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Below is a new article written by TZ350 and 250 Website member Jamie Linxwiler on his experiences building a replica TR3.
The article has been edited to remove company names apart from those who have contributed to this website in some way in the past, in keeping with our policy of not providing inadvertent "free advertising". It's a long story but the website was "used" for too long.
TR3 Replica RD 350
I thought it would be useful if I put together an up-to-date article on building a TR3 Replica RD 350, using parts and resources that are currently available. It is remarkably simple and straightforward to build a replica TR3, and you end up with a really fun project that performs extremely well.
Ever since the early 70's I have wanted a TR3 or TD3. Back in the day, poverty (spelled, college) got in the way. In more recent years, I wanted to race one in AHRMA, but I had trouble finding a good one that I could trust for a reasonable price. I had some major health problems in 2002 and early 2003 that short circuited my racing, and I eventually concluded this project was just the ticket to take my mind off my problems.
Picture: Jamie with his TR3 replica at the Tanacross circuit, Canada.
A word of warning: I am going to assume in this article a fair level of sophistication in the reader. Even though this project is relatively easy, compared to some more difficult bikes to build, you should not tackle anything like this without a lot of experience and a lot of bike savvy, or you should have the guidance of a friend who knows what he is doing. I like to fabricate and weld, and I have built a fair number of bikes, and I have been doing this since the 1960's. You must be the judge of your own mechanical and engineering talents, but remember, if it breaks while you are on it, you can get hurt, so act accordingly and be realistic about your talents.
One other point: why build a replica when you can buy and restore the real thing? Some of you will certainly disagree with me, but, basically, my theory is simple--to build a week in, week out race bike that is going to be seriously used and abused, worn out, and pitched up the road, I have always preferred something other than a bike valuable for its historic provenance, and I also prefer something for which you can easily get inexpensive and plentiful spares. And what's more, the overall cost of this project is much less than a used TR/TD, and you get to have all the fun of building it!
1. RELIABLE AND TRUSTWORTHY SUPPLIERS
The first basic key to this project is finding a good group of reliable and trustworthy suppliers. I cannot emphasize this enough. I started literally from scratch, with nothing, no donor bike, not even any parts, and I am in Alaska, very far away from any suppliers. I was thus very dependent on the quality of the people I was dealing with. The parts in this bike came to me in boxes, from reliable suppliers all over the US, without a single hitch, because all the suppliers I used were trustworthy. First, for the basic cycle parts, the frame came from a friend, the engine(s) came from a local junk yard, and the used wheel hubs, forks, axles, and related pieces came from (a Californian supplier) which has a large stock of used parts. Next, I used three primary sources of RD350 race parts in the (a Californian supplier); (a supplier in Florida), and Accu-Products in Ohio, and I can recommend all of them as fair, and honest, and reliable. There are other reliable suppliers, of course, but these are the ones I dealt with. The crankshaft (rebuilt, welded, with rods and mains and seals), PVL ignition, fairing, windshield, gas tank, seat, fender and fairing brackets came from Rick Merhar at Accu-Products in Ohio. The pipes and swingarm bushings and steering head bearings came from (a Californian supplier). The pistons, reeds and gaskets came from (a supplier in Florida). I also used other suppliers: the fork tubes came from (a supplier in Illinois); the wheels and spokes came from (a Californian supplier); the front brake caliper and disc and steering damper came off my garage floor (rejects from another race bike); and the carburetors came from the friend who supplied the frame.
The RD 350 frame is essentially identical in design to a TR3/TD3, except that it is made from heavy mild steel. It works just fine. It has a number of additional brackets welded on, and the seat loop and the passenger peg brackets are somewhat different, but it is basically the same thing. A friend gave me a frame, and I removed the battery box, air box, reflectors, kickstands, and so forth, and then used a body grinder to grind off the sidestand and centerstand brackets and various welded on tabs. I left the brackets for the rear fender, the coils, the gas tank mounts, etc., which are identical to the TR/TD frame. Don't cut anything off you will need, of course. Some folks cut off the seat loop and passenger peg mounts and fabricate something that looks more like a TR/TD, but I chose not to, to keep it simple.
I have always thought the 16 inch long RD swingarm was too short, especially for modern tires. To get some weight on the front wheel and to resist wheelies, I found a Yamaha DT2 dirt bike swingarm, which is 18 inches in length, and which otherwise fit right into the frame. I fabricated wheel spacers, and matched up brake stay arm and actuating rod parts to fit. I added bronze swingarm bushings and tapered roller bearing steering stem bearings. I used the standard triple clamps. I also mounted Works Performance shocks custom made for the swingarm (the mounts are in a different location than stock) and in a 14 inch length that added some ride height and swingarm angle.
Rick Merhar at Accu-Products is an excellent fabricator and supplied the chromoly TR/TD fairing mounts (which are literally indistinguishable from stock) and the patterns to use to locate them while you weld them onto the frame.
I added a vintage style Red Wing (Kawasaki Z-1) steering damper I had laying around, using brackets I fabricated.
I made a set of footpegs out of one inch aluminum rod, center drilled and knurled on the lathe. In the interests of getting some weight on the front wheel, I mounted the pegs at the front of the stock passenger peg brackets (the TD/TR pegs are about 4 inches farther back). This required trimming the stock fairing. I fabricated foot controls to fit. I fabricated the shifter out of heim joints, steel rod and a standard shift lever cut short. The rear brake was much easier--I just cut the stock pedal shorter and welded on a piece to push on. If I had mounted the pegs in the TR/TD location, I would have had to make a heim linkage for the brake pedal too.
I could easily have used TR3 cylinders, heads, pistons, expansion chambers and intake manifolds. I didn't, simply because those parts are expensive. Instead, I used RD 350 parts, in keeping with the approach I used on the whole bike--keep it cheap, and use stock RD parts as much as possible.
Each of the main suppliers mentioned above, and several others, also offer porting and engine building services, but I am a "do it yourselfer", so I did my own porting and engine building.
I include here some information for those of you who are also interested in doing your own engines.
The crankshaft is the heart of the engine, and Rick Merhar at Accu-Products built mine-welded, trued, with new rods, race bearings and seals, on his core. Maybe I am just lazy, but it is much easier to open the box and drop it in, than it is to find all the parts, assemble it, true it, and weld it, and the cost was only a little more than the cost of parts. Rick used RZ 350 rods, which have a slightly larger wrist pin bearing, but the same size wrist pin.
I used Banshee pistons, forgings from Wiseco. These expand a lot, so I set the skirt clearance at .0045. This is barely enough at race temps with the stock RD steel liners. I will continue to replace the pistons with the same size until it has perhaps .007 clearance or so, and then re-bore. The Banshee pistons have very large port windows in the back. On the RD 350, once it is fully ported, this results in the intake being open through 360 degrees, and the intake controlled only by the reed valves--it breathes plenty well through this big hole. Because AHRMA requires RD 350 reeds (no TZ 750, or RZ reedcages), I have used at different times both TDR and Boyesen reeds for the RD 350, and both seem to work very well up to 11,000 or so. Many years ago I built an RD 350 with the much larger TZ 750 reeds, and nowadays folks unconstrained by AHRMA rules build them with the larger RZ 350 reeds.
Because of AHRMA rules, I used 34 mm round slide Mikuni carburetors. Jetting is very different bike to bike, and your engine may use something drastically different--proceed at your own risk here. I start with 300 main jets, P-8 Needle Jets, 6F5 needle in the middle, 45 pilot jet, 2.5 or 3.0 slide, and a 2.0 air bleed jet. I use little foam sock air cleaners, because the track I usually run on is very dirty with lots of small rocks--the filters are not too restrictive, and whatever I lose in flow, I make up in extended engine life.
I use a new, modern PVL ignition (more or less the same as a Motoplat) timed at 1.8 mm.
I use 110 octane US race gas, with Motul mixed 24 to 1. I learned the hard way. Don't ask, it will only make me feel foolish.
I originally tried to use a stock tachometer on a fabricated bracket, but eventually bought a Scitsu tach instead, which worked well and fit under the fairing much better.
There is a lot of information on the internet about porting the RD350. For instance, the excellent Dale Alexander series "The Art of Squishing Things Until They Make Power" is very specific about porting the RD 350 motor, and it is on the internet in several different places. It is available on the Air-cooled RD website, http://www.aircooled-rd.com/, under "technical" and then "tips"; it is also available on the (a Californian supplier) site and at http://www.geocities.com/rssarma/articles/dale_1.htm. The Dale Alexander articles basically is a "how to" guide on building a good RD 350 cylinder--in summary, they suggest you raise the exhaust port 2 mm (27.5 mm from the top of the cylinder (TR/TD spec is to raise the exhaust port 4 mm to 25.5 mm from the top) and widen it, widen and lower the intake ports, significantly enlarge the transfers and the boost port, cut a 10 mm window in the cylinder wall at the base of the main transfer, turn the step off the top of the cylinder to allow use of the RD 400 head gasket, and set the squish at .032.
There is also a set of port maps and photos of various TZ, TR, and TD cylinders at http://www.erlenbachracing.com/ for those of you who wish to copy those more radical specs (more rpm, power, and heat).
I ported my first set of cylinders using the Alexander specs. The porting is fairly conservative, and yields a good spread of power. On my next set, I will experiment with more exhaust duration, like a TR/TD (25.5 mm from the top).
I use a set of Millenium pipes from (a Californian supplier). These work great, with lots of rpm and good midrange power. These are RD 350 pipes, not intended to be used under a fairing.
Because the head pipes come straight forward out of the cylinder some distance and hang down lower than TD/TR pipes, you must trim the front and bottom of the fairing to use these pipes in this application. Pro-Flo and Accu-Products, among others, also sell pipes. I initially used a set of Factory pipes -- identical to the Toomey pipes. They were very torquey and smooth, but I needed them back on my street bike. I have also built pipes in the past, using the formulas in the old Gordon Jennings Two Stroke Tuners Handbook (formulas very similar to the A. Graham Bell book). As anyone who has done this knows, this is a lot of work, and I don't think you necessarily save any money, or get a better pipe, doing it yourself.
Something I have not done yet is to have the heads cc'ed and modified to TR spec. I am using stock RD heads with.040 squish band clearance. There is probably more horsepower (and heat) in bringing the squish band clearance down to .032 and the combustion chamber volume down to 19cc.
You should carefully inspect all the transmission gears, bearings, and shafts. You don't want any problems here--if it seizes the transmission or breaks a gear, remember that this is downstream of the clutch and the back wheel can stop solid. I used stock gears, and a new clutch with stiffer race clutch springs. I cut the 90 degree tube off the nylon transmission breather boss, drilled a hole in the end, and slid a breather tube over the whole thing--if it loses a crank seal, then it will put a lot of pressure into the transmission case, and it thus needs to vent well or it can blow oil seals out.
I stayed with the stock size 530 chain, only because I already had several 530 sprockets, and a new 530 chain. If I had started from scratch on this, I would have gone to 520 chain. I will eventually make this change.
4. Suspension, Brakes and Wheels
I mentioned above I used the excellent Works Performance shocks. Outstanding shocks, of course, which is why they are the standard for vintage racing in the US.
I carefully rebuilt the stock forks, but realistically, they are grim for racing. While the tolerances in the stock fork damping pieces are quite close and precise, I suspect the problem is with the lack of effective piston rings on the damping rod pistons--the oil probably just flows around the piston and misses the entire damping system. My first effort this year will be to make better piston rings, and if that doesn't improve things, I will be trying the Race Tech Emulators in the hopes of improving the fork damping.
I used stock hubs with fresh wheel bearings, and I built them with big 7 gauge front and 8 gauge rear spokes from (a Californian supplier) for stiffness, and with WM 3 front and WM 4 rear Excel rims, also from (a Californian supplier) with Avon 110/80 AM 22 front, and 130/650 AM 23 rear. This is a much larger tire and rim combination than many others use on this bike, but I have used these tires and wheels in vintage racing for many years and like them very much. The Avons heat up quickly, wear well, resist overheating, and they have very good traction both turning and stopping. The tradeoff is that the bike doesn't steer particularly light.
For brakes, on the front I used a drilled 11.4 inch disc off a 1969 Honda CB 750 which I had lying around. It required enlarging the register (the center hole) to fit the hub, and the fabrication of a ring spacer to locate the disc farther from the spokes, for caliper clearance. I used a Grimeca 1055 caliper (twin to the Lockheed racing caliper) I had taken off another vintage race bike project, and I used the CP901 pads from (an American supplier). I fabricated a caliper bracket from 3/8 inch 7075 T6 aircraft aluminum to mount to the stock fork lugs.
The master cylinder is an 11 mm race piece, also from (an American supplier), with the size chosen off (an American supplier's) chart to have the right hydraulic ratio for good stopping. I made a stainless steel line to fit, with parts from the local race shop. On the back, I used Ferodo racing linings on the stock drum, also from (an American supplier.) The bike stops exceptionally well--it will pick the rear up in a very controllable way.
I used some really cool looking Pro-Flo CNC machined clip on handlebars, and a stock RD clutch perch with a really trick period lever from Accu-Products. Due to the PVL ignition, I use two kill buttons, one on each side, connected separately to the coils. This is standard AHRMA practice.
I fabricated some spools out of aluminum on the lathe which mount on the ends of the lower shock bolts (allen bolts) for the bike stand to engage on. I made a bike stand from two of the triangle bike stands that come with modern motocrossers, joined with 1/2 inch rod, and welded cut slotted washers on the top to pick up the spools.
5. FAIRING AND BODYWORK
I got the TZ 250 B fairing and brackets and Gustaffson windshield, the TR/TD/TZ seat, the front fender, the splash shield ,and the TD tank, all from Rick Merhar at Accu-Products. The fairing required trimming because I relocated the footpegs forward from the stock location, and to fit the pipes. The bodywork came in white. I haven't painted the standard TR/TD red stripes on it yet. Just lazy, I guess!
6. RUNNING IT
So how does it work? Great, just like you would expect. It is so light, it feels like a bicycle when you roll it around, and it handles and stops razor sharp on the track. So far I have kept it jetted a touch rich on the mains, to keep it cool and let it live, but it still pulls hard to 11,000, and it makes very good power.
Of course it would make more power and rpm if I used TR 3 cylinders, but that would cost perhaps $1000 more for all the necessary pieces, in good new condition, and that wasn't what I wanted to do here.
I cut some corners, no doubt, and I did not use the very lightest pieces money could buy for the frame and cylinder. However, the difference in weight between the very expensive TD/TR frame and cylinders, and the inexpensive RD parts I used, is not really noticeable, perhaps the weight of last night's dinner and beer (well, okay, several beers, and a big dinner).
Granted, to a knowledgeable eye, it is not a dead ringer for a genuine TD/TR. The pipes are the first hint something is not right, and the frame seat loop also gives it away. At a closer distance, the reed valves become apparent. But for the modest cost and the high level of performance, and the fun I had building it, it is close enough for me!
The following section is the latest update by Jamie, received January 2011..........
7. ENGINE AND TRANSMISSION AND CHASSIS UPDATES AFTER 6 SEASONS.
Okay, if you have read this far, you know where this bike was at the end of 2004. 255 lbs, worked and handled great.
I will proceed from there to where I am now, six seasons later, with a 430cc RD400 based engine, Harry Barlow porting and pipes, lightened crank, nikasil liner, 38 mm carburetors.
As I did the first time, I will simply name all my suppliers, and let Greg delete them if he wants to. (Sorry guys, its a long story .....Greg) These are the guys I use and have found to be reliable, but of course there are other good guys out there.
At the end of the 2004 season, I took the bike in the trim I described above to Barber, the last AHRMA race of the year, to see how close it was to competitive in AHRMA's all air-cooled Formula 500 class. Long story short, it lacked hp and torque. The fast guys were using 1976-77 RD400 engines, developed and ported by (name deleted), a British tuner who had been coming over to race AHRMA races a few times a year. His engines are very reliable and make very good power, but not because of radical porting. What they build works so well because of the combination they use.
Although very similar in design, compared to an RD350, the 76-77 RD 400 motor is better because it has larger displacement and longer rods (thus more torque), and a closer ratio transmission. It unfortunately also has a heavier crankshaft, which is the primary reason folks back in the day continued to race RD350's in preference to RD400's. The RD400 uses the same pistons, reeds, bearings and seals as the RD350, but the cases, crank, rods, cylinders, heads, clutch basket, primary and transmission gears, trans shafts, countershaft sprocket and other parts are all different. Since I couldn't reuse the parts, the RD350 race engine I had was basically a throwaway, and now it resides in my street RD.
I am definitely not one of the fast guys, so I needed all the help I could get---and that meant getting a (name deleted) ported RD400 into my frame. I got ahold of (name deleted), who was very forthcoming about information and he ported my cylinders the next time he was in the US. Since (name deleted) was only here a short time, I also talked to (name deleted), his friend, who has a two stroke shop in Clearwater, Florida. (name deleted) is a long time road racer, who has won AHRMA's Formula 500 class championship several times, using engines ported by (name deleted).
I have used two different engines.
The first was stock displacement, with a stock weight crank. I got the ported cylinders and the pipes from (name deleted) when he was visiting here in the US, and the head work done here in Alaska. Rick Merhar built the crankshaft. I used Wiseco forged Banshee pistons (same .0045 clearance as above), with an antifriction coating on the skirts, and ceramic coating on the tops. (name deleted) recommended (name deleted) for this, but other companies do it also. I used 38mm VM Mikunis jetted per (name deleted)'s specs, mounted in Yamaha twin cylinder snow machine manifolds with a boost bottle made by (name deleted) to improve torque, joined up to ported RD 400 reed cages (AHRMA requires stock OEM reed cages). These cages were the same as I used in my 350 engine (open the window upstream 5-7 mm, remove the divider, use a 3/8 inch thick reed cage spacer, and full width TDR reeds). I used my PVL ignition from the RD350, except that I time it at 2.1-2.2 mm BTDC, to account for the longer rods--this is still 19 degrees, just like 1.8 BTDC on the shorter rod.
(Names deleted) also strongly recommended undercutting and treating the transmission. In the interests of time I did not do that, and that proved to be a mistake, because the bike jumped out of gear a fair amount, sometimes at dangerous times like on fast straightaways while I was being drafted.
I first used it at the first race in 2005 in North Carolina. The engine was very overjetted and slow on the straights ( (name deleted) specs were for oxygenated fuel, and were 40 numbers high for normal race gas) but otherwise everything worked great. Memorably, it would pull up the front wheel when you flicked it from right to left in fourth gear leaving the chicane at Daytona. It had real steam.
I raced the bike that way through 2005 and 2006, and the only heavy maintenance was to change pistons every 300 miles. At Savannah 2007 it locked up the transmission on the cool down lap, so I drove through the night down to (name deleted) in Clearwater, installed a trans that (name deleted) had which had been modified for racing, rebuilt it (I discovered it had also spread the crank, which was terminal), and went on to Daytona and Miller and Albuquerque, that year, and then to Savannah and Daytona 2008.
This engine worked perfectly, but it did not accelerate the way I wanted from the middle of the turns onto the straights on the shorter race tracks. (name deleted) suggested using a light crank, and a big bore, so I started a second engine.
I got a second set of cylinders from (name deleted), sent them to (name deleted). They bored the cylinders to 66.5 mm (the absolute limit for RD liners) and then nikasiled them (on iron liners) so the last overbore would last. (name deleted) built me a crank lightened by about a pound, and supplied a second treated and undercut transmission. The crank is lightened by grinding off the counterweighting, resulting in an out of balance crank with less life, but it spins up much more quickly. I raced it the first time at Willow Springs 2008.
This engine is much better out of corners, and down straights, simply because of the increased displacement and lighter crankshaft. As expected, due to the lightened, out of balance crankshaft, it was also less reliable. It destroyed the crank at 775 miles, seizing solid while at max lean in the middle of the 85 mph last turn at Savannah this last February, 2010, on the last lap. I took a ride to the trees, but stayed on two wheels. Interestingly, it spread the center of the crank, on the mag side, not the outer flywheel on the drive side like they usually do. This may in part be because I revved it to 11,000 rpm. I suspect it would have lived longer with a rev limit of 10,000 rpm. Because one of my kids graduated from college and another one started college I had some family trips and this was the only time I raced in 2010.
I kept this engine exactly as (names deleted) said to with only two minor changes. I pulled the squish clearance down to about .036-- (name deleted) recommended .050 squish. To do this I used thin one piece RZ350 base gaskets, and thin head gaskets. This resulted in a noticeably cooler running and sharper engine that required less main jet. I also leaned the engine out a great deal (I don't use oxygenated fuel).
(Names deleted) have sort of moved on to other things, and so I got a replacement crankshaft from (name deleted), who is another long-time Yamaha road racer, and is quite successful at vintage two stroke tuning for AHRMA these days. He is a first-class guy, very reliable and reasonable. Again, there are others out there, but (name deleted) is who I chose to go to, and he tunes for a variety of current AHRMA roadracers, like David Crussel's Kawasaki H-1 R (2010 Formula 500 champion), and Ralph Hudson's Suzuki TR 500. (Name deleted) chose not to build an out of balance crank for me. Instead, he mixed and matched parts--the lighter outer pieces from a 1978 Daytona 400, with the earlier, and the stronger inner pieces from the 76-77 crankshaft. This results in a five ounce savings--not the pound I saved earlier, but this one may last longer. Since I had time, I finally opened up the bottoms of the transfers in the crankcases to match the ports--about a 1/4 inch in each direction forwards and backwards, and out to the outer edges of the ports about 3/16. (Name deleted) warned me this may result in blowing out base gaskets, but I thought I would try it and see.
As to frame and suspension mods, after 6 years of development I haven't changed very much:
First, as many do, I removed the top rear motor mount to keep from breaking cases or the front downtube, and to let the taller RD400 engine drop in easier. I also cut the inside rear corners of the top fins on the cylinders, to let me remove them with the engine in the frame (the RD350 cradle is shorter).
Second, in an effort to get more weight on the front wheel, (name deleted) of West Palm Beach, Florida made me a stock appearing TD3/TR3 tank that is 4 plus inches shorter, and a matching Vesco Daytona big butt seat that is longer by that amount. (Name deleted) is another longtime Yamaha racer and AHRMA regular, who has a body shop and does excellent paint and fiberglass work. I am big, and the extra room is much more comfortable, too. This helped lap times a surprising amount.
Third, above I said the RD350 front forks were initially grim. I had so much chatter that racers sometimes commented on it in the pits. After some experimentation, I fixed them with Race Tech parts. Race Tech makes cartridge fork "Emulator" kits to improve old-style damping rod forks (basically, the Emulator uses a spring controlled blow off valve to allow some variable high speed compression damping). I used the Emulator kit that drops in RD350 forks (3001) with a little adapter to raise the Emulator valve above the top of the damping rod. I used 40 lb. springs from Works Performance. I initially set it up exactly the way Race Tech said to (30 wt oil, 5 1/2 inches from the top, two turns of preload on the Emulator valve spring, using the spring that came in the kit). It was much better, but it still chattered a little, and in extremely high speed turns (like Turns 8 and 9 at Willow Springs) it deflected off small bumps, instead of absorbing them, unsettling the bike. Then Matt Wiley, Race Tech's race support guy at the races, helped me out. First, he gave me a different little adapter to put under the valve--this one had a piston ring on it to make all the oil go through the Emulator valve, to better control the chatter. Next, he traded out the little Emulator valve springs several times until we got to his softest spring, and I use them with no preload at all. Now, the forks work very well. Initially, the Race Tech parts may have been too stiff simply because they were valved for a heavier street bike.
Fourth, in high speed high g load corners, the bike remains very busy, flexing in the rear. I got (name deleted) to make me a 1 inch by 2 inch square tube chromoly swingarm to try and solve this problem. I have not used it yet, but I hope it will be more rigid than the DT2 motocross bike swingarm I am using now. This new swingarm is wide enough for big tires, and it has a lot of adjustment (16 1/2 to 19 inch length) to allow some experimentation, and to get some more weight on the front wheel.
Fifth, like most of the rest of AHRMA racers in this class I have switched from Avon AM22 and AM23 tires, to Dunlop KR 164 and 124 tires.
So after 6 years, it still weighs 255 pounds, it handles even better than it did, and it has lots more power than I started with.
Thanks Jamie for a great (now updated) article!
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