any ideas?

[porsche4786]

Anybody have any ideas on why the bike would do this? My friend is looking for a bike and I think this might be it if we can fix this problem.

http://portland.craigslist.org/mcy/162312766.html

"Here is a Suzuki GS500E, 1990. It's a good bike. Many fixes.

New pistons, rings, brakes, brake pads, calipers, handlebars, choke cable, cam chain tensioner, cylanders honed/miked, carbeurator fixed, and much more! I spent $2700.00 fixing this bike, but I want a change from this type of bike to a cruiser. There is 1 problem with this bike. It's something electrical. Riding for 30 minutes or more, it will bog down and need to cool down to run properly again. I've had all the work done by a shop and this is what they've told me. I'm ready to move onto something else. If you're inclined to do a little leg work and fix a bike for probably very little. Here's your chance.
Fully legal, registered to me, clean title, all that. This is a steal, I think. Hope to hear from you. "

[Alphamazing]

Overheating regulator possibly.

[Jake D]

Valve clearance is too tight. 

[porsche4786]

Here's an email I got back from him.

"The mileage is about 26,000. But, that was the mileage before the engine
work.  There are no major scratches or dents.  There's a small dent on the gas
tank, but hardly noticeable, and the electrical problem causes the bike to bog
down after about 30 minutes to an hour of riding, let it cool and it goes right
back to normal.  Kind of weird, but I don't want to fix it anymore.  Need a new
car, so that's why I'm selling it with all the new fixes for hardly anything."

[Jake D]

Yeah, it is the valve clearance, IMHO.  What electrical problem have you heard of that would do that?

[porsche4786]

The valves being too tight would cause this because when they get hot they expand and rub agains the walls?

[Jake D]

Expand and it looses compression.  Plus, once you lose compression, the valves let charged gases escape, exacerbating the problem and heating the valves even more. 

[roguegeek]

Even if that wasn't a problem, the bike is probably not worth the price he's asking.

[porsche4786]

Yeah, he probably won't get it. It does kinda have a lot of miles on it. GS's are kinda rare in this area it seems like, that's why I went out and bought an 05.

Even if that wasn't a problem, the bike is probably not worth the price he's asking.