carb help on an 86 vfr 700

i recently installed a wideband on my bike to help diagnose a hesitation problem above 8500. it idles at 14.0 and pegs below 10.0 when driving and under full aceleration. she is super rich.

it has the factory air box with brand new filter, it has a yosh slip on (i believe that is the brand name on it).

pulled the carbs and found it to have these jets in it. 118 and 38 which i guess are supost to be stock.

suggestions? perhapse they are not stock sizes and my info i have gotten is incorrect? any help would be greatly appreciated

 

anyone????????????????????

 

Needles

Do your needles look like a nail or do they have clips?

 

sorry Volks, I havent a clue what your talkin about.

your bike IDLES at 14,000 RPM... I.e you are about redlined while in Neutral?
I think I am missunderstanding your comment here. Would you clarify for me please.

the obvious answers here...
If you are running rich, you have too much fuel. Too much fuel can be;

not enough air
air delivery system is clogged somewhere
air filter is not correct size/rating
fuel pump is pushing too much fuel
fuel lines are over-sized
jets are not tuned properly
after market jets
jets have been modifiied
Idle setscrew is set too high
choke is broken

I would attempt this;
First, ensure the choke is working properly.
pull the gas tank, and use a jar of gas for the interim. remove the air filter and or the air filter top cover and filter. run the bike and check the idle. adjust the thumb screw until the bike dies. pull choke and start bike. it should start. when you de-choke, it should die. put the filter and filter cover back on, and repeat the proceedure, and note the turns of the idle thumb screw to get the bike to run at idle around 1800 RPM... choked, it should run around 2100 RPM.

Throttle rev the bike a few times under both conditions and note any unfamiliar smells, or if you see black smoke, or liquid out the exhaust pipes.

If you can not get the bike to run at either setting, your problem is in the fuel delivery. Either the fuel pump. or the jets themselves. Replacing the jets will be far cheaper than locating a new fuel pump.

just my $0.02 (with not really understanding the problem well)
sorry.

 

14.0 on a air fuel guage. i have a portable air fuel guage with a bung welded into the pipe. everything on the bike is stock as far as i know. me and my room mate pulled the carbs thinking it was going to have some aftermarket jets but they appear to be from the factory with a 118 and a 38 on the sides. the bike starts and runs great up till about 8500 rpms. after that it just drowns itself out and bogs.

as far as the needles i am not sure. we only pulled the bowls off, i guess i don't understand what you are looking for there. please elaborate a little more and i will get you an answer as soon as possible

 

Usually a hesitation above 8500 rpm would be a main jet issue, but it doesnt sound like your jets are oversized. Is the 118 the main? I think you need to start from scratch. Check the fuel screws for the correct setting then the needles. Are they stock? Have they been shimmed? Or are they tapered with an adjustable clip? Is the air box stock? No holes drilled in it? Stock filter? Not K&N. It's quite possible to be rich from 3000 RPM up to 6000 RPM and yet be way lean on top. I say that because I'm running a 124 MJ Drilled air box/ K&N filter, Stage 1 needles with a Yosh slip -on. You can always run it on a load control Dyno and put and end to any guess work. I did and it saved me a lot of work and aggrevation.

 

Dynojet

If some yahoo put a Dynojet kit in it the needles will have clips.

 

118 is the main. we just pulled the bowls off last night and used a flat head screw driver to pull the main and secondarys out to check the numbers on the side, which were 118 and 38.
we have not pulled anything else apart on the carbs. what would be the next step in seeing if it has diffrent/ aftermarket needles? how would i know stock from aftermarket?


and yes the air box is stock with no holes drilled and has a brand new honda air filter, has 35 miles on it.

 

Jets

You may just want to go by a shop and compair it to a new one, most shops should have a selection on hand. I did fall victim to a drilled out set of jets recently. Goofed around for quite a while before owner confessed to taking a drill to several sets of jets.

 

aS Toe cutter stated the stock needles will look more like a nail, while an aftermarket will have a tapered design. The top of the stock needle looks like the head of a nail, while the aftermarket will have small steps with a removable c-clip for adjustment. It is quite possible the main has been drilled out instead of doing it the proper way with the installation of a jet kit. If you were to simply buy a stage 1 jet kit and follow the instructions you should be right in the ball park.

 

oh that would suck. i will see what i can do. my room mate is a little more carb savy when it comes to bikes so when he gets off work we will tear into it a little further

awsome, it sounds as though you would have to be retarded to make a maistake on the identification of the needles. i will check them out when i get home tonight.

i really really apreciate all the help guys

 

welp done for the night. pulled the needles out and they look just like a nail so they are the stock ones. the thing that gets me is everything looks as though it has never been apart, everything is squeky clean, plugs are brand new and gaped at .030 , it looks as though it was deffinatly a garage bike for most if its life.

we have come to the conclusion that we are going to compare the mains to a new one and if thier is no visable diffrence we are going to go from the main size of 118 to a 112 and see how it looks on the wideband oxygen sensor.

this thing runs so good up till 8500- 9000 rpms it is amazing for a bike this old. i left it sit all winter walked out in the garage and fliped the choke over and it fired right up. i love the bike but would really like to wind it up to red line once in a while.

i really apreciate all the help and will report back with my findings soon

 

forgot to mention that i am going to bring the compression tester home tomarrow and make sure the cylinders compression tests good. i am sure that it is fine but might as well check it while i have it this far apart

 

Strange problem......

Did you check and set the float heights/fuel levels??

If you're into some experimentation, lower the fuel levels (raise the floats) about 2mm to lean it out and try again.......

try removing the air filter and do a high speed run

 

toecutter in your profile picture is that an 86 with a single sided swingarm?

sorry to thread jack. just curious.

 

call me stupid or naive but what the heck is a wideband...I know what a broadband is....

 

I can answer that for Toe yep sure is did it myself....neeeener neener neener.

it was a cake walk the easiest thing I've everdone...... okay i added the last part

 

it is a wide band oxygen sensor. it has a guage that reads out and tells you exactly where your fuel mixture is at....... rich or lean. 14.7 is considered stoitiometric efficency ......... 14.7 air particles to every 1 fuel .........but ussually a good number to hang around at full throtle is 13.0 ish.----- 10. 0 and below is excessivly rich and is the problem i am having


here is a link to a basic one. you simple weld a bung in your exhaust pipe or make a test pipe with the bung in it and install the o2 sensor then wire the guage to power and ground and BAM you have an air/ fuel reading

AEM UEGO Wideband Gauge 30-4100 for $218.11 Shipped, Universal Wideband Gauge

 

run it without the air box lid and filter /see what it does. My air box has a bunch of 1/2 holes drilled in it & a K/N filter.

 

There were no washers or shims added to the stock needles,and everything else looks good. A 118 MJ is stock. Could you be getting a rich reading @8500-9000 rpm due to a cylinder cutting out? Coils rarely go bad but it's a possiblity. Does this happen only under load or will it do it in nuetral?