1987 KX 500 rebuild time + parts interchange question

[Mike Grant]

Hey guys....new member here with a few questions about the bike I just bought. I purchased a 1987 KX 500 with an air leak as a project bike. I pulled the ignition cover and wiggled the the flywheel and noticed play so I'm going to be splitting the cases for sure at this point. And with my luck with bikes I'll put my money on a a cylinder re-plate and crank rebuild. Couple questions before I start ordering parts

-Since 87 pistons are as common as Unicorns I was going to order a 88-04 piston kit and have the cylinder head modified to work with the newer style piston. Is there any issues  with this swap besides the flat top vs dome of the pistons ?. Any recommendations for a piston kit and also someone to modify the head ?

-I was going to order the ALL BALLS crank bearing and seal kit and was wondering if anyone has had any problems with them ?

-If the cylinder turns out to need a re-plate , I was thinking about getting the cylinder ported if there was much to gain from extra cost. Any recommendation for company that can port my cylinder and re-plate

-My intake manifold (carb holder) is cracked and I am having no luck finding a 87 manifold.....can I use the 89-04  manifold on this engine ? 

I will be pulling the motor apart tomorrow and I will post with some pictures of the carnage

[dave916]

Later piston is fine but dont cut a window on the intake skirt
larry will cut the 87 head to suit and fit Compression Release Modification aswell http://www.kxriders.com/forums/index.php/topic,6445.0.html
I Would fit oem  crank bearings and seals

porting is already pretty good on the kx, A few casting flaws and a exhaust port polish is all u need unless you are looking for more topend the intake manifold should be pretty near

[Mike Grant]

Well I pulled the engine today and removed the top end off. It looks like the engine has already been apart at one time as someone has installed sleeve and a newer style 2 ring piston. They apparently thought one of the KIPS valves was optional on one side and left it out. It tried seizing the piston on this side. The wrist pin bearing fell apart when I was inspecting it so this thing was not to far away from grenading itself. The lower connecting rod bearing has play so I will be throwing a rod kit on it as well

So my parts list so far is looking like

-86.25mm or 86.50mm piston kit + bore
-Connecting rod rebuild kit......any recommended kit's ?
-OEM or All balls crank bearing + seals.
-Moose racing compete gasket and oil seal set
-Track down missing KIPS parts + Intake manifold

[Goat]

Welcome to the site. I have used All Balls bearing and seal kit with no issues. OEM is generally the way to go but sometimes it's hard to afford everything you need by sticking with OEM. I'm actually running an 87 with the All Balls kit for the past year.

As far as a connecting rod and rod bearings... I would stick with OEM. Seen way too many failures in the aftermarket rod kits. Even more so recently.

Cometic gasket kit is the only way to go.

I have an intake boot laying around that I don't need. I just found it and it's definitely usable. Has a few minor cracks starting on the outside but inside is perfect. PM me if you're interested.

Kips valves are almost as rare as unicorns lol Keep an eye on eBay frequently. As soon as I get a shop built and more tools I will be making some valves for the older kaws. That probably wont be until late spring though.

[Mike Grant]

I have been checking out as many threads as I can to try and figure out what the most reliable and proven parts are so I don't end up regretting any of my purchases. I came across something interesting last night when I was looking for kips valves. Check out this link and look at the KIPS removal they did on the engine


http://rpmmfg.com/1987KX600BBSS.aspx

-I know it would be ideal to keep the KIPS working but considering this is an 87 engine without the center KIPS valve which alters exhaust port timing and volume. Would I be missing out on much power?

-I was also wanting top purchase the Boyseen Rad valve because it cures the intake manifold cracking problem for good. I needed a new set of reeds anyways so this combined with a new intake boot puts me within $50 of a  Rad valve + a  bit of extra power to boot

-Also curious if purchasing a 39mm pwk is going to be worth the money compared to the stock round slide......sure looks alot better

So here's where I have my parts list right now.....hoping to order on tuesday

-Wossner 86.50mm bore piston kit
-Wossner or OEM connecting rod kit
-Cometic gasket kit
-All balls cranks kit
-Boyseen Rad valve

[sandblaster]

If your kips are locked open you will loose the smooth transition of your power delivery.
The engine will roll on then suddenly hit faster with power which is fine for drag racing or hill climbing, but not so good for much of anything else.
Boyesen's are good for making power lower in the RPM range whereas the V-Force reeds make power up higher in the rpm range.
I've never ran the round slide on a 500 so I have no comment there but there should be a few on this site with that experience.

-Wossner 86.50mm bore piston kit  - Good
-Wossner or OEM connecting rod kit  - Good - get your crank balanced..
-Cometic gasket kit  - Good
-All balls cranks kit  - can't comment on that, I use OEM or comparable German, British, US, Japanese, Swiss, no Chinese bearings
-Boyseen Rad valve - Boyesen's are good for making power lower in the RPM range whereas the V-Force reeds make power up higher in the rpm range.
So that depends on what you are wanting the engine to do, which pipe, ect.

[Mike Grant]

The Boyseen rad valve sounds like the ticket for me. I will be using the bottom to mid range power alot more then top end on the local tracks and trails I ride. My bike already has a Pro Circuit pipe with an FMF silencer so I hope the parts setup works together. My next big problem I am running into is finding a good pair of KIPS valves which looks like it is going to be a major pain in the ass.......any onr have a set they want to sell 

[Goat]

It's been a long time since I've ran the round slide carb but the Keihin PWK is an excellent carb and easy to tune. If you can find one cheap I say go for it but I don't think it's a justifiable purchase if it's more than $80 shipped. I paid something in the $50 range for mine to replace the Keihin PJ carb that came on my 87 that couldn't hold a tune or even keep an idle. The PJ has been a paperweight for 3 years now

I'm not sure about the rad valve as I have never used one but your pipe and silencer combo work good together. I had that setup on my 98 and tried it out on my 87 before I built the pipe I'm running now with a PC silencer. I run mostly track with some short runs through the trails.

[motopunk]

I have been checking out as many threads as I can to try and figure out what the most reliable and proven parts are so I don't end up regretting any of my purchases. I came across something interesting last night when I was looking for kips valves. Check out this link and look at the KIPS removal they did on the engine


http://rpmmfg.com/1987KX600BBSS.aspx

-I know it would be ideal to keep the KIPS working but considering this is an 87 engine without the center KIPS valve which alters exhaust port timing and volume. Would I be missing out on much power?

-I was also wanting top purchase the Boyseen Rad valve because it cures the intake manifold cracking problem for good. I needed a new set of reeds anyways so this combined with a new intake boot puts me within $50 of a  Rad valve + a  bit of extra power to boot

-Also curious if purchasing a 39mm pwk is going to be worth the money compared to the stock round slide......sure looks alot better

So here's where I have my parts list right now.....hoping to order on tuesday

-Wossner 86.50mm bore piston kit
-Wossner or OEM connecting rod kit
-Cometic gasket kit
-All balls cranks kit
-Boyseen Rad valve

the 86-88 engines with the 2-valve-kips are a powerhouse ... the newer 3-parts kips 89-2004 makes a little bit smoother power delivery from down low but the peak power is nearly the same like the 86-88 ...

conrod kits , crank bearings/seals and piston fit from 83-2004 ... i have on my 86 and 88 engine hotrod-conrod-kits , allballs bearing and seal kit and wössner 2-ring-pistons installed and i run it with 1:40 motul 800 premix oil ...

intake manifold is the same from 87-2004 you can get a new one at any kx-dealer... ;O)

[yeomans]

Mike, I can sort you out with some kips valves or if you only need the one for the left side.
Is it steel or aluminum valves in the head right now ? I've got a few to choose from.

I Just put that wossner rod in my 86

[Mike Grant]

I have aluminum drums on the motor right now. I sent you a PM Josh....let me know what you have and I will send money today