Topic: 1st cylinder isnt firing!!

[ateamsam]

Hey guys,

I'm a noob so here I go ... I noticed after warming up my bike that the pipe all the way on the left when on the bike isn't hot like the other three.  So, I'm assuming it isn't firing.  If this is true, then why would only one not fire?  Does the spark plug need to be changed?

Thanks,
Sam

[Patrick]

Check your spark plug. Switch the wires between the one and the four cylinders. If the problem follows the wire then your problem is the spark plug cap. If the problem stays at the number 1 cylinder then your problem is likely your plug.

Patrick

[B.O.X.N.I.F.E.]

Also, you can remove the plug, put it back in the boot, then lay the threads of your plug accross the engine case. Crank the motor, then you'll see if you have spark or not. Be careful not to shock yourself!

[TwoTired]

Certainly check for spark at the spark gap of the plug.  Or replace spark plugs with new.  Particularly if you don't know how long they've been in the engine.  Are you doing the routine tune up required every 3000 miles?

But...
There are four carbs, one for each cylinder.  What if gas didn't get to or flow from one of the carbs on that cold cylinder?

[d_soles]

Just do the simple process:

Combustion = Combustible Mixture (air+fuel) + Spark (at the right time helps) + Compression


Narrow it down using your noggin'.

Doug

[tlbranth]

Don't know what kind of scooter you have but if you can, pull #1 carb bowl and see if anything's in it. A word of caution: if the problem is electrical and you run the bike, the fuel pulled in will remove oil from the cylinder wall and cause damage - maybe significant damage. So if you'll be toying with it for long and you're not sure, use a 2-stroke mix.

[the technological J]

im kinda of a noob too but the first two things i would do is check for spark on the bad cylinder and you can unscrew the carb drain screw and see if any fuel comes out

[ateamsam]

Thanks for all the advice guys.  I just bought the 74' cb550 and am in the process of doing some of the light work I know I can do ... like cleaning the bike     I don't have any experience working on these bikes and don't have a lot of time until August to work on it so I'm going to try and do the stuff you guys recommended, like change the spark plugs, and see if that works.  I don't know when the bike was last tuned up so I bought 4 spark plugs and a gallon of oil.  I'll let you guys know what happens.

[Lenny55]

I'm having the same problem with cylinder 3.  I tried a new plug today and nothing, then i pulled the plug and cranked the bike over while grounding the pug on the engine.  Lots of spark.  So I guess i'm looking at a fuel issue?

If I unscrew the carb drain screw and there's no gas, what would be the next step?  For that matter if there is gas, what would be the next step?

I just had the carbs cleaned and synched by my local shop a couple of months ago.  As far as I know, I wasn't having this problem before I crashed and laid the bike down.

Any insight is appreciated, hope I'm not hijacking your thread Ateamsam.

[EverettShadowbrook]

I want to bump this. Having a similar problem with my #4.

[1timduke]

Hey, Lenny55, check your tappet clearances, as far as the carbs, if you are getting fuel to the bowl, the mixture may be too lean to fire (or rich).   Too lean --->vacuum leak from boots, missing sync screw, airscrew in wrong position, or other sinister culprits.   Does the cylinder not fire at all RPM ranges or just at idle?   Any backfiring?   Also, when it went down, did it skid on the points side (the right side).     

If this gets too much on this thread it may be a good idea to repost as ya'll two may have different problems, don't worry, someone will answer you question

-Tim

[Lenny55]

Hey Tim, the bike went down on the left side. I did hit the stator cover pretty hard I think because I tore the Honda plate off.   As far as the tappets go, I set them last night for the first time (also the first time I noticed the cylinder not firing).  I bought a new feeler guage today so I thought I'd check 'em again just for the hell of it.  They seem to be fine. The cylinder doesn't seem to fire at all, I took it for a short test ride last night and when I got back I noticed that it was barely warm at all.  No backfiring either.

[Lenny55]

Bump