More YZ100 '82-'83

Related:
Create New Tag

11/25/2018 2:20 PM
Edited Date/Time: 11/25/2018 2:21 PM

Hey guys, the 100 engine seized piston on 4th overbore, and wondering if Yamaha offered a 5th over. piston and ring? What about Wiseco......do they offer a 5th over?
Parker Johnstone?

|

Larry Navarro - Spring,TX. Damm glad to meetcha!

11/25/2018 4:20 PM

Send the cylinder to Millenium and have it plated back to the 4th bore. More durable and saves you from sleeving.

|

11/25/2018 4:22 PM

Or can it be bored up to a 125 piston? Not that you would ever consider anything like that...laughing

|

11/25/2018 4:45 PM
Edited Date/Time: 11/25/2018 5:02 PM

Wiseco used to make a 52mm piston for the 100's. There are some later model YZ80-85 that use a 52.50mm. Not sure if it could be made to work.

The old rule was .080 over, no larger. 52 will put it around 118cc.

|

11/26/2018 5:03 AM

I believe the 52mm takes it to 102cc, no?
Thanks Joe, I'll check that out.

|

Larry Navarro - Spring,TX. Damm glad to meetcha!

11/27/2018 3:29 PM

wfoyz250 wrote:

I believe the 52mm takes it to 102cc, no?
Thanks Joe, I'll check that out.

My math sucks. I think it is closer to 106cc with the 52mm piston. Just keep in mind, the further it is bored, the smaller the port openings become. Port timing gets a little retarded with each overbore. Shifts the power a bit, it should gain some low end power , at the expense of top end. If you can find the port map for the bike, a good porting person should be able to blue print it back to spec if the 52mm piston is used.

|

11/29/2018 9:02 AM

https://www.ebay.com/itm/Wiseco-Piston-Kit-52-00-Vintage-Yamaha-YZ100-76-77-78-79-80-81-82-83-MX-Ahrma/131499706652 Eric Gorr can do all that's needed just send this along with the cylinder. I'm waiting to do the same with my 82 100 J as well.

|

Yeah, I have no clue !!!

11/29/2018 1:23 PM

what all does Gorr do?

|

Larry Navarro - Spring,TX. Damm glad to meetcha!

11/29/2018 4:56 PM

He does it all including plating I believe. Port, bore, as well. I have had him do quite a few cylinders for me and have been pleased.

|

Yeah, I have no clue !!!

12/6/2018 7:48 AM

newmann wrote:

Send the cylinder to Millenium and have it plated back to the 4th bore. More durable and saves you from sleeving.

Why would you go the 4th bore and not original size? I am asking only because I may be doing mine and I haven't looked into what is available. I also do not know what my bike currently is.
What is the stock size?
What are the sizes of each over bore?

|

12/6/2018 3:53 PM

Just wondering with you YZ100 gurus- a few questions -

what would/ should an engine cost to buy (82/83) ? Good / medium or bad condition?

What was the preferred engine, the 82 or 83?

Love these bikes and the memories of that time. Also the trick stuff/ mods / racing these and resurrection that now goes on. Think I rode fastest I ever did in this period and also love the earlier YZ100's- 78- 81 and then the 82/83's.

I sort of want to get an 82 or 83 and thinking of maybe building one up if I can find engine / frame and parts etc. Quite rare here as they probably are there.

Also what are the main issues to look out for?

Thanks for any info.

|

Always was an excellent rider ...... at crashing usually

Moto Aspes, you know you want one