Stuttering Engine......

[Pigford]

Not a Zed, but thought I'd share how I fixed a recent annoying hesitancy that developed in my car. Okay, it may not have much in common with a Zed, but it is a petrol engine and Japanese!

The slight stutter showed "here & there" across the rev range, hot or cold, but was most noticable at lower revs (as often the case) when pulling away on part throttle. The throttle position didn't seem to effect much, but as the stutter was a bit random, it was hard to tell if it was FUEL or SPARK

Bonnet up - checked all leads, pipes, tubes, etc... etc.... Next I whipped the plugs out, gapped & cleaned them - NGK - and they looked quite good nick & all uniform light colour Time for a test drive, but no real difference.

Next it was off to Halfrauds for some REDEX Again, no real difference.

Hmmmmmm - although the stutter was slight & felt random across the revs, I still wasn't sure what was causing it

So, got a new set of plugs - NGK - from Halfrauds. Problem fixed Weird as the car was running fine and the stutter seemed to develop over night At least it was an easy fix - just finding the problem causes the hassle.

[000zeds]

Pigford as you probably know NGK seem to have a bit of a bad name lately !

Why not try some different ones

[Bps]

Interesting ......

The last couple off times I have taken my Zed out (1015 with CR31 carbs) it has been hesitant when cold and almost seems to stutter if I open it up a little when not fully warm (never used to) and seems to need a blast once warm to shake stutter out and that seems to sort it - not dependant on revs as such as starts low and then can move to middle revs once cleared in lower revs - so after 10 miles fully clear and does not come back that day even if left for a few hours to cool down.

It nearly always starts first time and soon ticks over well
I have NGK iridium plugs in for last 2500 miles and all good up till now

Any ideas?

[Pigford]

Interesting ......

The last couple off times I have taken my Zed out (1015 with CR31 carbs) it has been hesitant when cold and almost seems to stutter if I open it up a little when not fully warm (never used to) and seems to need a blast once warm to shake stutter out and that seems to sort it - not dependant on revs as such as starts low and then can move to middle revs once cleared in lower revs - so after 10 miles fully clear and does not come back that day even if left for a few hours to cool down.

It nearly always starts first time and soon ticks over well
I have NGK iridium plugs in for last 2500 miles and all good up till now

Any ideas?

As you have CR's - also with Mikuni RS, does it happen in colder weather? If so, most likely just "carb icing".... used to get it on me Zed with RS36's fitted

[Bps]

Hi Pigford,

Thanks that's interesting - would explain once warmed up it goes completely?
i have K&N fitted.

This morning it was around 11 degrees so not too cold and I am sure last winter it was colder than that some bright mornings I went out and I don't remember it doing that.

If it is Icing up - what is that exactly?
Is there anything I can do to prevent?
It was in a warmish garage then took out to start
what if you get caught out and temp drops when you get back on in evening will it still start just run lumpy until bike is fully warm and blasting warm air to the carb?

[Pigford]

It usually only happens for first mile or so in colder air or certain ambient conditions. The low pressure in the carb venturi atomizes the fuel (using energy to do this) and freezes (seperates) any moisture in the fuel. Thats why bikes in the 80's started fitting "pre-heaters" to the carbs...... or small feed pipes from the (water cooled) radiators.

Some say fuel additives cure it... but decent fuel helps a lot

[Bps]

Hi Pigford,

Thanks

I have been using star tron enzyme fuel additive this year (stabilises fuel if water in, improved starting etc. ) not sure if it works but bike has been running fine - I use it as the tank had slight surface rust inside
I usually use Shell or BP but recently have topped up with local garage which is not any major brand - I will stop that

Could be something else fuel wise - let's see - not too much an issue - good to know about your experience on CR icing so I am aware and check