Triumph Rat Motorcycle Forums banner
  • Hey everyone! Enter your ride HERE to be a part of October's Bike of the Month Challenge!
1 - 20 of 21 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 · (Edited)
Hey guys,
Here is the lowdown... I have a 70 tr6r, carb has a #3 cutaway filed down to be close to a 3 1/2, 220 main jet, .106 needle jet. Around 2.5 turns out on the air mixture screw, needle in leanest position. I have the stock emgo pipes and mufflers (without the crossover tube), pistons are .40 over. running a boyer w a tympanium, i believe the coils are 12v, maybe this is my problem?

I've been running b6es plugs because if I run B8es they will be completely fouled in just a few miles, where the bike won't be able to idle. The b6es are good for a little while but they too, especially if I'm cruising around the city with stop and go traffic - can get fouled up quite quickly as well. If I'm on the highway for a while they clear up a little bit but will still look far too rich.

While the bike is running it feels great, but if I'm the city waiting at a light it will just die. If I turn the headlight on, it will die in a matter of seconds (it's not an electrical problem, I've tested the battery and alternator and if I put in a new set of plugs it will idle with the headlight on no problem. also the battery, tympanium, boyer, stator and rotor are all less than a year old and i also put a new wire harness on as well. installed new rings this past winter as well.)

I'm thinking now that maybe it could be leaky valves? I occasionally see a lil bit of oiliness on the plugs (Actually, usually just the right plug, the right one is always ever so slightly more fouled than the left) though usually they are just sooty. It's terribly frustrating driving in the city or having to stop at a stop light and have your bike always shutting (especially at night with the headlight on) off or having to stay on the throttle so it doesn't shut off. Any ideas?

Cheers
 

·
Registered
Joined
·
6,533 Posts
I guess I have to ask why you had to file the slide cutaway in order to achieve the correct size. From that I assume this is not the original carb or at least not the original internals.

So, I'm no expert, but if you are truly suffering from an over-rich mixture and your jetting is all correct (although it looks like main is smaller than stock) here are my thoughts.

1. Needle jet is worn and no longer to spec
2. Jet Needle is worn and no longer to spec
3. Float is set too high and engine is flooding at idle. High speed can consume the added fuel, but still is running rich as a result.

You said you think your valves are leaking due to oil residue. So you mean valve guides, not valve seats. My experience with other engines is bad guides like to leak more at idle, or at least it appears that way. But I've had engines with really bad guides that used a lot of oil, smoked like a 2-stroke and yet ran decent because the oil will burn with the gas mixture until it gets really bad. But if you are fouling a new set of plugs in short order, I'm doubtful it would be oil from bad guides or your exhaust would look like an insect fogger when the engine was running. I would say the same for bad rings. I've seen engines with broken oil rings still run decent, although a tad smokey.

If all your internal bits are new, then I'd check your float level. If in doubt set it a tad low. Also make sure the float valve actually works properly. Put a piece of hose on the fuel inlet barbed fitting and blow into it with the carb upside down to see if it seals properly. Use your mouth, not a compressor.

One last possibility could be bad gas. Although I've run some nasty old stuff in non-bike engines with no preceiveable problems, I supposed bad gas could be as source of excess carbon. That's an easy fix and if not the case, you just put the gas removed from the bike in your lawnmower.

Hope this helps,
Rob
 

·
Registered
Joined
·
395 Posts
+1 Rob! Excellent diagnosis and great explanation.
When this happened to me, turned out to be broken valve guides. I tried lots of spark plugs before I realized they were not totally to blame. It seems to me that the Champion N3 worked the best for my 72 TR6RV.
Anyway, I'm waiting for my top end rebuild to be done. Hopefully this weekend. Can't wait to see the difference in plug coloration and longevity.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #4 · (Edited)
Thanks for your replies snakeoil and 75jazz.
The #3 slide was filed down because the tiger is supposed to run a #3.5 cutaway, I was running a #3 and I had an extra #3 which I filed down. I thought that should help with the rich condition, the difference between cutaways is a 1/16th of an inch so it wasn't much to file down, but it hasn't made a difference.
Engine doesn't really smoke at all, though I do burn quite a bit of oil. Almost a quart on a 250 mile ride, not sparing the horses. My friend when riding behind me says he sees some blue puffs occasionally, so thats probably valve guides. But is that enough to keep fouling plugs the way I do? I actually just replaced the float as mine was starting to crack where it hinges, though was still working properly. It has always idled nicely - until the plugs get fouled. With the new float, set to the right level, it's still running the same. I swapped needle jets as well as the needle itself and have seen no change.
I read somewhere (cant remember where, probably on here) that a boyer can foul plugs if it doesn't have 6v coils, but I don't know why that would be, and why it might not happen to everyone. I havent tried changing that yet, but so far im leaning toward valve guides. Mind you I'm running a much hotter plug than stock and still fouling them. I always run 93 octane, and get it from numerous sources in manhattan. Any other thoughts? Could a new carb solve my problems? I would think a worn out carb would just run lean.
 

·
Registered
Joined
·
316 Posts
I'm having a similar problem with idling on my TR7T that was not cured by replacement of battery, electronic ignition system and plugs but seemingly was after a 100mile+ fast run to the coast and back. The following a monsoon yesterday, the problem came back ...
 

·
Registered
Joined
·
6,533 Posts
I have Boyer's in two bikes and both run fine. I have no experience to be able to speak to a Boyer with 12v coils causing plugs to foul.

Maybe you do have an oil problem. 1 quart in 250 miles is kinda heavy oil useage to me. I would expect you to see carbon build up on the exhaust valves, piston dome, etc.. You should be baking carbon everywhere, not just on the plugs.

regards,
Rob
 

·
Registered
Joined
·
4,107 Posts
Try using Champion N3C's. Sounds crazy, I know, but it seems that the old ones like those plugs. You could also try opening up the gap a bit.........025 was from the days of the magneto.

The "village idiot" only uses Champions: Jim
 

·
Registered
Joined
·
220 Posts
I would return the carb to standard condition with the proper slide and the needle in the correct position and with new gaskets. I would also make sure the air cleaner was the correct kind, clean and fitted properly and that the choke was fully retracted.

Boyers should be used with 6 volt coils.

I have seen some discussion about raising or lowering float levels with Amal 900 series carbs. From my experience this is a waste of time as the float level wasn't designed to be altered - just make sure that the float has no leaks and isn't binding on its mounting.

Carbs and parts aren't particularly expensive. Why not buy a new, properly jetted one and swap it over? You will probably need the extra parts at some time anyway.

Start from a known correct point and work from there. If carb settings are correct then you should start looking elsewhere - poorly seated rings and worn guides could be a possibility although they would produce oily rather than sooty plugs.

Bruce
 

·
Registered
Joined
·
253 Posts
Change those coils to 6v, they are run in series so like lightbulbs in series the first will receive a bulk of the voltage and the second will receive a lot less, so in the analogy to lightbulbs one will glow reasonably bright but the second will be very dim.Does one cylinder foul first?
Also check that your alternator rotor is not coming loose on its boss and screwing up your timing marks
 

·
Registered
Joined
·
240 Posts
For me, ultimate anti fooled plug is NGK Iridium

I use same the four NGK CR8EIX on my Triumph T120RC with Pazon TwinPlug/cylinder PD2TTP since 20,000 miles
 

·
Registered
Joined
·
123 Posts
........ I do burn quite a bit of oil. Almost a quart on a 250 mile ride........
Assuming 50mpg, that's 5 gallons/40 pints of fuel and 1 quart/2 pints of oil.

That's a 20:1 two-stroke mix :eek:, most modern 2 strokes will happily run at a 50:1 mixture, no wonder it's fouling the plugs. :D
 

·
Premium Member
Joined
·
4,721 Posts
6V coils might help a little,but I don't think that's the full answer to the problem.There are other bikes using 2 x 12V coils,without fouling plugs.
Both coils do see the same voltage,provided they have equal primary resistance.The same amount of current flows through both coils to complete the circuit.

Sounds like the float level is good,the main jet is about right,slide cutaway is right and measures 7/32".

A lot of air coming in with the mixture screw at 2-1/2 turns out.Maybe the pilot jet is bigger than 0.016",and causing richness just above idle.You can always fit a 25 pilot jet in the main body above the float,to get your adjustment back around 1-1/2 full turns from bottomed.

I still suspect the needle-jet,even if its new.It must measure 0.106".It must have a 0.035" cross-drilled hole.Get a number 36 drill and measure it.It should measure 0.1065" at the flutes,and a little under 0.106" at the shank.If you measure a few of them ,you might find some slight differences (about 0.00025").
The shank of the drill should fit into your needle-jet but the flutes should not.At 0.1065",the needle-jet is worn out.

Your needle should measure 0.0985" on the parallel section.It should have 2 scribed lines above the clip grooves.

The jet-holder should have a round turned section protruding below the hexagon (like a washer stuck on a bolt-head).

The fit of the parallel section of the needle in the needle-jet has big effects around 1/4 throttle.Above 3/8 throttle you can adjust the mixture with the needle clip.

If everything looks good but its still too rich :
*enlarge the cross-drilled hole to 0.037",or even 0.039" .
*Try a 105 needle jet .
*Increase the cutaway to 4 (most effective below 1/4 throttle).
 

·
Registered
Joined
·
520 Posts
Try using Champion N3C's. Sounds crazy, I know, but it seems that the old ones like those plugs. You could also try opening up the gap a bit.........025 was from the days of the magneto.

The "village idiot" only uses Champions: Jim
HMMMMMM.....how does .03 sound ??....running sparx ignition on my 72 bonnie
 

·
Registered
Joined
·
6,533 Posts
Just talking to a friend who works on these every day and he said the new Boyers will work with 12v coils. So if yours is new, should be fine with 12v coils.

regards,
Rob
 

·
Registered
Joined
·
3,515 Posts
A year ago I would have argued that any plug would do, ie, either Champion or NGK.

On my 2000 mile adventure last year I set off with a set of NGK-B6ES (anyway the equivalent of the Champion N3C). Bike ran a treat all day, all good.

Next morning, nothing would start the old bitch. Being the good little boy scout that I am, I dived into the tool roll and out come a set of Champion N3C. In they go, the old tart fires first kick.

Ran a treat for the remainder of the journey.

Now, this is hardley conclusive evidence to support Champion over NGK, but I do not buy NGK for this engine anymore. RR
 

·
Registered
Joined
·
3,515 Posts
Almost a quart on a 250 mile ride, not sparing the horses.
Consuming oil at about 4 times the usual rate, would be a test on any plug. If you can afford to replace the oil at this rate, then try a Champion N4C and see if it lasts longer, One would expect it to. RR
 

·
Registered
Joined
·
520 Posts
just a quick comment bout that ......ngk numbers there plugs smaller the number the hotter.....so if champion did the same n4c would be a colder plug....and i had a similar experience with ngk in my bonnie , and agree, I no not ust them in my vintage machine ......Tom
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #19 ·
thanks everyone for your replies.
i havent had a chance to try anything else yet on the bike.
but it seems like it could be linked to my oil consumption.
though...the bike doesn't smoke, and i put in new rings this past winter.
why might it be burning so much oil?
i'm leaking quite a bit now from the top end, rocker boxes and also from the top of the pushrod tubes. i dont know if that could somehow be helping to foul the plugs, but i dont think so.

i need to order some champion plugs, but i dont think the solution will be quite that easy. it will foul a pair of b8es in half an hour, and b6es in a day or two (i can still run them but when at stoplights i have to stay on the throttle so it doesn't die on me), i guess i've already mentioned this.
 

·
Registered
Joined
·
2,786 Posts
thanks everyone for your replies.
i havent had a chance to try anything else yet on the bike.
but it seems like it could be linked to my oil consumption.
though...the bike doesn't smoke, and i put in new rings this past winter.
why might it be burning so much oil?
i'm leaking quite a bit now from the top end, rocker boxes and also from the top of the pushrod tubes. i dont know if that could somehow be helping to foul the plugs, but i dont think so.

i need to order some champion plugs, but i dont think the solution will be quite that easy. it will foul a pair of b8es in half an hour, and b6es in a day or two (i can still run them but when at stoplights i have to stay on the throttle so it doesn't die on me), i guess i've already mentioned this.
Worn or loose valve guides can result in significant oil consumption. You can see the oil in the ports on the head. On the intake stroke the oil can get sucked right in past the valve stems. I could rattle the valves in the guides on a '73 I purchased. I had the new intake guides grooved so that a seal would stay mounted. Some think this reduces the lubrication too much. I have stainless (Kibblewhite) valves. Others taper the top end of the guides so they tend to wipe off the valve stems without the oil accumulating in the area where it would get sucked into the chamber. The guides are available in oversize for a tighter fit with the head and better seal. Sealant can be used as an alternative if the guides don't wobble in the head. Guides are constructed from a variety of materials. Don't save money and get soft brass. Get the good stuff. Don't damage the head by a sloppy guide removal. A wet/dry compression test can tell you if your rings are damaged. Bob
 
1 - 20 of 21 Posts
Top