motor turns over half turn and stops dead

YA*AM*A*HEAD

YA*AM*A*HEAD

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went to a friends house to ride tonight .he has a 99 vmax 600 with 8000 miles ..started his sled and it sounded like it was running on 2 cylinders and after 200 feet it just died ....went to pull the rope and it was locked up tight ...pulled him home and pulled the plugs and motor turned about 3/4 away around and stopped dead like it was catching a ring on the exhaust port ....i was thinking it was the recoil broke and causing this ....so he pulled it a few times and it started to turn over with no problem .except for a little metal to metal rubbing sound ...turned it by hand several times and cleared up and sounded normal ...so we put new plugs in it and it started up ...running on 2 cylinders again ....while running we pulled plugs and found it to be the mag side cylinder ....i am thinking it is either the recoil has come apart causing it to jamb up ...or he cooked the cylinder cause i belive the float on that carb is stuck closed causing it not to get any oil ? carbs were just cleaned a week ago and ran perfect after we cleaned ..also this is a electric start sled but the battery was shot causing the tach not to register til you got it up to 3000 to 4000 rpms ...would a dead battery cause it to olny run on 2 cyilnders ? any suggestion would you might have would be great
 
broke a ring possibly and was fetched up on that, then might have fell in the exhaust port causing it to free up. do a compression test
 
compression test in deed is in order here,,this don't sound good,don;t run it
anymore,you may have big problems...
 
well we tested compression 120 across the board .....i was right the float was stuck ......and i mean stuck couldnt pull it out by hand had to use pliers ....i have never seen one stuck that bad ....so we cleaned it good again and reassembled ...and started the sled and it ran perfect again ....he wanted to add oil to the gas tank but i talked him out if it ...i know i read adding oil to the tank will actually lean it out ...can someone explain that to me again so i can explain it to him ...i tryied to explain that the oil is mixed in the fuel pump so that piston got hot and expanded causing it to lock up and when it cooled it shrank back ...that he might have scord that cylinder cause no oil and that might have been the metal to metal griding we herd ....does that sound about right ?
 
good to hear all's not lost,got worried when you said "metal to metal rubbing sound"..lol

the more oil you put in(through) your sled the less gass there is thus lean..gas and oil are mixed in the fuel pump then sent to each carb.
 
ok i think i figured out a way to explain it to him ....the sled requires 1 part gas and 1 part oil 1 part air ...it pumps gas pure part 1 ....and oil pumps 1 part pure oil ....to make a perfect mix .......if you add 1/2 part oil in the tank ..when it pumps from the tank it is olny getting 1/2 part gas and 1/2 part oil ....plus the 1 part oil from pump ...so that adds up to 1 1/2 parts oil and olny 1/2 part of gas....there for being lean...cause the carbs let in 1 part air for the 1/2 part gas it is really getting instead of the 1 to 1 but rich on oil ....does that make any sence to you ?
 
YA*AM*A*HEAD said:
ok i think i figured out a way to explain it to him ....the sled requires 1 part gas and 1 part oil 1 part air ...it pumps gas pure part 1 ....and oil pumps 1 part pure oil ....to make a perfect mix .......if you add 1/2 part oil in the tank ..when it pumps from the tank it is olny getting 1/2 part gas and 1/2 part oil ....plus the 1 part oil from pump ...so that adds up to 1 1/2 parts oil and olny 1/2 part of gas....there for being lean...cause the carbs let in 1 part air for the 1/2 part gas it is really getting instead of the 1 to 1 but rich on oil ....does that make any sence to you ?
Click to expand...
Ahhhh yea.......lol
 
ya i know it sounds crazy ...ill tell him and let him make the decision weather or not to add oil .....my guess is he did as soon as i left .....
 
yamaha pumps provide plenty of oil..but if he's unsure of the opreation
of the pump he could put a splash in and watch the bottle go down..just
for precaution measures..
 
If he locked it up from the piston with no oil, it cant look good on the inside?
I bet that the piston will seize from the metal it tore loose with-out the oil lubrication
 
any chance a piston skirt broke off & is locking up the crank when trying to turn?? i have seen it but the engine was already apart & not running at the time just turning the clutch??sorry if this was already asked but i didnt read the whold thread
 
we got it running ....no sign of damage ..and he ran the piss out of it ...and ran like a top .....guess we need to look and make sure the skirt didnt break and go through the exhaust port and sitting in the expansion chamber ....i hate to say it but i know him good enough that he probaly wont look into it ...just run it like it is ....me on the other hand i would have opened it as soon as i got home .....i am guessing it will blow before the season is over ....he thinks it was a fluke and all will be ok ...guess we will see :dunno:
 
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