Joined: Sat Dec 24, 2005 2:51 pm Posts: 125 Location: Moundsville, West Virginia
Engine update: I got a handful of new main jets and even a few new pilot jets and I also went ahead and bought/installed a new carb diaphragm because I've read that even a pin hole can screw with the performance. So now, everything in the carb is new and the carb itself cannot possibly get any cleaner, . I've tried a few different main and pilot jet settings and adjusted the air mix screw until I was cross-eyed, and it still spits and sputters at lower rpms and if it dies, then its very difficult to re-start. It also seems to lack power under load. I've always been pretty adept with small engines, but this thing is starting to get the better of me.
Here's what I know: 1. Compression seems ok at 148 psi 2. Has a strong blue spark. But I've noted that, sometimes as I'm cranking the engine, the spark intensity decreases and will sometimes appear to quit all-together. 3. I'm using fresh 91 octane. 4. Engine has proper oil level. 5. I've checked (and adjusted) the valve clearance per the repair manual. 6. I've verified that there are no air leaks in the intake. 7. I'm using a clean and properly oiled K&N pleated air filter, with a foam pre-filter. 8. The exhaust is unobstructed, 1.5" diameter tube with a free flowing muffler.
So I'm left wondering if this engine is just typically very temperamental with jetting and I just haven't found the sweet spot yet, or if I have a valve problem or if the coil, pick-up coil or CDI is just going bad.
If anyone has any thoughts, I could really use some guidance.
_________________ "I wish there was a way to tell you're in the good old days, before you've actually left them."
Joined: Wed Nov 28, 2007 2:21 am Posts: 18108 Images: 24 Location: Pacific NW
Does the color of the spark plug tell you if you are rich or lean? How does it run without the air filter verses with it installed? What happens when you run partial choke verses wide open? Do you have a clear fuel filter where you can see the gasoline flowing? Does it run out?
Joined: Sat Dec 24, 2005 2:51 pm Posts: 125 Location: Moundsville, West Virginia
The spark plug is still slightly blackened, so I'm thinking its still rich. Which confuses me because I currently have the stock jets back in (47.5 pilot and 127.5 main), and I'd think with the exhaust and air filter I have, shouldn't it be lean?? Having the choke "on" helps it run a little better, but having the air filter on/off makes no difference. I do have a clear fuel filter, but honestly, I've never watched it while running the engine. I'm going to "play" with it again over the weekend, so I'll keep an eye on that, thank you!
_________________ "I wish there was a way to tell you're in the good old days, before you've actually left them."
Joined: Sat Dec 24, 2005 2:51 pm Posts: 125 Location: Moundsville, West Virginia
It was the CDI. I had a friend helping over the weekend, putting another set of eyes on it, and the spark was very random. Tested some things and changed some other things. Then we figured we'd try another CDI just for good measure, and vroom! No more spitting and sputtering, no more hard starting and no more bogging/low power. Its a relief that its finally fixed, but also frustrating that I never thought of it sooner. Oh well, such is life. We rode it a bunch yesterday and had a blast. I haven't seen my daughters smile like that since before this whole COVID-19 pandemic started. Good times.
Thanks to everyone who read, commented and/or provided assistance.
_________________ "I wish there was a way to tell you're in the good old days, before you've actually left them."
Joined: Sat Dec 24, 2005 2:51 pm Posts: 125 Location: Moundsville, West Virginia
I've finally been putting some time on my little project. The thing really performs well, and so much better than the previous versions. I've been very happy with it. So, of course, each time I ride it, I'm a little tougher on it. Aaaaaaand I finally found the first weak point: rear suspension arms. After I figure out how to straighten this one out and weld up the cracks in both arms, I think I'll add some additional bracing.
Funny thing is, I've been so impressed with the performance, that I'm not even upset that the rear arms failed!
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_________________ "I wish there was a way to tell you're in the good old days, before you've actually left them."
Joined: Sat Dec 24, 2005 2:51 pm Posts: 125 Location: Moundsville, West Virginia
Thank you!
My daughters and I put a couple hours, and a couple gallons of fuel, through my home built buggies last night. It was such a blast! Its been a very long time since I've actually needed to use the headlights while riding. The beefed up rear arms are holding up well, but I do need to add some strength and rigidity to the frame in a couple places. And I really need to add a front skid plate and some side panels to deflect debris. Getting face-fulls of dirt and sticks is not as much fun as it was when I was a kid. lol The engine continues to run well, but idles too high after getting it up to temperature. I need to check the spark plug 1st, but could it be developing an air leak somewhere after everything gets warmed up? Or, is my naivety with this engine still preventing me from understanding it completely? I.E.: does it just take it 5-10 minutes to reach operating temperature and I have the idle set too high? Hmmm... I may need to continue experimenting.
_________________ "I wish there was a way to tell you're in the good old days, before you've actually left them."
Joined: Sat Dec 24, 2005 2:51 pm Posts: 125 Location: Moundsville, West Virginia
Rode the buggies while enjoying the beautiful weather this weekend. My daughter took a video from the passenger seat, of a lap around around our ride-able property. I've never shared a video nor have I yet uploaded anything to Youtube. I think the only way I've ever shared videos is on FB. Maybe I could put it up on the buggynews FB page and share the link here?
_________________ "I wish there was a way to tell you're in the good old days, before you've actually left them."
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. I've tried a few different main and pilot jet settings and adjusted the air mix screw until I was cross-eyed, and it still spits and sputters at lower rpms and if it dies, then its very difficult to re-start. It also seems to lack power under load. I've always been pretty adept with small engines, but this thing is starting to get the better of me.
I had a friend helping over the weekend, putting another set of eyes on it, and the spark was very random. Tested some things and changed some other things. Then we figured we'd try another CDI just for good measure, and vroom! No more spitting and sputtering, no more hard starting and no more bogging/low power. Its a relief that its finally fixed, but also frustrating that I never thought of it sooner. 
Oh well, such is life. We rode it a bunch yesterday and had a blast. I haven't seen my daughters smile like that since before this whole COVID-19 pandemic started. Good times.
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