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#836113 01/09/21 9:49 pm
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Hey guys, is there any sure way to tell of detonation or per-ignition is happening on one cylinder? With the silencers off the exhaust I can hear the miss on the right side much better. Left side fires like drum beat, perfect timing. First thing I did was checked the valve clearance on that side and sure enough it was too tight. I loosened it and it didn't skip a beat for couple days. Now, it seems every 4-5 strokes it misses on same right side at idle (too fast to hear more than idle but heavy vibration at said RPM could be related). I checked valve clearance again and all is still good there. I have also checked for carb gasket leaks and also all good there.

What methods can be used to troubleshoot from easy to difficult points, coil, timing advance or anything which could be causing this problem? Plugs are looking good just slight on the rich side where I want them for now with mufflers off.

Other things I have noticed different from left to right:

1. There is more exhaust compression coming out of the right side as if being shoved out from being held up too long which builds more pressure when valve finally opens. Or maybe this is normal and the left side is just lower on compression exhaust stroke? Any bare skin on my body such as top of foot is my exhaust compression gauge just behind pipe. It also feels hotter on right side.

2, Not really sure what to call this phenomenon...Riding down hill in gear letting up on throttle to start slowing down engine makes this unique sound as the downhill motion becomes more force than fuel burning. I don't know but it sounds more like a boat slowing down. Anyway, this always happens on the right side first with the slightest decrease in acceleration when going downhill. burrrrrrrrrrrr and the sound wave gets deeper in pitch with slower speed, much more forceful than just at idle. To call it "engine breaking" would be confusing. The engine is not breaking it is helping the bike slow down. Same as down shifting though but without downshifting smile. This engine drag always starts much sooner on right than left.

The bike is talking and telling me all these things but I'm still in language skool. Can someone please translate with logic? :))

Last edited by splash; 01/09/21 10:07 pm.

1970 Triumph tiger owner
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Hi Splash, Your first step is hot compression test. Ride bike a good 10 miles if possible to warm it up. Cold compression is quite variable & hard to trust.

This is the most accurate way to test compression.

Warm motor.

Back of spark plugs 2 turns. Reinstall plug wires. Start motor goose throttle 3-4 times to 3-4k or so. This blows out any carbon particles that fall off plug threads during breaking plugs looks. Bits of carbon can get stuck on valve seats. This blows that out. Remove plugs rest of way.

Screw in compression gauge. Hold full throttle. Kick motor & observe gauge. Count kicks. Keep kicking until gauge goes no higher. Often 10 kicks or more.

Put plugs back in finger tight. Start motor & goose it a few times. This puts oil back onto rings that was lost on opposite cylinder.

Remove plugs again. Screw compression gauge into opposite cylinder. Test as you did for the first cylinder. Don't forget to hold full throttle & count kicks.

The number of kicks depends on internal volume of gauge & hose, how good the check valves in gauge are. A low cylinder will often take extra kicks. But it's the highest pounds that make the difference.

I don't know what pistons you used. If normal 9.0 compression ratio, Expect about 165-170# hot. Cold can be 90-125 ish. A real crap shoot.

If compression is low on either side, you can test valves for leakage with cylinder leak down (leakage) tester. You need a compressor for that too. If valves are good you have bad rings or head gasket problem.

Good compression must be verified before doing other diagnosis.

Regarding tight valve, how tight was tight? If it had any clearance at all no damage would be done. If clearance was zero the valve is subject to burning very rapidly. The valve clearance gets wider on hot motor & maybe had some clearance hot?? Not suggesting you currently have valve problem, but tight valve leads to problems. Again, no speculation... Test compression hot. What is your results?

With the electrics we saw in headlight area, I'd most carefully look at electrics on right side coil & points. Also swap spark plugs left to right just in case faulty plug. You can also swap plug wires & coil left to right as needed. Only swap one thing at a time!! Then road test. I'd look over every inch of wire & every connector on bike. Especially with humidity & salt air. Cleaning every connector & using dielectric grease on them is what I'd do.

Noises are most hard to describe & diagnose online. I have no idea what it might be. I'd consider getting motor running well first. Look into muffler. It's not clogged or falling apart inside, blocking it?? I doubt it, but check. '70 Stock mufflers are straight through glass packs. You should see all the way through from rear with flash light.

As I recall your bike is Tiger. Single carb. Misfire one side only on Tiger is seldom carb.
Don


1973 Tiger 750
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the clearance was very minimal if any at all. I'll let ya know about the compression test. thanks

Still have issue with headlight I thought was fixed. It turned on before start up, It started with on worked fine then shut it down for 3 minutes as I turned key headlight did not come on. Started it up anyway with switches on. Rode about a half of a block and headlight comes on. Nearly same issue again which i thought i solve with completely bypassing ammeter and removing the guts of it all.

Last edited by splash; 01/10/21 10:21 am.

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Hi Splash, Headlight is symptom of greater problems with electrics.

Headlight quits, but motor not. So why?. Intermittent bad bulb? Poor power to light? Bad ground for light?

How does this effect electrics to ignition/spark? That is unknown.

Lucas got the prince of darkness name for a reason. The design of the wiring/connectors make them prone to corrosion. Factory was never concerned with long term durability.

Lucas components are actually not that bad. Most problems are in the connections. Followed by broken conductor inside insulation so can't be seen. Meaning the wire itself fractures inside insulation. Very common at head tube where harness flexes turning bars. That can be hard to find. Volt drop test with 40w simulated load is helpful.

But... again if I was in your shoes, I'd unplug, clean, apply dielectric grease to every bullet. Remove all the ground fasteners, clean & dielectric them. Look inside the snap connectors for split/cracked tubes. This is a lot of work. Will take many hours. Basically must be done though. It seems only way to make these connectors reliable. Still faster than pushing bike home or waiting for tow truck. There is no easy way for old Triumphs. You just have to do the work. The whole job, 100% or they will leave you angry, frustrated & walking.
Don


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If you insist on stock connectors, keep a pair of comfortable shoes handy. I have been useing these for a LONG time;

https://www.posi-products.com/posilock.html

Some have been on my 72 for 30 years. No problems.


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splash Offline OP
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I haven't touched it yet. I'm thinking about rewiring the whole thing instead of looking for a needle in a haystack. There isn't much to the electrical system,,,headlight, taillight, brakelight, horn, ignition switch and thats about it.

thanks Desco!

Last edited by splash; 01/11/21 12:14 am.

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Correct color wires go a long way towards keeping life simple;

http://www.britishwiring.com/PVC-Wires-s/67.htm

Cheap and they don't make you buy a mile of it. GREAT customer service.


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Hi Splash, Replacing harness with new one isn’t really hard. But time consuming. New harness doesn’t include sub harness like points or tail light sections. Doesn’t include most bullets.

As we speak I’m making new harness from scratch 73 Bonnie.
I got parts from British wiring.

It is a lot of work to fabricate harness. Give it some thought before you make one.
Don


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splash Offline OP
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OK, took for a spin and now the horn suddenly stopped working. Horn worked from start of ride. Only thing working is brake light. Still haven't compression tested yet. It was also missing real bad then that suddenly cleared up again. I could rewire bike and still have same problem. I keep wanting to point at the alternator for it all but from my understanding there is nothing really to go wrong there either except for the wiring again, eh? What ever it is I wish it would just break 100% so I could test different things. I wanna say it's something in main power supply. I mean if only the brake light works then that must be simply to the battery, switch, and light.

What is the purpose of the rectifier again? and is everything coming from there except the brake light? Could the lightswitch on the horn not grounding cause all or majority of this mess? Frustrating because it is so intermittent. If the alternator was bad and intermittent it would drain the battery and things would start falling off the Christmas tree slowly like this, right? Then when it does decide to work again and charge the battery the headlight would eventually turn back on again like it has before. Maybe I can check the ground wire tomorrow making sure it is tight to the case.

Last edited by splash; 01/11/21 8:12 am.

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The rectifier changes the AC smoke from the alternator into DC smoke for the battery.
All the lights, horn and ignition use DC
Your battery would drain if the alternator and rectifier were faulty.
If it has the original ignition switch this is probably faulty / intermittent, it can be checked using a meter set to Ohms, when ON it should read zero , when OFF , it should read big numbers or infinity. If it is not FC to zero when ON or wavers this may be one of your problems.

Last edited by gavin eisler; 01/11/21 10:10 am.

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Hi, for what you mention in the first comment, that is not perceived as detonation. Then, if the cut off is intermittent, the problem is a wire connection; for example from the alternator.

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I'd go with TR7RMans's advice, the one place that is NOT causing your problem is the alternator!

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Hi Splash, If you still have brake light, ignition switch is not the problem.

Your problem is distribution of power. Start by cleaning all the connectors inside the headlight shell. But first with headlight hanging out setting on fender, Turn on key & wiggle around wires. Turn bars lock to lock & wiggle around wires where they pass by head tube. Observe lights etc.

Test light on coil power will go dim or flash off if you loose power there while testing. So you can catch it with peripheral vision where it could be overlooked with volt meter.

As I recall you only have the single horn, no relay. Power comes from wires to ammeter. So the crimp is bad, or wire may be bad. Wiring diagram can be followed to trace wires, but it doesn't always show every snap connector.

Poor ground will do the darndest things. Volt drop is best test. But again wiggling red wires & removing all ground nuts/bolts, cleaning & apply dielectric is advised.

The Brown/white wire from ignition switch to headlight switch needs a careful look from ignition switch to headlight switch.

Ohm meter is an important tool. However it can't find volt drops reliably. You need to do volt drop test on each effected circuit. That takes understanding of each circuit & a large test load. Even then depending on the nature of the intermittent faults it may not show the fault.

I agree a total failure would be much easier. Thing is, you may have several problems.

Since battery doesn't seem to loose charge, as was stated, alternator is not cause of these problems.

You are most correct installing harness may not cure problem. I've learned over the last 50 years, good diagnosis leads to good repairs.

The saying, "it's better to be lucky than good" is most true!! However 99% of the time it takes a lot of effort to diagnose the root problem. I'd recommend you do web search on automotive pages on how to volt drop a circuit. Volt drop is a very valuable skill for any Triumph owner.
Don


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splash Offline OP
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Hot compression test:

60/90/120 right side under 5 kicks

60/90/110 10 kicks (Left side)


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Hi splash, Hmmm. Kind of low especially on left side.

Do you know exactly what compression ratio pistons you installed? How thick head gasket is?

A broken in motor 9.0 pistons, .050” thick head gasket will be 170-175#.

How many miles have you covered since overhaul?

Did you follow my procedure exactly?

Next step would be cylinder leak down test. That tests leakage at valves very accurately. If valves are good it means poor sealing rings. If valve(s) show leak hard to say how rings are. Remember this is if it failed test.

At the same time you have various electrical problems.

Where to start? Personally I’d sort electrics first.

Then put some miles on bike & see what happens. Electrical problems makes it hard to sort motor. Especially when it my kink out on road tests.
Don


1973 Tiger 750

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