likely to get bits in there. With main bearing i can't see bits locking it solid. Funny story though, i had an RD200 twin [in a PE250 frame] & stopped motor after a ride & touched the starter & went 'Bump' & was solid. Turned out the right side main had broken the cage & one ball had rolled out as it stopped & rolled through the ballance hole & when i touched the starter the bigend came around & hit the ball stopping it turning. You couldn't plan things like that but they keep happening to me haha.
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15 Feb 2020 15:23
MR.MONTERO
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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK #5
Great hearing from you again! When I blew the piston it was pretty clean. Only a large piece blew off the edge of the piston. But maybe there was more pieces than I thought. Can I just blast water in where the conrod is to flush out the bits? Is it ok to put water in there? After that how do you dry it out? What are thoughts on the kick crank? I’ll open up the right side and send some pics.

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15 Feb 2020 17:30
johninga
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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK #6
I have a LT2 and a LT3. LT2 had a stripped spline where the kick lever goes on. The LT3 had a broken kick starter shaft. This is how I got them. It seems that Yamaha built the LT's with undersized kick start assembles.

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15 Feb 2020 17:33 15 Feb 2020 17:35 by RT325.
RT325
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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK #7
Yep i do all sorts of dodgy thing to save money. I had mine upended on the handlebars but not easy to do. The blasting or just a good garden hose up in the should get out what wants to come out but anything lodged in tight will stay. Could just try it the right way up & put the garden hose in & try to float stuff out the top as it overflows. after your done then fill it with diesel or kerosene, i used petrol, then grab the conrod & wiz it over a few time & see how it feels & might feel a little rough but not terribly. Then of course you have to empty it out somehow the best way you can. I have one of the plastic petrol siphoning things with a squeezy bulb on top & get down between the flywheels. Maybe cut the angled end off the plastic pipe as mine has, so you can get most of it out. Squirt some oil into the bearing feed holes & conrod & see how ya go. Got a feeling though that its probably not going to go to plan [or my plan anyway]. No-one's going to second my water idea [but its cost nothing] & doing it with bike upended it all falls out as you go but ok needs oiling up after.

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15 Feb 2020 21:42
MR.MONTERO
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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK #8
Ok. I just spent a couple hours cleaning out the debris. First I started with old premixed gas. I sloshed it around in the motor and poured it out maybe 7-8 times. I then rotated the magneto by hand and with a telescopic magnet I grabbed all the shavings that would come up. I then did your recommendation and turned the motor upside down and hosed it out. I then did the premix gas 5-6 more times and used the telescopic magnet to grab more pieces. To my surprise I found 3 big chunks that looked like it was from the previous piston rings! Soon after I took my air compressor and tuned the motor over and gave it a good hose down with pressurized air. I can now move the magneto and have the piston and conrod move freely! I hope this solves why my kick crank got stuck half way. Tomorrow I’m going to try the premix gas and pressurized air again to feel confident about removing all metal shavings. Keep you posted!

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15 Feb 2020 23:14
RT325
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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK #9
Wow you've been busy, so that's interesting as only steel will stick to a magnet [the rings] or the bigend & main bearing cage. Any piston aluminium could've washed out hopefully with what you've been doing. You can't do any more without dismantling. Does take a lot to stop a motor turning so be careful not to ruin your rebored cylinder & new piston kit. What part of the world are you in [NZ for me]. Actually thinking back, i assembled LT2's new in "72 at work lol. That's going back a few haircuts [when i had hair].

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21 Feb 2020 15:45
MR.MONTERO
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:: 1972 YAMAHA LT2 100 KICK CRANK STUCK #10
Hi there!
I too have the same problem. The spline where the kick crank goes on is stripped and rounder out. So the kick crank has nothing to bind to when I kick down. Do you know how to replace the spline? What is that part called? Any advice would be helpful. Thanks!

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