Spark plugs

[Pat]

What's the general consensus on prefered candelas for the 500 (474cc) ?

[MickeyMoto]

What is the gap? Is the manual correct? Measured Hot or cold?

Troublemaker? Me?

[72degrees]

What is the gap? Is the manual correct? Measured Hot or cold?

Troublemaker? Me?

You forgot "fancy electrode material plugs aren't worth the extra cost".

Unfortunately, NGK BP7EVX is discontinued and the Iridium replacement (BPR7EIX) is a resistor plug (though I've seen *talk* that it needs a lower sparking voltage than an ES plug)

This site claims to have the EVX - though you have to wonder if they are very old stock or fake.
http://www.minispares.com/product/Classic/BP7EVX.aspx

Personally, I think a just few quid that might help give good sparks is worth every penny. "Why spoil the ship..."

[EVguru]

For a 500, I've run the same plain old NGK BP7ES plugs that I run in my 350 with good results.

I've had failures with every common brand of plug, except Magnetti Marelli. Champion and Bosch gave the most trouble, so I stick to NGK as the easiest brand to find that's given me the least trouble.

As for the recommended grade, look it up. There are several sources for the 'Blue Book' online, or you can download the Cagiva era manual from the club site if you're a member.

I tend to run the harder/colder grade (higher number with NGK) with no sign of fouling.

[Pat]

There's champions in there now and bike runs fine, I had three brand new BP7ES which my old ngk book lists as suitable for the 350 (Doesn't list 500 tch'), hanging about in the sied and was thinking of swapping them over out of boredom but I'll stick them under the seat for when the champions inevitably expire! Re hot or cold for valve clearances, I never asked the question, anyone whose used the missus oven or freezer to expand/contract metal to get it to fit will know the answer to that one! 3 litres of oil and cold engine valve clearance provisional people's front....South Wales chapter is open to new members. Anyone know if nippon denso list a suitable plug? And I'm guessing Mr Compton has a secret stash of BP7EVX down the back of the sofa..c'mon Paul own up!

[MickeyMoto]

MarkB recommends Champion... Or was that a joke.

[EVguru]

All plugs will eventually fail, but the troublesome brands were DOA, or failed within a few days. Sometimes it could take much longer if the weather conditions were right (or wrong, depending on how you look at it). A pinhole in the glaze allows moisture into the ceramic insulator. The classic symptom is the plug might fire when lain against the engine, but won't when installed, or held firmly against the engine. A secondary spark gap between the plug body and ground allows the plug to spark, even though the ceramic insulator is now partly conductive due to moisture. This is a trick used to clear a fouled plug on a two stroke, pull the plug cap off slightly to create a secondary gap. It can work with a flooded engine too.

If a bike came into my workshop running well, I wouldn't change the plugs just because of the brand and Champion might be very good these days, but I can remember going back to the motor factor to return yet another DOA plug to find him clearing his shelves of Champion plugs as they were all being sent back to Champion for inspection. Once bitten, etc.

On another occasion, a set of Bosch Platinums failed one by one as I drove my mother's Talbot Samba home after a service, I just about limped back to the dealer on one misfiring cylinder. They fitted another set, two of which failed, before they sent out for a different brand.

I've had the odd failed plug with NGK, but rarely and no failed sets.

I have fitted a set of BPR7EVIX (Iridium) plugs to a 500 that was having starting difficulties. That eventually turned out to be slightly weeping float needles and slightly high float levels. Just enough that it would either start first kick, or flood and pretty much refuse to start at all. It ran fine once started before and after the flooding was fixed, so I left them in there. I might try a set in my Sport when the decade old BP7ES plugs will no longer let me run out of revcounter at Cadwell.

I don't go by plug listings, I go by specification; For instance BP7ES is

(B) 14mm thread
(P) projected insulator (extends beyond threaded barrel)
(7) heat range 7
(E) thread reach 19mm
(S) standard electrode.

There are plenty of cross reference charts out there.

As for valve clearances, do they close up when hot, stay the same, or get larger?

The answer is YES! All of those can happen, it depends on the engine. If you have an Iron barrel and head, the valve will expand the most and the clearance will diminish. With an Aluminium barrel, the expansion of the barrel will most likely open the clearances more than the expansion of the valve will close them.

Much discussion on the email list went on about the tendency of 500s to burn out exhaust valves (mostly in the US) and the theory was put forward that 0.1mm was not enough clearance, because it closed up when hot. Nobody had actually checked apart from me apparently; They get slightly larger when hot. Too large a valve clearance can in fact cause valves to burn out. If you're no longer using the quieting ramps on the cam, the valve gets a much harder life being returned to it's seat.

[Pat]

Interesting last paragraph re exhaust valves on 500! In cars with heron heads it was common to open up the exhaust valve clearances 5-10% above nominal and cut the seats back 60 thou or so. In addition a smaller bore carb or smaller jets were employed to increase the venturi effect. This was a tuning trick to wring a few more ponies out and help reduce the risk of piston seizure with the herons potential to overheat the piston. That was 4/6cylinder water cooled cars tho, any thoughts?

[EVguru]

Never had problems in my Ford Xflow tunung days with either valves or pistons. Bore out +90 thou 1300 pistons in a 1600 to get high compression and 1690cc, add a Piper 285/2 or Kent 244 and a pair of 40mm Dellortos. Best results on road were with stock GT valves and careful porting. I may have been giving away 15bhp compared those running big valve heads, but my car was quicker real world due to the tractability.

I think that possibly the 500 exhaust valve is just a little too small for the capacity and runs hot, particularly with lower octane fuel. Low mileages and occasional use leading to valve seat corrosion went standing won't help.

[Pat]

The other way was flat crown pistons finishing about .3" down the bore. "Gave about 1700cc" and more performance without the issues...were fords really true crossbows tho?

[Pat]

Crossflow* bloody auto correct.

[MarkB]

It's the way I tell 'em Mike!

[norbert]

I allways used NGK BP7ES till I came across with the platin NGK BP7EVX. This ones for me are the best I ever tried, helping to start better and after 20000km no sign of wear!
When people began to talk about that they will disapear I bought some of them that will last a looong time. A few month ago a friend of mine found out that there were still some old stock ones. All the regulars from Hamburg ordered a few. Maybe he still knows how to get them. If it is so, I´m gonna tell you

norbert

[Ralph]

Seen quite a few failed NGK's recently so stuck some Denso ones in the Strada
they are cheap as they are used in some old Volvo or other and you can buy a set of
4 cheap, been in for about 5000 miles now no problems.

[TurboRestorer]

I've just bought 2 BP7EV plugs from ebay (£8 both), may not be in production but there are alot around for sale, just be aware some are cheap & some are asking extortionate prices.