Misfiring

[tony.mon]

It feels as if it is going in and out as usual. I have not physically checked though.

-said his wife.....

[Steve6088]

It feels as if it is going in and out as usual. I have not physically checked though.

-said his wife.....

That is just another problem I am having

It looks like the cause of this has been the vacuum hose for the rear cylinder has come off. As I have just got a blanked off hose connecting to nothing but I do have a blanked off hose for the front cylinder connected.

Where is the rear cylinder hose supposed to be connected to?

At least I have got to the bottom of this

[Wicky]

Should be connected from a plug adapter thing (same as wot 's on your front cylinder) buried beneath your carbs to your fuel tap to make the diaphragm flow fuel.

[tony.mon]

There is a second vacuum take-off point just under the intake manifold on the front cylinder as well as the rear.
The rear one as standard feeds the vac fuel tap; the front one is blanked off with an M6 cap head screw as standard, but may have been fitted with a length of hose, blanked off or stopped as you describe.
That's so that you can easily connect a vacuum gauge for carb balancing.
It's nothing to worry about; as long as it's capped off you can ignore it.

One of them at lest needs to fit onto the fuel tap at the 9 o'clock position, the other can remain blanked off and going nowhere.
An alternative is to tee them together and connect them both to the fuel tap.

Nothing goes onto the fuel tap at the vertically down position; it's a drain/air vent.

[benny hedges]

There is a second vacuum take-off point just under the intake manifold on the front cylinder as well as the rear.
the front one is blanked off with an M6 cap head screw as standard, .

M5 isn't it??? mine was

i think!

[tony.mon]

Ooops, yes it is.
Smaller of the two common vac balancer adaptors with most kits.
M5, not M6.

Well spotted

[benny hedges]

Ooops, yes it is.
Smaller of the two common vac balancer adaptors with most kits.
M5, not M6.

Well spotted

or the bit that screws in your push bike pump in case you're stuck for one

[Steve6088]

I have found the nipple on the rear cylinder and it doesn't have any tubing connected to it. However the only unconnected tubing is this one piece of blanked off tubing. How does this connect to the fuel tap and the rear cylinder?, as there is no split in the tubing.

Also there are no spare nipples on the fuel tap to connect any tubing to . The one at 9 o'clock has a nylon tube attached to it. I think my mechanic has made a mess up somewhere or I am being stupid.

[tony.mon]

No, your'e not being stupid, your "mechanic" has cocked it.

Connect the tube form the 9 o'clock position to the rear vac point, ensure that the front vac point is stopped securely, and all will be well.

Then name and shame the "mechanic".

[Wicky]

I think my mechanic has made a mess up somewhere or I am being stupid

Depends who had the tank off

IIRC Should be two thick rubbery fuel hoses 10mm that lead to front and rear carb
Plasticy vapour drain hose 8mm that leads down exiting nr belly pan
A rubbery fuel overflow hose 5mm, like above
And on early 16L tankedmodels a rubbery vacuum hose that connects from rear cylinder to the fuel tap on the back of the tap. 19L taps are subtly different.

Where does the nylon hose lead? Do you have a scotloiler fitted as there should be a T connector somewhere.

[Steve6088]

I can't work out where nylon tube at 9 o'clock is going. It feels like it is plugged into something between the carbs. It'll have to wait till the weekend.

The mechanic is usually spot on, I'll give him a ring tomorrow so I can work out what he has done.

[benny hedges]

im guessing he's accidentally attached one of the vacuum lines from the intakes under the carbs to the breather on the tap or its dangling loose somewhere and its drawing air in....
ive had similar myself when the pipe fell off the vacuum adapter.
i was concentrating on looking where the hoses were going without looking where they came from!


it ran like crap but sounded good!

[Steve6088]

I can't get my head around what my mechanic has done here.

1) Should this tube off the rear carb be attached to one of the holes under the tank? or is that blank tube sitting next to it supposed to be plugged into the carb ( in it's place). I am suspicous of pipe sitting there doing nothing.




2) Am I right in thinking that that the vacuum tube should be attached here? and then connected to the fuel tap. It has been left blank.



3) Where is this tube going, it was attached to the breather (bottom vertical hole) on the fuel tap?




Thanks. I am struggling here

[benny hedges]

the bottom pic..... the pipe from the rear cylinder inlet should go on the fuel tap at 90*, not downwards.....
the downwards one is a breather iirc...

if you suck on the horizontal stub (oo err) you can hear the diaphragm moving which allows fuel to flow.
the downwards breather is to allow the diaphragm to move back when the vacuum stops, cutting off the fuel.


your bike will misfire as it has a air leak at the rear inlet and also no fuel supply lol.
attach the tube from he rear inlet to the horizontal pipe on the tap.
the downward pipe just hangs down under the bike.

[parkergb6]

I had exactly this same problem. It turned out to be the bung from the carb balancing modifcation had come out. Who would have thought a small pipe could cause so many problems. good Luck.