No spark 87 trx200sx

[Doofy]

Hey guys I'm usually on the dirt bike forums so hopefully someone here can help. My buddy has an 87 honda trx200sx atv. He told me it does after about 20 mins. So I told him I'd look at it. After some wrenching and testing, I've narrowed it down. It shuts off after its been running for a good 15 mins. It then has no spark. If I let it sit for 10 mins or so I can start it again but will run for a few mins only. The loner I let it cool down the longer it will run without losing spark. I've replaced the spark plug and coil pack and nothing has changed. I was going to check the cdi next but instead of the older honda cdi woth points, this thing has a cdi box. Is there a way of testing it? I guess what I'm asking is, how can I test the cdi box or what else should I test that I can? I was just gonna buy a box for my buddy but had no idea they're in the 100 range. I was thinking like 15 bucks haha. Any help would be appreciated. I'm pretty good with fixing older dirt bikes, just never had a bike with cdi box. Any suggestions??

[justaskmenicley]

The only way you can test a CDI is by switching it with a known good one. If you get a manual for the thing it may say otherwise but thanks the only way I've heard of testing them. If you get a manual it will tell you how to test the rest of the components. I would test the regulator and stator next. If everything checks out run it until it has no spark and check it again. Test the cool again as well. I've heard of them being cracked and once they run and warm up it expands and you can't get a spark because the crack.