Can 1983 Honda VT-500 Meet the Vetter Challenge?

[renault_megane_dci]

Now that you have the O2 sensor fitted, you are that closer to fuel inject the bike. Tempted ?

[redyaris]

Not tempted at all.
What I will be doing is finding out the optimum jetting for the bike and aplication, to see how close, I can get to 2.35L/100km, 100mpg. An air/fuel ratio of 14.5:1 to 14.7:1 between 110km/h - 130km/h is the objective. The present/current jetting is #35 low speed jets and #112 main jets in both carbs. I suspect that I may be able to go down to #110 main jets which is the size used on other 250cc singe engines. The California version of the VT500 runs #108 main jets in the front cylinder so I may test the #108's if the #110's show an air/fuel ratio under 14.5:1...
My fuel Injected 2008 Yamaha WR 250 does not have an 02 sensor, nore do many of the other fuel injected bikes.

[redyaris]

Did 40km [25 mile] road test today with the #112 main jets and the #35 slow speed jets and the air/fuel guage tells me that at 120km/h [75mph]the air fuel ratio is 14:1, +/- 0.5, and 13.5:1 at idle at end of run. When accelerating the air/fuel ratio drops into the 13.xx:1 ratio and slowing down on trailing throatle it reads 17:1. It looks like I can go down to #110 main jets and maybe even #108's?
On Sunday when it's supposed to be warmer I will do a long [300km plus] test run to see what the fuel consumtion is...

[redyaris]

Road Test #112 main jets, #35 slow jets
112KM @/or above posted speed limits 80% @115km/h, 15% @100km/h
3.0L
2.68L/100km, 88mpg
ambiant air temp 15*C
some cross wind

The air/fuel guage readings were 14.0 under light load +/- 0.5 @ 110km/h+ [70mph+]
12.0 under acceleration +/- 0.5
16.5 with throatle closed +/- 0.5
I think I will try the #108 main jets next to see if they work well enough. If not then I can go back to the #110 main jets.

It seems like it has a built in lean burn?
The coolent temp is still a bit high for my liking, even though it is in the normal range?!

[redyaris]

The #108 main jets are in and ready for tomorrows test run. Maybe I can get into the 90mpg zone?

[redyaris]

The #108 main jets are too small. the bike does not accelerate well and the air/fuel ratio goes to 17:1 I will try the #110's next but I suspect that #112's are the best choice.
116km/3.1L = 2.67L/100km, 88mpg

[redyaris]

Did a short road test with the #110 main jets and the air/fuel guage reading at 100 - 120km/h is 14.5:1 +/- 0.5. It works but may be to close to the edge, I think I will see if I can get a #111 main jets. Tomorrow I may do a longer road test to see what the fuel consumption is.

[ldjessee00]

Pretty meticulous testing!

Good luck!

[redyaris]

What is interesting about this project is that because it is a shaft drive reducing engine rpm by changing final drive ratio is not practical or easy. Therefore if I can get 2.7L/100km [87mpg] in the Vegas/Barstow challenge with a 500cc V-twin, it will be quite an achievement and will show that if the rpm of the engine could be reduced [from 5000rpm at 70mph to 3000rpm at 70mph] then over 100mpg is within the range of a 500cc bike.
Changing main jets on this bike is a pain because the carbs are 'wedged' into a small space and must be partialy removed from the engine to gain access to the float bowl.

[redyaris]

I have re-installed the #112 main jets because the #110's caused the engine the boog for aprox 5 seconds and the air/fuel guage showed a ratio of 17:1 which slowly went down to 14:1 at which point, the bike began to accelerate. This will be the carb fuel set up for the Vegas - Barstow run. I hope to be able to replicate the 88 mpg I achieved at 75mph on the highway in windy conditions.