Valvemaster additive causing a misfire..?

[weeveetwin]

Hi guys

Having left Hartside Cafe, I filled up my MV at the filling station in Alston yesterday on my way home. I added the usual Castrol Valvemaster lead-replacement additive to the fuel - but overdid the amount I really needed. Almost immediately after setting off again (within a couple of miles) I felt a misfire begin, and it continued to misfire on-and-off for the next twenty miles. The engine had run perfectly well until I filled up with fuel, so it was either caused by some 'dirty' fuel from the Alston pumps, or the Valvemaster additive.

You can believe that I was on edge whilst crossing the moor twixt Alston and Highforce! I was the only vehicle on the road most of the time, and it is not the most hospitable of places to beak down! I had visions of sitting there alone in the darkness!! The odd thing is that the misfire seemed to clear up after about thirty miles, and was gone by the time I got home.

Anyone else ever overfilled with this stuff? Does it cause misfiring? (I got the impression that the plugs were fouling). I overfilled only a small amount (8ml added, instead of 4ml).

 

[239desmo]

Short answer is I don't know but will be interested to see any replies.
I use lead replacement additive and octane booster if not using super unleaded.
I used to try and work out the amounts involved to add but because amount of fuel being added was so small compared to say a car fuel tank I have resorted to putting in a squirt (long or short squirt depending on if it is 1 or 2 gallons) and then a short squirt for good luck.
I have been more concerned about possible damage with too little and until now hadn't considered possible damage of too much.
Have had heads off 2 bikes recently and no report of anything amiss so either I have not done enough miles for damage to show or my quirts are close enough to recommended dose.
Could be misfire is totally unrelated to this. (joys of elderly Italian bikes)

 

[alane]

.....I overfilled only a small amount (8ml added, instead of 4ml).

Y'mean overfilled by twice as much as you needed to
With the small amount of tank anyway (compared to car) it may have affected it but interested to see the chemical explanation.
After all, it adds 'lead' to reduce knocking and be kinder to valve seats.
Ma-in-law bought a crate load of lead substitute stuff cos she thought she had to fill up with that instead of petrol...and Halfrauds didn't question her spending 3 figures on it.

 

[weeveetwin]

Y'mean overfilled by twice as much as you needed to

Sorry alane, my earlier post was misleading, since it was posted in haste (..I was off out for a run in the sun! )

No, what really happened was this: I'd filled the tank with fuel, and used the correct amount of additive when I left the filling station at Framwellgate Moor on the outbound leg of my run. This took me all the way to Hartside Cafe.

Thinking I'd top it up again for my journey home, I called into the Alston filling station. I thought I'd probably used up nearly two gallons by then, so I squirted 8ml of Valvemaster into the tank (1ml per litre of petrol). However, when I actually filled the tank with petrol, I couldn't quite get a gallon in there (approx. 4 litres). This meant a 4ml overdose of Valvemaster.

The tank on this bike is an unusual shape (which I'd never before filled up to the brim) so I misjudged its capacity. It won't happen again!

(..on the up side, it does mean that I got all the way from Framwellgate Moor to Hartside Cafe on less than one gallon of fuel! That's over 50mpg, from a 530lb 36yr-old shaft-drive 750cc four, with over-large carbs and no air filters! )


Steve



ps. Valvemaster isn't a lead additive. It's Phosphorus based. Maybe this is why it 'apparently' fouled the plugs? I've been out on my Ducati today, so haven't had the chance to check 'em.