Gibbits YZ490A

[80-85 husky]

good news about the crank, big save for sure as long as the seals are good.

you should consider slipping new seals and mains in while its apart. not a lot of $$ for peace of mind. especially with a full sleeve job on the top end.

be a shame to seize it if a main seal poops out.

nice looking bike for sure

[smed]

It's a Wiseco

[sa63]

is this bike a pre 90 carryover model? or does it fall into pre 95?

[Gibbit]

Thanks fellers.  I wont worry about new mains but I will do the main seals while its apart.

I thought it was a wiseco.  What would people recommend? Going oem or wiseco piston for reliability (Im not after more power).

Yeah it will fall into the Pre 90 carryover model as they didn't even change the tank stickers from 1989.

[tony27]

OEM if you can find 1 on ebay, you can see for yourself why not to use wiseco if possible, standard piston kits are normally easiest to find

I think the marks in the head look more like casting flaws rather than cracks

[Gibbit]

OEM if you can find 1 on ebay, you can see for yourself why not to use wiseco if possible, standard piston kits are normally easiest to find

I think the marks in the head look more like casting flaws rather than cracks

Thanks Mate.  Ill go oem and get an order done from the US.

[Gibbit]

The 'Fatty' had a couple of cracks in it. I have plans to get a new one but not yet. I had a mate weld it up for me.




I had another mate clean the cylinder and head up a bit. Now I just have to wait for the piston to turn up so can send them off for a new sleeve and the infamous YZ490 head mod. I talked to Serco today. $650 for a new sleeve and the head mod. Expensive but it will be right for another 24years.

[80-85 husky]

whats the head mod in aid of? (excuse ignorance)

[Gibbit]

The YZ 490 where well known for being a bitch to jet correctly. They are either blubbering or pinging with very little in between.  With just a small machining to the head will make it much better and help with the detonation/pinging problem by changing the combustion flow.

[alexbrown64]

Hi Gibbit,
Good job on the 490.  Have you checked out Eric Gorr at Forward Motion http://eric-gorr.com/  See my YZ125K thread.  Eric Gorr has been doing cylinders for years and is has a fantastic rep.  I have sent him my cylinder, power valve and head.  He is soda blasting the lot, then resleeving the cylinder back to standard, then matching the power valve.  He ports the cylinder to the type of power you want and machines the head.  He then matches up a Wossner piston kit to suit.  $275 without piston kit, $100 extra with Wossner kit and they give 10% discount if your a VitalMX member.  I am getting mine posted to my American shipping forwarders as i will get a bunch of stuff sent back at the same time and the post works out heaps cheaper.  www.comgateway.com/
Cheers,
Alex

[80-85 husky]

also check out johhny o' thread on how to fix big bore pinging without the head mod... interesting reading. appears to be a totally different issue

[Gibbit]

Hi Gibbit,
Good job on the 490.  Have you checked out Eric Gorr at Forward Motion http://eric-gorr.com/  See my YZ125K thread.  Eric Gorr has been doing cylinders for years and is has a fantastic rep.  I have sent him my cylinder, power valve and head.  He is soda blasting the lot, then resleeving the cylinder back to standard, then matching the power valve.  He ports the cylinder to the type of power you want and machines the head.  He then matches up a Wossner piston kit to suit.  $275 without piston kit, $100 extra with Wossner kit and they give 10% discount if your a VitalMX member.  I am getting mine posted to my American shipping forwarders as i will get a bunch of stuff sent back at the same time and the post works out heaps cheaper.  www.comgateway.com/
Cheers,
Alex

The thought did cross my mind to send it to Eric but I want the bike going sooner rather than later, so I went locally. Serco have been around just as long as Forward Motion so they should know their stuff.

[Gibbit]

also check out johhny o' thread on how to fix big bore pinging without the head mod... interesting reading. appears to be a totally different issue

You got a link? I cant find it.

[Gibbit]

Seats done. Complete with gripper seat material in the center.

[Gibbit]

All back together again. Now it just needs some cosmetic work and new top and bottom shock bearings and she's ready.


http://youtu.be/sFCIjvoZNZs