Newer style top end on 86 Motor?

[JBKX]

Will a newer style (88 - up) cylinder work on a 86 bottom end?  Or does anyone have a newer style engine for sale for cheap?

[don46]

First of all, it's 89 and up, 88 is the same as yours. Anything can be done, how much work do you want to put into it? The cylinder will bolt right up to the cases if you leave the power valve out, which leads to your first problem, the 89 and up have 3 shafts for the KIPS yours has 2, and of course the cases are different, there is more meat on the 89 and up case for the 3rd valve shaft. I think you could have the case built up or maybe even use devcon and build the area up, then drill for the 3rd shaft. I don't think the area would have much stress against it and would really only require strength to support part of the valve. The second issue is the KIPS actuation arm that would have to be replaced, the newer units have a smaller KIPS drum, no deal there you could just buy the arm. and lastly the motor mount on the back of the head may be different, I say different because the head stay is much shorter on the pre 89 units, but the head is also much larger on the pre 89 units. Did I mention that you would need to change the head as well as the cylinder? you will.

Good luck let us know what you do, BTW why do you want to put on a newer cylinder? I think the pre 89 have a better port layout.

[JBKX]

Thanks for your help. 
The only reason I was asking was because my 86 starts so much harder that my 93.  I'm thinking about doing the compression release if I can't find a newer style motor cheap now.

[don46]

Junk the mikuni carb and get a Kehin, that'll help. You could put the newer ignition on with the bigger flywheel, that may help. I have a newer bottom end with an older cylinder, it starts every bit as good as the newer motors.

[puffy]

How do you tell just by looking from the outside the difference between the newer one and the older style.

[don46]

The cylinder and head on the older units are quite a bit bigger than the new ones, the older units had a water elbow bolted to the head going to the radiator, later units it was part of the head. pre 88 units used a nut to hold the countershaft on, 88 and on had a snap ring, but the 88 had the larger cylinder and head. Thats about all I can think of that is apparent from the outside, I guess it's one of those things you just know. Sorry I can't be more clear.

[puffy]

Mine has the bolt on water fitting on the head.But its a newer bike it was nate mccoys

[JBKX]

Junk the mikuni carb and get a Kehin, that'll help. You could put the newer ignition on with the bigger flywheel, that may help. I have a newer bottom end with an older cylinder, it starts every bit as good as the newer motors.

The Mikuni I'm running is a TM series bored to 41MM with a booster jet.  It runs very good once it is started (it's very similar to the carbs FTZ sells).  Does anyone have experiences and/or jetting tips for this type of carb on a KX500?

Also, can I put the newer ignition on and retain the larger flywheel?

[don46]

Mine has the bolt on water fitting on the head.But its a newer bike it was nate mccoys

I don't know who nate mccoy is, but if it has the bolt on fitting it is either an older top end or somebody has modified the head, all of the newer ones (89-04) are a cast piece of the head stock. If you want to take a picture I can tell you if its newer or older.

JBKX, I'm not sure I understand what your saying, so if I don't make sense, its not intentional. The 86-89 ignition is the same, they used a smaller flywheel, way smaller. These ignitions had 5 wires coming out of the CDI and 4 out of the stator. The older flywheel is about 3 1/2" in diameter the newer one are about 4 1/2" in diameter. So if you use an older ignition you need to use the whole thing, flywheel, stator, and CDI

[JBKX]

JBKX, I'm not sure I understand what your saying, so if I don't make sense, its not intentional. The 86-89 ignition is the same, they used a smaller flywheel, way smaller. These ignitions had 5 wires coming out of the CDI and 4 out of the stator. The older flywheel is about 3 1/2" in diameter the newer one are about 4 1/2" in diameter. So if you use an older ignition you need to use the whole thing, flywheel, stator, and CDI
[/quote]

I didn't make myself clear, sorry.
 
I do have everything except the CDI to switch it over to the newer style ignition system.  Is it that much better of a system to justify spending the $ to get the CDI?  If so, does anybody have a spare CDI for a good deal?

Has anyone ever ran the TM series Mikuni Flatslide carb with success?

[don46]

I think it really depends on what your doing with your bike, if your woods riding, it would probably be a better deal, if your dune riding what you have is better. I don't think the ignition is any better, it just has a heavier flywheel so it tames the beast, kinda like putting on a heavier flywheel.