cylinder and compression questions

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93750

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Im gonna be picking up a used cylinder and piston to fix one of mine that got scored.. my first question is.. are the cylinders the same on all the 750s? mine is a 93 and im just wondering if one off a 92 or 94 will work? i know they did some changes to the motor from 92 to 93 just not exactly sure what!... My next question is i have about 100-105 psi compression on the other 3 cylinders and my cocern is that if i put a used cylinder and piston and re ring that used piston that it will be higher than the other 3 since its got a new ring on it! Is this anything to be worried about or should i just put new rings on the other 3 while im at it? Or just not worry bout it?
 

Well..new rings across the board never hurt...but...what kind of comp gauge are you using? often long hose style ones, will read low..i got 70lbs on my freshly rebuilt vmax, using a cheap gauge..barrowed a friends snap on, and got a good reading then..

also, i could be wrong..but i believe there were port timming changes between the 92, and the 93/94 cylinders...93-94 are the same, but i believe 92`s are diferant...may want to get a 93 or 94 cylinder..

also on the comp thing..did you hold the throttle wide open? was the motor warm? cold?..how many pulls to get that 105 reading?
 
alright thanks! im not sure on the brand i borrowed it from a guy i work with but it did have a fairly long hose on it! maybe ill try and borrow a different one and see what i come up with. When i did the testing i never touched the throttle.. would opening the throttle make a difference? and the motor was cold. Is 105 a ok if it is accurate? seems a bit low to me but could be wrong!... Alright thanks for the info on the cylinders.. i was thinking the same thing but i wanted some other peoples opinions that know these sleds a little better!
 
well, if a 105 was the actuall correct reading, yeah that`d be low to the point of needing new rings...but it may still get ya through the winter...(keep spare plugs with ya)..
but what i`m thinking, is all 3 reading about the same, is probley a good sign...
and yeah, defiantly try it again with the flipper pegged to the bars...

how many pulls did it take to get that 105lb reading??
 
I was pulling it over pry 4-5 times to get reading.. still trying to track down another gauge to try.. but for right now im trying to find a used cylinder.. there is one in mich at a salvage yard but he is not sure what year it came off of.. he thinks a 93 but he also thinks that all the 750s used the same cylinders.. but the one he has has a different stamping number on the side.. is this a way to tell for sure which one i can use.. mine are stamped 8AXOO.. and the one he had was like 89A something or another.. im guessing i want one with the same stamping on the side! Am i right?
 
89A is a 92 cylinder. You want an 8AX cylinder the porting was changed in 93 (Like AL already posted).

In most cases consistent readings are what you are after, gauges will vary.

If it were me I'd probably change all the rings while I had it apart, unless it's a low mileage motor. How many miles are on the motor?

Ken
 
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Alright thanks for the help i figured thats what i needed.. are 94s the same?... there are about 4500 miles on the sled to my knowledge... that what the gauges say anyway! This is the second year that ive had it! Thanks for the help both of ya! now i just gotta track down a cylinder!
 
Could a person use a full set of four '92 cylinders on a '94 bottom end? What pistons should be used, would '93/'94 pistons work? I assume the '94 heads, carbs, and pipes would be fine with this setup.
 
If you use 92 jugs you will loose some HP with the porting, 93 and 94 pistons have a window in the piston and the 92's dont.
 
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