Moving up to 38mm carbs, which manifolds should I use

[EE]

You know my suggestions on the matter:  http://erlenbachracing.co/reedcages%20mods.htm

38 carbs you really need the banshee vforce's to flow that much air those are big carbs for an RD.. If you don't want to modify your intakes that much go vforce YZ85 at least and see how it performs. TZ750 reedcages with the adapter plates stopped when we got the RZ350 reedcage, same reedcage area smaller flange..

Mt thoughts from my website
RD/RZ Reedcage Modifications

As you increase performance in RD250,350 and 400's this is the basic order I take:
Stock/Unmodified Reedcage
Even on stock bikes I recommend replacing the factory steel reeds with fiber reeds. With the money you spend when you have to rebuild one of these engines to me worrying if one of those steel petals is going to break off and ruin my engine just isn't even worth it.

So there's "basically" three options:
-Some guys like using YZ125 petals part # 55Y-13613-00-00 because the reedcage they come off of is a 6 petal cage, they come as three individual petal joined at the bottom, so you buy 4 of these and cut one petal off of each reed.
- I like to use YZ85 reed petals part # 4ES-13613-00-00 they are a single petal so you buy 4, they bolt right on but you do have to trim the front edges to narrow them just a bit at the front easy peasy.
-Here in the US TDR makes a racing petal for the RD's, they are a single petal reed that bolt right on but are a little thicker than stock YZ85 or YZ125 petals so they bias topend performace a bit.
(There are of course other brands and materials but these are 3 great options)

The next step up would be:
Stock Modified Reedcages
For racing to move more air through these engines at some point you just can't afford not to at least modify the stock reedcages and some vintage racing organizations require that you retain the stock (although modified) reedcages.

Modifying RD/RZ Reedcages
The reedcage is one of the easiest to modify and first attacked pieces of a 2stroke. But remember this: From the tip of the air cleaner to the tip of the silencer your 2stroke is a series of varying sized and shaped passages dealing with varying rpm, load and harmonics so increasing the size (or shape) of any one point will only show a gain if that point was or has become a restriction.
With that said this is what I've found/learned to work on RD/RZ reedcages.



2 Strokes need to move alot of air through the reedvalve quickly. The easiest way to get the most air soonest (the quickly part) is to have alot of reed opening area at the very tip of the reedcage so that theres higher flow as soon as the reed opens (lower reed lifts).Since the majority of the action in a reedcage is at or starts at the tip  thats were I start. more airflow at lower reed lift is accomplished by moving the reed opening forward to within a mm or 2 of the tip this not only makes the reed opening longer but makes "A" thinner less of an obstruction. blend & shape towards the back "B" but do not knife edge, knife edges are for knifes not for 2strokes. Next smooth the sides "C" for a little more width & less turbulence but leave at least a mm for sealing. Next narrow the bridge, 4mm is fairly safe, 3 less safe.  Modifying the back of the reed opening "D" has the least effect due to the low reed lift there but is sometimes necessary. I use small fiber cut-off wheels & standard burrs for the rough work & an assortment of files & sandpaper for finishing.

I've never had the opportunity to experiment with the the angle of the horizontal divider but Tony Doukas of Tony Doukas Racing had this to say about it. "By changing the angle of the center divider that splits the cage top and bottom (The horizontal divider) you can alter the airflow so it pushes the reed petal at different angles. A steeper angle will give more bottom response but affect flow at high engine speeds.  A shallow angle will have less bottom end and create more flow at higher RPM's.  This is the normal angle we use as the Banshee engine it a mid to top end engine."

In higher output RD400s removing the bridge & using single petal YZ85 reeds or  "TDR" (Biases top end) works great.

The next step up would be:
YZ85 Reedcages
These supply a substantial increase in reedtip area and are single petal cages right out of the box. I use these as often as I can because they are a large improvement in reed area, very affordable, they don't require as much thinning of the intake port to get them in as any of the RZ/Banshee reedcage options do (which risks breaking through the casting), and because they are a rubber coated cage the reeds last a long time. I also like them because unlike using RZ/Banshee manifold with RD cages where you have to cut off the manifolds "ears" which are actually airflow guides.. You can narrow the RZ/Banshee manifold "ears" by 2mm on each side with a right angle sanding tool and they slip right in so you keep the guides and get the nice RZ/Banshee crossover ports to boot.

The next step up would be:
Moto Tassinari V-force YZ85 Reedcages
These reedcages provide even more airflow over the Stock YZ85 reedcages.

RZ Reedcages
I haven't dyno'd RZ350 Reedcages against YZ85 Moto Tassinari cages yet but my seat of the pants tells me that The YZ85 Moto Tassinari cages will out perform the of RZ350 Reed cages.

Modified RZ Reedcages
Why am I not saying RZ/Banshee Reedcages? Because the front edge of an RZ350 reedcage is just a little bit thinnner than a Banshee reedcage allowing you to get just a little bit more aiflow out of the RZ reedcage.

On RZ350 reedcages because theirs not much airflow at the rear of the reedcage opening just square off the openings and concentrate on narrowing the bridge and working on the front and sides of the reed openings increasing the airflow where it's most effective

Removing the bridge will work on the RZ cage but I don't unless it's  absolutely necessary as it can cause a bit of an upset at lower rpms. I don't recommend it, but if you have to don't move the reed openings back or square off the outer rear corners of the reed openings. This will give you about as much support as you can get without the bridge.




Moto Tassinari V-force Banshee Reedcages
It takes some work to get them into an RD and honestly are overkill for most RD's but they have handled up to 120hp in Banshee engines.



TZ750 - RZ350 Reedcages



I often hear people wanting to put TZ750 reedcages in an RD or RZ but as you can see from the picture the TZ750 & RZ350 reedcages have exactly the same actual "reedcage" area & thus flow rate. TZ cages were used because at the time RZ cages weren't around yet. TZ cages required either welding an adapter plate to the cyl or redrilling the mounting holes. RZ cages have the right mounting holes already & are slightly easier to fit in an RD because of the trimmed off edges at the base of the cage.
RZ Intake manifolds with RD reedcages

A good intake modification for the RDs is to use RZ350 intake manifolds with stock modified RD reedcages which allows you to use a boost bottle or crossover tube & still retain the stock reedcage. Since the bolt pattern is the same all you need to do is cut the 'ears' off the RZ manifolds that would fit into the RZ reedcage flush. Then put the manifold up against the RD reedcage & mark the difference in the openings on the cage, remove the manifold & cut there to match the two.





ReedCage Spacers

Spacers between the reedcage & the cylinder can be beneficial & are used to 1) unshroud the boost port when the airpath is obstructed or poor by design or when necessary when the boost port has been modified 2) Used to help in fitting a larger reedcage or 3) To increase crankcase volume.



Installing RZ reedcages into an RD




This is a common performance mod but 2 things first. 1) do you really need  it? I've personally put 70 rearwheel roadracing hp through modified RD reedcages. 2) It's time consuming. If you decide to do it be careful & take your time & you can do this a hundred times or rush & you'll hit daylight. Start by putting dykem on the face of the cylinders reed gasket surface & using the mounting hole threads as a guide mark as shown those limits have personally never let me down. now put the spacer you'll be using on the reedcage & measure from the face of the spacer to the tip of the cage measure that far into the intake & mark it 'all the way around' that way if you wipe out the marks on the sides you can still judge by the top & bottom marks. Then measure the reedcage tip & set an inside divider to that width, you'll port from the marks at the sides of the intake gasket surface to that width at the other marks you made inside the intake port. Now blend it in up to the liner. Then comes the fitting.
Using 2 long points cover bolts without reeds or reed stops on slide the cage with spacer in as far as it will go tap it a bit, remove & port were it marks the port. Repeat till it fits then put on the reeds & guides & repeat until it fits. Do a final cleanup & make sure the reeds don't hang up when fully opened.

[Plasticman]

I installed YZ85 reed cages w/new TDR petals with this upgrade.

Rob

[EE]

Hmm pics sure looked like modified stock RD cages with TDR reeds. Ed

[m in sc]

stock yz cages look like that, but with 34s alone i could feel the difference vs the v force.

[EE]

What year? All the YZ85 cages i've used have  a much squarer (and appears to be larger than those) opening on the manifold side and are gold anodized, larger radius's in the reed opening corners rear corners, longer center divider ect. Ed

[m in sc]

What year? All the YZ85 cages i've used have  a much squarer (and appears to be larger than those) opening on the manifold side and are gold anodized, larger radius's in the reed opening corners rear corners, longer center divider ect. Ed

You're right, ive seen them gold as well, and squarer. Might be an earlier year? These are yz85 cages from i think an 05 or 06?, unmolested. however, the ones Plasticman used looks like the corners were previously rounded a bit?

[teazer]

The reed cages in the original pictures do look like RD and it's easy to see where the center bar was removed. The YZ85 cages are slightly different in the corners and have a smoother cross bar.  They also have a step on one side to match the offset manifold that has to be removed.

So that raises the question of whether a particular year of YZ85 had smaller reed cages than the ones we have used.
 
On a TZ750 top end I use Blaster reeds and cages which are bigger than stock and were also used on some years of YZ80 IIRC.

[John Ritter]

Plasticman - Rob, I am about 70 miles north of you in Lawrenceburg, TN and know I have some of the snowmobile reeds and intakes for installing 38's, the reeds I install in something else but the manifolds are what I used a couple times in the past for RD's. You are welcome to come up and look at them and Banshee V-Force 3's as well. In fact I have my personal 400 cylinders off the engine so you can see the work needed to cut them in compared to your YZ85's which I feel are too small for 38's. Also you can see the carb dividers I use to assist bottom/mid range when going from low throttle to higher throttle, strongly recommended, and a friend of mine does a lot of divider work. If you like the manifolds you can have a pair (have to find them in storage bldg) because I'll never use them as my porting days are behind me except personal projects. Carl Anderson lives in Decatur, he is involved in AHRMA on the board and does a bit of porting if you need help with reed install. John Ritter

[rodneya]

The reed cages in the original pictures do look like RD and it's easy to see where the center bar was removed. The YZ85 cages are slightly different in the corners and have a smoother cross bar.  They also have a step on one side to match the offset manifold that has to be removed.

So that raises the question of whether a particular year of YZ85 had smaller reed cages than the ones we have used.
 
On a TZ750 top end I use Blaster reeds and cages which are bigger than stock and were also used on some years of YZ80 IIRC.

When I bought YZ85 V Force reeds it mentioned fitting 1993 to 2018 models. I
Mototasarini site has fitment from 1993 to 2001.

Offhand I dont remember what years the YZ85 was not made, but they all seem to have been the same.

[Plasticman]

Hmm pics sure looked like modified stock RD cages with TDR reeds. Ed

You're right.  After I took these pictures I realized I had YZ85 reed cages to use for this engine, so I removed the modified RD400 cages seen in the pictures and replaced them with the YZ85 cages.
For the record, the carb boots in the picture are only temporary.  I plan to replace them with ones that have a crossover.  These were all I had at the time.

Rob

[m in sc]

makes sense then. wasnt sure if they were modded and blasted ones. guess it depends if you want to mod your cyls more.  Thats why i suggested the rm reeds, they will fit right in. yz85 v force will as well if you had regular yz85 reeds in there at some point, just check for upper and lower outer reed clearance if you go that way. but a modded 2 petal yz85 or rd cage def will be an issue performance wise w/that big of a carb IMHO.

[Plasticman]

My biggest worry is that I won't get this combination to run right after spending a LOT of money on it.  The stock motor w/modified carbs and aftermarket exhaust ran great.  It was just much slower than all the guys I race with so getting left behind on the straights was getting boring. We'll see what happens.  Baby steps should get me where I want to be.  It's all for the fun and amusement of racing.

Rob

[1976RD400C]

If you are going from a stock motor to a race ported, heads reworked, with bigger carbs and reeds, and new chambers I think you are going to be surprised at the difference. I wouldn't worry a bit about it. Jetting may take some time.

[EE]

Now it makes sense lol! i was gonna say i have spent ALOT of time into the wee hours of the night putting every size reed cage into RD's and that sure didn't look like a YZ85 reedcage!
Take John up on that offer if at all possible!! John is an amazing tuner and a good friend, he's just lucky i live in CA or he'd never get any sleep cuase we'd be building all kinds of odd and fast things!!!! Ed

[Plasticman]

John is a little over an hour from me.  I forgot to mention, the new chambers going on are Swarbricks.  Lyn was nice enough to sell me a set he had for an RD400.  I just need to weld on the mounting tabs and they are ready to go.

Rob