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Old 06-19-2012, 06:35 AM   #1
mudmantra OP
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Fixing the 1980 yz465

I just picked up a YZ465 and intend to set it up for trail riding. Yes I know the IT465/490, it better for trail use. But I like the way the YZ465 looks and it's what I have. Step 1 is to just get the YZ465 running. I kicked it over a few times and the compression ratio, seems to be real high. I wonder if the IT465 compression ratio is lower? I found the compression ratio for the IT465 at 7.1:1. But I don't know the YZ465 compression ratio. Any idea's on how to set this machine up better for woods riding?
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Old 06-20-2012, 07:17 AM   #2
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Why don't you get it running first and then see if you want to live with a 30+ year old big bore MX bike. If the bike isn't "mint" you can figure on dropping some big $ to get it to the point ridable as a trail bike. My 465G model runs well in the woods but it's a bit of work to enjoy the ride.
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Old 06-20-2012, 06:08 PM   #3
mudmantra OP
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Originally Posted by wfopete View Post
Why don't you get it running first and then see if you want to live with a 30+ year old big bore MX bike. If the bike isn't "mint" you can figure on dropping some big $ to get it to the point ridable as a trail bike. My 465G model runs well in the woods but it's a bit of work to enjoy the ride.
Thanks. I figured out how to start it and got it running. The compression is pretty high, and kicking it over is a bit tricky. At first the carburetor was flooding, but it's not now. I still need to fix a lot more. I took a ride up in the woods. It was a blast, I can't wait to fix a few things and ride it again. I'm still looking for idea's to make it even more trail ready.
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Old 06-21-2012, 06:13 AM   #4
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A few idea's I've been thinking about. #1 is the crankshaft heavier in the IT465 motor? The crankshaft in the IT490 looks a lot heavier, but I can't tell with the IT465. #2 has anyone here installed a crankshaft from an IT465/490, and did it work? If I could just slow the power band hit a little, I think it would help a lot. Right now when it hits, it's instant wheel spinning, fun, but not very useful. Any other idea's on how to smooth out the power band would be good too.
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Old 06-21-2012, 07:34 AM   #5
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Re cc the head or add a couple gaskets to lower the comp , a flywheel weight, go up a tooth on fr sprocket and or go down a bunch on the back is going to be the cheapest route to tame the horsepower. If theres a porting speciallist in your area you could have them take a shot at getting a smoother powercurve out of it but it ain't cheap. In any case the bike is to old to start throwing money at so just ride it and if you want a real woodsbike save up and get the real thing. There are people looking for vintage bikes to race in special classes and you may be able to make some money on it if its in any kind of original condition yet.
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Old 06-21-2012, 08:00 PM   #6
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Thanks for the advice. I really like the bike, so I'll ride it even if it just stays the way it is. If I can improve the low end power and smooth out the hit a mid-range, that would be even better. I've checked a few tips on improving the head design, that appears to also slightly lower the compression ratio. Plus this mod should make jetting the bike easier. I'll check into the flywheel weights also.
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Old 06-23-2012, 06:10 AM   #7
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I checked into flywheels and the magneto flywheel on the IT465 has the exact same part number. And by that I guess it has the exact same weight. The crankshaft is another story. The IT465 crankshaft looks a lot heavier, and the IT490 crankshaft looks even heavier yet. The YZ465 crankshaft looks to be the same size, But it has more and larger hole machined out of it, to reduce weight. The motor runs now, so I'm not going to pull it apart just to change the crankshaft. Might be something to try on my spare YZ490 motor though.
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Old 06-24-2012, 07:39 PM   #8
Kevin K
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Have Eric Gorr port the cylinder for your style of riding. He can also fix the head to keep the motor from detonating.
His prices are very reasonable.His porting will cost less than a IT crank.
You may want to try the ignition coil from Black Ops Moto .It really cranks out a big blue arc to help the motor pull right off the bottom. With it and one or 2 more teeth on the counter shaft I can't see you needing more than that
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Old 06-25-2012, 06:20 AM   #9
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Have Eric Gorr port the cylinder for your style of riding. He can also fix the head to keep the motor from detonating.
His prices are very reasonable.His porting will cost less than a IT crank.
You may want to try the ignition coil from Black Ops Moto .It really cranks out a big blue arc to help the motor pull right off the bottom. With it and one or 2 more teeth on the counter shaft I can't see you needing more than that
Thanks I'll check into the porting work and cylinder head mods by Eric Gorr. I know the YZ490 really responds well to the cylinder head mod. Dose it also help the YZ465? I'm forced to run pump gas, so I'm thinking about the Cylinder head mod also. Just unclear if it's the thing to do on the YZ465. Gearing, I was thinking on gearing it down a little to reduce 1st gear speed a bit. I know gearing it up would reduce the tire spin, but I'd like to reduce my contact speed with the trees.
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Old 06-27-2012, 06:23 AM   #10
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I took the bike up in the woods for some more riding. It now seems to me, that a real improvement would be to get the low speed jetting and mid range jetting spot on. It seems that the stock jetting might be on the rich side. Sounds like it may be a good idea to look at the reeds too. I could get a set of Boyesen reeds for a low enough cost. I wonder if they would be an improvement. VFORCE reeds would be more, but still not to expensive. Yes, it's not a woods bike, but I had a lot of fun anyway.
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Old 06-27-2012, 06:52 PM   #11
anotherguy
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Getting the jetting spot on was the best thing I did for my '80 465. It now pulls clean from idle to where it signs off.
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Old 06-27-2012, 09:55 PM   #12
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Getting the jetting spot on was the best thing I did for my '80 465. It now pulls clean from idle to where it signs off.
Cool. Any details on the jetting that worked for you? I've been collecting info on jetting the YZ465. So far most install a slightly smaller pilot jet, main jet and modify the slide cutaway to 3.5. Each one, I've checked use's a different needle jet, at different clip positions. I also I think slightly different carburetors are in use. One is the Stock 38mm round slide and the other is a replacement Mikuni 38mm round slide. I don't know how different they are?
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Old 06-28-2012, 05:51 AM   #13
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45 pilot/40 if really hot out,1 to 2 turns on mixture screw(yeah it's that finicky,or is it me?),stock slide,Q-0 needle jet,6F8 needle,400 main. I run a DG National pipe and a Uni filter in the stock airbox. I ride from 500 to 2000 feet above sea level.

That's for premium E10 pump gas,I fatten the needle up a click or two and raise the main for VP U 4.4 race fuel. It isn't cheap but the bike runs so much better and consistent with it the money is of little concern.
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Old 06-28-2012, 09:36 PM   #14
mudmantra OP
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Originally Posted by anotherguy View Post
45 pilot/40 if really hot out,1 to 2 turns on mixture screw(yeah it's that finicky,or is it me?),stock slide,Q-0 needle jet,6F8 needle,400 main. I run a DG National pipe and a Uni filter in the stock airbox. I ride from 500 to 2000 feet above sea level.

That's for premium E10 pump gas,I fatten the needle up a click or two and raise the main for VP U 4.4 race fuel. It isn't cheap but the bike runs so much better and consistent with it the money is of little concern.
Thanks. That gives me another look at the jetting for these machines. I ordered a float valve and gasket for the carburetor. I'll clean it and check all the jets. Who know's whats in it now. The first time I ran the motor, the carburetor was over flowing. I shut the gas off and started the motor. I then rode it almost 1/4 mile before it ran out of gas in the carburetor. I turned the gas on, and it hasn't overflowed since. I'm thinking it might be a good idea to pull it apart and take a look soon.
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Old 06-29-2012, 05:28 AM   #15
mudmantra OP
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Quote:
Originally Posted by anotherguy View Post
45 pilot/40 if really hot out,1 to 2 turns on mixture screw(yeah it's that finicky,or is it me?),stock slide,Q-0 needle jet,6F8 needle,400 main. I run a DG National pipe and a Uni filter in the stock airbox. I ride from 500 to 2000 feet above sea level.

That's for premium E10 pump gas,I fatten the needle up a click or two and raise the main for VP U 4.4 race fuel. It isn't cheap but the bike runs so much better and consistent with it the money is of little concern.
Also, I forgot to ask. Are you using the stock YZ465 carburetor? I'm thinking it might be a good idea for me to replace the needle jet and needle on my 1980 YZ465 carburetor.
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