What Head Is This? 430, 420 Or 500?

I am new to this forum but have done a fair amount of searching to find the model of this head and piston. I have not found much info that can let me know.

To give context: My friends 82' 430XC recently had a ring failure. I decided to re build it for him.

I found a used head recently and after measuring my original head and piston, having the seller measure the head and piston for sale and doing hours of research on identification marks and measurements I bought the head and piston.

After I received the new/used head it was different in a few key areas.

#1 the outside cooling fin dimensions are larger in all directions.

#2 the spark plug hole is centered. The original head has the hole to the riders right of center.

# 3the shape of the piston top, the shape of the top of the head (they are both chamfered vs the 430 being square edged) and the presence of to piston rings vs the 430 having 1 ring.

#4 the biggest difference is that the cylinder from base to head is around 3mm shorter than the OG head. This causes interference at the top of the stroke making the head unusable for my 430.

So, what head is this?

I'll try to attach photos here.

The measurements that are the same are:

the width of the cylinder
the width of the piston
the height of the piston
the head bolt pattern measurements

I will be selling this head and piston. It's in good shape but won't work for my application. If you know what it is it would be helpful for me to know before I list it.

Here is a dropbox folder with images of the head and piston.

https://www.dropbox.com/sh/pch2srjmlt6zg6x/AAARImagqTsu83d2MGeixKDla?dl=0

a fewthings
first I don't claim to have a lot of knowledge on att things 430 air coooled
the piston in the pic looks aftermarket, probably a Wiseco
2nd I had an 82 430, while I don't have it now I thought the plug was centered, but could be wrong
the 430 and 500 share a bore, just a stroke difference
hopefully a well researched air cooled person will be along with more

Let’s see if i can help . The 500 had a bore and stroke of 86x84 and also had 10fins along with the reed valve block cast into the cylinder unlike your pictures . An 81 430 was 86x84 and i do believe the plug is angles to the right . Now for the 420 , it had 86 x 71 mm stroke which could be the hieght difference that you are measuring . So if you are going to sell it be aware the 390 engine was 83x71 , same stroke but different bore . If those studs have the same spacing it might be able to be used there . So i’m thinking you may have a cylinder and head from a 420 auto on your hands . If I’ve made a mistake , I’mm sure someone will correct me .

http://www.cafehusky.com/threads/1983-xc500.87850/page-6
Post 115, It's not a 83 500 head.

It is a 420 auto cylinder and head. The bore is maxed out. The last piston size for the 420 is 87.00mm. This will also fit the 1980 390.

Marty

Thanks so much for the responses! I’ll list it as a 420 Auto head. Is the classifieds here or eBay the best place to list?

classifieds here are pretty slow...but would be nice to list here anyway. might really help someone out

Posted on the classifieds and on eBay.