I finally got around to doing a little tuning on the 780 clutch. My belt wasn’t going up all the way and from looking at pictures of other clutches, this was pretty common.
The picture doesn’t do it justice, but there is a good size gap between the belt and the sheaves. That gap represents wasted movement of the clutch that doesn’t translate into any movement of the cart.
I took the cover off the clutch and pressed the spider down until I had just a slight gap between belt and sheaves.
I cut down and aluminum ring from some scrap so that it fit properly under the clip.
Now the belt goes all the way to the top.
A while back I did away with the engine set to idle at a stop. When I was putting everything together, I took out some of the slack in the belt. Between the tighter belt and the belt riding higher in the drive clutch, there is a noticeable difference in the speed of the cart. My tach broke so I will have to wait and get a new speed vs. RPM to compare to the original set-up.
It was nice having the PZ30 carb on the cart with so many more aspects to control with the jetting. But the performance was starting to act a little erratic after 800 miles. With the cheap Chinese manufacturing, I didn’t have high expectations on longevity.
Before going back to the Keihin that came on the GX390, I thought I would try the 24mm 3 circuit carb from VC.
Getting the epoxied, broken off low speed screw out wasnt that bad with some silver solder and a spare PZ30 jet. Ugly, but it worked.
The flux made a mess though. It came of easily with some carb cleaner.
The low speed screw on this 24mm carb is a different size than the Keihin/clone carbs. Since I had the solder out, I used another jet from the PZ30 and made a “new” screw from the original. The PZ30 jet provided a nice shoulder for the spring.
All cleaned up with the adjustable main jet.
On the cart:
It fired right up and with just a little time spent adjusting the jetting, it is running pretty well.
One last ride before the rains from Michael start hitting us.
It is the first week of October, the leaves are falling and it is getting dark at 7:30 pm, but it is still 90 degrees in the afternoon.
With the warm weather and no rain, I have had no problems driving the cart around.
My Chinese Vegas Carts 780 clutch had these weights and yellow springs (who knows what tension or strength they really were).
When I got my genuine Comet 780, I didn’t even try the 106 gram weights with the yellow springs it came with. I assumed it was going to be similar to the CVC clutch.
I first tried the green springs with the 106 g weights and really liked the low engagement and how much more quiet things were when going 20 mph or less due to the engine turning less RPM. But the little 390 just didn’t have the grunt for that combination. It definitely struggled on some of the larger hills. On flat ground it was awesome though.
Then I tried the green springs with 91 gram weights. That was a much better set-up for the 390. I thought I was going to keep that combination until I had another person on the cart and noticed that performance suffered on hills again. It wasn’t a big difference, but noticeable. I considered keeping that set-up though because most of the time it is just me on the cart. But the weather is still warm and thought I would try the yellow/106 set-up that came with the Comet.
This is what the 91 gram weights looked like after about 4 hours of use. The color on the weights has faded.
Engaging the green springs on the weights was easy, the stiffer yellow springs takes some effort.
Back to the original set-up.
I went out for a night drive last night with the yellow/106 set-up and I am definitely keeping it. Acceleration and hill climbing is so much better than the other two combinations I tried. If I had a larger engine, the 106/green set-up would have worked out really well for the type of driving I do.
Got the new fuel pump from Amazon yesterday. It is in a Briggs & Stratton box but made by Mikuni. Not crazy about the housing being plastic, but I’ll see how long it lasts. I will get a rebuild kit for the aluminum one so I have it as a back-up.
The fuel filters are full of gas again and I can see gas flowing into the top one near the tank. All good again.
And the vent filter is doing its job. After two rides and 22 miles, the carburetor bowl is free of debris.
Some of that debris clogged up the carb. With a combination of carb clearner, guitar strings and compressed air, I got it all cleaned out.
The plug is looking pretty good. Despite getting near the end of September, it is still humid and 90-92 for afternoon highs. Hopefully sometime soon I will need to work on winter jetting.
Despite this being a genuine Mikuni:
It isn’t holding up too well, considering there are less than 75 hours on it. This diaphragm had gas behind it.