Hitchcocks Forum

I have been having multiple starting problems, including some alarming engine noises as it turned over. I thought I may even have had to renew the sprag clutch (expensive, as you have to buy the whole assembly, not just the clutch bit, for this model). Yesterday I spoke to someone in the Hitchcock's Spares Dept and after following his advice bought a new NGK irridium spark plug, reference BPR6EIX. Starting problems seem to be solved, the engine runs more smoothly and has appreciably more power. THANK YOU Hitchcocks and I hope this is helpful to other C5 riders.

Good news Ian but....erm....don't some riders on here advise not to use iridium plugs?

Why is this? What difference does it make to the bikes performance, good or otherwise? It would be interesting to know.
Gaz

Iridium plugs will usually make for easier starting but make no difference to performance. The other benefit is they last longer. As I have said before, the iridium plug in the Bullet was only changed after nearly 20,000 kms because the engine needed a hotter plug. Iridium plugs, as far as I know, only come with a built-in resistor, R in the part number , so you have to be careful to check if there is not a resistor plug cap or resistor HT lead already fitted. They are a fit and forget item, and are usually fitted to new cars which have spark plugs nearly impossible to change without dismantling half the engine.

Iridium plugs? Some here swear by them others swear at them.

I believe you would have got the same result by fitting an ordinary NGK plug. Having tried the iridium one I went back to NGK BPR6ES. The EFI engine seems susceptible to plug fouling because (IMHO) the tickover cannot be leaned off enough (unless the PC5 can address this - I don't know). On mine this is true whether I run closed loop (ie O2 sensor connected) or open loop (O2 sensor disconnected and eliminator fitted). It does run better overall in the latter state.

Yup, new plug on my C5 fixed starting and missing but - The iridium has a tiny pinhead for an electrode. On mine it fouled up rather quickly, because there's only a small area to get dirty and then it cannot get a spark through, so it misses more which fouls the plug and the internals up with soot. Some swear by them, I swear at them. I then tried several of the usual suspects and ended up with the BPR5ES which is a car plug rather than the BPR6ES lawnmower plug. They look a bit different, the 5 looks better made and is about half a step hotter than the 6, both are equivalent to a Bosch 7 (the OEM CGT plug), the 6 is also equivalent to a Bosch 8 (the OEM B5/C5 plug). The oem plugs are weird Bosch-India RE specials not Bosch. A little more heat in the plug may burn the crud off better, if you ride hard you may want a cooler plug but most Bullets aren't ridden like that. Do check the colour but injector reads lighter than a carb does. The R in the legend is resistor so you need a non-suppressor HT cap (my oem metal HT cap fell apart anyway). The oem C5 is a twin electrode and impossible to clean but the CGT 535 plug is normal nose shape. The 535 has opened ports but head, valves and piston crown the same, hence plug clearance is interchangeable. Check HT lead is long enough and not strained, pulling itself out of the HT cap.