I know I've talked about this about a year ago, but I just can't figure this out, and I've dumped a ton of $ into my bike.
My 1967 T120R just won't run correctly at all. It pops, spits, backfires, etc. Now I have bad hesitation on acceleration. Here is what I've done: (I'm running 93 Octane by the way)
Replaced both coils, condensers, plugs, wires, points. I've checked, double, triple checked the point gap, timing, etc. Made sure the cams on the points plate are free and look good.
Rebuilt the AMAL Carbs (Monobloc 389), cleaned well, replaced with factory AMAL parts. Replaced the Slides (3.5), springs, needles, etc. Checked to make sure both are sliding in sync.
Rebuilt from the barrel up with new rings, had the valves rehoned and seated, checked the valve clearance with both a dial indicator and feeler gauges. Checked compression and is perfect.
I have see a slight white smoke exiting the exhaust on the good running side (Right). I do have velocity stacks and bobber mufflers.
I'm lost. Anyone in the Cincinnati area/vicinity interested in taking a crack at this? I'd really really like to get this bike running good. I know it ran good in the past until it sat for a number of years. I darn near have a brand new bike with the parts i've put into it! I appreciate all and any help!
The ignition is completely stock. I did not pull any timing gears, as I had no reason to do so. Valve timing I've checked using the method of watching the valves open and close through the intake and exhaust and checking to make sure i'm at the right setting. I've also run the bike for about 3 miles and then came back, rechecked again, and re-torqued the head.
Im with Tiger on this one. Years ago my '76 T140 ran great then popped and farted then ran again. There was no rhyme or reason, or consistancy. I checked everything, replaced every other thing. Still no good. It turned out to be loose rivets on the original ign switch. And they had that green goop on em too. I cleaned em with brake cleaner (cancer in a can!) and peened the rivets some more. No probs after that. Goodluck!
1950 Speed Twin outfit 1951 Thunderbird outfit (76 degree racebike, or is it 90 deg now?) 1955 BSA D3 minibike outfit Triumph solo's
Prime Suspect: Electrical. Switches and condition of harness are always first. However, 1967 has may also have AC running in the DC harness. See the GABMA article on bypassing the lighting switch... RIGHT HERE
Second Suspect: Ignition timing. This is a pre-strobe bike and people (even "Triumph mechanics") have forgotten how to do this job properly because strobe lamps have made things so easy on the newer bikes. There's simply a million ways to screw this job up: like having a BSA auto-advance unit installed. The AAU could be brand new, but advance the wrong direction. Duh!
You need the help of an authorized Triumph technician.
To run that badly because of engine grounding,there would be measurable resistance between the engine and battery +VE terminal (like 1 ohm or more).
It would be simple enough to test Tiger's ignition switch theory;wire another switch from the battery -VE to the coils.Include a fuse if you don't already have one on your battery +VE ground lead.With both switches on,there should be plenty of power to the coils.
Bad switch/bad ground should effect both cylinders,not just one. If there is an electrical problem,I think you'll find it between the coil +VE terminal and the points.I still wouldn't rule out a bad condensor or bad connecion/bad ground. You should be using the later AAU with 160 degrees dwell.Points close for 160 degrees,then open for 200 degrees.It would still run with the earlier 86 degree AAU. Does this have the 4CA breaker plate with condensors on the plate,or the later 6CA breaker plate?
My manual says #3 slide,and "D" needle.A 3-1/2 slide wouldn't make that much difference.Are the pilot jets both clear?
Ok, I took off the ignition switch tonight, and the body has a crack in it, and the black part of it is wobbly around the rivets, so i'm not messing around with it and a new one is already on the way.
To answer a few peoples questions:
It is a 12 Volt Bike, Positive Ground. The wire harness is in good shape, a good ground, etc. The Points plate is 4CA. I strobe timed this bike, and it is dead perfect each time, at advance. It starts on the first kick!
I have 389/95 carbs, and in my book the slide is 3.5, the needle is Type D, needle jet is .106, pilot jet is 25, and main is 330. I was having leaking problems off the float cover, so I tapped out the screws to metric, replaced with allen head, and then used Hylomar on the gasket thinly to seal. Problem solved with no air or fuel leaks, plus it looks better than those flat head screws!
I will let everyone know if the switch works. Otherwise...can I borrow one of you for mechanic for a day?
Looking at the valves to see if they open/close does not tell you they are timed correctly to the crank. How much play is there between the point cam and the post? It does not require much to cause the timing to wander all over.
The single carb had a 1 3/16" in 67 and a twin set up should run ok, too, but wouldn't be standard on a road T120. If the carbs are too big you just lose some top end.
The ignition system on the 67 is absolutely fine, normally. My TR6R is as sweet as a nut, town or higher speeds. The only things that made it bad were bad connections in the cable that runs to the points.
Check right through the electrics, battery, zener, the lot.
Make sure that the points springs aren't touching the timing cover. Put some insulation tape on the cover if they are close. Make sure that the black fibre insulators are preventing the condensers from touching the case, too.
Check the wiring to the auxiliary condensers is ok. You have four condensers all together on a 67. Check that the condensers themselves are all ok.
Check the carb float levels by switching off the fuel and attaching a thin tube to the end of the pilot jet of each carb. When you remove the pilot jet cap remember that some fuel will come out! Bend the tube up next to the float bowl. The level in the tube should be at the same height as the pip on the float chamber cover once you turn on the fuel again. If the fuel level is correct then the bike should run reasonably well, even if the carbs are knackered. Check the fuel is getting through ok.
It should still run ok with non standard silencers as long as they aren't too short. The bike would run smoothly with just the headers but would be gutless. The standard system works best but wouldn't stop hesitation.
This isn't perfectly clear to me... I can read it two ways.
The way I want to read this description is the engine is shutting off for brief instant giving you the feeling the engine is hesitating. It is as if someone turned off the switch for an instant. Often the engine will pick-up running if the throttle is closed just a tad. You often can work through the hesitation using the throttle. One of the fuel delivery systems in play at this throttle opening is not delivering enough fuel. (Spitting back through the carb can be symptom of a too lean condition.)
But we all use language differently and I have heard people use the word hesitation to describe that at a particular throttle opening the bike begins to loose power and appears to be hesitating. It continues to run through the hesitation, although very roughly. The bike is 8 stroking and opening the throttle will allow the engine to work through the momentary richness. One of the fuel delivery systems in play at this throttle opening is delivering to much fuel.
One Rule of Thumb I have found to be handy diagnosing these kinds of problems is: If it happens at the same THROTTLE OPENING it is usually carburetion. If it happens at the same RPM it is usually ignition. It doesn't always work out that way, but I find it a very good way of approaching a given problem.
I remembered another thing that made my bike run roughly. I had taped over all the holes in the air cleaner when I washed the bike and forgot to take them off. The bike still ran ok through the town funnily enough but when I went to accelerate in the country it just wouldn't have it. It must have sucked a a fair bit of air through somewhere!
Ok, I will clarify to help this out, then I will take a video and post it, because seeing is believing!
I did replace all 4 condensors. I replaced both coils. I replaced the points. I replaced the spark plugs and wires. I made sure nothing is touching, etc.
When i first started the bike this year after doing all the work, bike ran fine, standard first start up of the year...
Fast forward 3 weeks (and the problem I had last year, last time)
When I start the bike, COLD, I hold the throttle slightly to keep it running (because obviously the bike doesn't have a choke). In doing so, the bike will spit, pop, out of the left side, if I remove the left plug, the engine sounds the same, doesn't change like it would if you were adjusting the carbs.
So if i let off the throttle, it will idle fine with low pops, unnoticeable. If I take it out for a ride, and I give it gas it feels as though it's running on one cylinder, and then all of a sudden it gains power like it's running on both, but it runs horrible, like it's hesitating to accelerate.
That's why i'm seeking someone else, I've just put way too much time into this bike for it to run so poorly all the time.
By the way, here was a video of last year, before I replaced anything electrical:
Back in the introduction you said, "Rebuilt the AMAL Carbs (Monobloc 389), cleaned well, replaced with factory AMAL parts. Replaced the Slides (3.5), springs, needles, etc."
Just to be sure, You do not mean that you had them re-sleeved, do you?
Also some AMAL needle jets were defective. So just because it is stamped AMAL does not mean it is correct. The jet size stamped on them did not correspond to the actual size. The only way to know is to measure the jet with gauges or buy some from someone who can, and has. The needle jets do have a cross drilled hole in them, correct? How many rings on the top of the needle? There was one other problem with the jets. It has to do with the threads, and makes it possible to distort the orifice and damage the seat. This I am not so sure of, as I have never actually seen this. But again, getting the correct jets from a real expert, that is actually aware of these problems would help eliminate these potentialities.
Did you read what John wrote? Have you marked your throttle? Once you do, then you will be able to tell if the problems happens at the same RPM, or the same throttle position.
Then try what John said. Roll on throttle or roll off a bit. Which helps if either? You also try closing the petcock at the problem area and see if it improves or not. If you have chokes on you could try applying them. If you do not have chokes, verify the top of the carb is on the correct way. Verify that the clip and needle are seated properly under the spring.
How many turns out do you have to turn idle air screws?
It seems you have larger carbs, different exhaust, and velocity stacks instead of air filters, than stock. So you may be stuck jetting or all those differences. So after all you may have to use a different size jet. But getting an idea which way may save you a few bucks.
Lose the velocity stacks see if that helps. Add air filters. See if that helps. I can not see the mufflers, because my bandwidth does not support video. Are they reverse cone megaphones? Maybe you have a case of megaphonitis?
You say this problem arrived last year. How? How fast? Was anything done just before that? How many things were done, if any? Did the bike ever run correctly when you had it? Some history is in order.
One more thing. If I may ask. You say it spits and pops. Where? Out the mufflers, or out the carb?
Just one more thing. The balance tube between the carbs is sound?
If not throttle position but RPM:
Then we are back to the electrics.
If not electrics:
Then we are back to some weird timing anomaly. Like is the points cam on squarely so it is not become eccentric. Or advance unit not working. Some after market points are no good. Or, or, or.
Again some history would help.
Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
1.) No i did not resleeve the carbs. Needle jets do have cross drilled holes. Off the top of my head, I don't remember which ring on the top of the needle.
2.) I did read what John wrote, I'm having the issue at the same RPM and the same Throttle.
3.) Idle air screws out 1.5 turns.
4.) I really don't want to loose the velocity stacks, the back has had them on since 1968, it ran fine back then, I would think it should run close to the same now.
5.) The spitting, popping and semi-backfire sounds comes from the exhaust. Balance tube between the carbs is tight, brand new, heavily crimped, I read on GAMBA to use black fuel hose, used that.
History of the bike: Bike ran fine up until 1970's, backfired out of carb, caught leg on fire, etc. etc. Bike sat until 1991. Rebuilt and replaced clutches. 2000 got bike out of hiding. Ran ok, but not perfect. Had it looked at by a gentleman that has built 1950's to 1970's Triumphs, BSA's, Norton's, etc. 2006, Carb gunked itself. Rebuilt carbs, cleaned up carbs in heavy duty stottered solvent. Had leaking valve covers, cleaned, replaced all seals. Sent head/valves to be checked, as compression was low. New Exhaust valves inserted. Started having oil out of breather tube. Was recommended to check rings. Replaced rings, had barrel honed down .001 to remove glazing. Bike ran good for like a week. Last year, checked points, and checked timing. Original owner wrote in book that left side ran better with smaller gap on points, but put to factory. Found out bike was still not running good, as we started to have white smoke out of exhaust. Found that left coil was oozing a type of grease. Then found out that left condenser in points cover just fell apart. Fixed leaking carbs.
I was going to replace with an EI, but was told that points are good, just stick with that.
I know that the new switch comes tomorrow, hoping that may have something to do with it, otherwise I don't know.
I know that the new switch comes tomorrow, hoping that may have something to do with it, otherwise I don't know.
Sorry. I thought you already had it in, and still the problem persisted, because you posted it was coming and then posted again, so I just assumed it did not fix the problem. Lets sleep on it and wait for the switch.
I am having a bit of a problem understanding the history, except that it is a history of problems starting with the carbs setting your leg on fire, and for that it was banished.
Then carbs were cleaned, and then rings (new rings or same rings?) and hone job, and it ran good for a week only. Then you set points to factory from previous owner's smaller gap on one side. (check wobble on cam, and just how was it determined the points were good? What I am getting at is there may be a reason why the PO found the smaller gap on one side to work.), and then it ran worse because there was white smoke out exhaust (which side or both). Then electrical problems were found, (coil and condenser). Then the leaking carbs were fixed (how? Because there are some gaskets that will hold the float down, which is back to Dave's (I think. idea to check fuel level in bowl, which can effect mixture.) and here we are. Correct?
I feel your pain. I really do. But that is a bit more of a litany of frustration than a history. Hence the title of the thread? Keep at it. The people here will help.
Oh and I know you respect the man who fixed many bikes, but just how was it determined that all that was needed was a hone job? What clearances, etc. were found for wear, and what clearances for new, or old rings? etc. And after that, how was it broken in? See, many top end jobs do fail. Many because of improper oil, or method of breaking in to reseat rings. So there are many things here, that are unknown. You did replace the coil and condenser, correct?
But lets just hope it is just the switch. See ya, manna.
Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Everything is neat and tidy. My ground is to the oil tank mount. I do have ignition capacitors under the tank, and they were replaced as well (and I double checked the wiring schematic to make sure the wires were to the correct + and - on the coils.
My ignition switch did not arrive today, hopefully tomorrow.
Then I'm going to crate the bike up, and send it to Richard, if it doesn't work.
I honestly believe its not in the ignition, I think it's in the carbs.
Wow, lots of variables to consider but since it seems you noted that the left cyl. may be suspect would it be worth swapping carbs left to right and see if those issues follow over? Your description of idle scenario of popping, spitting back on left and pulling lt. plug not making a difference then when on the road acting like it was running on one cyl. to suddenly taking off suggests maybe a left carb problem to me and the simplest thing would be to switch side for side, costs nothing also...of course, try that new ignition switch first...Mark
One thing's for sure, you have checked everything, and still must have missed something. Switches can be by-passed so that's easily checked, but sometimes you get sub standard, faulty or wrong parts, which can be harder to detect. I've had similar symptoms from following causes:
Faulty HT leads can give similar indications as fuelling problems. I replaced a set on a 79- T140 this week, instant cure. Changed from graphite to copper core. Are the condensers NOS? These have a shelf life, and failing ones can give all kinds of symptoms, but spitting back and banging in the exhaust are common. Wrong material isolation washers behind the points. I used hard rubber washers once (30 years ago...) but had to change back. Symptoms were a little different though, more like suddenly cutting out for a time and then run OK for a bit again. Wire connectors may look OK but may be corroded or be poorly crimped or soldered. IME quite common. Wrong carb needle. Sometimes found in Concentrics (68 type vs later), not sure about Monoblocs. Velocity stacks and non standard mufflers WILL give you headaches unless you're quite experienced. I would steal or borrow a set of standard exhausts and take off the stacks, to eliminate, or otherwise, these items.
You seem to be an organized person, you'll get there in the end!