(ENGINE) counter weight question

 
 
 
 
Old 04-05-06, 12:43 PM
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(ENGINE) counter weight question

is there any diff from a 85 12a and a 82 12a? i went to put my clutch on that was on my 82 12a on to the 85 and the flywheel is way diff so i need to change flywheels...do i need to change anything else? or am i ok
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Old 04-05-06, 12:48 PM
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The 82 12As had heavier rotors and smaller cluch discs. I do believe you need to keep them matched.

Mazdatrix or RB, forget which one, has a flywheel and counter weight section. You might get a more definitive answer ther.
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Old 04-05-06, 12:54 PM
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if the ideal 12-A engine is 83.5-85 rotors (lightest rotors) and 81-82 flywheel (lightest stock flywheel = 23 lbs roughly), then you should do fine.
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Old 04-05-06, 12:55 PM
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err that kinda sucks....my stage2 clutch masters is going to do me no good if i cant use that flywheel
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Old 04-05-06, 01:00 PM
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so thats 1 vote for its ok and 1 vote for its not..................damn
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Old 04-05-06, 03:52 PM
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counterweight should match rotors.
get a lightweight flywheel and find a 79-82 weight.
make sure it is a 225mm flywheel and you will be able to keep your clutch.
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Old 04-05-06, 05:11 PM
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Originally Posted by Midwest 7's
counterweight should match rotors.
get a lightweight flywheel and find a 79-82 weight.
make sure it is a 225mm flywheel and you will be able to keep your clutch.
^^ What he said.
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Old 04-05-06, 10:35 PM
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Technically, the 82 flywheel won't balance perfectly on your 85 engine but you can get away with it. You will get a very minor vibration around 1700 rpm and then it goes away pretty quickly as the engine revs and you won't get it again until about 7200-7300rpm and then again it goes away pretty quickly as the revs climb. I ran one this way for several years. Lots of IT racers ran the same setup years ago.
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Old 04-05-06, 10:42 PM
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^^^^ woot this makes me
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Old 04-05-06, 10:45 PM
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Originally Posted by RX3SP
Technically, the 82 flywheel won't balance perfectly on your 85 engine but you can get away with it. You will get a very minor vibration around 1700 rpm and then it goes away pretty quickly as the engine revs and you won't get it again until about 7200-7300rpm and then again it goes away pretty quickly as the revs climb. I ran one this way for several years. Lots of IT racers ran the same setup years ago.
i would still advise against it.
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Old 04-05-06, 10:49 PM
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lol yeah i know and i know better than to run it.....but its in the car as of right now..ive not started it yet like that errr i dont feel like droping the trans so soon
if it can be run like this with out blowing up than i will run it like this for a few weeks till i get the money to get a diff clutch
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Old 04-05-06, 11:06 PM
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^^ diff flywheel.
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Old 04-05-06, 11:10 PM
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noi have the 85 flywheel but the clutch is no good. and my 82 motor is no good but had a stage 2 clutch masters in it...so i have good motor bad clutch and bad motor and good clutch
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Old 04-05-06, 11:17 PM
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You'll be fine with it, especially for just a few weeks. Who knows, you might just decide you like it and run it for a few years like me! Actually, I did that combo on two engines. One was a J-spec 6 port 12a and the other was an 85 us spec 4 port 12a.
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Old 04-06-06, 12:30 AM
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Originally Posted by RX3SP
You'll be fine with it, especially for just a few weeks. Who knows, you might just decide you like it and run it for a few years like me! Actually, I did that combo on two engines. One was a J-spec 6 port 12a and the other was an 85 us spec 4 port 12a.
Did you pull any of these engines down? Any abnormal wear?
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Old 04-06-06, 12:54 AM
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The vibration will cause accelerated wear on the bearings, all 4 of them. At high rpms, as the bearings wear, there will be more movement and flex in the e-shaft. Damage will increase and include chatter marks on the housings and eventually munched apex grooves on the rotors and worse than average wear of the irons.

I understand the desire to use good, on hand parts and save money by not having to replace them. What it comes down to is spend a little now, or a lot more later, your choice.
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Old 04-06-06, 02:16 AM
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Your best options:

- get a 225mm clutch, use 85 flywheel

- get an aftermarket lightweight 215mm flywheel w/ 85 counterweight and use current clutch
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Old 04-06-06, 07:04 AM
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what damages. When I first bought my ITA RX-3, it came with 23 lbs flwywheel and 85 rotors. Transferred it to another bro's FB and he ran it hard with an IDA until he decided to go with a 13-B streetport. I got the motor back and there arent damages internally.
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Old 04-06-06, 02:47 PM
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I didn't note any abnormal wear in either of the 84-85 engines that I ran the 81-82 flywheel either. I know plenty of IT racers that used the same combo with no noticeable increased wear or failure.
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