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Discussion Starter #1
I'm rebuilding my 954 engine, after taking the engine apart my mechanic showed me why i need another head, thats not a problem because i have a head on my low miles 929 with a crack case.
the thing is i need pistons i was going to buy them used on ebay, but after talking to people and my mechanic i was told to get them new.
Any way is their a big difference between OEM piston and aftermarket piston (like JE or weisco) other than price. I know that aftermarket has more compression 13:5:1 if i'm not mistaken. but i was also was told that aftermarket piston slap untill they heat up. Is that good or bad.
BOTTOM LINE, IS IT WORTH IT OR SHOULD I STAY WITH OEM????????
 

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I'm rebuilding my 954 engine, after taking the engine apart my mechanic showed me why i need another head, thats not a problem because i have a head on my low miles 929 with a crack case.
the thing is i need pistons i was going to buy them used on ebay, but after talking to people and my mechanic i was told to get them new.
Any way is their a big difference between OEM piston and aftermarket piston (like JE or weisco) other than price. I know that aftermarket has more compression 13:5:1 if i'm not mistaken. but i was also was told that aftermarket piston slap untill they heat up. Is that good or bad.
BOTTOM LINE, IS IT WORTH IT OR SHOULD I STAY WITH OEM????????
I wouldn't build the engine with used pistons unless they're in very new condition.
I can't imagine why aftermarket pistons would be more prone to slap if the engine has been built properly. Compression is only higher than stock if that's what you specifiy you want. I'd ask the aftermarket manufacturers to tell me the weights of their pistons complete with rings and pins to compare to the OEM items. The OEM pistons are very light already and aren't prone to failure so I'd go with them if others have no other advantages.
What is wrong with your pistons?
 

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Discussion Starter #3 (Edited)
This what happen Blade (let me make along story short), Somebody cut me off on my 929 i go down stator cover brakes and took peice of the case with it, insurance wrote the bike off and paid me. brought the bike back for $500, they didn't salvage it because of the year. Any way if i'm going to buy another engine might as well buy a bigger one 954. i found this [email protected]@ hole in brooklyn NY with one, i checked it out but didn't see the weld on the case behind the stator. I called the guy up he assured me the engine runs. (the engine did run), anyway i took it as a $700 dollar loss. I didn't want to buy another engine and not know what i might be getting, i figure might as well rebuild the engine and know what i have. due to the fact that i didn't feel comfortable riding with a crack case i brought one off ebay for like $250 buck. i had intentions of doing it myself but felt that i might be getting ahead of myself. so i took it to a shop that under cut my gears for my zx9 3 years ago. All he was suppose to do is swap everything from one case to the other. but when he took apart the engine he saw that whio ever put the engine together put the pistons in backward. if i'm not mistaken the bigger valve where hitting the smaller part of the piston and made a grove on the piston and the valve on the head was bent.
The oem is like $500 and the aftermarket are $750 (weisco),
So what do u think Blade?????????
Can u explain to me the compression, what difference doesit make.
and i would like to know are the cams on the 954 better than the 929
 

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Is there a difference between 929 cams and 954 cams?????
Yes, nominally about one-tenth of a mm more lift on the 954. Measure them before swapping though as minimum spec 954 and maximum spec 929 are pretty much the same.
 

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This what happen Blade (let me make along story short), Somebody cut me off on my 929 i go down stator cover brakes and took peice of the case with it, insurance wrote the bike off and paid me. brought the bike back for $500, they didn't salvage it because of the year. Any way if i'm going to buy another engine might as well buy a bigger one 954. i found this [email protected]@ hole in brooklyn NY with one, i checked it out but didn't see the weld on the case behind the stator. I called the guy up he assured me the engine runs. (the engine did run), anyway i took it as a $700 dollar loss. I didn't want to buy another engine and not know what i might be getting, i figure might as well rebuild the engine and know what i have. due to the fact that i didn't feel comfortable riding with a crack case i brought one off ebay for like $250 buck. i had intentions of doing it myself but felt that i might be getting ahead of myself. so i took it to a shop that under cut my gears for my zx9 3 years ago. All he was suppose to do is swap everything from one case to the other. but when he took apart the engine he saw that whio ever put the engine together put the pistons in backward. if i'm not mistaken the bigger valve where hitting the smaller part of the piston and made a grove on the piston and the valve on the head was bent.
The oem is like $500 and the aftermarket are $750 (weisco),
So what do u think Blade?????????
Can u explain to me the compression, what difference doesit make.
and i would like to know are the cams on the 954 better than the 929

I agree, if you're replacing the engine anyway then the 954 is the better choice, and probably easier to find as well.
Was the welded crack actually leaking?
For $250 do you mean you only bought the lower crankcase half? You need a good mechanic if you're only going to swap half the crankcase.
Bent valves do not require replacement of the head, just the valves usually.

Increasing the static compression ratio of the engine simply means that you are compressing the gas further before you ignite it. But compressing a gas causes heat which increases the risk of the gas reaching flashpoint and igniting early - detonation. So you need to run a higher octane fuel that has a higher detonation resistance. I recommend always running the highest quality fuel you can get anyway though.
 

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There is a gentleman here, (moregrip) that is parting his bike and if the motor is half as nice as the forks he sent me you should grab it. Can't say enough good things about him as there was a overcharge which I did not know about, and never would, that was refunded to my account. Low miles, and in excellent shape.
Bob
 

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I would guess that the difference between and aftermarket piston and a stock piston would be negligible. The higher compression will get you a slight increase in power, but you probably wouldn't actually feel it. Are you going to get the cylinders honed or bored out? If you are going for just a hone, then you can just use stock pistons and rings, and I wouldn't spend the extra cash on the aftermarket pistons. If you are going to bore the cylinders, then you are going to need to buy an over sized piston anyways, so then I would go for after market, and go for an over bore kit, in which you would increase your cc's by about 50cc's or more.
As for used vs. new, that is a gamble. I bought used JE over bore pistons on ebay for my 93 900RR. When I got them, they were in good shape except for one very small nick on the skirt on one piston. The first place I took the block and pistons to to get the block bored out wouldn't do it. He said that small nick could cause a failure under the high loads experienced in the engine. The second guy I took it to was a drag racer, had competed at Bonneville, and had been in the business for 30+ years, said it was no problem. 10000km later, and no problems (knock on wood). It is a risk though, and I knew that, but considering the price on the kit, I thought it was worth it. In the end, I still had to buy new rings and wrist pin clips from JE, so I didn't save that much over a new complete kit.
 
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