1990 VFR750 fuel out the exhaust...

Alright, so this has been an ongoing project since late November and it's come to the point where I must turn to my friends here on VFRWorld for assistance because I have no clue what the hell is going on right now with this bike!

The bike originally came to me with an 'overheating' problem and for general maintenance work. My buddy said that the bike sat in his garage for nearly 4 months in the Yuma summer heat, and that he brought it out to ride it and it wouldn't run right. I had him swap the filter and put fresh fuel in it, which got it running. Then he said it would only run like 20 minutes and then just die out and wouldn't turn over at all. So, he brought it up to me to take a look at it and do some other work like a new brake lever, oil change, coolant flush, chain lube and adjust, and a good cleaning. Seemed pretty simple so I told him I'd do it.

Long story short, the hot start problem turned out to be a bad R/R putting out 21.2 VDC to the battery and overheating the battery which shut the whole system down. Replaced the R/R and it ran fine for a 30 mile trip around the area. Shut the bike down and left it for a few days and then decided to do the fluid changes. Went to fire it up and it just clicked. Battery was fresh and so I did a voltage check which showed excessive drain with the starter button pressed (9.8 VDC) and then an Amp drain test showed -9.2 Amps when the max should be around 4 Amps. Figured there was an unwanted ground somewhere in the starting system and checked all the wires and relays. Nothing.

The bike sat for almost 2 months in the garage from that point because my schedule got screwed up and I didn't have time to do anything at all with the bikes. Every time I set aside time to fix it something else would come up. My buddy wasn't worried much cause it was too cold to ride anyways, which didn't help my motivation any.

The owner decided he wanted to try and sell the VFR cause he wanted a cruiser and my co-worker had been eyeing this thing like candy, so I hooked them up and the sale commenced. Now it was time to fix the ground problem.

I invited my buddy from school who is an electrical whiz to take a look. He double checked all my work and found 2 wires that were corroded, cleaned em up and then discovered that the ground to the fuel pump has high resistance. *Note: the fuel pump ran constantly when brought to me, and had since my buddy had bought it last year*

We tested the fuel pump and relay. Both checked out fine, so we jumped the ground. The bike turned over and with full choke and a little twist of the throttle she eventually fired up. I was all excited that it finally ran and then the guys started yelling and I turned around to see a rooster tail of fuel spraying out the exhaust and into the driveway! Shutting it down, the fuel continued to drip out of the exhaust's bottom hole. Much kitty litter and a ton of cursing later, we could only think that the carb jets had clogged and me twisting the throttle may have sucked excess fuel into the engine. It had been sitting a while anyways so we all agreed to pull the carbs and clean them up.

As I made the calls to get the parts ordered and take care of some other business, my buddy and the new owner pulled the tank, filter plate and carb rack off the bike. I realized that this was probably a bad idea since I hadn't seen what was taken off and where everything went as far as the hoses and routing. Eh, I did my '86 ok... how much harder can it be? LOL yeah....

This weekend the new owner and myself cleaned the carbs. I was VERY meticulous and made sure that every passageway was clear... swapped out every gasket that was included in the kits... and double checked air flow through each system. After about an hour or so trying to reassemble the carbs and getting the hose routing right (never again will I allow someone else to touch my projects!)... I got the carbs back on, the tank installed, put some fresh fuel into her belly, primed the bowls and then turned the key.

Again... *click* WTF?

After determining that the click was the starter locked up at a hot spot (the original unwanted ground and probably the reason that the R/R burned up) I got pissed off and hit the starter about a dozen times, not expecting anything to fix itself mind you... just out of frustration.

Low and behold, the damn thing started turning and I was able to get it running for about 20 seconds! It idled fine, sounded great and proved that the bike was still in working condition, which excited me much! Then the bike coughed and died, wouldn't restart, sputtered, wouldn't turn, sputtered, and then fired up again... smoking white out the exhaust and then died. The fuel was dripping out the bottom yet again!

I gave up.

I have no idea where to go from here. *obviously the starter will get replaced*

I've never seen fuel pour out of the exhaust like this before.

No ideas.

Help?

 

For some reason the needle and seat are not closing on one or more carb. You need to pluck them back off and inspect the float, needle, and seat with a sharp eye and bench test them.

 

yeah, it's a California bike, Tink.

Toe, I examined the float needles cause they weren't included in the kits for some reason. They all seemed to be ok, but they were a bit pointed more than they should have been. However, the fuel pump is not coming on and there wasn't enough fuel to really gravity feed to the point of overfilling the bowls... at least I don't think so.

 

That does bring up another question(s) that I had about this particular carb setup...

1) The middle rail on the carb set doesn't seem to have any hoses on it (didn't see it when it was taken off like I stated earlier, and since the new owner couldn't remember if there actually was one and my buddy was/is in Payson till tonight I couldn't verify) and the diagrams in the manual don't show very good clarity or detail. I'm assuming that that is the vent to air for the bowls/jets, but shouldn't it have a hose connected to it instead of just being an open port on the rail directly below the carbs?

2) You mention that the funnels were removed from your set... what purpose do the funnels have as far as performance goes, and would omitting those from the assembly have a negative effect on it? My '86 doesn't have them, and aside from slightly concentrating the airflow prior to entry to the Venturi I don't see any purpose for the funnels to be on there.

I'll have to ask if they want to replace the carbs or not. Right now they are looking at $140 for new float sets and $399 for a new starter... unless anyone has a used starter that they are willing to part with? I'm going to call Bob's Used Cycles and see if he has a starter lying around down there that works. Can't see dropping $400 for a starter if we don't have to.

 

yes, crank case breather was installed. It's the middle rail that is open air. Plate, box and tank installed.

 

Guess I should update this...

After replacing the float needles and setting them to 9mm (they were 12, 12,17, & 15mm) the bike ran fine on idle, and I sync'd the carbs and did an idle drop. The starter and fuel pump needed replaced. The bike ran great until it warmed up and then it started smoking like a bitch! When you came to a stop it'd fall on it's face and die. Give it a minute and it'd fire right back up.

I verified that I had all the hoses routed properly and everything was where it was supposed to be. No fuel or water in the oil. Smoke had no obvious odor of either, just fuel. I assumed that it was just burning off the excess that had wandered it's way into the system during it's issues. I gave the bike to the owner and told him to run the piss out of it for the next week while I was on vacay and to let me know how she did.

Each day he called and told me the same thing. Started up fine, idled beautifully, shifts perfect. When it gets hot, it starts to smoke and at the end of the 7 mile trip to work it's smoking steady like a 70's guzzler.

I was totally thinking that I was gonna have to work on her some more when I got home until he called me last night and said "I took her on the freeway after work and got on it a bit. It smoked a bit while I was on the ramp and by the time I hit the 70 mile mark on the trip from when I reset it when you gave it to me on Saturday, it just stopped smoking. Hasn't smoked since!"

OK... guess it's all good now

 

Sweet....nothing fixes a bike better than riding the piss out of it on the hwy :smile: