1978 Yamaha SR 500 hard to start

KirkN · Posted: Fri Apr 22, 2011 6:14 am Post subject:

Yep, that's a real problem.

On another forum, a buddy of mine converted a Kawasaki KZ400 twin to a single-carb setup. He struggled and struggled with jetting and rich running until he discovered the single carb he was using was from a Honda CR250 2-stroker. Had the little "hood" over the needle jet as Catfish describes. He swapped the carb for a 'conventional' 4-stroke carb and problem solved!

YD3 · Posted: Fri Apr 22, 2011 7:18 pm Post subject:

Thanks Capt and Kirk, ( no Star Trek pun intended!!)

I will definitely check the tube in the carb. To update on my ride, it did make it @ 160 miles but it was not without incident. The first gas stop was @ 40 miles in and @ 20 minutes long. I could tell after the 5th kick it was not going to go. Two other people that own SR's tried it and nothing. We pushed it and nothing. The main group left and I decided to put in a new plug. 1 kick and it started and idled like new. My friend had put a colortune tester on the carb to adjust the mixture and the old plug looked like it was burning perfect. That plug had not been in the bike over 100 miles. It ran great in fact so good that I caught up with the others as they stopped for lunch. After lunch, 3 kicks and running.

The next section of the ride was hilly and curvy road that ended at a 4 lane. Everyone took the opportunity to open their bike up a little. I stayed near the front and my bike was still pulling hard at 85 mph. It has a 36mm Mikuni, K+N filter, and supertrapp pipe. The motor is stock with stock cam. At the next stop which was @ 40 miles, everyone commented on how good the bike sounded and how well it ran. That stop was @ 10 minutes long and I just let it run.

I turn off heading home, get @ 5 miles from the house, pull up to a stop sign and it dies as if you turned the key off. 2 kicks and it is back running and makes it home.

As well as it ran, I believe that the tune of the carb is about right. The plug reads perfect. I am going to go thru the ignition side of the wiring and clean all the connections. While I'm at it, I think I will check the resistance on the coil and the stator. I will also check the carb because I think it may have the "tower" around the needle. I will know tomorrow.

Thanks again for all the help and I will let you know.