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 Post subject: Re: 2 seater near completion?
PostPosted: Thu May 07, 2020 7:45 am 
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Joined: Sat Dec 24, 2005 2:51 pm
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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, :lol: . 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. [-o<

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 Post subject: Re: 2 seater near completion?
PostPosted: Thu May 07, 2020 9:51 am 
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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?

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 Post subject: Re: 2 seater near completion?
PostPosted: Fri May 08, 2020 8:14 am 
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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!

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 Post subject: Re: 2 seater near completion?
PostPosted: Mon May 11, 2020 6:46 am 
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Location: Moundsville, West Virginia
It was the CDI. #-o 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. :oops: 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.

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 Post subject: Re: 2 seater near completion?
PostPosted: Wed Jun 03, 2020 7:38 am 
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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! :o


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