Neat little oddball bike, zero info.

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Messages - Vintagetz

Turning Wrenches / Re: Intake spacers,
September 24, 2023, 04:26:22 PM
The also allow you to put larger reeds in with less porting.  The spacers are virtually required to put V-force Banshee reeds into an RD.  The intake boxes taper will normally break out if you open them enough to get the reed in with a spacer.
I have a complete RD400 suspension setup.  The forks are from a race bike.  I did not do the internal work, they came on an RD250 racer I purchased, it was professionally built.  We ran it at Daytona Ahrma in the Mid 2000's and won the Daytona Ahrma race with them (they work well) it is Forks, clipon's master cylinder, caliper SS Line Triple clamps Axle and spacers for a 350 spoked wheel.

Legs need to be polished, new seals and fresh oil.

I also have a complete rear swingarm, caliper bracket and caliper setup.

would be great for a 350 Disc conversion bike.  I struggle to price it, want a fair price, the calipers need rebuilding and it all needs a good clean up

Can anyone throw a dart at a fair value?
Turning Wrenches / Re: IT175 pistoned RD400 motor
April 05, 2023, 06:50:00 PM
They work well, they lower the intake port which improves the intake timing.  I built high performance RD350 and  400 motors using IT pistons in the late 70's.  Nothing really to be afraid of other than you have to be careful of which year IT piston you use / purchase.  There are two versions, and only one of them has the ring pin location that is correct for the RD port layout.  I use blaster pistons in my race motor now,  They may have the same pin offset as the IT piston.  I think I have a used blaster piston that I am not going to use, it would let you see if it is an appropriate match for your cylinders.

Looking at your cylinders they appear to be 2VO (Daytoma) this is a good high-performance casting.
Show Off / Re: New RD race parts
March 12, 2023, 01:23:18 PM
Quote from: m in sc on March 07, 2023, 03:43:48 PM
sweet. these from ralph as well? ie not the indian ones?

Yes, I bought them a long time ago and my intent was to get them machined for a couple of race motors.  the machine shop that Ralph uses got really busy and will only do a full run.  Ralph has the molds but the foundry he used went out of business.
Show Off / New RD race parts
March 07, 2023, 03:15:46 PM
I purchased multiple sets of the WEBCO re-pop castings,  they are the better A355 material.

I was waiting to have them machined but waited too long to have them done by the original machine shop,  I have a source to cut them,  one set for the new 250 race bike and another for the 400, one set is for my buddy's 400.
Stan is a friend, a VERY talented builder, racer, and rider of both 2 strokes and 4 strokes.
Turning Wrenches / Re: Tuning AC RD350 front suspension
February 14, 2023, 05:55:30 AM
Quote from: JBeasty on February 14, 2023, 01:54:09 AM
A few questions...

Since I have an adapter, I don't need to cut the pin correct? It clears with room to spare. Will it effect oil flow much if I leave it in there?

Also I've got one fork put together, but I'm not sure how to get the allen head bolt in the bottom of the fork tight without the damper rod spinning. I don't want to hit it with an impact driver (like I did to get it loose), for fear of breaking it off at the head or worse. I think the torque spec is 11 - 22 ft-lb.

I'm gonna go pick up some fork oil tomorrow, was thinking 10 wt to start? Manual says 144 ml (4.87 oz), but should I instead bring it up to a certain level above the cartridge emulator? I know a lot of this is gonna be trail and error, just looking for an educated guesstimate.

with a 9KG spring 15 wt is what I use.

I made a tool for my Daytona damper rods, it is a T handle with a metric bolt welded to it, the top of the rod has a 12-point female "socket" the bolt engages.

You  could make a tool that has a couple of pins sticking down that would engage the cross pin with a T handle at the top.
Turning Wrenches / Re: Tuning AC RD350 front suspension
February 13, 2023, 10:13:47 AM
Very nice work !
It is not likely an issue on a street RD, the TZs have the same difference between the 250 and 350 as far as primary ratios.  If you run a 350 top end on an engine with a 250 primary you will very likely break gears. (transmissions are the same). 
Turning Wrenches / Re: Tuning AC RD350 front suspension
February 12, 2023, 04:22:32 PM
I use racetech valves in my race forks and they gave me a huge improvement. 

The pictures above are perfect to show the modifications and the adapter.

This has been covered in various answers, I will try and share my experience with installing and tuning emulators..

Fork Springs are a VERY IMPORTANT part of getting the front end right.

the stock damper rod uses fixed-diameter orifices, which means they are not speed-sensitive.

First, understand standing what each component does.

The spring holds the front end of the bike up  (I use straight-wound springs)  the more the bike and rider weigh the stronger the spring you need.

Compression damping absorbs the energy of a bump and also controls the rate of spring compression during braking and at times both.

Rebound controls the release of energy stored in the compressed spring as the front end rebounds from a bump or braking or a combination of both.

The gold valves provide speed-sensitive compression damping through a combination of a washer stack and an adjustable spring with rebound damping being controlled by the weight of the oil.  the more you tighten the spring the more it restricts the flow of oil during fork compression.  Too much compression damping will lead to post-bump chatter,  this can be while straight up and down under braking or leaned over in a corner (VERY SCARY).  Not enough can lead to over-compression (front-end dive) under braking.

The reason the damper rods have to be drilled out is that the existing compression damping system must be eliminated, it uses the smaller diameter holes to restrict oil flow BUT it provides very little in the way of speed-sensitive damping, speed meaning the rate of available flow to adjust for the speed at which the forks are compressing.

You can see the small diameter bleed holes at the base of the damper rod, these get drilled out to 5/16"/8mm.   My forks use Daytona damper rods which do not have the flow restrictor on the top of the rod, they are the same as the RZ350 with an open top and RZ350 emulators drop right in.

There need to be 3 sets of larger drilled holes through the damper rod.  On most forks, there are two smaller sets at the bottom about 10mm apart and at 90 degrees to each other.  a 3rd set is drilled the same distance above at 90 degrees to the top set (use a pilot drill to add the 3rd set or you will have an issue drilling them straight.  They don't have to be perfectly aligned, they are there to pass as much volume of oil as possible up to the gold valve.

NOTE THE HOLES NEED TO BE WELL DEBURRED, drilling through the tubing will leave some nasty burs that can fall off later (I use a dremel with a small ball end burr)

For the early damper rods and 400 damper rods an adapter that seats on top of the rod and provides a nice flat surface for the emulator to sit on is all that is needed.  the spring seats on top of the emulator holding it in place. 

As was previously stated if the top of the damper rod is open and the same ID as the steel rod this is all you need together with the adapter.  400 Damper rods other than Daytona) need to have the top cut off.  While doing it on a lathe makes for a nice even cut it is not absolutely necessary as the emulator sits on top of the adapter - spacer. it needs to be cut off far enough down so the emulator fully seats and fits flat on the adapter spacer. I think a nice even cut with a hack saw that is fully deburred will work fine.

Adjusting compression is a matter of adjusting the tension on the spring.  I run mine at 3.5 - 4 turns down.  you back the center screw out until the spring is loose, then wind it back until the spring is in contact with the emulator and the top washer under the head of the allen, then count the turns down. The fewer turns from contact the lighter the compression damping.  Too much compression damping with cause the front to chatter as - after you hit a bump.

Rebound damping is controlled by bleed back holes in the damper. Rebound is adjusted but changing the weight of the fork oil, I use 15wt.

Once you have modified the damper rod it is only a matter of assembling the new setup.


This is an important part of the upgrade.  I run between an 8.5KG and 9KG straight wound spring,  I can't really tell much of a difference.

As far as setting pre-load, sag is an important indicator that you have the preload correct,  Max at Traxxion dynamics gave me a rule that I have always followed for pre-load, a spring should never be compressed more than 20mm-3/4", if you need to compress it more than that you need to go to a stiffer spring.  I run a 10mm spacer. PVC makes a fine spacer

I can understand that for street use a progressive spring will yield a more compliant ride at lower speeds, I'm not worried about that on the track as even the out-lap is at a good pace.

I have not modified any  76-78 400 forks, all of my stuff has been Daytona, RZ, FZ/FZR and R6.  I will try and film doing a set, honestly, it can be done with a standard drill, a center punch, a couple of drill bits, and a saw if you are careful and pay attention to detail. 

Show Off / Re: My new 2stroke toy...........
February 03, 2023, 07:09:22 AM
Quote from: busa1300 on February 01, 2023, 08:50:31 PM
Looks like a piece of art.
If it's light enough, I'd hang it on a wall after I was done with it
Good luck getting back on the track this year.

After a lot of input from friends, I am reconsidering racing it. I have located a chassis, it does not have the swing arm, linkage or rear brake.  If I can locate the balance of those parts I can build a matching bike.  A buddy suggested the same and it is light enough to mount on the wall.  He suggested the NOS bike on the wall with a matching racer parked under it.
Show Off / Re: My new 2stroke toy...........
January 29, 2023, 09:23:18 AM
It was absolutely like Christmas.......   Holy crap is it light... 
Show Off / Re: My new 2stroke toy...........
January 27, 2023, 06:38:42 PM
It arrived a day early, yesterday in good order.  I am on the flight home, I will get my hands on it tomorrow AM.. Just want to sit on it and make 2stroke noises  :whoop: :whoop: :whoop:
Show Off / Re: My new 2stroke toy...........
January 25, 2023, 07:28:54 PM
It will arrive Friday afternoon, I get home late Friday night.  My neighbor is going to receive it, I will get my hands on it Saturday AM!!!

I am going to pull all the original parts off the bike and properly store them.  Fairing, seat, front end compete including brakes and master cylinder, wheels, motor, gauges, graves bracket, pegs, shock motor, carbs, ignition and pipes.

Probably easier to say I am going to use the frame and swingarm.

I have a used tank that needs a little correction, its perfect cosmetically someone moved the petcock I think for a 4 stroke conversion, move it back to the stock location.  Carbon seat, new T fairing, U front end with dual disc, 17" Technomagnesio wheels, and new controls.  I will use a Mychron 5 for instrumentation.  I have a new Works sealed motor complete with all accessories and pipes.  I will probably purchase a Penske shock. I hope to have it on the track by late spring.  I will probably start with the 250 motor to get used to the bike,  preparing another motor and pipes for the 320cc top end for an upgrade.
Show Off / Re: My new 2stroke toy...........
January 23, 2023, 06:29:31 AM
No It was auction in the good old USA,  I am going to E-mail you