Ethanol Gas and Jet change?

Ok, my carb guy just called, he's done cleaning em (86 VF500F) and mentioned that i should go up one on the slow jet (35 to 38) cause he thinks older bikes don't do so well with the ethanol in gas. I tried messin with jets on a previous bike and it was a BAD expierience. She never ran right. So, is stock ok? or is it safe to go up one?

 

I don't have an answer to your question, but I have a question of my own. I own a boat, so I'm well aware of what Ethanol does, but how does changing the jet have anything to do with Ethanol?

 

dunno. Maybe its thinning it out? He wants me to go up one so i'll put more gas to it. I can see his point, but is it necessary? After reading many carb rebuild posts it was never mentioned. I was just lookin to see if anyone had an opinon. Personally im gonna stick with stock just cuz i want it to run. I don't have a second bike so experimenting is out of the question.

 

I never had any problem with running any gas on my old VF500

 

Our gas has 10% ethanol. so if it has less energy than gas... and only being 10% of the mix, yeah i probably shouldn't worry. When it comes time (if it fires) i'll do like the clymer says to adjust idle. It states: set screws 2 turns from seat. turn all in half turn each until drop of 50 rpm (reset idle speed) then start at ( I dont remember which cylinder) and turn until a drop of 50 rpm. (after resetting idle speed.) at drop of rpm, turn idle screw 1 turn in, reset idle speed. (in or out im not sure right now but I will reference the manual) And somehow I feel like im missin somethin. ( I will use an rpm guage not the tach.) Is this the proper Idle drop way?

 

Oh knock the carb guy all you want! I don't know him from adam and i dont care. Thats why im posting here. god I'm such a junkie i have been on this site for like 3hrs straight every night scince i got the damn thing. After reading i find to trust the judgement of this site. Tomorrow I'll see how good a job he did and go from there. I did have a good feeling about him though... If you can imagine one of the hillbillys from the begining of Deliverance (not the rapers but the ones who drove thier trucks.) thats him. Probably doesn't know much aside from bikes but thats ok.

 

A little off subject but is there a difference between cali carbs and 49 staters other than the vaccum hoses?

 

As tink stated the alcohol that is now in fuel has less BTU per cube than gas. The feds restrict the amount that goes in fuel but there are some local stores that have been caught running as high as 20% of the good ole corn mash. Any time you replace any amount of volume with another that contains a lesser amount of BTU you need to increase the ratio of fuel to air. An extreme example of this is a weed eater v and RC plane engine that runs "nitro" fuel (generally 5-15% nitromethane, 5-15% lubricant and the rest alcohol). Generally weed eaters are around 30cc and will run a long time on 4oz of fuel, a 3.5cc RC engine on the same size tank with alcohol may only run 15-20 minutes because the mixture is a lot richer to support proper combustion. One thing about alcohol in your gas is that it burns slower and cooler than gas so it can actually hide or prevent spark knock/ pre ignition so you don't notice the slightly lean run. That is basically one of the corner stones of hot rodding, moon shiners figured out they could throw the hooch in the tank, shave the heads, throw a bigger carb on (bigger jets) and play with the timing more than a stock engine would withstand. With the maximum legal amount set at 10% I honestly don't see a huge reason to change jets, the mixture would be affected just as much by a cold morning v a hot day as it would by 5-10% mixed in. On the other hand it wouldn't hurt to go up one size on the jets to put it closer to the stock ratio but again, as said before, your bike is old and there are so many variables that the only way to tell for sure what you need to do with it would be with an EG analyzer. HERE is a list with BTU of fuels, you can see the mixed has a lower BTU rating than straight gas and since BTU is the amount of "work" locked in the fuel you can also see you need more of it to do the same work but there is very little percentage difference per gallon. Your not dumping gallons into the engine but more like micro or milliliters and with that low of a percentage on that low of a volume you can see the negligible difference unless your anal about stuff. sorry the ole lady is watching american idol so being long winded here was better (for me) than listening to that lol.

 

:defence: yeah i know that trick. thanks for your input! I'm gonna start stock n like tinkerin said, watch the idle adjustment. now my concern is which carb set? i got a set for an 84 500 and the 86 500 (cali carbs) I went with the cali carb to be cleaned cause of the same year, but i did notice someone gained mileage from a set of 85 carbs.

maybe i'll do both. my wife watches alot of deadliest women. yeah, NOT COOL. so i'll just hide in the garage :biggrin:

 

Sorry I don't have any of my old text books at hand. I also know from first hand experience the gas/nitro fuel, I fly rc planes.

Alcohol also oxygenates the fuel and releases that oxygen during the burn which is another reason you richen the mixture with alcohol.

 

The tuner tunes with what's at hand, go home drain your 83 octane 10% ethanol pump gas and go back with blue fuel and I'm pretty sure they would change a few things. There is a little bit of difference in tuning for emissions and tuning for power, the later ignoring exhaust emission and attempting to reach peak power. Emissions tuning is an attempt to get the least emissions with out leaning to the point of engine damage. As for the emission station, 99% of those guys wouldn't have a clue how to rebuild a carb, heck I'd put money on it that if some of them didn't have the book or computer to tell them what type of induction an engine had they wouldn't have a clue if it had a carb or FI.

If I recall correctly the 84 carbs did have bigger bores and were more an all out set up and the later models were geared more to midrange and economy. I know my 84 is kinda doggy in the middle and feels like a scooter but around 9k it comes alive, if you shift at red line on the roads around here it's down right scary. haven't rode any of the newer ones so I can't compare it.

 

again, alcohol contains an amount of oxygen that is released in the burn. 14.3:1 is on the exhaust side, when you replace part of an oxygen free fuel with one containing oxygen with the exact same jets it's going to show a slightly leaner condition on the exhaust side since some oxygen rode in with the fuel. In turn you make the mixture richer on the intake side to get the outcome you are referring to on the exhaust side. Similar to using nitrous-oxide which contains an oxidizer (oxygen), you HAVE to make the mixture richer to use (unless you want a grenade due to over leaning) it to maintain to end result you are referring to. I'm pretty sure we're talking about the same thing just from a different angle.

 

Oh yeah, and the 2 SBC and 1 SBF stroker I had tuned, they did ask for mean altitude and fuel to be used.