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Old 10-05-2010, 01:37 PM
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Default Yz490 mods


Does anyone out there know if the yz490 can be stroked? if so to what length, 3mil, 4mil, etc?? Trying to build a drag bike
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Old 03-20-2011, 09:40 AM
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Location: pa
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HI I purchased a 1990 YZ 490 i have a procircuit pipe and boysen reeds to put in it when i get the cylinder back from the machine shop but was wondering if anyone knew of someone in pa that could do the head mod for me or someone that I could send it to, to have it done.
Thank you
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Old 03-26-2011, 07:39 AM
Garrison's Avatar
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Location: michigan
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The same machine shop that's doing the jug I would think can do the head mod as well
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Old 05-05-2011, 01:51 PM
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Location: Oakley, CA
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I just recently bought a 1983 YZ 490 Roller. Also 1982 YZ 490 Frame, Shock, Swing Arm, Triple Clamps and Forks. 1982 YZ 490 Bottom End and a 1983 YZ 490 Top End.

I am going to be building a 1983 Broc Glover Replica YZ 490. (I might build a 1982 Hakan Carlqvist Replica with the 1982 YZ 490 later).

I used to own a 1987 Yamaha YZ490 back in 1990 and this is what I did to it.

Porting and Head Mod: Eric Gorr (this was the 2 best things I ever could of done to this bike). I was sponsored by DGY at the time. Eric Gorr did their motor work.

Note: I should of had him perform his Carb Slide Modification also but I didn't

2 Black Cylinder Fin Plugs on each side instead of just 1

FMF Pipe and Silencer

Noleen Revalved Rear Shock

Pro Circuit Modified Forks (Non-Cartridge)

Sidewinder Sprockets and Chain (1 Tooth More in the Rear then stock)

O'Neal Aluminum Handle Bars

I am going to pay more attention to detail this time around with my 1983 YZ 490 project, but if any of you out there want your YZ 490 to run like a champion then there is a nice run down that will get you there. The main thing is to have "ERIC GORR" Port your Cylinder and preform the Head Mod.
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Old 08-18-2011, 11:54 AM
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Location: Picture Butte, Alberta. Canada
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Is anyone still looking at this thread??
I'm looking for some info on 465's.. I recently picked a complete 465 motor up off Kijiji for a $100 bucks, and I wanted to put it in a Yamaha Warrior I have kick'n around..

I was wondering if I could use the head off a newer 490 on it, and make enuf torque to pull that heavy old quad around? Are the crank, and rod the same on a 465 as a 490?? I'm just look'n to run pump gas, and make around 50hp..

I was also look'n for some help to jet it when I'm done putting this thing together..
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Old 12-04-2011, 06:37 AM
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Location: Eastern NC
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just picked up a 87 490...awesome power but the vibration is a killer...anything to smooth this beast down some??

---------- Post added at 08:37 AM ---------- Previous post was at 08:37 AM ----------

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Old 12-04-2011, 04:35 PM
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Location: Maple Falls
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clean lookin 490 66!! one thing you can do is get rubber mounted handle bar clamps that will work and then thats about all you can do without putting it in another frame
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Old 04-22-2016, 07:45 AM
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Location: Texas
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My brother has a yz490 and I'm going to get his head modified at the machine shop at work, but he is worried that it will get damaged in the process because the head is not perfectly balanced. I purchased a spark plug mandrel to do the lathe operation, however he thinks it is risky. He was under the impression that the head should be held stationary by the mandrel while the tool did the cutting. So I want to hear from someone who has actually done this mod to find out if they used a lathe to spin the head at head rpm or if the head was held stationary while the tool did the work.

Please let me know! Thanks!
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