Fork bushing alignment

I suspected the front fork was tweaked after how bad I saw the fishmouth was messed up. After I removed the bushings I checked for alignment by attempting to slide a A1169 3/4″ axle through both bores. Sliding the axle in from the top I found it would only go into the bottom bore by about 1/4″.

Sliding it in from the bottom was much worse. It was off front to rear and side to side by almost 1/4″. I suspect it got tweaked when the top kingpin bolt fell out putting a huge force on the bottom bolt.

I used the axle to straighten the bottom bore by putting the fork on the shop floor and standing on it in different directions. It took a lot more force than I expected. Finally the axle went straight through both bores. I would have used a FB1012-6-Delrin plastic bushing in the bottom if I had not been able to bend the fork back in alignment.

Kingpin bushings

The kingpin bushings are BOST-BRONZ oil impregnated sintered bronze bushings part number FB1012-6. These are the equivalent of my FB1012-6-841 bushings. The top one was not too bad but the bottom one is cracked and wore out at an angle due to the bottom hole of the fishmouth tapped at an angle. If I had not been able to fix the bottom threaded hole I would have used one of my FB1012-6-DELRIN bushings on the bottom because it will tolerate quite a bit of misalignment since the plastic can flow a bit. I will use FB1012-6-660 bronze bushings top and bottom because they hold up better than the 841 sintered bushings.

West Bend 82001 rod bolts

I did not rebuild the West Bend 82001 go kart engine because it did not need it. I did replace the rod bolts with 7/8″ long Torx bolts. I am not comfortable with the original 5/8″ long bolts. The Torx bolts are grade 8 just like the originals but they feel a lot more positive when I torque them to 90 inch pounds. I have run into WB820s with rounded out hex head bolts. They are difficult to remove.

West Bend 82001

The 82001 engines came with a single 1/32″ thick head shim. Jim Cavanaugh said he put in another head shim to reduce compression to make the engine easier to start. This engine did have 2 1/32″ thick head shims but was still difficult to pull over. I stuck in another 1/16″ shim for a total of 1/8″. The go kart racers use electric starters and I can certainly understand why.

The extra 1/16″ head shim made it difficult to install the head tin. I had to do some minor trimming with my die grinder to get it to fit. I also had to drill the front engine mount to get the bolt in.

The Krylon Caramel Latte paint is a good color match but has a bit too much metal flake.

I did not paint the carb after stripping it since most of the original paint survived. There was no gold under the yellow paint on the elbow which makes sense because 82001s did not have elbows. I think the elbow is a Nethercutt casting not West Bend.

Filter base safety wire

The original air filter base is a mess since it was drilled off center. This is the best one I could find short of robbing another bike. I had to braze a hole in the middle that I drilled maybe 20 years ago before I figured out that I could use olive jar lids as tops. I used a A1399 base gasket, Wacker 30491 filter clips, 20-6620 15% Ethanol rated Tygon tubing, A1233 choke screws and the original screws that are drilled for safety wire.

Reed cage

I opened up the reed cage to work better with single petal carbon fiber reeds. This will help get back the HP I lost by reducing the compression and backing off ignition timing to get this engine easier to start.

The center dividers were removed and the ends of the screws ground flush with the inside of the reed cage.

82001 porting

Since I gave up some power by adding a 1/16″ head shim I decided to improve air flow through the engine by doing a minor porting job. The engine now has a total of 1/8″ head shims which is the maximum and will make the engine easier to pull over. Since the engine runs so well I am not going to take it apart so I can’t do my normal porting job but I can smooth over the dead sharp corners at the intake ports without disturbing the chrome plated cylinder wall.

I have been using the same Chicago Pneumatic die grinder and carbide burr for close to 40 years. Fluid Dynamics was my favorite class in college and served me well when I designed a large industrial flow bench for a pipe fitting manufacturer. I built my own flow bench for SCCA Formula Vee race car carbs and calibrated it to the industrial flow bench. I still have the calibration plates. I used the flow bench on Rokon carbs and cylinder ports years ago. This minor mod and a reed cage mod is worth about a 10% increase in air flow. That translates to a 10% increase in HP on an engine dyno.

I did the port job with the piston closing off the ports so metal would not get inside the engine. I stuck a balled up paper towel in the opening into the crank case.

HL134A Carb

I finally got the yellow and green paint stripped off the HL134A carb. It was originally painted gold. I will repaint it gold when I have the entire engine back together and ready to paint. It has a couple features that are not on the later carbs. First it uses 2 screws on both the throttle and choke plates versus 1 screw. It has a 1″ bore where it bolts up to the intake elbow but the throttle bore is 15/16″ offset to the top of the carb. The choke plate has 4 flats instead of a hole to allow some air in for starting on full choke.

I did manage to snap off the special throttle shaft in my attempt to straighten it. I was able to replace it with a HL173A shaft. My Rust Bucket MK1 does have a HL134A with the double screw shafts. It was also rebuilt by Mark Wood. I might swap it out if I get ambitious. The Hi needle is 1 1/8 turns out and the Lo needle is 1 1/4 turns out.

Carb elbow

The MK0 carb elbow is an Aluminum casting. It is identical to the MK1 carb elbow except both bolt patterns are 1.813″ for the Tillotson HL134a carb. The MK1 JLO LK101L elbow has a 1.813″ bolt pattern for the same HL134a carb and a 44 mm pattern for the JLO engine. It only has provision for the pulse port at the bottom not top and bottom like every West Bend 820 carb elbow I have ever seen. The MK0 elbow has the pulse port drilled, the MK1 JLO elbow does not since the JLO is piston port scavenged not loop scavenged like the Benders.

The 1″ bore MK0 elbow is on the left, a 7/8″ bore MK2 elbow is in the middle and a new US820 1″ bore elbow is on the right in the top picture.

The MK0 elbow is taller and longer and does not require a spacer between the reed cage and elbow like the MK1 and MK2 elbows do.

Throttle shaft boo boo

I noticed the throttle shaft was bent early on. I rode it anyway because I was not going very far from my house. I broke a throttle shaft years ago and I can assure you a broken throttle shaft is a show stopper. I tried to ride the bike home with the idle turned way up but that did not work.

The MK0 throttle shaft was bent maybe 15 degrees which meant it was probably also cracked. Mark Wood had already informed me that it was a special 2 screw throttle shaft and that he had no spares. I decided to confirm that I had a spare single screw shaft and plate before I attempted to straighten the bent shaft. I knew there was a good chance it would break in the straightening attempt……. So I was not surprised when it broke.

I was surprised when I found out that the plate was a different diameter then any HL carb I have ever worked on. Turns out it has a 15/16″ diameter plate. I only have 13/16″, 7/8″ and 1″ throttle plates in stock. The HL134A has a 1″ bore at the gasket face but it steps down to 15/16″ at the throttle plate. So I drilled a third hole in the HL134a plate and installed it using a A1233 high flow screw.