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Dumbfounded

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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Help!!!!. My 79 750e wont fire in the number one cylinder. The compression is good, I have spark to the plug. replaced the plug three times. The coil (replaced) is 4.4 ohms across. The jets are not clogged. The floats are set and working. The points are set at .014. The air filter is new and not blocked in any way. Cylinders 2,3,4 are running great. The plug does get wet when running the bike. Why won't it fire? :?

ANY suggestions would be appreciated.

Thanks Dave W.
Mount Joy Pa
 
Replace the plug boot. They break down with age and fail.

Kim
 
Ignition lead and or spark plug cap is about all that is left to replace.
Dink
 
The plug boots came with the coil when I replaced that on saturday. The old coil didn't appear to be bad, but I'm baffled

Thanks, keep the suggestions coming

Dave W.
 
Try swapping the 1 and 4 leads as they fire at the same time. If the problem goes to the other cylinder it is a lead/boot specific problem. otherwise might be a carburettor problem leading to flloding/running too rich on the cylinder. Could also be a dud plug, so try swapping plugs from another cylinder. These are the easy options..after that let us know!
 
saaz thanks for the advice but I've already tried that. I am really at a loss. I am going to have someone else check my timing, maybe its off a bit. Wouldn't that effect the number four as well though

Dave W.
 
Just remeber..its only basic mechanics!

1 & 4 are the same timing as well. If the carb is ok, might be the cylinder (rings sticking, valve adjustment etc). Flooding rich might just be a matter of the carb float sticking.
 
I used to think it was basic mechanics......before I pulled all of my hair out. The floats are set and working and the compression is good (120)

I'll have to go into the valves I guess.

Thanks for everything
Dave W.
Mount Joy, Pa
 
Dave,

When I got my bike, it did the same thing. My #1 cylinder just kept on running way too rich.......plug kept getting wet and fouling. I would put in a new plug, it'd run great. Would last about 150-200 miles then same thing - plug/cylinder just kept running progressively worse. I tried leaning out the carb as much as possible, double and triple-checked float height(s), re-did the carbs about 3 or 4 times, new plug boots, new ignition coils, experimented with air filter - all with no effect. It was always most noticeable when trying to start the bike. It would take longer and longer for bike to warm up, as plug got more fouled, then eventually (regardless of how long you let it warm up), it would run on only 3 cylinders (4th cylinder intermittantly catching for a spurt or two during driving, but that was it).

Just for the hell of it, I got a different set of carbs from e-bay. I cleaned them up and put them on. That was 1-1/2 years ago, haven't had a problem since.

Not saying it's the carbs, but a pretty good chance you might also have one that was "possessed" like mine. Never could find any fault in that carb - and I did everything. I switched out all jets between the different carbs, did same with diaphragms, float valves, etc.........was always just the #1 that gave problems. And I'm pretty sure that all passages are clean too (although I don't have the ability to blow out with compressed air). Wish you good luck!!! :)
 
Re: Dumbfounded

Pull the carbs off and replace the "O" ring between the carb induction boot and the cylinder head on number one carb. It will run just fine then. :-) :-) Youse aint got no working induction system on number one. :-) :-)

Earl




herco said:
Help!!!!. My 79 750e wont fire in the number one cylinder. The compression is good, I have spark to the plug. replaced the plug three times. The coil (replaced) is 4.4 ohms across. The jets are not clogged. The floats are set and working. The points are set at .014. The air filter is new and not blocked in any way. Cylinders 2,3,4 are running great. The plug does get wet when running the bike. Why won't it fire? :?

ANY suggestions would be appreciated.

Thanks Dave W.
Mount Joy Pa
Click to expand...
 
I got her torn apart again and I will replace those "o" rings. Do you get the complete assembly or is there an inner ring I have to look for? I'se got to gets my induction systems workin. (good advice as always Earlfor)

Since I'm this close to the head gasket can I replace it w/o sending the head out for inspection. It was seeping a small amount, nothing a quick wipe with a rag couldn't fix, but since i'm close would it be worthwhile replacing it. I'm picturing just cleaning the surfaces, putting the gasket on and torquing to spec's. Is it that easy?

When I was removing the throttle and choke cables from the carbs a small spring fell free. I've never noticed that spring before. Does anywhere know where it belongs? Its about an inch long and silver/ gray in color. Its not the large spring which pulls the carbs closed, thats still attached. Those little springs are my nemisis.

Is there a way to tell what size jets I have inside the carbs? I can't find any markings.

Thanks for all of the help guys, I'm learning a lot about the bike (the hard way) and am actually enjoying it.

Dave W.
Mount Joy, Pa.
 
Dave,

It's probably not the one, but only spring I can think of off hand is the one at the end of the idle-speed adjust screw/knob which would've fallen off, if you unsrewed the idle-speed adjust screw out all the way. It's about 1/2 to 1" in length and 1/4 " diameter.
 
Thanks for the quick response. I forgot to mention that spring, That one is where it's supposed to be.

Do you remember someone here explaining the method of synching carbs with out a vacuum guage. I want to check them one more time before I replace them. I can't find the post though.

Thanks,
Dave W.
 
((((( I'm not sure if I was clear..... I did not mean the "O" rings inside the carbs. The "O" ring I was referring to is about 1 inch diameter and there is only one for each induction tube. It rests in a groove on the induction tube end that is mated to the cylinder head. The "O" ring goes between the induction tube and the cylinder head. There isnt any kind of "assembly", it is only a large "O" ring.)))
herco said:
........got her torn apart again and I will replace those "o" rings. Do you get the complete assembly or is there an inner ring I have to look for? I'se got to gets my induction systems workin. (good advice as always Earlfor)



(((((( I assume you are talking about replacing the valve cover gasket and if that is the case, sure, I would go ahead and replace it if it is leaking. If youre actually talking about the cylinder head, I would not go to that much work for a tiny leak that is taken care of with an occasional wipe with a rag. If you have a torque wrench, you might be able to stop the weep by retorquing the bolts.))))))
QUOTE:...... Since I'm this close to the head gasket can I replace it w/o sending the head out for inspection. It was seeping a small amount, nothing a quick wipe with a rag couldn't fix, but since i'm close would it be worthwhile replacing it. I'm picturing just cleaning the surfaces, putting the gasket on and torquing to spec's. Is it that easy?


((((( I cant think of any small springs on the throttle or choke cables. ))))
QUOTE....When I was removing the throttle and choke cables from the carbs a small spring fell free. I've never noticed that spring before. Does anywhere know where it belongs?


(((((Usually there will be a number stamped on the jet, but I find the only way I can read it is to take it out, hold it under a strong light and use a LARGE magnifying glass. :-) )))))
QUOTE;....Is there a way to tell what size jets I have inside the carbs? I can't find any markings.

Earl
Click to expand...
 
Thanks Earlfor,
I will be replacing the valve cover gasket. And I'll try retorquing the heads.

The "O" ring is that complete plastic housing. I guess I'm asking if the new "O" rings screw right on at the two screw holes, or if there is an inner ring I need to worry about. I'm not looking at the induction tubes right now, but I think they're larger than an inch in diameter. They're probably closer to two inches.

I know I have a long way to go, but it will be worth it. I'm on a mission, If I have to touch it, its getting replaced.

Thanks, Dave W.
 
If you want to know if its that one carb giving you trouble start the bike and drain that carb bowl, put a small cup under it so the gas wont fill back up in the bowl and you know that carb is empty. now spray some starter fluid into the throat of the carb and if the cylinder fires and the bike runs on four you know its the carb. Be careful !
 
Dave the o-ring they are talking about is between the intake and the head if you go here there is a very good picture of it. http://home.att.net/~robert.barr/intake.html When you get the new ones they will be round not flat like in the picture. ( thought I had gotten the wrong thing when I first picked them up :oops: )
 
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