This has been answered before but I can't find it. I need new plugs and Champion N3's are hard to find locally. Crossover chart says NGK B8ES but memory says this is wrong. Clarification please and thanks!
Thanks Guys, Last August I finally fitted the Tri-Spark ignition kit and have been running it with the same Champion N3C (Copper) plugs that were already in it.
The Tri-Spark was timed with a strobe whereas the old points were static timed.
Now , a year later, have been seeing a stumbling sputter that was intermittent but now is more pronounced at idle on up. [previously the bike would start up and run just fine for a 4 mile jaunt to house #2 and sit for an hour or so, on re-start the bike would skip a few beats on initial take-off and then settle down]
Am focusing now on the Mikuni carbs which have 5 yrs. old air filters that appear to be the washable type but am not sure. .
Right now the filters are off and I have re-set the air/fuel mixture's and ridden it as such but the stumbling has gotten worse.
So it seems a reasonable effort to try a new set of plugs and see what happens, hence the posted question.
Notwithstanding the Ethanol gas we have, the Mikuni manual method to set the air/fuel mixture is to set the carb at 20 % higher than idle rpm and adjust in or out until highest rpm is found, this works and the carbs respond to it. Next step is to bring the carb back down to idle rpm and do the same adjustment for highest rpm, this step is not so easy to discern. . . Then ,of course, the other carb has to be adjusted the same way.
Some history: AGM battery is now about 5 years old and will show 13+ volts after riding with the headlamp off.
Tri-Spark unit is also old as it sat in the toolbox for 3 years before it was fitted- this unit came from Steve Kelley's own bike to replace a unit that had failed due to insufficient clearance from the stator to the rotor.
The cylinder head has never been off since my time and I suspect a lot of carbon build-up as it always seemed to run rich with the points setup.
That is in a nutshell where I'm at, at the moment.
Edit info: the bike is almost 30 yrs. old since new to me and so are the aftermarket "Dunstall Decibel" mufflers which could be rusted out inside? Maybe I should try removing them just to make sure of no restrictions. ?
Last edited by JBMorris; 07/27/138:25 pm. Reason: mufflers
Scroll down the tech articles for a few simple tests. I use B7ES and find them quite satisfactory. A pair of Denso IW22's cured a high altitude intermittent misfire on the 68 I never could figure out. Don't know anything about Mikuni's but they must have some orifices that would benefit from some spray carb cleaner. If the bike sits a lot, dump the fuel into your car and fill up with fresh gas. Seems to me Mikuni's have some internal rubber parts the could be rotted. Maybe someone who knows can help out. If you only ride it 4 miles at a time take it out on the highway and run the crap out of it. A 5 year old battery would be my first suspect.
Last edited by desco; 07/28/1311:44 am. Reason: spelling
1968 T120R 1972 T120RV Any advice given is without a warranty expressed or implied.
They do, it's called the B8EVX (used to be just B8EV), been using 'em for decades. The V has a wider heat range than the equivalent S.
Haven't tried the resistor BR8EIX.
Originally Posted By: desco
Had a bad experience with Nippon Denso plugs.
Using N3 or B8ES in the T160, they'd last barely 3-4000 miles before one or other would start misfiring, when the manuals all said I should get 10,000. A blast on a plug cleaning machine would keep 'em going for a bit longer but essentially I was on a hiding to nothing and I got into the habit of changing the plugs every service.
Once I changed to B8EV, not only did I get the 10,000 miles out of a set, I got a noticeable (2-3 mpg) fuel consumption improvement too.
I moved to London and got a Jap bike for work (as a courier); looking for any fuel consumption improvement on that, NGK didn't do V equivalents for its 12mm plugs but ND did something similar so I fitted a pair. After about 3,000 miles, I began to get poor starting; called ND and they said, "Yes, you're supposed to change them every 3,000 miles." Given I wasn't seeing any better mpg from the Jap bike with the expensive ND's with the unobtanium/costalotium alloy electrodes, that I should also change 'em every 3,000 miles, rather than the plain-Jane NGK's every 10,000, you can probably guess what I replaced the ND's with ... Never tried ND's since in anything ...
I went with B8EV originally 'cos they were easy to get hold of then, the stinkwheels like LC Yams and similar used 'em but even the local Triumph dealers stocked 'em. I've stuck with 'em and moved to the X but, if you can get N3G easier, go for it.
I hope NGK plugs are of better quality now then they were back in 1966, when my Honda 305 scrambler came stock with them. That bike would go through a pair of 'em within 2,000 miles. After going through two more pairs of the NGKs, I bought two pairs of AC plugs, and installed a pair. When I sold the bike 8,000 miles later, I gave the UNUSED second pair of AC plugs to the new owner. The ones in the engine were still going strong.
Just slapped in a new set of NGKB8ES and still has a flat spot at 60 mph cruising speed . Seems to be carb related or bad gas or throttle cable related- hard to say. . Checked batt. voltage after and 13.3 volts with no headlamp for a short run. None of the local auto-stores had them but the nearest bike shop had plenty, NGK a bit cheaper than Champ's- he only had N3C for sale, all his own Triumph's had NGK fitted. Local Guru
I've seen dirty and or restrictive air filters cause the 60 mph flat spot.
Thanks Hill-Bill, They were off on this run and I am thinking of some type of Velocity Stack setup just for the hellofit! Today was /is a beautiful clear day and no dust so did a quick run. Added a bit of fuel stabilizer to the tank. . .
IMHO, B8ES is too cold for any Brit bike. B7ES runs much, much better.
The modern NGK cross-ref chart shows B8ES as correct, but the older charts showed B7ES. It's like NGK engineers are going purely by cross-ref themselves without any testing. One simple trip around the block will show you that B8ES will simply not burn fuel in an efficient manner.
I agree that the cross-over from Champion to NGK is not 1:1. That is, they are not exact equivalents. Note that ~1965-1980 Triumphs cert Champion N3, but models from the early 60's referenced Champion N4, a hotter plug.