B25 Rough Running..missing slightly

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B25 Rough Running..missing slightly

Post by bonnietiler » Mon Sep 07, 2020 8:26 am

My B25 went sour on me..BOYER died, I replaced with a bank account rinsing Trispark, this works fine bike starts well Etc but, there is ALWAYS a "but" isn't there? If it was a twin I'd say it was running on one cylinder, it revs but there is a feeling that something is missing, it has new coil and ignition and produces a bright juicy spark, I checked the fuel flow and cleaned both taps and replaced one.
Any thoughts before I whip the head off in a flurry of "Spanner-action"?
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Brian

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Re: B25 Rough Running..missing slightly

Post by kommando » Mon Sep 07, 2020 8:44 am

May just be the different advance curve, have you strobbed it to check the fully advanced point is correct.
Last edited by kommando on Mon Sep 07, 2020 9:12 pm, edited 1 time in total.

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Re: B25 Rough Running..missing slightly

Post by minetymenace » Mon Sep 07, 2020 9:19 am

Kommando has probably nailed it succinctly.

Before you have an uncontrollable spanner frenzy:

Double check the ignition.
1. Make sure you have the Trispark "B" version....I think this is marked on the stator somewhere.
2. Go through the timing routine again. Do not trust the marks on the alternator, use the TDC pin or rod down the plughole method (in which case don't look for TDC, but find two equal altitude points either side of TDC and bisect the marks on your degree wheel). It is worth getting the timing spot on to a known point, as electronic ignition doesn't alter with time, you should be able to set and forget (the caveat being slight adjustment for fuel).
3. Have a careful look at the HT side of things, treat it to a new plug (beware of cheap fakes) and lead, and/or make sure it is not breaking down to ground anywhere.

I know you have done it before and you think you did it right, but doing it again, take your time, use Zen, alcohol or other seditive of choice to keep you relaxed and stay focused. Use a different method to check your results .....then you know that this is good.

Give your carb a service. Work through it methodically, destroying the ozone layer with carb cleaner and blow out your jets and passages, then those of the carb. Check the jets, slide and needle for wear and size, check the float level and reassemble with default screw settings.

Fresh fuel in the tank and it will run. if not reach for the 9/16th, 1/2" AF and the BFH.
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Re: B25 Rough Running..missing slightly

Post by bonnietiler » Mon Sep 07, 2020 11:25 am

I will indeed do all those things as you suggest Grasshopper, the mystical machinations of the Light single BSA/Triumph are as an Alchemist converting base metal into purest gold, would constructing a cauldron out of a NOS Cotton Double Gloucester crankcase and within a boiling brew of eye of Frog, slug juice and 1 imperial gallon of bat urine do the trick? This was suggested by Radco all those years ago in Practical Motorcycle Maintenance? Bob Curry suggested donning a Freshly hewn Antler horn headpiece, casting all raiment aside conferring a double coating of Engineers Blue to the old Gentlemens vegatation (using a rusty wire brush of course) a vigorous Druidic dance and chant by the light of a waxing moon, got to be worth a try?

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Re: B25 Rough Running..missing slightly

Post by minetymenace » Mon Sep 07, 2020 12:15 pm

:laugh You nutter! :laugh
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Re: B25 Rough Running..missing slightly

Post by Canberra » Mon Sep 07, 2020 2:34 pm

So that's where I have been going wrong all these years :shock: Brilliant :!:

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Re: B25 Rough Running..missing slightly

Post by skippy » Tue Sep 08, 2020 12:24 am

I'm with Kommando, sounds like it is a bit retarded.
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Re: B25 Rough Running..missing slightly

Post by JB » Wed Sep 09, 2020 8:50 am

If it's running and miss-firing as you say and especially so if the carb is old, then there's a good chance that a worn needle jet is causing a regular miss-fire due to richness. Needle jets are really cheap and a new one will completely transform any bike running with a worn one.

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Re: B25 Rough Running..missing slightly

Post by Jeff K » Wed Sep 09, 2020 7:58 pm

I think that the Tri Spark is like the USA made power Arc in that they both spark three times. I have installed a several of the Power Arcs units and the first thing that I noticed every time, was the idle speed jumped up a couple of hundred rpm and the bikes ran noticeable smoother. Since your problem started with the new EI, I would suspect incorrect timing or a bad unit.
Jeff

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Re: B25 Rough Running..missing slightly

Post by kommando » Thu Sep 10, 2020 1:38 pm

The Tri spark does not spark 3 times, the Tri part comes from it being initially designed to fit a Triumph Trident.

What it does have is an idle stabilisation curve, as the revs drop below 1000 rpm the timing is advanced to keep the revs up.

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Re: B25 Rough Running..missing slightly

Post by minetymenace » Thu Sep 10, 2020 4:52 pm

kommando wrote:advanced to keep the revs up
<201 do you mean that?
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Re: B25 Rough Running..missing slightly

Post by kommando » Thu Sep 10, 2020 10:41 pm

Yes, at tickover revs if you advance the timing the revs increase.

Digital Pazon curve with idle stabilisation. Analogue Pazon's don't have this feature.

Image


Just read any thread on high tickover with points, first item to check is the AAU as if it jams before being fully retarded then the revs stay high.
Last edited by kommando on Fri Sep 11, 2020 9:28 am, edited 2 times in total.

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Re: B25 Rough Running..missing slightly

Post by skippy » Fri Sep 11, 2020 12:16 am

That is the major failing of the cheap pazon and maybe some others as idle revs drop so does the advance which lowers the revs and so on.
So a healthy idle speed is a good think in this case. You pays your money and gets the technology for the price.
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Re: B25 Rough Running..missing slightly

Post by Jeff K » Fri Sep 11, 2020 1:59 am

"You pays your money and gets the technology for the price." Yes indeed!. The Power Arc is not cheap at all. But you get a choice of 4 built in spark advance curves---
Regular gas mild
Regular gas wild
Premium gas mild
Premium gas wild
And it has a built in port to hook up your laptop to it so you can adjust the spark advance to suit your special needs and you can reset the rev limiter to where you want it.
But again, not cheap. You pay for the extras. I have installed several and have been very happy with them. Once I get caught up on a pile of other projects, I will be putting another one in a 1974 TR5T.
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Re: B25 Rough Running..missing slightly

Post by bonnietiler » Wed Sep 23, 2020 9:09 am

The B25 confounds all and sundry and now (what!) the capricious gremlin chooses to run well.
It was not hale and hearty, asymptomatic it was, it looked absolutely fine, it sparked well and fuel was emanating sufficiently from a rebuilt Amal, but hmmm...
It was decided upon to remove the Trispark and start over again. I systematically timed it to perfection using the Crankshaft notch and yet it still ran like yours truly in an Olympic trial,,,slowly, badly and it ran out of puff quickly. So I bit the proverbial bullet, installed my Uber Deaf-tone earplugs and connected my trusty Gunsun strobe, revved this sulky, truculent teenager to 4000rpm or so and with all the static measurements absolutely bang on the timing was in fact a mile out. So, in a fit of good old British bodging, I held a wet finger up to the breeze checked the Pine-Cone and the strip of seaweed on the door, girded my loins turned my truss up a notch and I manually adjusted everything until the strobe lined up beautifully (nothing else does) and it runs like a bloodhound lapping milk.....hey ho...twas ever thus

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Re: B25 Rough Running..missing slightly

Post by minetymenace » Wed Sep 23, 2020 12:54 pm

I guess you had it firing on TDC...with your eloquent writing skills I have to remind you (and everyone else) of the Tales of Woe section, I'm sure you are capable of recounting some ripping yarn that would raise our lock-down spirits.

Glad you got it sorted!
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Re: B25 Rough Running..missing slightly

Post by nopdog » Wed Sep 23, 2020 10:13 pm

LMFAO

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Re: B25 Rough Running..missing slightly

Post by kommando » Thu Sep 24, 2020 7:47 am

Now you just have to worry about the Trispark faiing, not unknown. Never trust any electronics stuffed into a hot small space.

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