Changed all belts and most fluids on my 2000 U-320 this weekend and NAPA told me that the Gates 7274 belt called for in the FT manual comes up as a hose not a belt. I then also checked on-line and got the same result. However, I still had a Gates 7274 in the original slip cover so I noted the dimensions and went back to NAPA. With NAPA's help I found that a 3L270 has almost the exact dimensions as my old 7274 so I bought one, installed it and ran the generator under load for about 30 minutes and it seems to be fine. Tension is good. Keeping the NOS 7274 as a back up. Not sure if anyone else had this problem yet.
Gates 7375 XL is what I have as a spare when I changed the belt about 2 years. Also have the 3 cylinder 10 KW Isuzu.
The dimensions of the 7335 are 3/8X34-1/8. That is inches. Also belt that I have is cogged.
The Gates 7274 is a metric belt, 6mm wide and 390mm long. That is approximately 5/16" of an inch wide and just over 27" long. The 3L270 is 3/8" wide and 27" long and cogged. It goes on the pulleys easily and does not seem to have undue tension. The generator in my 2000 U-320 only has two pulleys with no idler pulley, so length is critical. I do not under stand now a belt any longer than 27" could possibly work on my generator Perhaps a 1/2" wide 28"-30" might work in a pinch but I would be concerned that it would not stay in the pulleys due to the width. 34 1/8" seems totally wrong unless you have a different pulley setup. Have you physically checked your spare against what is really on your unit?
The generator does have an idler pulley, not the spring loaded type but fixed to the block. We have different year coaches and that may explain the difference in belts. In other words there are 3 pulleys. This made me notice tht the belt needed tightening. What a pain.
That could be as mine only has 2 pulleys and neither is adjustable to change the tension.