Triumphrat

GleaminTwin · 11-10-2009, 04:08 PM

I'm going to change the spark plugs in my motor, just as routine maintenance. For a 1970 TR6R (with a Boyer ignition if that makes a bit of difference) what spark plug brand/part number is suitable and also what spark plug gap should I set them to?? I apologize if this is an overly simple question, but I just want to make sure I put the right plugs in it. I don't ride the bike particularly hard but do like to cruise for sustained parkway riding at about 65, also when it's in the city obviously then there's more stop and go type riding or at least in general slower riding. Is one plug model hotter and therefore more suitable for round town riding and then one plug a notch cooler and better for freeway riding? What's a good all around plug (and plug gap) for equal time spent in round town use and light open roads use in the 60 - 70 mph range (I don't rev it much above 4,500 rpm's on the highway, and probably cruise at 3,500 rpm's most of the time). I know, I could just take out the plugs in it now and get the same ones, but I thought I'd ask what you guys are using so I make sure I make the informed decision.

PS, I learned a lot reading this forum about routine maintenance such as putting about a cup of fresh oil in the crankcase when you do an oil change (after reinstalling the drain plug) so the cams get oil right away when you start the bike after finishing the oil change. That seems like an important thing to do but it's not in the shop manual to do that.

So .. about those spark plugs, which brand/part no. should I go with??

68TR6R · 11-10-2009, 04:10 PM

Champion N3 are my personal first choice. Never had good luck with NGK.

psasak · 11-10-2009, 04:51 PM

Same here... '72 TR6R and '68 BSA A65L... I had been told NGKs were the way to go - kept fouling them. I put in N3C Champions and no more problems!

GrandPaulZ · 11-10-2009, 04:57 PM

Triumph 650 - all years, all models - Champion N3C.

Always worked best for me, even in my race bike.

epynt1050 · 11-10-2009, 05:06 PM

Quote:

Originally Posted by GleaminTwin

What's a good all around plug (and plug gap)

First the easy part. Champion are generally considered the best for classic Triumphs and the plug gap should be 25 thou.

As to the best spec no, this question has been going on since about 1906 when the first plugs became available without agreement. The factory initially recommended N3 before switching to N4, then back to N3 and finally N5 towards the end. In 1970, the recommendation was N4.
However, in the UK, being generally wet and cold, the hotter N5 was the usual fitment.

GleaminTwin · 11-10-2009, 11:10 PM

Well, I recently had a problem with badly fouling the spark plug on my '66 Lambretta 200 cc 2 stroke now that I am riding it mainly in the city with corresponding low revs and lots of idling. The plugs I was using as supplied from my Lambretta mechanic were Champion N3C. So, I checked out the next hotter plug for that model which is N4C, but no one in NYC carried it, so instead bought the NGK equivalent B7ES and put it in, now it seems to run well. Also changed the air/fuel mixture by leaning it out quite a bit.

So, I alreay have 3 leftover N3C's from my spare plug stash for the Lambretta that it looks like I can use in my TR6R, sweet, what a coincidence. 25 thou for the plug gap, check.

Thanks .. GleaminTwin

Caulky · 11-11-2009, 06:36 AM

If your Boyer is electronic type, you should use either resistor loaded plug caps or plugs with `R` in the part number or equivalent.

GleaminTwin · 11-11-2009, 11:21 AM

Hey Caulky, thanks for the additional information. My bike has a Boyer Mark III Black Box electronic ignition, runs off a wire to the 12 volt battery. The bike has two 6 volt coils (used to be 12 volt coils but it was switched to 6 volt ones to run the boyer, I think they are wired in series).

I think the spark plug caps currently installed are relatively small (about 1" long) and I think unmarked, rubber type. How can I tell by looking at them if they're resistor type?

Worst case I can just remove the plugs that are in it and replace with identical ones, but if they are not resistor type plugs and the caps are not resistor type then the bike isn't set up right. Obviously I'd like to get it right, so is there a way I can tell if the plug caps on it now are the resistor type?

Thanks .. GleaminTwin

Caulky · 11-11-2009, 12:37 PM

GleaminTwin, remove the HT lead or cap and measure the resistance.
A `loaded` type will be around 5000 Ohms.
Similarly, a resisted plug will also measure 5K Ohms between the central electrodes.
The reason for this, is to reduce the spark spikes and electrical noise being fed back to the electronic ignition circuitry.
Irrepairable damage can occur.

GleaminTwin · 11-11-2009, 01:48 PM

Caulky, I have no idea how to measure the resistance, not that experienced I guess as a mechanic. I guess I can remove the plugs in there now, if they have an "R" in their part #, I'll just replace with the same type, assuming that the plug caps are the non resistor type. If the plugs don't have an "R" in the part #, then I'll have to assume the plug caps aren't resistor type (I don't think they were replaced when the Boyer was installed) and that therefore the bike wasn't set up right, and I'll just buy new non resistor plug caps (to be on the safe side just in case the current caps are resistor type since I can't tell them apart just by looking) and buy new resistor type spark plugs so that at least I know going forward what's installed rather than guessing. Who knew?? I thought spark plug caps were spark plug caps and spark plugs were spark plugs, had no idea there's resistor types of both and that with a Boyer electronic ignition you need a resistor type plug or cap.

With my Lambretta, I have an electronic ignition, but definately runs on a different principle than the Boyer because my Lmabretta doesn't even have a battery at all, it appears from talking to my Lambretta sources that there's no mention of using a resistor type plug or cap with that type of electronic ignition, but the Boyer is totally different running of the 12 volt battery source, etc. Well, learn something new everyday.

Cheers .. Gleamintwin