HELP!! what grade and amount of fork oil should I use in my 43mm YZ490 front forks?

HELP!! what grade and amount of fork oil should I use in my 43mm YZ490 front forks? to get the best performance from them.

They are fitted on a Yamaha TT500

Thanks.

Try ATF (about 7 wt) or 5 wt fork oil. I used both when I raced a 1982 yz490

on a TT500, you may want to try something heavier. maybe some Showa SS10?

Start with five inches from to top(no springs, fully compressed) and tune from there.

On that note, what springs are they? stock forks(for a YZ490)? what year? Have you considered Race Tech Emulators?

Try ATF (about 7 wt) or 5 wt fork oil. I used both when I raced a 1982 yz490

Thanks for that:thumbsup:

on a TT500, you may want to try something heavier. maybe some Showa SS10?

Start with five inches from to top(no springs, fully compressed) and tune from there.

On that note, what springs are they? stock forks(for a YZ490)? what year? Have you considered Race Tech Emulators?

Hi 500xc, yeah thought I better mention that it was a TT500 (bit heavier then the 1982 YZ490 that the forks came off) and the springs are stock. Sorry but I'm having a bit of a blonde moment is this what you mean? Do I remove the springs and then push the inner tubes down until they hit the bottom of the outter tubes and then fill the forks with oil 5 inches from the top. Then extend the outter tubes back out again reinsert the springs and reassemble the forks???

Do you know where I can get just the emulators with out buying the kits???

Thanks man:ride:

Hi 500xc, yeah thought I better mention that it was a TT500 (bit heavier then the 1982 YZ490 that the forks came off) and the springs are stock. Sorry but I'm having a bit of a blonde moment is this what you mean? Do I remove the springs and then push the inner tubes down until they hit the bottom of the outter tubes and then fill the forks with oil 5 inches from the top. Then extend the outter tubes back out again reinsert the springs and reassemble the forks???

Do you know where I can get just the emulators with out buying the kits???

Thanks man:ride:

Yes, that's what I meant. I also run the forks thru the stroke a couple times before I measure the oil height. Better to ask than to be sorry later!

You might want to invest in heavier springs, as the bike is a good 40 lbs heavier than even the worst YZ490. Depending on your weight, you might even want to go the custom Cannon springs route.

I haven't the foggiest clue, I personally don't run them because I'm that oddball that KTM used to make suspension for (hello midstroke harshness!:bonk:)

Yes, that's what I meant. I also run the forks thru the stroke a couple times before I measure the oil height. Better to ask than to be sorry later!

You might want to invest in heavier springs, as the bike is a good 40 lbs heavier than even the worst YZ490. Depending on your weight, you might even want to go the custom Cannon springs route.

I haven't the foggiest clue, I personally don't run them because I'm that oddball that KTM used to make suspension for (hello midstroke harshness!:bonk:)

Im 6.1 @ 221 pounds

What do you reckon about these springs Eibach Moto-Springs, fork Springs Kit (adjustable) The springs are 19-3/8 inches long; 1-3/8 inches diameter.Distributed by White Bros. Part No. 32-431; Elbach Part No. 998.043.1 Rate: 21 to 26 lbs/in, (0.38 to 0.46 kg/mm).

Cheers:ride:

A picture of the beast!

I'm completely rebuilding it.

DSCN4433.jpg

That's a purty HL replica!

Those springs seem awful light, as I'm currently running them on a 81 PE250!

I'm 6'5, 180, and they seem about perfect for me.

How did the bike act before?

Those are progressive rate springs, better for off road/trail riding. You can get up to .52 for the 43mm from Race Tech.

That's a purty HL replica!

Those springs seem awful light, as I'm currently running them on a 81 PE250!

I'm 6'5, 180, and they seem about perfect for me.

How did the bike act before?

No those are some springs that I could have purchased, lucky I didn't. I just pulled my forks to bits an low and behold there were some nice big babies already in there, at first I just assumed they were stock, sweet! I have gone with 15w oil instead of the 10w that was used before.

Sorry 500XC thats no atempt at trying to build a HL replica. I'm into rebuilding original stuff. Its a 1981 yamaha TT500H matching numbers etc etc that I am currently rebuilding with some enhanced suspension bits. The engine has had some adjustments made to it aswell.

Will post pictures when I have finished

:bonk:

Those are progressive rate springs, better for off road/trail riding. You can get up to .52 for the 43mm from Race Tech.

Thanks SMarquez!!:bonk:

No those are some springs that I could have purchased, lucky I didn't. I just pulled my forks to bits an low and behold there were some nice big babies already in there, at first I just assumed they were stock, sweet! I have gone with 15w oil instead of the 10w that was used before.

Sorry 500XC thats no atempt at trying to build a HL replica. I'm into rebuilding original stuff. Its a 1981 yamaha TT500H matching numbers etc etc that I am currently rebuilding with some enhanced suspension bits. The engine has had some adjustments made to it aswell.

Will post pictures when I have finished

:bonk:

Woo, that's still pretty sweet, and a purty bike!

I'd almost be afraid to ride it, so kudos to you.

I'm used to seeing XTs and TTs built into HLs, and my buddy's uncle even has a restored one!

Any explanation on what "adjustments" the engine's received? Buddy who's uncle owns the HL has an 78 XT500 with a spare motor he's planning on hopping up a bit. What he plans after that, I have no clue:banghead:

Woo, that's still pretty sweet, and a purty bike!

I'd almost be afraid to ride it, so kudos to you.

I'm used to seeing XTs and TTs built into HLs, and my buddy's uncle even has a restored one!

Any explanation on what "adjustments" the engine's received? Buddy who's uncle owns the HL has an 78 XT500 with a spare motor he's planning on hopping up a bit. What he plans after that, I have no clue:banghead:

I didn't go for the 90mm big bore I keep it standard as the bore was in excellent condition but it has a Wisco 87mm 12:1 piston in there for good measure.

At some stage someone had put a early model tt500 head on it with the smaller intake valve and cooling fin's. I got rid of that head and went for the bigger valve and fin version that should have been on it in the first place. The intake port has been polished and a Megacycle cam (251-30) thrown into the mix. Megacycle heavy duty R/D valve spring kit with aluminium tops has been used along with new cam feeding oil hole rockers. The rocker adjusters are swival top. Each rocker has a oil line feeding them. Went for longer lasting valve seals and not the standard ones you buy in the gasket kits or from Yamaha. Copper head gasket of course, I think thats it for the Head??

Put some nice high speed C3/CS? bearings onto the crank and replaced every other bearing that needed to be replace. All oil seals were replaced.

Carby is a single cable round slide mikuni 38mm that has been bored out to 39mm. Carby has a angled long K&N filter as well as a extended oil breather line comming of the left crankcase with a K&N filter on top of that.

Thats about it for the engine!:bonk:

seehogs stole my advice, had the best of luck with GM trans fluid, in my 79 Kawa KDX 175

I didn't go for the 90mm big bore I keep it standard as the bore was in excellent condition but it has a Wisco 87mm 12:1 piston in there for good measure.

At some stage someone had put a early model tt500 head on it with the smaller intake valve and cooling fin's. I got rid of that head and went for the bigger valve and fin version that should have been on it in the first place. The intake port has been polished and a Megacycle cam (251-30) thrown into the mix. Megacycle heavy duty R/D valve spring kit with aluminium tops has been used along with new cam feeding oil hole rockers. The rocker adjusters are swival top. Each rocker has a oil line feeding them. Went for longer lasting valve seals and not the standard ones you buy in the gasket kits or from Yamaha. Copper head gasket of course, I think thats it for the Head??

Put some nice high speed C3/CS? bearings onto the crank and replaced every other bearing that needed to be replace. All oil seals were replaced.

Carby is a single cable round slide mikuni 38mm that has been bored out to 39mm. Carby has a angled long K&N filter as well as a extended oil breather line comming of the left crankcase with a K&N filter on top of that.

Thats about it for the engine!:lol:

There's only one acceptable reply to an engine that tasty.

drool.gif:ride:

I wonder if I can use the same oil feed mod on a DR500 to keep it from eating valves... :smirk:

There's only one acceptable reply to an engine that tasty.

drool.gif:lol:

I wonder if I can use the same oil feed mod on a DR500 to keep it from eating valves... :ride:

I,m not to sure?? got me on that one.:smirk:

Just finished rebuiding my engine, will put some pic;s up soon.

I guess you already have the forks done, so I am a lil late, but I have a 1985 YZ 490 with the Simons upgrades and I put 15wt in at 200mm height. I also have 4 inches of spacers between the fork springs and the air bleed valve. Im only 5-6, 160, but they worked great during the race at Hardrock last weekend. I would think with your size, you could raise the height a lil bit and it would work better, especially on a 500.

I guess you already have the forks done, so I am a lil late, but I have a 1985 YZ 490 with the Simons upgrades and I put 15wt in at 200mm height. I also have 4 inches of spacers between the fork springs and the air bleed valve. Im only 5-6, 160, but they worked great during the race at Hardrock last weekend. I would think with your size, you could raise the height a lil bit and it would work better, especially on a 500.

Hi, got 15wt at a height of about 120mm (springs out inner tubes compressed) and 85mm spacers. havn't tried them yet as I havn't finished rebuilding the bike.

Cheers:thumbsup:

A bit late with this but at 120mm you'll be close to hydraulic lock (seal blower). 15W will be a bit on the heavy side without blowoff valving, it will feel good until the suspension has to move at high speed.

On my XR the spring displaces 114mm of oil height in a 37mm fork.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now