Removed a little bit of material on the CVTech driven clutch and got the sheaves a little closer together. Not a huge difference but a lot of little things add up.
It turns out there are a couple of easy ways to tell if you just received an genuine Comet 780 clutch that was made in the U.S. or a cheap Chinese copy.
A real Comet should come in a box with some paperwork and a couple of parts:
My CVC (Chinese Vegas Carts) came wrapped in bubblewrap.
If you flip the clutch over, on the back of the fixed sheave there should be some numbers cast into the sheave. Here is the back of the Comet:
And here is the back of the CVC:
One other thing you can do to check without touching a thing, the moveable sheave has three tabs that can be seen from the outside of the clutch. Here is the Comet:
This is the worn out CVC moveable sheave that I replaced. Notice no tabs on the outside edge:
If you really want to dig in and start taking things apart, the next thing you can check is what type of threads the clutch is set-up for. If you remove the dome cover, the Comet will have standard threads, in this case 1/4-20. The bolts holding down the pins for the roller weights are the same. My CVC was threaded with metric M6 threads and bolts.
Also with the dome cover removed, you can take a look at the locking plates that are holding the weights in place. Here the Comet has the locking plate folded up:
And then here is the CVC with the flat locking plate.
The Comet moveable sheave will also have some numbers cast into it. This also shows the tabs I mentioned before:
No numbers whatsoever on the CVC moveable sheave:
If you keep going and take the weights off, there is a difference there as well. The weights are designed differently. The CVC on the left has metal guides integrated into the arms of the weight. The Comet weight is on the right. Plastic spacers fit into those larger openings as seen below. So you have metal-on-metal vs. plastic-on-metal.
Despite buying my clutch from a reputable place, it is looking like I have a Chinese knock-off.
I noticed a week or two ago that the moveable sheave of my clutch was wobbling quite a bit. With the engine off, if I grabbed the sheave at the 9 and 3 o’clock position, I could rock the sheave side to side. I ordered a new sheave from beltpalace.com along with some different weights and springs to test out.
My back is still sore and I didn’t want push it by pulling the engine out of the cart. So I dropped the swingarm instead:
The first thing I noticed was that the locking plates weren’t bent over on the bolts holding the roller arms in place.
This is how I pulled the spider off the hub. The 2nd thing that was strange was that I had to use metric M6 bolts to thread into the spider. Glad I still keep a container full of bolts from the Japanese dirt bikes I’ve owned over the ears. I thought that Comet was a U.S. company and expected them to use standard threads/bolts.
And this is how sloppy the hub and moveable sheave are:
The bushings that the guide pins ride in were well worn. The scary thing is that this clutch has less than 75 hours on it!
So finally on to getting the clutch put back together. The hub bushing and casting around the bushing were thicker on the new sheave compared to the original:
I tried to thread the M6 bolts into the new sheave and they wouldn’t go. Turns out the new hub is threaded for 1/4″ – 20 threads. But it wasn’t until I tried to slide the new sheave over the hub that I that it became painfully obvious that this wasn’t going to be an easy project. The new sheave didn’t come close to sliding over the hub, the ID of the bushing was too small.
So I sat back and tried to figure out what to do. The evidence certainly pointed to my clutch being a cheap copy – it wore out very quickly, all the threads were metric and the lock tabs weren’t bent over. I was feeling pretty confident that beltpalace.com was selling OEM parts or at least OEM spec parts. The springs and weights were all bagged as Comet parts.
And if the new sheave wasn’t made by Comet, it was at least a better copy with standard threads. I finally decided to make this sheave work. I doubted I could find a knock-off sheave that would fit my clutch and it wouldn’t be worth it as it would wear out quickly as well. After about an hour of working on it, I finally got the new sheave to fit over the hub. I had to run out to the hardware store to get three 1/4″-20 bolts. And after installing the springs and weights, I made sure to bend over the locking tabs.
I also had to take some material off the sheave so it would slide up high enough and not interfere with the spider.
Now I just need to get the clutch put back on the engine.
Not only was the running light too bright, but with it mounted so high is was almost blinding at night.
With no Radio Shacks nearby, I got this from Amazon for $6.80.
After experimenting with different resistors and different combinations, I settled on two 2K ohm resistors wired in series.
Now I have a running light:
I am going to finally cover up this opening in the electric dash:
I am going to try and use as much of my failed shroud as I can. The first cut is always the hardest:
I am going to get the sensor and magnet mounted first. I didn’t want to have to drill anything on the Jake’s spindles or weld anything, so I mounted the magnet to one of the bolts holding the disk in place. I doubt that this extra weight so close to the center of the wheel will cause much of an imbalance.
I made up this bracket that will be bolted in place on the spindle:
And here is where this bracket mounts:
I made a cutout for the base of the computer:
I’m using a strap across the bottom two mounting bolts to hold the base in place:
I didn’t polish the face of the plate, but used some finer sandpaper to get some of the grinding marks out:
This computer goes down to centimeters. I measured the circumference of my tire and come up with 143.5 cm. I can only add whole numbers, so I went with 144 cm. Opened the GPS app on my phone and drove around the neighborhood. This should be about the most accurate test of the GPS as there aren’t any trees in the way and most of the almost one mile loop is straight.
And then I went for a drive on the paths through the woods. The discrepancy wasn’t too bad:
A couple of weeks ago I noticed the disk brakes making some noise right at the start of a drive. It would only do it when the brakes were cold and go away after a minute. Yesterday I figured I would finally look into why they have suddenly started making noise. I started with the drivers side wheel in the air and when I spun the tire, I was amazed at how much the caliper was rocking back and forth. I couldn’t believe how warped the rotor was.
I pulled the tire off and then got the rotor off. When I checked the rotor, it wasn’t warped. I then broke out the dial indicator. There was no good place to mount the indicator on the front suspension, luckily the big anvil provided a solid base.
So after getting it set-up, this is what I find:
At this point I thought the hub must be warped. I popped out the spacer that was short and traded places with the one on the other side. When I spun the hub around again, the same spacer in a different location was still coming up low. So now it looks like the spacer is the problem. I pulled all 4 spacers and checked the hub. It looked good.
Taking the spacers to the table saw top, I found that the shoulders weren’t the same.
I don’t have a lathe or a mill, so I improvised with what I do have – a file and a drill press.
After several hours of taking metal off, checking, taking metal off, checking, this was what I ended up with. I am feeling pretty good about this. When I rebuilt two-stroke cranks, the run-out spec was .001″ for most of them. I am really close to that here:
I am kicking myself for not catching this when I installed the brakes. I just didn’t hear anything and definitely didn’t have any vibration or pulsating from the pedal. But now that I look at how the caliper is mounted, I see why.
The passenger side wasn’t nearly as bad, but I spent some time and got the run-out near .001″ as well.
This shroud took longer to make than it stayed on the cart. Sunday I went to the local elementary school with a laser temp gun and a 10mm socket & ratchet to test the effectiveness of the shroud I made.
The engine was somewhat warm from an earlier ride. I took the shroud off since it was cool and then drove about a mile to the school. Driving around the parking lot was 1.03 miles. For all testing, I tried to maintain 20 mph and 3k RPM.
I did 4 laps and pulled over and took a temp reading. I then did another 4 laps and did another reading. The results were pretty close to each other so I felt good about that. I simply laid the shroud on top of the engine and didn’t bolt it down. I didn’t want to impact the temp readings while I took the minute or two to remove the 3 bolts that held the shroud on. With the shroud on, I drove 4 more laps, removed the shroud and took a temp reading in the same spot as before. I put the shroud back on and did another 4 laps. I pulled the shroud and took the final reading.
The results were not what I expected and had hoped for. With the shroud on, the engine ran about 10 degrees hotter.
The laser temp guns read a little strange when you try to use them on shiny or semi-shiny surfaces. So this morning I thought I would try something different. I put one of the prob from my digital thermometers that I use for smoking in between 2 of the cylinder fins and then packed it in place with aluminum foil.
This time I drove around the neighborhood. It is a mile circle that is relatively flat, so I can maintain a constant speed fairly well. I thought I would go 15mph instead of the 20mph from yesterday. I thought this might even the odds between the shroud and no shroud. I had already been out for a 9 mile drive, so the engine was already warmed up.
With the temp probe in place and the shroud off, I drove around the neighborhood and took a picture of the temperature monitor as I pulled in front of the house. After a mile at 15 mph, this was the temperature:
Since I could see the temperature without lifting the seat, I bolted the shroud on this time and went around the neighborhood again. Another mile at 15 mph and this was the reading with the shroud on:
I don’t think my laser temp gun was very accurate and there are certainly some flaws with this digital thermometer test. But since both methods showed that the engine was hotter with the shroud than without, that is good enough for me. Clearly there is plenty of cooler air flowing up and around the engine compared to the confined warmer air that the fan is blowing around and down the cylinder head. I would guess that if you drove 5 mph the results might be different. But who only drives 5 mph?
I finally got two projects that have been on the back burner for a while done. With those completed, all I have are stainless steel scraps and am just about out of gas.
The first project was making a shroud to better direct the airflow from the fan around and down the cooling fins. I spent way more time than I thought it would take on this. It isn’t pretty, but it works really well. I tired to make the cover fit tight in areas I didn’t want air to escape from. With the engine running, the air from the fan will blow off leaves off the ground directly under the engine. Forcing that hot air down, instead of just the area under the seat should help cool things off.
This project went way faster than I expected. I’ve been meaning to cover up with mangled hole where I had to make the electric body fit the gas frame.
Luckily I had one piece of stainless that was just big enough to cover it. I tapped the 4 holes so I could just thread in 4 SS bolts.
It is kind of hard to tell, but the cut end of each bolt is sitting below the surface of the plate. That way I can weld them together but grind off the excess.