blowing out of 1st cyl. carb

[fourk]

my 77 750four k is blowing out of the 1st cyl. happend riding normal at 50 mph normal rpm

[cdaiscool]

What do you mean that its blowing out of the 1st cylinder? Have you done a compression or leakdown test?

Motor-related issues aren't speed-related. They're rpm-related or load-related; if it happens at 4k rpm while riding, it'll happen at 4k rpm in 1st, 2nd, 3rd, 4th, or 5th. And probably while idling @ 4k rpm.

[fourk]

no,it just happend yesterday.i changed all 4 carbs just now & its still doing it.

[fourk]

its only doing it out of the 1st carb

[cdaiscool]

I still have no idea what you mean by its blowing out the cylinder. What is blowing out? Do you mean the cylinder cuts out, and you're running on 3 cylinders? If so, how do you know its cylinder 1 only?

If its not cutting out, then I've got zero idea wtf you're referring to.

Give us as much information as you have. I'd rather see a 4-page book than another 1-line reply, as that will have the information that the gurus (not me in ANY sort) can use to help you. Probably.

[fourk]

the fuel is blowing out the first cyl. carb instead of sucking it in, blowing gas into the breather.it is only doing this in the no. 1 cyl. i changed all 4 carbs thinking it may be flooding out but its still doing the same thing. it is not hitting on that cyl. although it is getting spark.(checked the plug)was running poorly on the way home.

[cdaiscool]

Do you have a vent in the fuel bowls? Sounds like they're pressurized. There should be something that makes sure they are not pressurized.

Carbs work by the piston causing a vacuum, and this sucking fuel up from the bowl through the jet, mixing with air also sucked in, and being pulled into the chamber.

If you are blowing gas somewhere else, that means its likely not venting out the vacuum that is caused. You need to find where the vent is on your particular set of carbs (internet, possibly the FSM on the home page here) and make sure its not plugged.

[Lucky 1]

Maybe he means coughing out of the carb. Not a steady blow.

[shinyribs]

If you have one cylinder spitting fuel back through the carb it could be valve related. If the intake valve happens to be open while the piston is coming up under compression it can push the fuel/air charge back the the carb.  

Did the bike bike start making any new ticking sounds?

My $0.02 would be to check your valve adjustment (at least on that one affected cylinder) and if that looks good you may need to do a compression or leak down test to see it you have a bad valve.

[fourk]

thanks,that is what i will try.it is a nice bike that i ride all year in tn.

[fourk]

also, yes it did start making small ticking sound.

[shinyribs]

Hmm.Is the ticking sound coming from the same side of the valvecover as the #1 carb is located?


The reason I ask is when my chopper started spitting back like your, it developed a ticking sound at the same time. I would adjust the valves and the ticking and spitting back would stop. After a short period( around 200 miles) it would all come back.Spitting back on #1 carb,ticking under left side of the valve cover. I ended up finding that the oiling hole in the cam tower that lubricates the #1 cam lobes was plugged with a ball of silicone and it wiped out those lobes. As a result,somehow,it would cause the carb to spit back at the same time. Luckily,I had a spare cam and replaced the parts. I have yet to ride it since repairing it,but I'm fairly confident it will cure it.

I'm not trying to scare you,just letting you know what happened to me. If you remove the access ports on the valve cover and start the bike you can look inside and see if it is oiling the cam properly. It won't be a huge wave of oil in there,but you should be able to see the cam lobes sloshing around in a fair amount of oil.

Like I said,I dont wanna scare you,just trying to compare to my recent experiences. I hope this is not your problem and maybe yours valves just need a little adjusting.Fingers crossed....

[Lucky 1]

Well.........

[fourk]

my 750 four cam

[Piute]

                                             

[cdaiscool]

[shinyribs]

 Um...ouch! Well,mystery solved!Sorry about that man.Good luck getting her going again.