Help! Dropping Cylinders as I Ride...

[Hired_Goon]

I'm picking fuel too. My bike starts missing on 1 and 2 during highway cruising. Flick the left petcock to prime and it smooths out.

Basically starving for gas. I live with it cos I can't be bothered fixing the petcock.

Seems "someone" probably over stretched the spring when he was rebuilding the petcock.

[gman]

Hi guys,
This gets better, i have a problem on my 79 XS in that number 2 cylinder will not fire at all !! got spark, got petrol ( i think)
but cannot get to the bottom of it

[mro]

( i think)

If sure ignition working...
leaves compression and "(I thunk)"
odds are it's "(I thunk)"


mro

[AlanB]

Hi Gman,

Favourite for no2 is a vac leak from the vacuum advance line. It goes from the carb body on no2 (not the "boot", or manifold!) down to the ignition system under the left side cover on the engine.

If it is drawing air somewhere along that line, no2 will not idle.

Are you on the UK forum site?; we have a few members close to you!

CLICK HERE!

AlanB

[trbig]

If you've got spark and compression, it's time to look at the carbs. Take it out for a short ride and get on it wide open. If it picks up all 4 cylinders @ 3500-4000 then it's either the pilot jet stopped up with some little piece of junk.. or it's flooding out the carb somehow... maybe a pilot jet loose or float needle not sealing.


Tod

[gman]

Mank thanks guys,
i will check the compression !!!
AlanB, you have given me loads of help on the uk site, many thanks,
I am P***ed that my project looks great and only know i find these problems !!
I just want to to get the XSon the road

will post when i carry out the compression test because if i have a low reading ( less than 100 ) i will need loads of help

Have fun and be safe

Gary

[AlanB]

Hi Gman,

Don't get too despondent if you get a low reading on no2; if it has been getting fuel, but not running, the bore will have been well washed with petrol, and you will get a low reading. Try a dose of oil down the plughole, and turn it over a few times, then recheck. The oil will make a temporary seal round the bore. If it comes up, then you may still have a sticky ring, rather than a major problem........ It may free off once you get it running.

If oil doesn't help, the problem is valve-related; check clearances before ripping the head off.

Keep in touch!

AlanB

[BlueOxD350]

Problem Solved: Starving Cyl #3 and 4.

Thanks all for your input. I couldn't have done it without you. I've learned more about my bike in the last 36 hours than I had in the last 36 months.

With patience I didn't know I had, I managed to pull the float bowls off of #3 and #4 carbs without removing them from the bike... drop the float and needle, and remove and clean the screens. And shot some brakleen up the port to flush out the residual gunk. Wow what a difference. Fuel flow is up 500%.
My initial 20 mile roadtest showed no hesitation or dropped cylinders.
So, wish me luck. I'm off in seven hours for a 1200 mile run ...
I'll let you know next week if I made it back, too!
-Dan.

[luischia]

Good luck on that trip, and as a friend used to say

KEEP THE RUBBER SIDE DOWN!!!!!!!!!