Hey All, Does anyone know if an OW31 Top End will bolt on to a RD 400 bottom end?
wrong stroke but the pattern is the same
Can R5 cases be used?
yes.
Do you mean a genuine ex works 6 port with reed valves or just any TZ750 top end? I have an early TZ750A top end on a set of RD350 cases with RD transmission and TZ waterpump and crank. All TZ750 top ends have the same bolt pattern as an RD250/350/400.
Yes Teaser, a reproduction 6 port with reed valves. Can a RD400 crank be built with 110mm rods?
You can use 110mm rods
or a 5mm base gasket from Cometic... or 4mm and take the port change
Might want to consider the rod/stroke ratio if for street. You would be going from an already 1.85:1 to 1.77:1, no problem on a well maintained race setup. Just a thought.
Would a LC setup like this be too hot for the street?
Not exactly the best set up for the street. If you want to use the RD400 bottom end, keep the 115mm rods, use a lift plate and then work out what changes you need to make to porting to make that all work.
6 transfers are better than 4, but you could usefully increase the reed area and use even larger carbs if you insist on using that top end.
I fitted a 409-OO 64MM bore "TZ700" on an RD350 bottom end and it is really mild. For the street it would be best to port it to what you want in terms of port timings to get the time/are that matches how you plan to use it. You can use any of the commercially available software such as Bimotion or MOTA to devise targets and port dimensions to match those targets.
For the street, I think an RZ or Banshee bottom end with Athena 421 or CPI top end would make a lot more power. You need an RZ transmission though. Banshee ratios are not the best.
I have a TZ/RDLC motor in one of my street bikes and I love it. Runs awesome and makes really good power. If you are looking for power though I'd bet Teazer is right about using an RZ or Banshee motor, but in my mind there's just something about the "TZ" part of it that's just really cool.
OK All, If I want to build a dirt drag engine for the 400cc gas class, 500 foot dirt track, can be 410cc max but 4 strokes can be 450cc. What's the best setup? Any and all opinions accepted! Joe
long rod 375 setup id say.
but if you are working w a 400 setup, that limits a few things, so id either trade out the 400 lower end for a 350 one as the options get more spread out (375 setup, etc) or track down a set of air-cooled 400 cyls and have them ported to the moon.
I'd use the motor I have but only more heavily ported with 40 or 42 lectrons or a heavily built banshee motor at the max bore size and still be under the class limit, also with giant carbs.
I'm with JSpooner. If I already had a solid 400 foundation, I would develop that as far as it can go with much bigger reeds and carbs and ports.
if I was starting from scratch I would seriously consider a built Banshee with say a 421 CPI or Athena top end or larger and build a motor that could make way more HP that a ported 400.
If I had access to a 6 port TZ350D/E top end, I would sit down and work out target port-time areas and then work out if a 62mm bottom end would work and where would the ports need to end up.
Either way, I would start by working out HP targets and work through what I would have to do to achieve them before I started to sink tons of cash into the project. And if all budget becomes an issue as it does with all my projects, work out what you can do to a 400 to get as far as you need to go. Not a lot of point in sinking say $10 grand in a fully built banshee motor to win a $5 trophy and bragging rights.
OK All, I do have 2 rd400 complete engines and 2 r5 engines. One of the r5's is setup as a real TR3 top end with 34mm mikuni's, TR3 CDI, and factory chambers. The rules at the drag strip state that motorcycles must use motorcycle engines. Technically, a Banshee engine is a quad engine. Not sure which way to go A/C or L/C?
id go aircooled 400. simpler. no chance of blowing coolant all over the track either. also longer stroke = more torque
Banshee is just an RZ350 without powervalves and with different gear ratios, so I wouldn't worry too much about that, but you already have RD400 cores to work with, so it seems to me that's the logical approach.
Now work out how much HP you want and if the RD400 cylinders will get you there or if the TZ750 top end can be made to work for your application with a spacer plate. Both approaches will require a fair amount of time on the porting bench, so start calculating.
I'd go water cooled. I'd take your R5 cases and put one of your RD400 transmissions in it and then I'd port the shit out of that OW31 cylinder you mentioned, get some giant carbs like I mentioned before and have some pipes built that give you the power delivery you need for drag racing. The reason I'd use the R5 cases is because that TZ cylinder will bolt right on and no rod or stroke change is needed and no spacer plate needed. Blaster reed cages fit the TZ cylinders perfectly.
So, one of the rd400 engines that I have came all apart when I purchased a complete rd400 barn find with that extra engine. The parts are all there, but the crank has a bad rod bearing. Assuming that the crank needs rebuilt,
If 110mm rods are used instead of 115mm rods, could we then use the OW31 top end without a spacer?
wont the pistons hit the crank? also the different stoke? why not just either use the other r5 bottom if you insist on using that top end?
Quote from: JR on December 04, 2023, 11:17:35 AMSo, one of the rd400 engines that I have came all apart when I purchased a complete rd400 barn find with that extra engine. The parts are all there, but the crank has a bad rod bearing. Assuming that the crank needs rebuilt,
If 110mm rods are used instead of 115mm rods, could we then use the OW31 top end without a spacer?
The 400 crank still has a different stroke regardless of rod length. Why not use the R5 bottom end? I'm sure the 400 bottom end could be made to work with the correct spacer plate, porting changes, etc, but why? It works perfectly on an air cooled 350 bottom end. It works even better on an LC bottom end because then you have the built in water pump you don't have to think about.
JR, last year when we discussed this if I remember correctly you were adamant about using the R5 bottom and exactly 410cc and finishing in 2nd place was out of the question, this required bore/stroke/rod changes, dyno time, crank balancing etc making for a costly build. Now that I see you are allowing a 400 into the mix a much more logical build is possible, by the way, do not short rod the 400, go 120 or maybe 122 to 125. You are running in the dirt and a short rod might cause wheel spin, you need to hook up right out of the hole. My first thoughts without studying it would be 2R9 cylinders @ 64.75mm bore, crank build, porting, 40 Lectrons, 6 petal reeds etc.
John, I didn't think that you were still interested in building this motor for me. I would be happy to have you do this project! As far as the 2R9 cylinders, I was having problems locating a set for sale last year. Joe
Joe, I was only suggesting a possible build combination, I have to pass, I'm finishing up odds and end customer jobs, not taking on anything new. I have several personal projects of my own I'd like to see completed. One is a stroked GT80 for our RD60, a very intense 175 drag engine, revamp the current 175 drag engine for nitrous, reassemble our RD400 land speed engine and dyno build pipes for it, finish the land speed FJ1100 chassis and build a 400 bottom with sleeved and injected R5 with a Procharger engine and my son reminded me Monday I promised him a 522cc build for our street RD400, I better live to be 100 because at the rate I'm going it will take until then.