Boring the kx500

[Tim short]

I was just curious about other member that have bored their kx500

How much and did you have to do any mods to the head ?

I am forced to over bore because of slight cylinder damage i was thinking a .20 or .40 over ? thought?

thanks

[Foxx4Beaver]

I believe once you get to 88mm on the bore, you need to modify the head, but don't hold me on that. I'm at 88.5mm(535cc), and I believe I was told once you get to 88mm it needs to be done....but I also needed to have my center exhaust valve modified to accept the larger bore, as will at 88mm, otherwise catastrophe would result.
If you're really serious about going that much bigger...I strongly suggest Todd Pinnsonault...he did mine, and he's done several other members as well.

you can contact him here....
http://www.kxriders.com/forums/index.php?action=profile;u=1767
http://www.kxriders.com/forums/index.php/topic,10028.0.html    

[Foxx4Beaver]

another thing to consider if it's in your budget....is having the crank balanced/trued...this really makes a huge difference when you start going bigger on the bore size, because these things will vibrate themselves to death, and put your arms to sleep otherwise!...and Pinnsonault can and will do that too....worth every cent if you can afford it!!

[Motorrad]

91mm bore on my bike.

[sugilite]

I "sleeved" mine out to about 530cc and really regretted it. It never made as much power as the standard one and noticibly loses power as it gets hot. I'm putting mine back to standard as a result - worth the extra expense of getting a cylinder re-plated in my opinion.

[umberto]

My bike is at 88 mm, which was done when Millennium Technologies re-sleeved my cylinder.  They put in a LA sleeve and then bored it to 88 mm to fit the Wossner piston I already had.  I purchased my running 1988 engine off eBay, and it came with a cylinder that was sleeved with a 1989 and up sleeve and had no KIPS valves at all.  I purchased another head with KIPS valves and it was already sleeved and bored to 88 mm, but it was worn out.  I only rode the stock bore 1988/1989 sleeve head a little bit before redoing he engine, and I don't remember a ton of difference in vibration between the stock bore head and the 88 mm head.  My bottom end was done when I bought the motor off eBay, and it looks to be welded and balanced, so I may not be the best person to comment on vibration.  When the carb is set up correctly, it really rips. 

[ninja]

... worth the extra expense of getting a cylinder re-plated in my opinion. 8>)

Yup, stock bore & re-plate recently on the last conventional fork '89 

[Foxx4Beaver]

I "sleeved" mine out to about 530cc and really regretted it. It never made as much power as the standard one and noticibly loses power as it gets hot. I'm putting mine back to standard as a result - worth the extra expense of getting a cylinder re-plated in my opinion.

who did the work?
mine's not sleeved...and makes considerably more power than the standard squared motor, with the way I had Pinnsonault set it up.

[sandblaster]

91mm bore on my bike.

Mmmmmm.... Special 

[Tim short]

Thanks for the responses
do i need to do anything to the head if i put a 87mm piston in ?

[Foxx4Beaver]

Thanks for the responses
do i need to do anything to the head if i put a 87mm piston in ?

you're good....once you get to 88mm, then the head needs to be modified.

[Motorrad]

91mm bore on my bike.

Mmmmmm.... Special 

But it's just stock... Just ask all the guys I raced this weekend.... That's what I told them....  Muahahaha

[Tim short]

Okay cool thanks for the reply i guess ill get an 87 then, this project seems like it will be lengthy, i just painted the frame and am ordering the piston, then ill send it out to get bored, then i will have to figure out my power valve crisis and the lacking front brake, But by the time its done it should ride really nice and ill have a piece of mind knowing everything thats needed fixing has gotten it.

[Foxx4Beaver]

Okay cool thanks for the reply i guess ill get an 87 then, this project seems like it will be lengthy, i just painted the frame and am ordering the piston, then ill send it out to get bored, then i will have to figure out my power valve crisis and the lacking front brake, But by the time its done it should ride really nice and ill have a piece of mind knowing everything thats needed fixing has gotten it.

post some pics when you get some time!

"how-to"...
http://www.kxriders.com/forums/index.php/topic,10040.0.html

[Tim short]

[img]http://i1039.photobucket.com/albums/a478/Kx500er/Mobile%20Uploads/image_zpsjr6kkily.jpeg/img]

[img]http://i1039.photobucket.com/albums/a478/Kx500er/Mobile%20Uploads/image_zps3qvbo4ca.jpeg/img]

[img]http://i1039.photobucket.com/albums/a478/Kx500er/Mobile%20Uploads/image_zpswvtzyn4h.jpeg/img]

shes not much right now but i can say she's 100% mine :0

The real kicker for me is i ordered a 86mm piston just find find out i wasted my time and needs to get bored out (sorry about the whining, you could say i have dirt bike fever, i only got this last month and have ridden it a handful of times )

Im looking forward to riding it at mx338(southwick ma) this spring