Is it gapping, ignition coil, or something else? - Page 4 - Triumph Forum: Triumph Rat Motorcycle Forums
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post #31 of 38 (permalink) Old 12-10-2012, 07:42 AM
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When you replaced the white plastic guides in the carbs did you make sure none of the feet were obstructing the holes in the pistons ?
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post #32 of 38 (permalink) Old 12-10-2012, 01:54 PM Thread Starter
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Yes indeed. I've seen that the plastic thing with feet has little shallow slots to fit into in the slide. If you look down into the slide you'll see that it has a definite position to slot into. Thus I've always found it hard to imagine slotting it in and having it cover up that little hole.

However, I just let gravity put the white holder in. I don't push on it or anything. Is that fine?
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post #33 of 38 (permalink) Old 12-10-2012, 05:00 PM
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maybe you need a set of these https://secure.powerapt.com/smartcarb-green.php no jets to worry about...

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post #34 of 38 (permalink) Old 12-12-2012, 08:41 PM Thread Starter
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After further testing, I have a gut feeling that that the fuel metering by the idle mixture screw is nonlinear. The reason I think this is that because there is a distinct and sudden change in engine character between 1-1.75 turns out to 2.0-2.5 turns out. Immediately, the richer settings produces better throttle response and idling characteristics and less coughs back through the intake and airbox.

Perhaps it's the taper of the needle or the fuel mix requirements of the engine, but I think 2.0-2.5 turns might be the optimal operating range for my 790 engine at least (regardless of jet size, to a point). Thus, I'm going to try the 40 size jets at 2.5 turns out and see how the bike copes.
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post #35 of 38 (permalink) Old 12-18-2012, 03:41 AM Thread Starter
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Regapped one of my plugs to right at .8mm. Messed with the mixture screws again and have 'em right at around 2 turns out.

Bike starts right up on a 50-degree day and picks up on the enrichener very nicely. I'll leave it on the enrichener for a half a mile and then push it in and the bike will settle into a nice steady idle.

Still stumbles now again with hesitation at part throttle, but it's running much much better.
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post #36 of 38 (permalink) Old 12-18-2012, 08:05 AM
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Keep in mind it wont reach normal operating temperature for at least 15 - 20 minutes and the odd stumble can be expected until then. It's no good setting the mixtures to run well with a cold engine or it'll be too rich when hot.
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post #37 of 38 (permalink) Old 12-18-2012, 12:08 PM
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Quote:
Originally Posted by luckyduck View Post
Still stumbles now again with hesitation at part throttle, but it's running much much better.

That's about where I'm at now as well. I have a spare igniter and P/U coil that I want to try for nits-n-giggles, but being wet/cold, not sure when I'll have an opportunity to do that. If I do, I'm still going to do one at a time so I can eliminate either one or both as possible causes.

Did you ever crack your alternator cover to check the gap on the P/U coil?

I'm just curious if either running Iridium plugs or simply indexing the plugs wouldn't take care of the occasional hiccup or stumble at dead stop idle.

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post #38 of 38 (permalink) Old 12-18-2012, 05:05 PM Thread Starter
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I've decided to wait on that job until my next oil change (in about 3000 miles).
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