I've decided to upgrade the breathing on my RD400. This is my vintage road race motorcycle, so it has a race-only port job and the heads have been reworked. I'm adding Swarbrick expansion chambers on the exit side and was thinking that 38mm Mikunis (VM38) will do the trick on the intake side. I have to run round slide, VM type carbs to be legal in my racing class. The problem is, I'm not sure which intake would be best for this upgrade. Here are the two intakes, the stock looking intake, a product from UPP (see picture 1) and the Banshee type intake (see picture 2). Which would work better for my application? Or does it matter?
Picture 1
(https://i.imgur.com/AoBH5uQ.jpg)
Picture 2
(https://i.imgur.com/FHRcwco.jpg)
Rob
either will work fine, but the second ones have a longer runner so depends on the length of the intake tract you want. i would recommend supporting them at the back of the carb somehow though, i've torn manifolds over a few years with them just 'hanging out' there, VMs are heavy.
I think the UPP ones are made of silicone, which is slippery ?? Well, I had them with my with 34mm carbs and no support of the carb. Took it to a track day. The track was kind of bumpy and the carb popped out of the manifold at full throttle. The sound it made was like blowing a motor and it scared the crap out of me.
Quote from: 1976RD400C on December 31, 2019, 09:58:17 AM
I think the UPP ones are made of silicone, which is slippery ?? Well, I had them with my with 34mm carbs and no support of the carb. Took it to a track day. The track was kind of bumpy and the carb popped out of the manifold at full throttle. The sound it made was like blowing a motor and it scared the crap out of me.
Made of urethane, so a lot like silicone. They last about 3 years here in Florida.
I just use some 60 grit sandpaper on my spigot on the carb to roughen it up a bit.
Chuck
For what it's worth, some AHRMA guys I know like Tony Doukas swear by the UFO inserts. It's supposed make the round slide VMs have a flow more like the TMs.
http://thunderproducts.com/product/u-f-o-ultimate-flow-optimizer/
Rob, go look for a set of these...
'97 -01 Vmax 500 600 700 8CR-13555-00-00
They now make re-pop's from SPI, I don't know how good they are yet.
I always just bought used OEM Yamaha ones from ebay.
I also have my TSR/Barlow designed boost bottles for this setup too. If you do buy a TSR boost bottle from me I have some jetting specs to get you close on the 36-38's.
Chuck
You will have to re-drill them...
Jim's F-500 RD400 engine with the 36mm carbs using these manifolds.
(https://photos.imageevent.com/supertune/carbstuff/websize/20170411_165734.jpg)
(https://photos.imageevent.com/supertune/carbstuff/websize/20170411_175641.jpg)
(https://photos.imageevent.com/supertune/carbstuff/websize/20170411_175720.jpg)
(https://photos.imageevent.com/supertune/carbstuff/websize/20170411_180849.jpg)
I was in the middle of installing my new carbs/manifolds when I notice there was a LOT of aluminum reed cage material in the air flow path.
(https://i.imgur.com/EwaygCY.jpg)
So I marked the area that was exposed, removed the manifold and took another picture to show how much of the reed cage was blocking the air stream.
(https://i.imgur.com/8grqbl5.jpg)
Is this normal, or can I grind away at the upper/lower areas. I looked at the sides, there isn't enough aluminum to really grind away in that area without creating daylight.
Rob
I've modded mine in the past like you are suggesting. with 38s you might want to go to some v-force reeds,. thats a LOT of air flow.
Quote from: m in sc on January 13, 2020, 11:28:37 AM
I've modded mine in the past like you are suggesting. with 38s you might want to go to some v-force reeds,. thats a LOT of air flow.
I was thinking along those lines. Trying to do this incrementally.
Rob
id do the reeds at the same time TBH.
Quote from: m in sc on January 13, 2020, 11:28:37 AM
I've modded mine in the past like you are suggesting. with 38s you might want to go to some v-force reeds,. thats a LOT of air flow.
FWIW, a reduction in cross section along any flow path is actually less of a restriction than an increase in cross section. However, any abrupt step or mismatch is a bad thing, and should be eliminated.
Wouldn't RZ reeds be better suited than RD reeds for big carbs? After all the RZ reeds are as big as TZ 750 reeds, just with an RD sized mounting flange. And the TZ had 34 mm oem carbs, I guess often replaced by 36 or 38 mm Lectrons.
you can fit rm100 v force reeds in rd cycls without modifying the cyls, have double the tip area and will outflow rz reeds.
Back before RZs and V Force I fitted TZ750 reeds (same as '78 IT175). An adapter plate had to be welded on and intake hogged out. Since TZ manifolds seem hard to get and I wanted to upgrade with a cross over tube I found Tri-Z manifolds fit the larger bolt pattern. The intake tract has no obstructions. I have 34mm carbs with single petal TDR reeds.
(https://i.ibb.co/xGCVP8B/20200113-122148.jpg) (https://ibb.co/GkxgB38)
Some spare parts to get the idea
(https://i.ibb.co/yRpz5r8/SANY2122.jpg) (https://ibb.co/7zQ3VqG)
(https://i.ibb.co/km8VDX2/SANY2123.jpg) (https://ibb.co/5K8XjLh)
TZ manifold
(https://i.ibb.co/ZmVBSJw/SANY2128.jpg) (https://ibb.co/16LrMnp)
Tri-Z manifold
(https://i.ibb.co/8cy4X4T/SANY2120.jpg) (https://ibb.co/16CJbJh)
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.
I installed YZ85 reed cages w/new TDR petals with this upgrade.
Rob
Hmm pics sure looked like modified stock RD cages with TDR reeds. Ed
stock yz cages look like that, but with 34s alone i could feel the difference vs the v force.
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
Quote from: EE on January 13, 2020, 11:52:47 PM
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?
(http://www.2strokeworld.net/wp-content/uploads/general-tech/reeds/DSC04306-scaled.jpg)
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.
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
Quote from: teazer on January 14, 2020, 09:10:14 AM
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.
Quote from: EE on January 13, 2020, 10:28:17 PM
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
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.
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
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.
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
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
This thread makes me wonder how much is gained by using larger carburettors on RDs.
As far as I understand, one of the main limitations/restrictions in all the 64 mm bore RD350/ 400/LC/YPVS engines is the transfer ports/ ducts. This due to the fairly tight bore spacing.
Next restriction would be the reed valve cavity. It can only be widened so much without a major effort.
So where does carb size become a limiting factor? After all, the RZ had well over 50 rwhp with stock 26mm (?) carbs. And some claim up towards 70 hp with 30 or 32 mm carbs.
I do realize the TZ350F came with 38 mm carbs, but had no reed valves.
up high it matters, i know that there was a guy int he uk that pulled 70 hp out of an r5 with 28s. saw the vid of the dyno run, it was VERY radical and ported to the moon, and did not last long. :devil:
however, i can definitely feel the difference between 30mm and the 34mm carbs. There have been times where i have considered going down to 32's or 30s again, but if they are tuned right the large carbs work really well IF the mods support it, however, typically with minor mods, slapping 34s on a stock motor with chambers will make it pretty terrible for street riding.
That being said, hes doing a track bike, so the mods need to be there as well, and the main theme after we all figured out what reed he actually had was: go with reeds that flow more.
Quote from: Plasticman on January 14, 2020, 03:47:17 PM
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
You'll be happy with those Swarbricks.
The 34s work real well on my bike that has the modified TZ cages and transfer port work done. I'm surprised how they can be jetted right on. If you get it up on the pipe holding it at 3/4 throttle and then open it up you notice it for sure. It's like a 4 barrel carb kicking in on a V8. A have a stock RZ350 that seems to run as it should, revs up to 10000, power valve working good, and the RD accelerates faster.
Quote from: Dvsrd on January 16, 2020, 06:23:49 PM
This thread makes me wonder how much is gained by using larger carburettors on RDs.
As far as I understand, one of the main limitations/restrictions in all the 64 mm bore RD350/ 400/LC/YPVS engines is the transfer ports/ ducts. This due to the fairly tight bore spacing.
Next restriction would be the reed valve cavity. It can only be widened so much without a major effort.
So where does carb size become a limiting factor? After all, the RZ had well over 50 rwhp with stock 26mm (?) carbs. And some claim up towards 70 hp with 30 or 32 mm carbs.
I do realize the TZ350F came with 38 mm carbs, but had no reed valves.
Keep in mind, what I'm putting together is a race only machine. I'm hoping it spends a LOT of time in the middle and upper end of the RPM range. If I was building something for the street then I would stay around a carb size of 30-34mm. But the other RD's I'm racing against are running 38's and have engines built by Harry Barlow. Once this upgrade is complete and tested, I fully expect fuel supply and traction to be the next two hurdles to overcome.
Rob
Are the brakes nice and strong on this bike that is going to carburate it's way to the lead? :thumbs: :burnout:
I would suggest that you look at any reed cage set up you might be tempted to use and compare the effective reed area when the reeds are wide open and compare that to the carb cross sectional area.
Another useful approach is to look at say a late model RM250 or YZ250 to measure port area and reed area to see if you're in the ballpark. No point in fitting huge crabs if the inlet restriction is tiny reeds/cages.
Another place you could look is Arctic Cat triples and Polaris triples with 200-300cc cylinders, and then look at their transfer port area to ensure that they are all in balance.
Polaris XCR9800 reed blocks are reeds are probably a touch large, so try a set from an Arctic Cat triple ZRT Thundercat or whatever they called them. That's what I want to weld onto a set of RD400 cylinders with lift plates to get enough port-time area.
You could just buy a set of OW31 reed valve TZ750 cylinders if the rules allowed it, or a set of TZ350G 6 port cylinders and add reed blocks and boost ports.
Quote from: teazer on January 20, 2020, 07:45:35 PM
You could just buy a set of OW31 reed valve TZ750 cylinders if the rules allowed it, or a set of TZ350G 6 port cylinders and add reed blocks and boost ports.
With all the crazy shit people do these days you'd think someone could take an OW31 cylinder, remove the water jacket and fabricate/weld some fins on it so it would be legal to race against the RD400s. 🤔
Quote from: 1976RD400C on January 20, 2020, 07:41:23 PM
Are the brakes nice and strong on this bike that is going to carburate it's way to the lead? :thumbs: :burnout:
I sure hope so. FZR600 disc, stock RD400 front caliper, Cannondale motorcycle master cylinder. All stock, OEM rear setup, for now.
Rob
talk to me about this master cyl. :umm:
I think they used Magura components...?
Wade
Yes V force reeds would definatly be a good choice , more reed tip area plus more reactive material , more pedals doing less work , every part of power band will improve . I have another recomendation for you , the carbs I build with venturi dividers , makes for a linear power band , its like opening 4 small carbs in series . Air velocity stays high throughout , Stronger pull out of corners and basicly any time the throttle is rolled on . You might be interrested in checking out my web site richstaylordporting,com
And always the use of UFOs is a must . They make a round slide out flow a flat slide carb up to 13/16 throttle opening ,
Rich
Quote from: racerclam on January 22, 2020, 12:42:09 PM
And always the use of UFOs is a must . They make a round slide out flow a flat slide carb up to 13/16 throttle opening ,
Rich
The UFO's I ordered showed up yesterday.
Rob
Quote from: racerclam on January 22, 2020, 12:38:02 PM
Yes V force reeds would definatly be a good choice , more reed tip area plus more reactive material , more pedals doing less work , every part of power band will improve . I have another recomendation for you , the carbs I build with venturi dividers , makes for a linear power band , its like opening 4 small carbs in series . Air velocity stays high throughout , Stronger pull out of corners and basicly any time the throttle is rolled on . You might be interrested in checking out my web site richstaylordporting,com
I've always wondered if those work.
Rob
UFOs work well , I build alot of carbs and all round slide carbs get them along with venturi dividers . The new UFOs are easier to install than the old ones , I helped Lon on redisgning them for this purpose .
Rich
What are UFO ?
Quote from: ~JM~ on January 23, 2020, 08:50:36 AM
What are UFO ?
Dime City Cycles has a nice explanation on them. You can purchase UFOs from many places.
DESCRIPTION
The UFO is a simple, trouble free, aerodynamic piece that fits VM Mikuni carburetors from 30 mm through 44 mm. The UFO makes a normal round slide carburetor out-perform the more expensive flat slide carburetor by eliminating turbulence and increasing air flow and velocity, creating a highly atomized fuel charge. Normal gains are 3/4 to 1 HP per 100 cc of engine displacement on 4 stroke engines and 1 1/2 to 2 HP per 100cc of engine displacement on 2 stroke engines. (Minimal rejetting and tuning are required).
(https://i.imgur.com/fMVUv9R.jpg)
Source: https://www.dimecitycycles.com/ultimate-flow-optimizer-ufo-mikuni-vm30-vm32-vm34.html (https://www.dimecitycycles.com/ultimate-flow-optimizer-ufo-mikuni-vm30-vm32-vm34.html)
Rob
I had RB install divider plates in my TDR's TM28ss carbs about 10 years ago.
Hard to tell the improvement as he did a bunch of other stuff (bored carbs to 29.5mm, skimmed head, etc)at the same time.
Will def be going in to do the reeds and intake as soon as I'm done with my LC, as the TDR is still running the 30 year old stock reeds and it feels pretty flat thru the midrange and made a lot less power than I expected when I had it on the dyno last year. :whistle:
UFOs are also available for banshee 26mm carbs . I modify UFOs to fit other sizes also wuite often .
Rich
Has anyone seen any published results of airflow or power with UFOs or dividers? I'd love to see the smoke effects or even better actual CFM changes and dyno results at part to full throttle.
Quote from: Jspooner on January 20, 2020, 09:08:24 PM
Quote from: teazer on January 20, 2020, 07:45:35 PM
You could just buy a set of OW31 reed valve TZ750 cylinders if the rules allowed it, or a set of TZ350G 6 port cylinders and add reed blocks and boost ports.
With all the crazy shit people do these days you'd think someone could take an OW31 cylinder, remove the water jacket and fabricate/weld some fins on it so it would be legal to race against the RD400s. 🤔
Or just mill 6mm or so off the top of some RD400 pots and slide the same amount under with a lift plate. That would get port timing into the same region. Now all we have to do is to remove the port dividers and replicate 3G3 6 transfer ports. And that would still need much larger reed boxes and cages. Arctic cat or Polaris XCR triples come to mind as alternatives.
TZ750 cages are too small for TZ750 cylinders. They were fine on a 90hp motor, but not so ideal for more power. I use Blaster reeds on a single 700 (TZ750A) barrel and 6 petals on a 375. There are probably better reeds out now and to be clear, I bought the 6 petal cylinders. I can't claim credit for them.
But if the class rules are stock cages, that sort of limits things.
I dont have dyno results on my dividers . But lots of customer results . You can see some on the testimonial page of my web site richstaylordporting.com what you can expect is linear power on ANY machine you put them on . There is a RD 400 road racer in that page that I did all the port work on as well as carbs , His first report before I did any port work was a much harder pull out of corners and he did dyno it and also gined 1 hp through out although that is not alot , the stronger linear power was . There is also a 2016 TM 125 on there that proved my thoughts that with the dividers a power valve would not be necessary , so he disconnected the electronic PV and connected it to a choke lever cable acuated PV and he reported better performance from off idle to top . I have done many carbs for some customers , I jst compleated a 6th carb for one guy and have done 15 for a top snowmobile racer . Doinf four more right now . THEY WORK . The ones RB did used only dividers at 1/2 throttle which has sone benefit , BUT does not compare to having one at 1/2 qnd 3/4 throttle positions , its like opening 4 small carbs in series , air speed stays constant . If any one want more evidence I can hook you up with my customers directly , They wouldnt mind at all.
Rich
Have you decided how your bike is going to inhale yet? :guinness:
Quote from: 1976RD400C on January 26, 2020, 01:56:22 PM
Have you decided how your bike is going to inhale yet? :guinness:
Probably in big gulps.
Rob
TZ/RZ sized single petal TDR reeds installed
(https://i.ibb.co/kD4WQ0c/SANY0188.jpg) (https://ibb.co/dpPzG6K)
Oh yeah, that's the stuff!
Wade