+7mm Crank OEM Cylinder Porting

[slinger]

Mark is correct in what he is saying!

As you have CNC machined heads they SHOULD be machined to the correct spacing of 102mm, I use hollow dowels to locate heads. The head studs run through the hollow dowels, so you will have a counter bore in the cylinders and counter bores in the head to line up the 102 spacing just like a SBC or BBC this is what known as a register!
You need to do this because your running the piston up into the head chambers quite a bit 3-ish mm so it needs to line up with the bores.

[JanBros]

http://www.kr-1s.co.uk/manual/parts.php

nr 92043 on the top pic are dowels, just holow bushes that fit perfectly in the head and in the cylinder. they make sure the head is always positionned perfectly to the cylinders and can not shift sideways.
they can be either in seperate holes or inside the holes where the bolts/studs go through to tighten them together.

[Smoker]

Okay, now I understand what dowling is, and why it's important.
Guessing the studs need to be removed, but that's okay.
Do the dowels press into the cylinder, or head - or do they come out when the head and cylinder are separated. Just curious, not important.

I always try to find these answers by searching, before I ask you guys.
Very much appreciate the two-stroke lessons.
The info isn't wasted. I'll try do do the dowling.

Jan- I previously mentioned that we're using nozzles in the pipe stingers. Jeff knew about it, but I was clueless, until you brought it up.

I'll do my best, but any tips or mods you guys think would be good on a +7mm stock cylinder build, I'll try to make it happen.

Thanks, much Glyn.

[OldTZracer]

Have a look at a TZ cylinder & head. The pins/dowels can be relatively small, even like 3/16" or so, and can just be snug enough to pull out with your fingers so they don't interfere with torquing the head.

[RuZty]

Smoker, the arrangement Glyn is referring to is the same as the cylinder location to the case. The stud hole in the case is counterbored for a hollow dowel, which then locates the cylinder on the stud with a matching counterbore. You only need 2 per part.

[Questo vecchio rz]

[quote=Smoker
Also having difficulty researching +7mm OEM cylinder mods. Not so popular anymore, because of all the aftermarket cylinders.
[/quote]

I looked into this a couple years ago, and same initial result. Had a couple yes it can be done...but there were no details to follow. Except for mention of the port timings would become not optimal. Looks as if there may be a work around as listed above, which is nice for folks.

TDR E- mailed me with a reply and said it's doable but not with the YPVS cylinders.And I believe the guy from Ireland with the Moto 3 project did as well, but no details were given, if I recall he possible asked for money as to how it was accomplished in his case. It's been awhile..so my memory may not be intact.
TDR assured me a Chettah or Serval would be far more powerful / reliable motor, with the Serval offering good low RPM characteristics.
But Tony was saying he had plans for a selection of RZ based engines coming, but that appears to never have come to fruition.
I know what your saying /thinking though, It would be nice to have the YPVS setup. I think I would have paid to have one built.
Hope you build it, and we can follow your progress and how you make out on your build.

Best Wishes.

[two-stroke-brit]

YEP, i did it to my LC350 head.
i will see if i still have the pics.
mark

[two-stroke-brit]

http://www.rzrd500.com/phpBB3/viewtopic ... 15&t=13282

the pic shows were the 2 dowels fitted to the head
hope this helps
mark

[slinger]

@ Smoker
Just keep it simple apart from whats been mentioned in this thread your guy should concentrate on the exhaust port to achieve the best blowdown of the cylinder can't stress that enough. As for the dowels and there fitment a nice interference fit in the barrels and a little looser in the head, typically I would have around .05-.07mm clearance which works just fine!
But the key to make this work is a set of pipes designed for this engine combo and not a generic pipe.

[(F5)]

Just like dowls usually found on base interface. Sliding fit tube around the studs, about 10mm long and 5+mm bored into both mating parts.

[Smoker]

@ Smoker
Just keep it simple apart from whats been mentioned in this thread your guy should concentrate on the exhaust port to achieve the best blowdown of the cylinder can't stress that enough. As for the dowels and there fitment a nice interference fit in the barrels and a little looser in the head, typically I would have around .05-.07mm clearance which works just fine!
But the key to make this work is a set of pipes designed for this engine combo and not a generic pipe.

Appreciate the info a lot.

Any other recommendations, or cool mods, for a +7mm, OEM cylinder build would be great.

Now considering Hybrid ceramic bearings, instead of TZ bearings. Also looking at REM polishing the tranny, friction coating and undercutting. Expensive, though.

Pipe performance will again be compromised by custom fitment/shape. I'm confident Jeff Henise will make the most of my design. He made a lot of changes to my pipe design for the supermoto pipes. I wanted full custom, but I would call them 1/2 custom, 1/2 race.

You were probably smart to pass on building my pipes.
Pain in the ass....

[kenny]

You can almost do any stroke upto +10mm on std cylinders and no spacer too. You just need the correct rod and piston timing edge height combo. I have done the +10mm in CAD and it fits but needs a shorter rod. This will accelerate wear in the engine but it is ok if you dont do loads of miles between rebuilds.

[Smoker]

You can almost do any stroke upto +10mm on std cylinders and no spacer too. You just need the correct rod and piston timing edge height combo. I have done the +10mm in CAD and it fits but needs a shorter rod. This will accelerate wear in the engine but it is ok if you dont do loads of miles between rebuilds.

Thanks, Kenny. Good to hear from you, too.

First, it doesn't look like the larger reedcage mod is going to work, and now I'm getting pushback on this +7mm idea. Has anyone ever actually done a +7mm build with OEM RZ cylinders???

I'm starting to think it might not be a good idea, but don't know why.

I was talking to Roger about building another engine, then when I said I wanted the OEM +7mm build, he never got back to me.

I asked Ed about the OEM +7 build, he hasn't done one.

Now, Allen at CT Racing is recommending a +4 build, over a +7mm build. Not sure why, but will try to speak with him, soon.

Read a post in this thread that TDR was going to do the OEM +7 build, but it hasn't been seen.

I'd like to do something a little different than most, but I don't have enough time left to try something new.

[Questo vecchio rz]

Allen and his ( wife)!!, know their craft.
We've been dealing with them for many many years. Straight talk, NO bullshit their 4mm Banshee puts up 70 h.p.( real on a Dyno ) and they are a proponent of stock carbs delivering that figure too.
How many championships has Alan been part of? Literally Countless. There knowledge is not to be dismissed.
Realisticlly in a street RZ +4 mm with porting to suit that goal, I wouldn't expect more than 65 real h.p. max, but with Ed's porting and careful headwork...70+ aint outta the question.
There Dyno tune service is reasonable and very helpful on tuning a build.

Try Tony @ TDR here regarding your 7mm, he'll explain your options and pros n cons. A few have stressed to me that they will not run the piston Into the head they just don't wanna do it. And also mentioned the Xtra 3mm ain't worth the effort especially on a YPVS. Listen to what they say and let it help in your decision either way....60-70 h.p.(real) is frankly a screaming RZ. My Banshee is a basic stroker 4mm knocking on 70h.p. With a wall of Tq....it's pretty damned fast.
But when compared to a well ported Cheetah or Serval cylinder...its down a honest 20 -25 h.p. depending upon the port specs.

[JanBros]

collected all the parts to built a +7mm with stock Banshee cylinders a couple of years ago, but other projects keep getting in the way. Will make my own head to accept the piston's sticking out of the cylinders.
there is no reason at all why it can not be done, especialy as a good 2-stroke is as square as possible. an RD/RZ might even be better of with a bigger stroke than bore to compensate for the crap transfer ducts.