324.5 cc Bonneville should be 649 when all is right - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 71 (permalink) Old 03-15-2019, 05:25 PM Thread Starter
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324.5 cc Bonneville should be 649 when all is right

Throwing parts at it such as 2 brand new coils all in vain.

A....... Good compression both cylinders

B........ New plugs

C...... Both sides spark

D....... Points in good shape and adjustment

E........... New Concentric carbs

F........... Tappet clearance correct as good compression indicates.

G........ Fires on right cylinder only

HELP!!!!!! 🙏
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post #2 of 71 (permalink) Old 03-15-2019, 05:43 PM
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Some history as to why you're throwing parts at it would be helpful, eg when it last ran well, what happened when that changed etc.

Also more detailed info, eg "good compression" is useless, a number is much better.

Does it run on right cylinder only, or just popping and banging?
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post #3 of 71 (permalink) Old 03-15-2019, 06:21 PM
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Is it getting fuel on the "offending" cylinder? Is the bike timed properly? Playing the "devil's advocate" here, I realize, but start with the simple stuff, again. You might get lucky. If I remember correctly, the 1968 Triumph ignition system is like having 2 separate ones, so if one is out of time, so to speak, you'll have spark, but not at the correct time.
Hope this helps: Jim

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post #4 of 71 (permalink) Old 03-15-2019, 08:11 PM Thread Starter
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Quote:
so to speak, you'll have spark, but not at the correct time.
Would it be accurate to say that if the right side that is firing is timed correctly and both set of points open exactly relative to the breaker cam position
and gap is set properly all should fall into place?
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post #5 of 71 (permalink) Old 03-15-2019, 08:21 PM Thread Starter
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Quote:
Originally Posted by koan58 View Post
Some history as to why you're throwing parts at it would be helpful, eg when it last ran well, what happened when that changed etc.

Also more detailed info, eg "good compression" is useless, a number is much better.

Does it run on right cylinder only, or just popping and banging?
It last ran well in 2008.It runs on the right and pops on the left. Wish I had more details.
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post #6 of 71 (permalink) Old 03-16-2019, 04:27 AM
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Hi Stopngo, Start by verifying the choke is not accidently stuck on. Look into air horn of carb & give full throttle. The choke slides should be full up with choke off.

Verify the throttle slides lift evenly or at least very close, & close freely.

The '68 Bonnie has dual points. The timing is set individually for each set of points. What backing plate does you points have? You should have the 6CA late type points plate. On this late version the backing plate has 2 sub plates screwed to it. The points are then screwed to the sub plates. This allows you to set point gap to .015". Then each points mounting plate can be moved independently to set timing. If you find you lack range of movement on a sub plate, you rotate the main (round) backing plate as needed. Then start all over with gap & timing each set of points.

Just in case you have early type points plate. It's just round plate with 2 sets of points screwed to it. You set gap. Set timing on one set of points by rotating backing plate. Then adjust point gap of other set of points to set timing for those points. Still keeping gap relatively close to spec. A little tricky, but doable. Triumph started with the easier system for model year '68 so you should have the late points/plate.

In the photo there is a hash mark on end of points cam at about 8 o'clock. Line up points rubbing block with that while gapping points to .015"

If timing is way off it will run quite bad or not at all. In this case starting with static timing can be very helpful. Then proceed with strobe timing. Static timing is covered in shop manual. It is important to power a strobe timing light from a separate battery, not bike battery.

Properly set & serviced points are extremely reliable & allow starting with a dead battery.

I know you said has spark both sides, but is it a strong spark & does it still spark at higher rpm than kick start cranking speed?

One thing you might have happening is the points are not closing strongly. Held open with finger nail or screw driver when released, the points must snap closed with a decided click & force. Verify this. If the points spring is skewed it can put pivot in a bind. This is very common.

Normally the front points is for left cylinder.

Also look very closely at the wires attached to points spring stud. The plastic insulator spacers must be good condition & properly placed. Sometimes on bottom of wire, the insulation wears thin & can short to the timing cover. Very common. You can put a layer of tape on it until it is replaced. Also look very closely, & visually inspect every inch of wires points, to coils. Actually look over every wire on bike for faults you can see like worn insulation or pinched wires.

Also the points contact faces must be perfectly clean & dry. Parts wash on a strip of copy paper works well. Even gas will work in a pinch. Rotate motor so points are closed. Open with finger nail & insert a strip of paper soaked in cleaner. Close points until they put tension on paper. Wiggle paper around. Then dry contact faces with strip of paper. Do this until no oil or black shows on paper. I cut paper in 1/4" wide strips 3" long. Alcohol works good too. But if really dirty the other seems better for me.

Points should allow for starting with dead or low battery, but what is battery voltage key off? A good battery makes for easier starting & better spark. You want to have about 12.6v or more. Charge battery if needed. Disconnect battery during charging so you don't over heat Zener diode.

What is your voltage to coils (both). You may be getting low volts to left coil for some reason. With poor voltage you can get spark with plug removed, but not installed during compression stroke.

If the carb tickles freely it's getting gas. But is the gas actually getting into the carb throat? That can be hard to tell. I'd remove idle mixture screw at least. Shoot some carb cleaner spray with the straw into the bore. That might blow the jet free. Hard to remove idle jet for cleaning with carb installed. Take bowl drain out when you do this. Compressed air into bore for mixture screw is very helpful, but again make sure bowl drain is removed. Often you can at least temporarily clear idle fuel passage doing this.

I would remove valve adjuster caps & verify you at least have clearance on all 4 valves. I know you said compression is good, but you need to leave no stone unturned. As was stated, you need to go back to basics.

If you have:
Compression
Air getting in through carbs
Fuel getting through carbs
Spark
Timing is correct or close
Motor will start & run. If it doesn't one or more of above is faulty.

You've got some work to do. Take your time. Verify everything is ok best you can.

Here is photo of the later points plate.
Don
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Last edited by TR7RVMan; 03-16-2019 at 04:31 AM. Reason: changed sentences
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post #7 of 71 (permalink) Old 03-16-2019, 04:55 AM
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Hi,

Quote:
Originally Posted by Stopngo View Post
Throwing parts at it such as 2 brand new coils all in vain.
If you don't have them already, throwing money at a compression tester and multi-meter would be less "in vain"; you need a more-comprehensive toolkit to keep these old heaps going ...

Compression tester should screw into plug holes (press-in type are cheaper but don't include the necessary assistant), hold WOT and kick the engine over 'til the pressure stops rising. Check both cylinders the same way, pressures should be within ~10 psi/700 millibars of each other. Actual pressures more useful than "Good compression".

Multi-meter is so you can check new coil and electrical connections between it and engine.

Thought: try disconnecting the non-working cylinder's connection to its condenser - as standard, one of two male spade terminals protruding from a black rubber 'box' under the tank front mounting; if the wiring's standard, offending cylinder's condenser wire is the same colours as its points wire. Having disconnected, if the offending cylinder fires normally, the condenser is donald*; replace both as the other one isn't far behind.

Hth.

Regards,

* If you haven't come across the term before, it's English rhyming slang, short for "donald ducked".
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Last edited by StuartMac; 03-16-2019 at 04:59 AM.
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post #8 of 71 (permalink) Old 03-16-2019, 10:32 AM Thread Starter
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Thanks. all for the well laid out homework assignment. I am lucky enough to have an original Factory Workshop Manual but wish I was more understanding of electrical basics.

It will take time before I get back to you as I sift through all your info.

A lot of what is mentioned has been done but I will certainly do it all over if need be.

Carbs have been completely dismantled and every detail followed in the manual. Carbs are new with about 200 miles on them from 2008.

Timing is confirmed and point gaps and point contact checked with ohm meter but the suggestion about the insulator on the moving contacts is of great interest and will be scrutinized today.

Of equally immediate interest is that condensor pack under the front tank mounts which will also be high on the agenda. Thanks for that directive. It might be a winner.

Anyhow as one of my neighbors always said.......... Let's not talk it to death.... Let's do something even if its wrong. 💡🙏 Will keep you informed when news is available.
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post #9 of 71 (permalink) Old 03-16-2019, 06:22 PM Thread Starter
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Quote:
Having disconnected, if the offending cylinder fires normally, the condenser is donald*;
Im afraid to ask a silly question here but does the above suggest it will run without the condenser? Is there a way to bench test the condenser with a multimeter?
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post #10 of 71 (permalink) Old 03-16-2019, 06:52 PM
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Hi Stopngo,
The engine will run without a condenser, but you will burn your points out very quickly.

To test, remove the condenser.
Put the multimeter on Ohms, touch one probe on the case the other on the wire. Hold for a few seconds, this will charge the condenser from the multimeters battery.
Leave it for a minute.
Now change to DC 20volts, and put the probes back as before, the condenser should show the voltage from the multimeterís battery. The voltage reading will drop as the condenser discharges through the multimeter.
No voltage reading indicates it is bad, holding the voltage for a minute indicates it is good.

Condensers tend to deteriorate with age, heat, vibration, I like to think of them as a service item that needs regular replacement.

Regards
Peg.
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