yamaha porting book

[bcredneck]

i figered some of you guys would like to port your own motor but are scared of messing up your motor so i borrow this book i will be getting more and better pics later tonight but this is basicly whats in it
edit: contrary to what VAhuffie said page 161 to 163 are non motor specific most info on thease pages can be helpfull to most 2 strokes please dont make negitive coments unless you read thouse pages some other pages contain info that is also non motor specific what you do with this info is your choice do not compain that some one was nice enough to make this book avalible online as you wont find it anywhere else ive checked

[HuffieVA]

"Piston port induction" is an alternative to reed valves on a 2-Stroke, so its not necessarily a book on porting but on "Piston Port Induction" engined bikes like the Yamaha AT 125's and I believe early YZ's and MX's (other companies as well, Rotax used it longer than anyone else I think) prior to the reed valve engines becoming popular, smiler configuration to that of a chainsaw cylinder. It may have some "porting" suggestions but they would be engine specific to the models covered in the book... (What I'm saying is, don't take that book, grab a Dremel and start hacking away at your Tri-Z cylinder, you will not be happy with the results)

[bcredneck]

you have no idea what your talking about theres even info on what reeds to use in the book have you even seen a old yz motor

[bcredneck]

unless i imagind this but then it would have been hard to get this pic

[HuffieVA]

you have no idea what your talking about theres even info on what reeds to use in the book have you even seen a old yz motor

Yea Smartass, I currently have:

1970 AT125, 1973 AT125, 1974 DT125, 1978 YZ250 (reed valve engine) in my garage

and have formerly had

75 DT400 and several 80's and 90's YZ's

Now before you make yourself look foolish read the back cover of the book where it lists the models that the book applies to

If the back cover is missing, Ill send you a picture of my copy, would you like to see the 80 - 175cc version as well?

Yes there are still ports in a reed valve two stroke, but you have a model specific repair book, not a guide to porting...

Ill accept your apology in advance

[bcredneck]

there are no 125s in my book

[HuffieVA]

But by all means feel free to go out and ruin your port timing by using the wrong book...

[HuffieVA]

there are no 125s in my book

Probably because its for 250 - 400, get your panties out of the wad their in and look at the back cover

[bcredneck]

some people like to get at least basic info on what there doing it also expains basic tuneing and alot of other helpfull stuff people would like to know if you dont whant to read it then look at a differnt thead i didnt come on here to argue with you im posting for people who would like some basic info on porting

[HuffieVA]

Yes its called a repair manual, I was just letting you know that it does not explain the art of high performance two stroke porting like you originally thought (or at least sort of stated), it wasn't to argue with you, just make sure you didn't go out and start grinding away at the ports on your trike or someone elses for that matter... With that being said, there are some good books out there on porting, its just that this is not what this particular book was written for

[bcredneck]

it expains quite alot i just dont have thous pages on here yet im working on getting update: there here now

[bcredneck]

i used this book on a 75 yz 250 but after i was done the owner filled it up with striat gas and took it for a rip so i never got to ride it

[RubberSalt]

I entered the information for the 250cc for image 25 in my program here. It's actualy not to bad on the timinings. 184.4 exhaust duration, 117.4 on the main transfers, 122.2 on the aux transfers, 119.8 on the boost port. This gives a blowdown of 31.1 degrees. Most ported engines have 30-35 degrees of blowdown. This is the time from when the exhaust opens to when the transfers open. This is somewhat similar to what i run on my trikes.

And that book does explain port modifications for more power, it's not just a repair manual. On page 8, in the first picture posted here, it states that it gives demisions for maximum power, this is more than stock... lol read the book before you say what it is not :-p

[bcredneck]

i thought you might like this

[RubberSalt]

I wounder what is in the 80 - 175cc. I really want to see how close I am to yamaha on the 175 stuff lol