It has been a while since I updated this thread.
I finally got the engine to run well again. I bought a good set of used carbs from a last generation of the EX250, and they have different slide needles than the early models.....not sure if that is what helped cure the problem. I bumped up the main set a couple sizes and shimmed the needles 2 washers when I mounted them - and the bike runs well again. I don't know what was wrong with the other carbs - maybe they are just getting old and are very sensitive to the slide diaphragm getting old and stiff. The running problem seems to be related to a very lean condition that occurs at a steady cruising speed - when a gust of wind comes along and slows the bike down......it feels like the slide doesn't react and the engine goes into a lean surge condition. Whatever the issue...the replacement carbs fixed the problem.
I rode the little Ninja down to the Barber Vintage Motorcycle event in Birmingham Alabama. The first day I rode down to Lynchburg, TN and spent the night with MMRanch, the next day I rode down to Auburn, AL and spent the night with Stewmills, the following day we rode to Birmingham and spent the day at Barber's, then on Saturday night and Sunday I finished the ride home.....it was a bit over 1,400 miles!
The stock seat is not adequate for long rides, and I had a 1" thick foam pad taped to the seat....my butt still got horribly tired by the 4th day of riding.
This is what the stock seat from Blue Collar Bobber looks like. It is rounded and has padding in the middle, but very little on the edges where my buns contact the seat.
The Blue Collar Bobber seat pan is a thick piece of steel and is pretty heavy - so I decided to build my own seat pan. I put 2 sided carpet tape on the frame, fuel tank and rear fender/body - then put cardboard on the tape in the shape I wanted the seat bottom to be. I then put packing tape over the cardboard to work as a bond breaker and allow the seat pan to be pulled off the cardboard once the resin had cured. I put 2 layers of fiberglass cloth down first:
Then to get better stiffness I cut strips of PVC molding and heated them in my oven at 215 degrees - then bent them into shape while they were still warm. The PVC cools and gets stiff very quickly, you have to bend them very fast and work them into shape with 4-5 heating cycles. I then epoxied the PVC strips into place.
I soldered a stainless nut onto a large washer for the seat mounting bolt, and I epoxied the nut and washer to the seat pan. I then put pieces of the corrugated plastic yard signs that I had cut to fill in the space between the PVC reinforcement, and then placed a couple of layers of fiberglass "mat" over the PVC. I learned that the matt did not want to make the sharp bends over the PVC, and it would have been better to use the mat on the flat bottom, and the fiberglass cloth over the PVC reinforcements.....and the PVC pieces should have been rounded to allow the fiberglass cloth to make the bends easier.
The seat pan ended up a bit thicker than heavier than I imagined - but it is incredibly strong.....I could have made it a bit thinner and lighter and it would have been fine. The top ended up being a bit lumpy and uneven....but the foam that gets glued onto the pan won't care.
Here is a piece of black plastic pulled over the seat to show the shape I am working for - the seat will be flat from side to side and provide more padding on the edges.
I will take the finished seat pan up to Ronny Price upholstery and have them add the padding and sew a new cover.
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