Triumph Rat Motorcycle Forums banner

1 - 20 of 38 Posts

·
Registered
Joined
·
1,460 Posts
Discussion Starter #1
Going to try some NGK iridium plugs in my 74 t150. #7's or #8's?
 

·
Registered
Joined
·
1,443 Posts
What's the normal heat range for a copper core? Stuart says an Iridium plug has a wider heat range...Are you trying to mask an igntion problem? Have unusual riding conditions ? They are $25 for three? Perhaps try a NGK competition plug with the cut back ground electrode, about $3 each...They are non resistor....In my race bike I believe they made a very slight increase in power over the NGK fine wire plugs I was using...Supposedly the wider ground electrode have a stronger spark kernal..But the ony way to know is try them all ....:wink2:
 

·
Premium Member
Joined
·
3,429 Posts
Going to try some NGK iridium plugs in my 74 t150. #7's or #8's?
Houston - so good to hear from you again.

Opinions are a dime a dozen, but a top Triumph mechanic who's been a factory-trained expert since '69 says NGK's threads often strip the aluminum threads on Triumph heads.......and I had that very experience using them on my '73 Trident.....
 
  • Like
Reactions: KADUTZ

·
Moderator
Joined
·
7,233 Posts
Hi GN,

Opinions are a dime a dozen,
Otoh, I've used NGK's exclusively since about 1979 and never stripped a thread in any head, Triumph or other. Mind, I also always fit plugs with a little Copaslip on the thread, after cleaning any thread on a plug being reused.

Hth.

Regards,
 

·
Registered
Joined
·
1,443 Posts
I've been running NGK BR8EIX plugs on my 73 T150 for years. I pay $3.50 for them at Advance Auto. Bob
$8.19 each at Advance Auto here in NY, between $7-9 from all the other discount stores online...You're getting a deal...
 

·
Registered
Joined
·
415 Posts
Hi GN,

Opinions are a dime a dozen,
Otoh, I've used NGK's exclusively since about 1979 and never stripped a thread in any head, Triumph or other. Mind, I also always fit plugs with a little Copaslip on the thread, after cleaning any thread on a plug being reused.

Hth.

Regards,
I've never stripped one either, dozens of vehicles and lots of plug changes of various makes over many years but I am interested; how does the make of plug affect the chance of thread damage? Surely over-torquing is the main risk, OR do some plugs promote cross threading?
 

·
Registered
Joined
·
1,753 Posts
The main risk is carbon build up on exposed threads...most don't have exposed thread (thankfully) but those that do - and it only needs to be half a turn - will work the thread every time you remove the plug. Carbon build up is hard and abrasive.

I have a head on my Trident [that I bought at a swap meet many moons ago] that had the centre hole damaged, and the other two not looking great. I used time serts on them and they are fine.

On my T140W the last turn or two are exposed, when I got the bike one hole had already been helicoiled [and it had very low mileage on it]. This only made exposed thread section longer....but the carbon didn't wear the helicoil out, all it did was pick it up and as the plug came out so did the helicoil. This happened to be in middle of nowhere at the end of the earth. I had to get towed for miles by my mate.

Needless to say I have now repaired that head with time serts as well.

I don't think the make of plug is an issue, but the exposed thread can be, you need to use plug washers to lift the plug and make sure that your thread is covered.
 

·
Registered
Joined
·
5,505 Posts
Houston - so good to hear from you again.

Opinions are a dime a dozen, but a top Triumph mechanic who's been a factory-trained expert since '69 says NGK's threads often strip the aluminum threads on Triumph heads.......and I had that very experience using them on my '73 Trident.....

Gator your friend is wise. Anyone out there can use what they want but in the late 70's Triumph had a Service Bulletin issued that stated Champion was the Recommended plug. The reasons were flaking plating and the heat ranges were not a direct crossover on the other brands.


K
 

·
Registered
Joined
·
5,505 Posts
So does it mean the length of NGK Irydium plugs thread differs from conventional plugs?

Don't have the answer to that. I'll try to remember to look at the Bulletin when I get home


K
 

·
Registered
Joined
·
1,294 Posts
So does it mean the length of NGK Irydium plugs thread differs from conventional plugs?
I think I would tend to doubt Triumphs (BSA’s) ability to produce heads of uniform thickness on it’s worn out machinery and casting dies, rather than question the ability of NGK to produce plugs with equal thread lengths.

Regards
Peg.
 

·
Moderator
Joined
·
7,233 Posts
Hi Peg,

I think I would tend to doubt Triumphs (BSA’s) ability to produce heads of uniform thickness on it’s worn out machinery and casting dies,
Don't believe all the stories from the doom-'n'-gloom merchants ... ;) Aiui, if a given casting wasn't produced by Small Heath's own foundry - which also produced castings for other companies both inside and outside BSA - BSA's usual outside supplier was HDA (High Duty Alloys), which was part of Hawker Siddley ...

Hth.

Regards,
 

·
Registered
Joined
·
415 Posts
How interesting: My father worked as structural engineer at Hawker Siddley, then designer at Avro and finally chief designer, military in-flight at BAE so I know a little about this.

The reason HS brought metal works in house (by acquiring High Duty Alloys and others) was not a cost-saving exercise, it was to control quality. Previously they imported alloys, and some structural failures, with deadly consequences (e.g.wing spars and leading edge on the B1 Vulcan, such as at Syerston) were as a direct result of inconsistencies in 3rd party supplied alloys (very small differences in alloy composition but significant impact, quite literally...).

I will ask him if he was aware of Hawkers selling alloy or non-aviation castings outside the group as it surprises me. Perhaps this was actually before Hawker's acquisition? If so the quality and consistency of the alloy and castings on BSA and Triumph heads may still be in question. When HS bought HDA the company were one of those 3td parties supplying variable quality, once HS had acquired them, HS were able to control quality. Which was the whole point of the exercise.

However, I don't think Peg was questioning quality of metal directly, just the consistency in head manufacturing due to tired old processes and tooling at the factory. If HS made the heads for BSA and Triumph then I imagine they would be high-quality but it just seems odd that they would, knowing how they struggled to keep up with the HS demands.

Cheers,
Ian
 

·
Registered
Joined
·
1,753 Posts
Also keep in mind that the spark plug thread length is affected by the top of the thread. Repeated working of the thread can wear down the spark plugs seat. Next time you remove your plugs check it out, you will see a ring around the hole where the spark plug washer has been tightened [overtightened?]. This effectively shortens the thread and exposes thread in the combustion chamber, so it could have left the factory fine, but time and use has changed things.

IMO anyone that has their sparkplug holes helicoiled is asking for trouble. And it makes the fit even worse...because helicoil repairs rely on parent metal, so generally the helicoil is slightly shorter than the original thread = more exposed thread on your spark plug than you originally had. And by the way, if you have a helicoil that is longer than the parent material expect big issues because the exposed helicoil section will glow red hot and create pre ignition and all sorts engine damaging problems.

A timesert also relies on parent material but because of how it grips that parent material you can actually use one that is a few thou longer and once installed sand its back to the roof of the combustion chamber with no issues.

Lazy people try to fit thread repair kits in the bike using lots of grease to 'trap' the swarf...I have seen it done and yes it does work, but IMO it is really just a 'get out of jail free' card. Head off install is really the better long term dependable fix.
 

·
Moderator
Joined
·
7,233 Posts
Hi Ian,

Excellent! :thumb New information about these old heaps decades after they were last made.

Certainly I know on triples, HDA heads (cast on them) are much preferred to "AM" (that company's name escapes me right now but I can find out), the latter more often being poorly-cast, infamously inside the centre exhaust port. :( Certainly some HDA heads have other letters cast or stamped on them, which aiui allowed a casting to be traced to both furnace and batch, which might've been part of HS's improved quality control process?

Hth.

Regards,
 

·
Registered
Joined
·
1,402 Posts
+1 what Stuart said.
Original AM head of my Trident had all 3 exhaust ports cast wrong and choking on gases.
Had to port it during machining a head for last rebuild.
 

·
Registered
Joined
·
5,505 Posts
Okie Dokie we back about the use of various sparking plugs in Triumphs.

I was in error in that what I stated was not in an 'Official' Service Bulletin my mistake. It was, however, in the book given to the Mechanic's at the Factory Training Class held for Triumph Mechanics. The one I will quote from is from the 1978 Service Seminar.

In the book is the following statement: "Avoid using Japanese plugs. The threads are plated with a material the flakes and blisters, this in turn can damage the threads in the aluminum head. Also, there is NO Japanese spark plug with the exactly proper het range. Suggest using Champion N3 or KLG FE80." I would also point out in the book the word NO is underlined.

So do as you wish that was Triumph USA's advice to their Service people in 1978.


I also found an old Service Bulletin last night dealing with recommended spark plugs

Number : (GENERAL) 8/72
Subject : Proper Spark Plugs
Models : All
Date: 10/31/72

PROPER SPARK PLUGS

Recently an investigation of two 'B' Range units, which for no apparent reason, had suffered seized and holed pistons revealed that the failures were caused by the wrong spark plugs which were too hot.

In talking to the mechanics involved, we found that, during the routine service and tune-up, the Champion N-3 spark plugs had been removed and another brand installed, using a conversion chart to determine the heat range needed. This conversion chart was the start of the trouble, as the information was wrong, as is often the case. (Note in the Bulletin the word wrong is double underscored)

USE THE PROPER SPARK PLUG HEAT RANGE ( Note all capitals were used and this was also underscored)

We strongly recommend the use of CHAMPION spark plugs in our motorcycles due to their proven reliability; however if you choose to use another brand, be certain to use the proper heat range (SEE CHART BELOW)

(I shall not attempt to recreate the chart but will list the bikes and plugs mentioned)

Champion Normal street N-4 , High Speed Touring N-62
K.L.G. Normal Street FE80 High-Speed Touring FE100
N.G.K. Normal Street B8E High-Speed Touring B9E

The above plugs are for T100C and T100R models


Champion Normal Street N-3 High-Speed Touring N-60
K.L.G. Normal Street FE100 High-Speed Touring FE220
N.G.K. Normal Street B9E High-Speed Touring B10E

The above plugs were listed for the following models T25, TR5T, TR6, T120, TR7RV, T140V, T150V, TRX75.


Note the Bulletin was issued in October of 1972 so it would be applicable to 1973 models. Also please note the information from the 1978 Service Seminar would have been written PRIOR to the introduction of the T140E model.



K
 
1 - 20 of 38 Posts
Top