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  1. Kyosho Circuit 20 Options Parts - At times it seems like an impossible task to track down these rare items as there is no hobby shop to walk into that has an inventory of 1980's stock of Kyosho Circuit 20 parts to choose from off the wall and purchase. From what I can recall my local hobby shop did not stock much if any 1/8 scale nitro kits, just 3.5cc engines? The Tower Hobbies catalog supplied everything I needed vs what you read in the RC magazines at the time. We all know 1/8 scale nitro was the pinnacle of R/C racing and that it was VERY expensive verses what you could get from any electric R/C package. Well let's go over the latest option part I have acquired from the land of the rising sun and talk about its advantages. The rear bearings on the original kit work well but do have some limitations within its original design. It allows the rear axle to move around due to its single bearing use within the rear suspension arm and I think Kyosho knew this after designing and putting the part into production? Options are always an after the fact or sales tactics to help those that want improved performance or separate those from others. I consider it a must upgrade if you can find one! The original CB-15 single row bearing (8x22x7) works find but at 12grams each in weight with a tolerance of 2.5~3mm in articulation, I think this is the reason when it lands off a high speed jump it's a bit squarish/violent left to right movement requiring more attention on the steering to keep it going straight? Think of it this way it's adding unwanted toe-out under acceleration or landings of jumps making it harder to control. The CB-95 Rear Wheel Double Bearing (8x14x4) only weighs 10g and keeps things more perpendicular with only about 0.5mm in articulation. This option should help keep it within a straight line off the jumps and under acceleration. Something to note from a different manufacture was the Hirobo New Rusher 8 which was released in 1981. It offered a dual bearing setup as stock but a heavy addition to stabilize the rear end. As you can tell almost all modern RC cars use dual bearings to keep things stabilized. Always impressive to see how the early pioneers of RC stride to always improve on things.
  2. Great Upgrade from 30 PRODUCT CO,LTD. I wonder if they ever made anything for the Circuit 20 Series?
  3. When it comes to understanding or tuning the Cirucit 20 with its rear trailing arm suspension (zero toe-in & no rear camber) it usually consist of a few items; a single or dual shock damper, springs and soft tires with a medium foam insert and in our case the RARE rear stabilizer CB-37. Our goal is to set up the Racing Baja to be as fast and controllable as possible so we will always want more grip and that comes from the tire in contact with the surface. More tire contact means more grip, which means more power down, and therefore going faster. So lets identify a few design challenges to take benefit of the rear stabilizer: high center of gravity, overall weight - 3561g (7.85 lbs) in race trim, weight distribution - F 32.5% / R 67.5%. The CB-37 Front & Rear Stabilizer Kit first appeared as an option for the Circuit Buggy Kit Nr. 2010 originally released in 1976. From what I have seen within the early Kyosho catalongs from 77 thru 79 are some amazing images of the stabilizer kit. I have to say this is a RARE item here in the USA as I seem to only find images in Japan where it's applied. It could also be used on the Fairlady 240Z Kit Nr. 2282 if desired. When I did find my CB-37 Stabilizer kit it came from Hong Kong but, I felt it was a worth while purchase due to the preformance benefits. This is a 2.6mm (0.102") diameter high tensile strength steel rod held together with a 1.2mm (0.047") diameter wire with dual twist on each end utilizing 2 number of coils slid thru a piece of fuel tubing over the stabilizer bar, this is before the times of adjustable threaded rods with ball ends that you see on modern sway bar kits. As rare as it was it was something I felt necessary in order to take the Racing Baja the next level as lately I could see/feel out on track the excessive roll in the turns due to it's high center of gravity and rear weight bias that something was needed to help balance out the rear end. The Installation! This is no mere open the package and bolt on and go if used on the Circuit 20 Extra, it was designed specifically for early Circuit 20 buggies which have modification slots on the rear chassis plates to accommodate the rear stabilizer vs the Circuit 20 Extra which eliminated these slots as they preferred you to use the CB-121 Stabilizer. Correction: It was never an option to use the CB-121 for the Circuit 20 Extra! Why? Get your tools ready and prepare on how to utilize those special measuring devices to mark for the drill press and hope you get everything aligned right! Now what R/C enthusiast or kit have we built where you have to drill holes in order to utilize the parts? In today's world of R/C this does not apply! However this is a factory Kyosho option but, it must have come about after the production run of the rear suspension trailing arms as to why no markings or 3mm diameter pre-drilled holes exist for the stabilizer. Let's pause for a moment and go over all the various things we have gone thru since we started this restoration project, by far this is my favorite option to add due to the complexity of the installation, it brought back memories of building R/C airplanes and perhaps that was the thinking at the time for Kyosho? The CB-121 Rear Stabilizer was the second evolution of a stabilizer offered for the Circuit 20 series introduced on the Rowdy Baja Kit Nr. 2289 released in 1980. This second version took on the same geometry pick up points on how the stabilizer worked but it was moved forward to avoid the hitting the CB-104 Circuit Muffler during the rear suspension trailing travel and no drill press required. The hardware was upgraded but limited to the interference if using a rear shock due to the CB-9 being only 27mm (1.0629") wide from the chassis frame making the rear end narrower and the stabilizer would rub against the added rear shock. The Circuit 20 Extra which offers a wider stance due to CB-154 being 39mm (1.535") wide.
  4. Front rolling resistance check! I upgraded to the CB-101 front sealed ball-bearings which is an OPTIONS PART for the R/C racing enthusiast over the bronze metal bushing that come stock for the CB-80 front wheels for a smoother operation. I was only able to find one set and have not seen another anywhere on the planet. Keeping it within its original package until another is found, I used the original bearings to measure and see what the internet could yield, as we are all looking for that extra edge. Our goal is to speed things up as much as possible and enhance the performance of the Circuit 20 Extra Racing Baja while reducing friction, which would result in improved speed and steering control while reducing corning friction that occurs as the bronze metal bushing press against the wheel, washers and or wheel nut. 6x10x3mm Precision Ball Bearing NOTE: If you go without flanged bearing you will need to use a plastic or brass spacer cut to size (3mm or 1/8") to fill in the gap otherwise the bearing fall inside and then your wheel is rubbing again the large washer or wheel nut creating friction. You should be able to find at any hardware store. Due to how small the bearing are I noticed there was some friction when mating up against the inner washer or wheel nut so, I optioned to use a copper washer that provides adequate spacing under load to keep the bearing inner race away from anything that could rub against the outer flange or wheel. M6x8x1.0mm copper washer When you compare the width of the bronze metal bushings it's amazing that ball-bearings can be made this small to fit within the front wheels. This would have to be the smallest front bearing I have ever seen on a 1/8 scale R/C let along 1/10 which all use a more robust size. Perhaps technology was not there in 1975 or a design flaw that went un-noticed into production for the wheel size to accommodate ball-bearing in the future? Let's see how long they last before they need to be replaced under full race conditions as we all all know how rough the front end endures with the bumps and jumps and high speed turns where the suspension is bouncing all over the place.
  5. Weather conditions have not been corporative these last few months, we went from extreme heat/dry condition to fairly wet/damp in the blink of an eye! Our last attempt ended with rain but, we did manage to get some laps in and try out some of the upgrades. Minor service/inspection on the gear box and all is well just minor oil leaks from the output bearings. I think it would have been helpful if they had a seal within the inside or outside of the bearing as the transmission oil seems to flow right out during various lateral turns and it makes a huge mess as it collects dust and grime from the track. As you can see from the photo, I am using the black clutch material vs the green. Not sure if there is a difference? Was hoping to see how the Kyosho Integra 4WD Presto (Kit Nr. 3059) also known as the Vanning compares to the Racing Baja but, rain ended the event! To be continued...
  6. The early kits started with a simple bar for a protective bumper with a rubber damper secured by a clamp that connected to the ladder frame. Simple, effective and lightweight as the various models were introduced thru the series, we see a variety of bumpers designs for each kit to protect the front suspension components. With the introduction of Kydex as used on the front bumper of early kits we see an improved longer lasting solution. Kydex is a type of thermoplastic acrylic-polyvinyl chloride composite material perfect for formability, rigidity and toughness perfect for entry level driving or high-speed excursions. Technology is great when it benefits our hobby and often, we have to think why parts are designed the way they are and it's purpose to protect the investment at the time? With speeds up to 50 mph (80 Km/h) and the front bumper providing additional uplift on an already light front end this had to be a concern? Searching for an optimum setup can the air flow at +/- 25 mph (40 Km/h) using the CB-114 front bumper which acts more like an air dam while providing uplift be a race issue? Uplift is something you never what at the front as it only decreases front grip. Blasting thru high speed jumps it's also very noticeable. The Mint Las Vegas front bumper seems to solve the issue providing up lift/down lift reducing aerodynamic drag. Things are only getting better as materials get stronger, just look at any modern 1/8 scale buggy with it's minimal front bumper. As R/C cars were still evolving at a blistering rate perhaps it was to prolong the enjoyment of operating a 1/8 scale nitro buggy avoiding a front-end fracture that would end the enjoyment of your new nitro purchase. Kyosho kits are always enjoyable to build with the detailed diagram instructions for assembly giving us the opportunity to reproduce that box art photograph! Again, we don't find many r/c manufactures like Parma, Hot Trick or CRP who all made various bumpers for almost every r/c kit at the time? The more I dig into the history of these circuit series buggy's the less I find. Circuit Buggy / Fairlady - Part Number 59 (CB-23) - Single Bar Design California Baja - Part Number 65 (LD-1) - Rectangle Plate Design Rowdy Baja - Part Number 20 (CB-114) - Flat Plate Design Landjump / Circuit 20 Extra - Part Number 65 (LD-1) or Part Number 20 (CB-114) - Diagonal/Vertical Plate Design Mint Las Vegas / Vanning - Part Number 92 (LD-1) - Diagonal/Inverted Plate Design If we look back before 1980 when these early kits were available, it was a different time as r/c publications or magazines had all the information with most hobby shops placing ads promoting how to get a hold of the latest kits. If that was the case it must have been an exciting time in the late 70's to get your hands on an 1/8 scale nitro kit. More run time and more realistic sound and performance then any electric buggy at the time. I would have to assume the target audience for these kits are amateur at best behind the 2-channel stick radio controller, thinking they were Fangio or Jacky Ickx. What better way to protect the nitro experience then an oversized bumper to allow the most inexperienced driver another attempt vs sitting out the session with a broken front trailing arm.
  7. The Circuit 20 Series all use the same steel clutch shoes (CB-28) and 1mm diameter retainer springs (CB-67) secured to the flywheel pins and align within the 28mm clutch bell. It’s suggested to cement the inner side of clutch bell liner with epoxy or rubber type glue. The centrifugal clutch is such a vital component and has an endless range of adjustability for various tracks and driving styles in order to extract as much power from the 3.5cc (.21) engine and deliver to the rear wheels. We will focus on what Kyosho developed and changes made across their 1/8 scale nitro range leading up to the mid 80’s. Going thru my original Racing Baja parts indicates a better understanding as I noticed the clutch bell did not have the liner (SD-56)? Was it due to the liner eventually wearing out and no replacement parts available that allowed the clutch to slip more to improve performance? From the last track session, I noticed when the clutch engages mid to full throttle the front wheels lifts off the ground, indicating strong engagement. Two things that need to be sorted out; weight bias and more slippage from the clutch to allow a more linear engagement. Aside from the previous mentioned adjusting the front/rear ride heights will also help keep the front wheels down. Adding more weight to the front would help but that’s not an option I’m willing to explore at this time due to the excessive weight required to make a notable difference on top of an already heavy buggy. During the late 70’s and early 80’s 1/8th scale on-road racing was developing on all major continents and most manufacturers were using Nylon or Teflon type clutch pads without a liner within the clutch bell. Even the French based Yankee and Italian Garbo had more technology then Kyosho at this time as to why it took Kyosho a long time to win at the European World Championship. Let’s compare the differences between the steel vs nylon clutch shoes and see what the performance differences could yield. Steel Pads: 3.64g each (total w/ springs: 8.12g) Nylon Pads: 3.06g each (total w/ spring: 6.59g) The evolution starts with the Circuit Buggy using steel pads w/ clutch liner glued to clutch bell, this was applied to all the Circuit 20 series up until the 1984 Landjump Integra 4WD which then revised to steel pads w/ clutch liner non-glued to clutch bell? We can only speculate that to much power was extracted within a turn causing the buggy to lose traction or having to slow down in order to keep the momentum going? With introduction of the 1985 Circuit 2000 series we see the PFTE clutch pads with radial spring (KC-45) being used on Impacta or Mint Las Vegas as an option. This third change would become the standard for all 1/8 scale nitro's within the market.
  8. Very well done, looks like the actual art box car! Colors and decals look spot on. Bonus for the Enya 21 CX what a powerful engine from the 80's! Welcome to the ultimately rare Racing Baja club. In regard to rear shock option image, I developed that as an aftermarket product that someone would have made back in the 80's, will be testing my design this autumn.
  9. With the development of the Landjump evolving into the integral 4WD going on in the background from the early 80’s we see the rise of the Vanning kit (Nr. 3045) soon to be released in 1987 as a premier four-wheel-drive platform from Kyosho at the time. The writing is on the wall that Circuit 20 Series is coming to an end. Before the release of that kit from Kyosho let’s dive into some options that could have been used at the time for the racing Baja from the Landjump 4WD integral kit (Nr. 3011) from 1984. The Landjump 4WD Integral seems to be the only kit that offers something a bit different, CB-89A damper spring (rear) as standard equipment. You can source the item as a replacement but, it’s a rare item! The spring has 18 coils versus the stock 14 coils as used on the Kyosho Impacta (Nr. 3048) or Mint Las Vegas (Nr. 3049) from 1985. The 14 coils spring seem to have rolled over into the Vanning rear suspension part number (KC 19). What are the specs for the CB-89A spring and why was it not used on the Vanning? I took some general measurements and it’s the same wire diameter thickness only more coils. It ranges about 10 percent softer then the KC-19 spring and it’s 7.5mm (0.3”) longer. That means it has 7.5mm of extra length preloaded to fit on the shock.
  10. 2023 Pre-Season Testing April 22, 2023 (Bee R/C Raceway, TX - USA) There are so many interesting storylines this year, get up to speed with everything you need to know about 2023's Vintage R/C 1/8 Scale pre-season testing session - which took place at Private R/C Racetrack with Team Drivers, Track Length: 540' (165 meters) length 10 turn race course with crossover jump. 1983 Kyosho Racing Baja: Warm Up, Practice Laps - In Action on Track! & Enya Sound! Alive after 40 Years! 40th Anniversary of their legendary Racing Baja Circuit 20 Extra is proving to be a true winner! Röthbauer GmbH with some practice video testing his original 1983 Kyosho 1/8th Nitro buggy [Circuit 20 Extra Nr. 3045]. Took over a year to track down all the required parts arriving from all over the globe to bring this 40 year old vintage nitro back to life!
  11. Fix 1: Steering Servo Over the years since the early 80’s of 1/8 scale off-road racing, it seems obvious more servo speed/torque would always be welcome for steering and brake usage. It used to be either Kraft, Airtronics or Futaba that offered the servo standard at that time with average specs like the Futaba S148 (3.0kg-cm) 41.7 oz-in (.28 sec/60 deg @ 4.8V or 6V) which was very common at the time. Even though the early servos were weak in power they preformed well until you hit something hard that would either strip the servo horn or break an internal plastic gear. I think the manufacturers caught on and improved there products with metal gears and ball bearing as the hobby kept evolving. As an R/C hobbyist we all sooner or later have learned the lessons required to change or modify something in order to keep the operation ongoing. From what I remember it was due to not having quick access for replacement parts which meant over a week before it arrived if mail ordered. Yes, we often did a weekend run to the nearest hobby shop for just a few parts to satisfy our passion. It’s hard to imagine how we justified a Saturday for travels to the nearest hobby shop for a few dollars in parts. That alone shows just how dedicated we were in those times, sounds familiar I bet. Fix 2: Servo Saver + Linkage This should be the at the top of the list of things to modify or upgrade if you plan on running your Circuit 20 Baja! The original circuit series servo saver spring is far to weak and even if you compress the spring with additional washers to stiffen it up, it’s still to soft for track usage. If we build a timeline starting with the Circuit 20 Series (CB-87), and add the LandJump (LD-47), Mint Las Vegas (KC-3), Burns DX (BS-22), etc. you will notice that with each version the servo saver spring stiffness was improved. This benefit alone as radio and servo technology progressed seems to be a key ingredient in off road racing, remember power is nothing without control. The Graupner Racing Baja Nr. 4948 version has the required steering setup for competitive racing and that is the system I will be testing next. The two steering kits are visibly different but, I’m looking forward to the larger diameter linkage rods and hardware plus stiffener plate for the stronger servo saver (KC-3) which has a more precise feel, eliminating the excessive play from the airplane type L-bends and Z-bends that connect with a Du-Bro ez-link type connection. It should allow for better steering response and more control threw the turns, hopefully more stable on jumping and landing. If your buggy’s steering setup is dialed in you will notice how important all these elements are for racing. Steering feel should be responsive when you drive thru a series of turns doing exactly what you command versus what feels like a lazy servo saver struggling to do its job. Fix 3: Front & Rear Suspension The six red anodized shocks did there job but, now I have to find the right combination for off-road racing. When it comes to high speed turns and a variety of jumps that changes everything not to mention we have a limited selection of front springs and no known option for the rear. I went with a conservative setup using CB-88 (silver - hard) at the front and dual CB-89 (gold - soft) at the rear. Traction was good out of the turns and on the straights but, a different strategy will be required for the entering the turns and jumps as things will speed up due to the improved steering going forward. Somewhere during a more aggressive lap session the rear spring (CB-12) popped off, was it the rebound or just not tight enough on the collet? Going forward I will now add the coil-over kit using the gold springs for the front shocks and will be experimenting with various settings to generate a good baseline setup.
  12. Some Action photos during testing, video coming soon…
  13. 2023 Vintage R/C - Pre-Season Testing It’s hard to believe that it’s been a year and a half since I started this journey towards restoring my 1983 Racing Baja, finding good usable parts was the biggest challenge. If it had not been for a group of friends developing an RC track for modern day 1/10 scale racing I think my off-road race car would still be in the attic on a shelf next to an old printer. It’s been a very slow and challenging adventure and now the action is about to begin. The Circuit 20 Series (1976-1983) has kept the original design with aluminum alloy ladder-frame, plastic electric box, clutch and drivetrain, tires, even optional damped shocks for improved suspension control. During this time a good variety of engines were available for some serious off road entertainment. As for performance well let’s just see if we can take it to race level and unlock its potential to govern why they called it Circuit 20 Extra Racing Baja. Anticipation was high this past weekend as weather at the track was favorable to allow for some good practice sessions with the stock buggy configuration. The past two years racing SC6.2 & B6.2D Spec 13.5 has brought my skillset back into the groove which helps, I still remember the steering was its weakest point aside from the heavy rear weight bias (Distribution: F 32.5% / R 67.5%) but chose to use the original setup to gather a solid baseline before we go thru the various upgrades that were made available at the time. Overall weight: 3561g (7.85 lbs) in race trim. Best Lap Time: 29.85 sec The 1/8 scale vintage nitro journey really begins here, it will be faced with many challenges before we get into the fast lane. Our track is a 1/10 (not 1/8) scale course with a total track length of 540' (165 meters) in length with 10 turns and a crossover jump with 4 speed bumps so, there is issue number one. The Enya 21CX is doing alright but the carburetor and buggy is to big and heavy for our track, most 1/8 scale tracks are three times larger with longer straights where 50+ mph speeds can be achieved. I have very little room for error with the short and narrow lanes. It’s a true handful but, what a JOY it was during our pre-testing evaluation. Control through the turns is awful as it has Massive under steer (due to original servo saver) you actually have to back off throttle or it will just plow outward and hit the barrier. That alone takes the fun out of this buggy but it’s a fixable issue. Acceleration as you enter and exit the turns is where the excitement is out on track especially if your battling for track position during a race. The suspension did its job well, one of the rear shock eyelet’s broke when pushing a bit faster then we should have thru the speed bumps. Other items came loose from engine vibration, more thread lock needed. The lexan body took a beating from all the various flips and crashes but that was expected as were developing these circuit 20 buggy’s for vintage race competition. Rear traction from the X352 tires preformed well, many times the front end would come off the ground as the engine rpm spend up allowing for clutch engagement. The differential was most impressive keeping the car under control everywhere, especially the turns. Never once did the car spin out of control in a turn. As for the brakes, it’s in a range that is acceptable for now, when the power gets on at the end of the main straight I have to break early, again this is more on the transmitter settings and poor performance from the servo saver. You don’t want the brakes to strong as that will just rob you of the momentum needed going thru various turns. After a few tanks of fuel, we can draw our conclusion and while it seems like a lot of issues the Racing Baja has the potential to be a serious racer. How many other vintage 1/8 scale 2 wheel drive buggies from this era have the capability to win may be unknown, a past we can only relive today to try and better understand.
  14. Final batch of parts arrived for the ENYA 21CX Racing S (Model 4201) off-road nitro engine, new front and rear internal bearings and gaskets. The very critical items that do not last forever and if used will need service at some point. I pressed out the old and reinstalled the new with a few drops of after run lubricant before sealing up the rear with a new gasket. Assembly of the piston and sleeve dropped into the engine case paying special attention to the alignment of the exhaust port while tightening up the cylinder head to keep things lined up. Medium silicon piston in chromed aluminum liner (Al-Chrome) with an advanced connecting rod with dual oil holes at crank side and a single hole at piston side for additional lubrication with phosphor bronze bushing at each end. I removed the current OS MAX 21FSR-B (model 2607) engine that is using a Type 2K carburetor for dialing in the Racing Baja to obtain a good feel for steering, suspension, acceleration and braking, what a blast for a 40 year old race car. To gauge a more accurate benchmark I am using the same carb and exhaust for the 21CX engine. The ENYA Racing S slide carb (21CXS40) pulls in the opposite direction where the typical rotary arm is located, on the right side. Perfect orientation for an Associated RC500. Lucky the OS MAX Type 2K carb fits right in. With the engine now fitted to the Racing Baja it’s time to run a few tanks extra rich for break-in purpose. More to follow as we prepare to get some video and photos out on track! Going up and down the street or backyard does not do this car justice but did help to identify where extra thread locker (blue) is required!
  15. Sometimes we just get lucky finding various used RC items for sale and there is alway a small risk involved. That’s part of the hunt that takes time and it’s either good to use and rebuild, or straight into the trash can. A small risk to get something that is somewhat rare to find at a fair price I guess is the norm with vintage RC parts these days. I managed to get a hold of an ENYA 21CX Racing S engine, the very one on the Racing Baja box front cover (box art). Actually the box illustrates the 21CX Racing G with rotary carb but, the body casting, internals and head are the same. This combination is what Kyosho thought best represented a racing car package at the time. I am really looking forward to getting this engine up and running, assuming all goes well. The engine I got needed a lot of parts in order to work and I was surprised to find them available out on the web. Simply strip down and clean/inspect and remove used/worn items, wait for parts to arrive then reassemble. The exhaust face needed some refacing to seal up good to the exhaust muffler. The piston pin and wrist pin snap rings that connect to the piston are tiny! I chose to use a McCoy MC-8 glow plug vs the more robust OS No. 8 which seem to be the norm? Seems like the previous owner pushed this engine beyond the limits! The Racing S engine comes with a slide carb that uses a small Venturi as an option for more tune-ability. 21CX Racing S engine - 8.5mm slide type carburetor w/ optional 6.5mm Venturi 21CX Racing G engine - 7mm rotary type carburetor. ENYA 21CX Racing S = 0.9 bhp @ 28,000 rpm Lately I’ve been on the engine program, breaking in various motors and setting up the Transmitter throttle end point adjustment (Throttle EPA) and brake linkage to the servo. This is the most involving area that requires additional patients due to modern electronics being digital with various sub menus, etc. nothing like the classic analog Futaba Magnum FP-T3PG with all those rotary knobs.
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