+7mm Crank OEM Cylinder Porting

[Smoker]

Looking for porting specs and exhaust port duration for a +7mm crank, OEM cylinder, 66mm piston engine.

Is this info available, or a big secret?

When Roger gave me the specs on my +4mm, 378cc engine, he asked me not to share the info.

Maybe need to check the Banshee Forums?

[JonW]

Roger will have these too but yes the banshee guys will know I'd think. Very few of us run a +7. Arron does I think, but with Athena cyls.

[Questo vecchio rz]

Hey Pete, Here are a few people you can try that do know. ( I often don't like sharing builders names) As internet know it alls often cause unnecessary drama, but this forum is generally easy going, and these builders have very good if not stellar reputations.

Two are members here. You may or may not get recommendations or specs...who knows, some guys don't really care ?

There are variables if the YPVS cylinders vs Banshee that we know need consideration.
1.) Tony here @ TDR, he's fluent in the 4mm & 7mn from his roadracers.
2.) Gus @ Driveline.....the same.
3.) Cam @ Redline Racing, Oregon his Banshee Serval builds have few equals..He's pretty helpful. Just saying his motors are the shit...He's my pick for my future Banshee Serval motor....period. 1st & foremost He's not a ego dickhead... he's very professional and knows his math and great at helping on jetting..he's very good
4.) Herr Jugs Racing( HJR), San Diego.
He's done quite a few RZs, and a very good reputation.
5.) There's also a special mention of Jim Passion of Passion Racing Engines, his 11 port Banshee motors just scream !!! There really fast motors.... Not sure what he would do with YPVS cylinders. He's pretty hard to get hold of. Hes on my final list for a land speed motor I may one-day do...I'll need LOTS of h.p./ RPM... top end and a very narrow powerband just what his motor design does...breathe lots of air.

Good Luck, share what info you feel you can..that's what a vintage community does

[Smoker]

Thanks, much!

I wouldn't reveal anyone's "secret" techniques.

Just curious if there are standard porting specs available.

[brrrappp]

The only time I've ever seen porting specs disclosed is when someone gets a cylinder back from a job and takes measurements. The builders keep that information Top Secret since it is their income and reputation source. Porting tools are cheap and everyone would do it if the good specs were easy to come by.

[Smoker]

The only time I've ever seen porting specs disclosed is when someone gets a cylinder back from a job and takes measurements. The builders keep that information Top Secret since it is their income and reputation source. Porting tools are cheap and everyone would do it if the good specs were easy to come by.

This is what I was getting at... and I understand.

I'm hoping, I'll have help from those who know.

[Questo vecchio rz]

I must disagree a little here and say, That porting specs are are generally not secret. Any of the builders I listed will provide you what your specs are.(as long as you are buying their services) But most will also advise you of what they think a good recommendation will be.
I would.....never.. let anyone work on my motors without telling me exactly WTF there doing.
That being said, It's generally not cool to go around sharing that info, ( IF and ONLY if.. they prefer that you do not). Many do & that's understandable, as Smoker mentioned regarding Wickeds wishes.
There's obviously more than just port/ head specs that make a motor a good or great performing package.
And many good builders know that, their motors will perform better and longer with them assembling them to their professional meticulous standards. There just far better at what they do, than the hacks.and that's simply the difference.
Proper porting tooling is well ,well past the average Hone Depot Dremel cost....It ain't cheap. That being said, one can when careful have fair to good results with cheapie tools..but it's all in the touch of the mechanic..
pastI have all my port specs for my Banshee and Tri -Z build.
Some folks don't care, they just want their bike to perform better. .that's fine. But I prefer to know what I have,and know it's done the best I can afford for my budget.

Bottom line: It's my engine. Builders/ Tuners...work for me. I paid for it...it's mine to do what I want with,...period
However....when asked not to due to so due to competition engines. .Respect should be given.

[slinger]

Smoker there shouldn't be any secrets using OEM cylinders with a +7mm stroke, you will be looking to set the cylinder so the EX is at 196-198* and the transfers will sit around 130* nothing you can do about that. A spacer will be needed along with a dowelled head

[JanBros]

I wouldn't reveal anyone's "secret" techniques.

there are no secrets, everything is out there, you just have to look for it

[Smoker]

Smoker there shouldn't be any secrets using OEM cylinders with a +7mm stroke, you will be looking to set the cylinder so the EX is at 196-198* and the transfers will sit around 130* nothing you can do about that. A spacer will be needed along with a dowelled head

Thanks! I'm just trying to learn what I can about building a +7mm engine.

Already have good guys to do the actual work.

The engine has removable domes, so hoping I don't need a spacer. Does that change the numbers?

[Smoker]

there are no secrets, everything is out there, you just have to look for it

I'm still looking....

Maybe I need to join the ProBoards.

[slinger]

I use a spacer and machine the bottom of the cylinder to achieve to port timing I like! It would be highly recommended to dowel/register the cylinder head as there is so much slop between clamp studs and head. Removable insert will be just awesome but they need to be in the correct position to the bore with a +7mm stroke crank.

[Smoker]

I use a spacer and machine the bottom of the cylinder to achieve to port timing I like! It would be highly recommended to dowel/register the cylinder head as there is so much slop between clamp studs and head. Removable insert will be just awesome but they need to be in the correct position to the bore with a +7mm stroke crank.

I (mostly) understand what you are saying, and thanks.

Well, don't really understand registering. Guessing it means to measure the stud placement and stud OD vs. the hole placement and hole ID in the head?

If a stud were not in the perfect position, I understand how to use a template to drill a new hole for an oversized stepped stud.

If the holes in the head are oversized, I'm not sure how to correct it. By "dowling", do you mean inserting custom machined (larger OD) studs? That's the only thing I can think of. Actually sounds like a good idea.

I do have an aftermarket billet head. If it was properly designed - maybe the slop is removed? I can measure the holes in the aftermarket head, but don't have a stock head on hand to compare.

I've done well assembling (modified) engines, but I don't have much experience or knowledge of engineering/machining the actual mods. Also having difficulty researching +7mm OEM cylinder mods. Not so popular anymore, because of all the aftermarket cylinders.

[two-stroke-brit]

When he says dowel and register.
it means to locate the head to the best position centered over both bores.
then drilled and doweled in place.
because there is more slop in the cylinder stud/head than you have clearance
mark

[Smoker]

When he says dowel and register.
it means to locate the head to the best position centered over both bores.
then drilled and doweled in place.
because there is more slop in the cylinder stud/head than you have clearance
mark

You mean drilling extra holes in the head, and extra holes in the cylinders? Then pressing or threading locating dowels into the cylinders?

Where would the dowels be placed?