NGK plugs

[Pauarc]

D8eA plugs seem to foul up has anyone run d7ea plugs which runs hotter

[Johnwebley]

On my 3 bikes, I have switched to Nippon Denso,

In the case of the Yamaha, it has made a tremendous improvement



Sent from my SM-A750FN using Tapatalk

[Martin6]

D8eA plugs seem to foul up has anyone run d7ea plugs which runs hotter

I was experiencing this too. I've found setting the air screw slightly leaner (1/8th turn) than I would have had it, just based on tickover response, has sorted it for all bar cyl 1. I'm now trying a further 1/8th turn out on no.1 and so far it's fine, but only tried 25 miles on that setting. The other things to double check are float heights set too high and needle too high. Maybe check your compression levels, too low can give sooty plugs.

[Pauarc]

Fond this about plug fouling

[Pauarc]

Compression all around 160, float set 26mm, needles on 3 grove, air screws 1-1/8th out, 40 slow jet 120main I have got some 110 coming

[K2-K6]

Have you got plug gaps set really tight on minimum specified range ?

[Pauarc]

Plugs set loose .6mm should be .6 to .7

[Pauarc]

With spark tester they jump 10mm  should be 7mm min I think

[K2-K6]

I always find it difficult in equating "test" sparks against reality of running.  I know that it obviously denotes energy expelled, but without compression and distributed fuel load taken into practical account.

If they are staying a dark colour, possibly sooting a little, then it would be reasonable to run with the idle air screw turned further out to bring it slightly leaner at very low speeds.

That won't change the ultimate flow of idle jet at it's maximum (they are effective a long way into throttle opening on these engine/carb combination) It will change the slope of fuelling from absolute base rpm (going leaner) but arrive at the same maximum flow (because of the 40 jet size) to give potentially cleaner combustion at just the lowest operating rpm range while leaving exactly the same fuelling as the throttles get wider and transition toward the main jet coming more on stream.

[Martin6]

I did 120 miles today on my further out settings of the air screw. Worked well. No fouling evident. I'm guessing that as the carbs age and wear, more fuel is getting through and the additional tweak of the air screw is helping to even that out at low throttle running. Maybe give it a try?

[Pauarc]

What have you got the air screws set at now martin6

[Martin6]

I started at 1 out. It was best for a decent tickover at 1200 to 1300 rpm. No.s 3 and 4 plugs were fine. No.s 1 and 2 were sooting up, particularly no.1 and after 30 or so miles I was noticing some hesitation on low throttle. I moved 1 and 2 only, a further 1/8th out. No.2 plug was then fine. No.1 was still sooty, but not as bad as previous.  I then came out a further 1/8th on No.1.

However, I don't think the specific settings are the key, it's the process. If the jets and passages in the carbs are good and fully clean and float levels good, boots tight on the manifolds and airbox and the bike rolls on nicely when you’re more than, say, 1/4 throttle, then fine tuning of the air screw is where I'd start. Idling and in traffic, even at 40-50mph at low to mid revs, that's what's in play. 👍

[Martin6]

Just to add. I didn't vacuum sync the carbs, but I did spend a bit of time getting them working evenly on the workbench, once they were all back on the gantry. One little trick is, once they look good, check there is no looseness on the top of each slider. Just wobble the top of the spindle, where the adjusters are, with a finger. If one is more loose than the others, then it has not quite seated down and is a little higher than the others. Not very well explained, hope you get my drift.

[Pauarc]

I will have to try 1and 1/8th and see they are all at 1 now which gave me a tick over of 1000 carb have been vac sync but they are all sooty

[Martin6]

Nothing to lose by giving it a try and a nice excuse for a run out in the sunshine. 👍

I have no science for this, but I prefer a marginally higher tickover on my old bikes. Maybe helps oil circulation and battery charging, but I feel it puts less strain on the chains as well, as there is momentum to help keep everything smoother. Quite possibly it's rubbish, but I feel happier! 

Not much extra, but I've set mine around 1200 to 1300 rpm. Still plenty of engine braking on a ride.