84 Z650 F4

[FergZ650]

I have a 84 reg Z650 which I am having a few problems with. I noticed, on a web search, that there was a post on this site about an F4.

My bike has been rebuilt before I got it and it has also been in at a bike shop to have the carbs set up.

Problem is I do not know if the pipes from the carbs have been put on correctly.

They are as follows.

Carb 1. Blank cap
Carb 2. Vacuum pipe to petrol tap.
Carb 3. Pipe to top of airbox (???)
Carb 4. Blank cap.

Can anyone help. The third carb open pipe to the air box does not seen right but it runs better with this fitted

Thanks in advance

[AL MARSHALL]

if number 3 carb pipe is from the intake rubber then it should be blanked off.however the carbs may have breather pipes that should go to the air box but they will come straight off the carb bodies.

[FergZ650]

Thanks for the quick reply. The pipes are on the body of the carbs and on the output side. But only on carb no 3. That is what seems wrong?? This must effect the mixture of this carb only.

[AL MARSHALL]

pics required

[FergZ650]

This is how I got the bike.

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[AL MARSHALL]

blank it off like the other two.last one goes to vacuum tap

[FergZ650]

Okay, been there, done that. Thats what is strange. Bike runs like shit when this is blanked off. The bike shop set it up like that and could not get it to work. Replaced pipe as photo and big improvement but certainly not right. It drops off power at about 5000rpm. If I drop a cog and give it stick it will pull through but as soon as I go back to top, the revs drop to 5000 and I loose power again. The bike is also fitted with a Harris exhaust.

I have been hunting for images of an F4 model and have only managed to come up with the one below which also seems to show this pipe fitted to the airbox. I was hoping someone on here would have an F4 model and could post photos or tell me how theirs is configured.

What I have found out so far:

The F4 was the last model made. From 81 they had different carbs fitted and the F4 had the airbox from the Z750L. (also engine cases).

The air filter on the F4 is also different because it uses the Z750L airbox.

The american model had an emission control system which utilised the vacuum pipes from no2 and no3 carb and was connected to the cam covers and then to the airbox via a vacuum switch. This is probably not a very good description but there is a diagram in the Clymer Manual.

[tlc]

The second picture shows the vent pipes from the float bowls to the airbox.
Blank these off and your bowls won`t fill !

Your first pic has vacuum blanking plugs on and I would guess that these are your gauge take off points of which one is used to operate the fuel tap.

[FergZ650]

The vent pipes (the clear/brownish ones) from the bowls in the second picture are from the bowls and are vented to atmosphere. On the second picture shown they are routed over the airbox and vent under the seat.

My bike has them routed under the airbox and vented just behind the swing arm pivot. Routing does not make any difference.

The arrow points to the black pipe in question. It show it routed from the top of the airbox to the front of the carbs.

As I said before.

Carbs 1 & 4 have blanking caps. Carb 2 has the vacuum pipe connected to the petrol tap vacuum switch. Its the pipe shown in the first picture (arrowed red) that is in question. The consensus of opinion seems to be to blank it off but like I said before the bike does not run well like that (I have to slip stream grey haired old ladies in Micras to keep up)

Anyone have a photo of a F4 with original set up??

[tlc]

Can you check if there is a vacuum at this pipe when the engine is running !

[FergZ650]

Yes, there is a vacuum. If I block it off it changes the engine revs/note

[tlc]

I`m lost there then !
As I suggested I think that should be blanked as it`s a vacuum gauge take off point.

Maybe there is another fault and someone else could suggest the cure ?

[KWACKERZ1]

I am just qouting this from memory so I could be wrong here!
But I think that one the pipes would run onto the side of an emissions valve contraption that sits above the breathers. The the valve thing then has two thicker pipes that goto the butterfly valves on the top of the cam box and then another thick pipe that goes to the airbox.

The third carb pipe just sucks open the emissions control valve. So the act of blanking this off should have no affect on the performance of the carbs.
I have removed this on loads of kwacks and it has never made any difference.

If I were you I would try putting the pipe from carb 3 onto the vacumn petrol tap and blanking off the number 2 one to see if you still get the same negative affect you have when you blank off number 3.

As Chris and others have said the blanking off should not affect the carb performance unless you have other problems. When you get the crap performance is this reflected in the colour of your plugs? Have you checked and replaced the plugs? Also check out your diaghrams in the carbs as these are notoriously problematic if they are slightly porious due to old age and can cause intermitent and hard to trace problems. NRP do cv carb refurbs. HOPE THIS HELPS

[FergZ650]

Thanks. The emissions valve contraption is only fitted to the american models and you are indeed correct that on the american models this sucks open the vacuum valve. On the uk models this is not fitted.

If I were you I would try putting the pipe from carb 3 onto the vacumn petrol tap and blanking off the number 2 one to see if you still get the same negative affect you have when you blank off number 3.

Will try this idea.

When you get the crap performance is this reflected in the colour of your plugs? Have you checked and replaced the plugs?

Plugs have been replaced. Carb 3 runs a bit rich when plugged.

Also check out your diaghrams in the carbs as these are notoriously problematic if they are slightly porious due to old age and can cause intermitent and hard to trace problems. NRP do cv carb refurbs. HOPE THIS HELPS

I have someone currently looking at this. He has just phoned me and he thinks this could be the route of the problem. He says they are not holed but are very sloppy and stretched. (no wise cracks please!!) He also suggested NRP I think you have to send the diagrams and sliders away and get them to replace them. About £32 each.

Still do not have the answer to the pipe off carb3 but this may have been a botch by the previous owner. The consensus of opinion and logic would suggest that blanking it off is the correct solution.

Thanks for the help. I will report back as I am away to pick the bike up this afternoon.

I will try and post back on progress and hopefully it will be useful to others.

Stewart

[kev edwards]

That number 3 should definately be plugged , there is only a pipe to the fuel tap on uk bikes , if it were a us bike it would have vaccum to the emisions control valve also , the answer is blank it off and reset the carbs your self,my own experience tells me that a number of work shops can't be arsed to balance carbs properly hence why i have my own vac testers.
good luck.