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Discussion Starter · #1 ·
Finally got to really ride my 720 today and smoked alot of machines. Especially a stroked and big bore banshee. but i pulled in driveway squeezed the clutch in and clunk! so im guessing my rod is done. Whats after the 720 are the +8 cranks better than hotrods?
 

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Discussion Starter · #3 ·
I have to put it in gear and roll it backwards and it will only go about six inches. then if i hit the starter it cranks for a quarter second untill it goes CLUNK and stops. pertty sure its serious. to deppresed to tear it down. wating till after work tomorrow. I dont know how good HotRods warranty is. But im guessing i'll be stuck buying a whole crank.
 

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Discussion Starter · #4 ·
been trying to do some research for my next build and cant find alot of info about a 762 anybody out there run one? Or how drivable through the trails they are with still being reliable?
 

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The bigger you go the more reliability goes down. You can only get so much power out of a engine. When you start exceeding what the mfg designed the motor stuff can come up. Other wise 800 cc+ machines would be feesable for daily drivers.
 

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Maybe a 105mm bore, stock stroke with a three plugger. I know my 102mm is wild.
 

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Discussion Starter · #7 ·
I know im definatly hooked on the three plug head. I think id be happy with the 105 bore and my +4 crank if i can keep it on pump gas. if i could have 80 hp for 250-300 hours on it ill be satisfied.
 

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Sounds like you sheared the key way on the counter balancer. That is what happened to mine and was the way I bought it. When the key way shears the balancer just dangles and the crank hits it. If you weren't at a real High RPM then you might still be OK. Pull off the clutch cover and check it out. When the locking washer is re used then thats when it seems to do it. I use locktite a new lock washer and 2 spot welds so it don't happen to me again. I would try that before ripping her apart again and building more of a motor...
 

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Discussion Starter · #9 ·
Now that sounds like a great posibility. and it wasnt revved. it coasted into the driveway at about twenty pulled clutch in and literally CLUNK! Now i really cant wait till after work. I hope its somthing simple. I just looked at the trail tech and it only has three hours and one minute. if i have to rebuild im definitally not going to be so impatient on the break in
 

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Mine would only turn a little bit one way and wouldn't crank over at all. You might have got lucky. Did you say you have only 3 hours on your build? Mine put a dent in the rod so it wouldn't spin freely but would spin. If you do have to buy a new crank then you could get a barkers +6mil and run you piston and cylinder as I'm sure they are in great shape still. That would make it a 735 and the +6 need the offset piston like you have and would be able to use it still.

I didn't want to order a new lock washer last year one time and put it together and reused the old one. Had to take it apart a week later because my clutch was slipping and that nut was loose after just a few rides. Now I use a new one every time and Red locktite and bend both tabs.
 

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Discussion Starter · #11 ·
Well I started from the top and i think im a hair lean yet

Then on to the valves


And then i found the winner

I reused the lock tab and it failed
 

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Discussion Starter · #12 ·
Well the stupid lock tab washer was 3.46 and a whole ten dollors for shipping. Damn yamaha dealers. Wish there was a whole dealer on ebay.
 

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Discussion Starter · #15 ·
wow! that crank twisted pertty good. im feeling lucky my motor turns over real good and no shavings and i cant see any bends or twists.
 

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Didn't twist. The counter balance came loose and smacked the base of the rod locking up the bearing.
 

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Discussion Starter · #17 ·
ha. i cant belive i didnt catch the rest of your crank floating from the rod. ya thats locked up good
 

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Discussion Starter · #19 ·
No. i forgot actually. i found the keyway just laying in there. it was unscathed. i think the deceleration of squeezing the clutch in was just enough for it to slide out and stop everything. in fact the nut and washer were laying on the shifter drum.
 
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