Do A4's have a rough patch?

[sprint]

Bought the A4 in Jan and completed restoration a few weeks ago. Still have a few teething problems with it still running a bit rough below 1500/1600.

Not sure if No 2 pot is fully working as it's silencer is always slightly cooler than the rest.

Both No 1 and No 2 had partial pilot jet blockage and not sure if No 2 still have something inside the internal pilot jet bore?

Engine still running very rich with the plugs black and sooty, despite numerous checks and adjustment of the levels. Above 2K the bike is smooth and responsive. Have just fitted a Dyno S electronic ignition in the hope that it may have cured the low rev problem and whilst it is a bit smoother it is still not right and runs a bit rough with poor pick up. Tick over is around 1300 and below that it with not run 'chatters' and stalls.

I have also noticed that that up to just under 3K it runs smooth but between 3 to around 3.4K it goes through a fairly rough patch with a lot of vibration, is this normal for these engines?

[z1bman]

check the valve timing

[Pigford]

The 26mm carbs are prone to being "poor" on initial pick-up. It's usually just on pulling away from busy traffic lights... stall and swear

remember they are a 40yr old designed carb, running crap modern fuel, with associated wear

[PAULJAC47]

Check your float heights with a manometer,are u using Ngk plugs?if so get some nippon denso! get a gunson colour tune and check mixtures,are your carbs balanced correctly? is all jetting correct for the bike and exhaust,have you checked seals on chokes?check ignition advances correctly and also static,is valve timing spot on?My A4 was smooth and responsive!

[Zed man]

Check the coils.. Mine started running rough, then take tank off, to find a crack along the middle of one... Now I know why..

[sprint]

Thanks for the replies.

The bike is smooth through most of the rev range and picks up cleanly from 1500 revs, but get to 3K and it hits a harsh/rough spot to around 3K5 is that typical?

The bike is fitted with gen Kwak exhaust system and is fitted with electronic ignition, using mechanical advance, which has been strobed and is fine. Carbs fitted with all std jets which were ultrasonically cleaned. It is fitted with NGK plugs, as are all of my bike and I have never had any problems with them.

Float levels have been checked several times and are all around the 4mm level.

Tick over is around 1350/1400 as below that it does 'snatch' and runs rough and will stall.

[PAULJAC47]

Hi are the jets genuine?some of the repro sets are very poor,what position is the main jet set ? should be middle one,have you done all the checks i have said? if so let us know the results.As Piggy says the carbs are also suspect could well be wear and tear or blockages.And no A4,s are not typically rough at all.It should tick over at 1k revs no bother.

What is the compression of each pot,cold and hot with the throttle wide open?are all your carb rubbers pliant and tight?a known good set of carbs would be a good idea if you are able to...refer to my previous reply..Cheers Paul J

[jonhunt]

I have 26mm carbs on my z1a absolutely no rough patch,or difficult pick

[DavidZ1R]

From experience with carbs that have been ultrasonic cleaned, you must flush out all the bits with tin carb cleaner after, the ultrasonic cleaning does leave a residue if not flushed out, enough to block the pilot jets.

[sprint]

From experience with carbs that have been ultrasonic cleaned, you must flush out all the bits with tin carb cleaner after, the ultrasonic cleaning does leave a residue if not flushed out, enough to block the pilot jets.

I only removed and ultrasonically cleaned the various jet etc, not the complete carbs.

However, following the re-build the air jets of No's 1 and 2 strangely became partially blocked so I replaced them. .

[sprint]

Hi are the jets genuine?some of the repro sets are very poor,what position is the main jet set ? should be middle one,have you done all the checks i have said? if so let us know the results.As Piggy says the carbs are also suspect could well be wear and tear or blockages.And no A4,s are not typically rough at all.It should tick over at 1k revs no bother.

What is the compression of each pot,cold and hot with the throttle wide open?are all your carb rubbers pliant and tight?a known good set of carbs would be a good idea if you are able to...refer to my previous reply..Cheers Paul J

All jets original std except for a couple of repro air jets that replaced the blocked original ones. Don't believe that they are the problem?

Needle is in the middle position, as per book and as indicated pick up is good and strong, just the rough patch around 3K and the poor tickover below 1K3. Will check carb balance again.

All carb rubbers are pliable with clamps tight. Will check the compression but don't have access to another set of carbs.

Would like to find somebody with a bike rolling road as that may be the quickest way to identify what the problem may be?

[Dodgy Z1B]

From experience with carbs that have been ultrasonic cleaned, you must flush out all the bits with tin carb cleaner after, the ultrasonic cleaning does leave a residue if not flushed out, enough to block the pilot jets.

I only removed and ultrasonically cleaned the various jet etc, not the complete carbs.

However, following the re-build the air jets of No's 1 and 2 strangely became partially blocked so I replaced them. .

Try getting the complete carbs cleaned sounds like primary jet on no2 blocked somewhere in carb if you adjust mixture screw does this make any difference if not something blocked , also as not heating up as fast as the rest of the cylinders is a sign of this aswell. Same problem on vmax which are very prone to this.

[sprint]

Compression test gives 130/135 psi with hot engine and around 120 psi cold, so don't feel there is a problem with the pistons/rings or valves.

I find that closing any of the air screws, in turn, does not make much difference to the running. I know that they can't all be blocked as the bike simply would not run at low revs/speed.

All plugs are black and sooty, which clearly indicated that it is running rich, unless that is normal with the crap we have for petrol nowadays? The carb levels have been repeatedly checked and are around 4mm. Choke seals/o-rings are fine.

I guess that all I have left to try now is to take the carbs off again and go through all the orifices with a high pressure air line, though I am a bit concerned if there is crap in them that the compressed air could just simply compact what is already there?

[KeithZ1R]

torque up the engine mounts

[Mowjoe]

My A4 has a slight hesitatation around 2500 to 3000 rpm where it transitions from pilot to main jets but it was much worse before I did all the things you have done, and also the coil 12v supply relay mod and Nippon Denso plugs just to be sure. I have pattern 4x4 zorst system and found it was runninng lean above 4000 rpm so tried raising the main needles 1 slot and now she runs near a nuff for an old bird on sh**e fuel.