Hard Starting

It is possible to flood it - I have done that in the invariable dillemma when the engine is warm-ish (to tickle or not to tickle.... hmmm...). I typically hold the throttle open a bit when I am cold tickling and stop immediately when the carb overflows. That way I know that a little bit of fuel has run into the cylinders.

If it is flooded, shut the fuel off, hold the throttle wide open, and the 3rd kick (back when I kicked it), it would start typically.

Do you have any vacuum leaks? I typically have the tighten the manifold fasteners a few times per season and after any ride of significant length.

What plugs are you using? I have a preference for platinum or iridium plugs - they seem to last forever and never foul.

FWIW

I'm no expert, but a couple of thoughts:
-Have you tried charging the battery, might be a discharge in the new wiring over time?
-How far out is the pilot air screw? With light throttle, the carbs will still be on the pilot circuit and initially introducing more air, might just be adjusted far too rich?

Derek Wilson said:

It is possible to flood it - I have done that in the invariable dillemma when the engine is warm-ish (to tickle or not to tickle.... hmmm...). I typically hold the throttle open a bit when I am cold tickling and stop immediately when the carb overflows. That way I know that a little bit of fuel has run into the cylinders.

If it is flooded, shut the fuel off, hold the throttle wide open, and the 3rd kick (back when I kicked it), it would start typically.

Do you have any vacuum leaks? I typically have the tighten the manifold fasteners a few times per season and after any ride of significant length.

What plugs are you using? I have a preference for platinum or iridium plugs - they seem to last forever and never foul.

FWIW

Click to expand...

Previously ran Champion N7YC or NGK BPR7ES, with non-resistor caps. When bike came back from shop, they'd replaced the cables & caps were 5kOhm NGK's, and fitted NGK BR8ES plugs...so was running 10kOhm total...but it was running and starting fine. I suspected maybe the lower temp plugs and higher resistance may have started fouling plugs faster, leading to the harder starts after only a week of test riding....so switched back to non-resistor plugs...but exactly same harder starts.
I've got some good suggestions to check into.

We've got a week of rain right now so not a lot of troubleshooting can be done for a bit.

Mart UK said:

I'm no expert, but a couple of thoughts:
-Have you tried charging the battery, might be a discharge in the new wiring over time?
-How far out is the pilot air screw? With light throttle, the carbs will still be on the pilot circuit and initially introducing more air, might just be adjusted far too rich?

Click to expand...

I give the battery regular top ups on a Battery Tender so it should be in good shape charge wise. Pilot screws are near they 1-1/2 turn out points...with some minor tweaking around there.

I would make note the positions of everything on the carb.

Then I would do it the old fashioned way: set slide heights with a drill bit at idle height, make sure they top out at same pull point at WOT, air screws 1 1/2 out. Start and warm up and do the fast idle air screw dance and then when that is happy do the idle speed adjustment, using both ears/hands behind exhaust till happy.

Does it start easy enough? Let it get cold. Does it start easy enough?

If so or not, recheck with you vacuum guage.maybe it is out?

You can always revert to your previous settings.

Just because the battery measures as fully charged and that you keep it topped up with a battery tender
does not mean the battery is good. How many amps does it measure under a load (e.g. with lights and
ignition on)? Better yet take the battery to a battery store and get it tested.

gortnipper said:

I would make note the positions of everything on the carb.

Then I would do it the old fashioned way: set slide heights with a drill bit at idle height, make sure they top out at same pull point at WOT, air screws 1 1/2 out. Start and warm up and do the fast idle air screw dance and then when that is happy do the idle speed adjustment, using both ears/hands behind exhaust till happy.

Does it start easy enough? Let it get cold. Does it start easy enough?

If so or not, recheck with you vacuum guage.maybe it is out?

You can always revert to your previous settings.

Click to expand...

When you release the twist grip from wide open, when you have no stop screws , you should only hear a single click when the slides hit bottom. If you hear a double click, wind the slides up to full throttle and check they are equal with your finger

acotrel said:

When you release the twist grip from wide open, when you have no stop screws , you should only hear a single click when the slides hit bottom. If you hear a double click, wind the slides up to full throttle and check they are equal with your finger

Click to expand...

Yup. I use my fingernail to feel for a snag.

acotrel said:

When you release the twist grip from wide open, when you have no stop screws , you should only hear a single click when the slides hit bottom. If you hear a double click, wind the slides up to full throttle and check they are equal with your finger

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Tornado, Al mentions a good trick here AND the ‘without stop screws‘ is important.

If you take them out you know they’re not set uneven, if the ARE set uneven then you're setting yourself up wrong from the start.

Remove them and ensure that the tiniest ‘off the stop’ throttle movement is the same for both. Then, when happy, re insert the stop screws and, again by feel, screw them in until they JUST touch the slides. Now you know that every partial turn will effect each slide evenely.

I would advise setting the slides up like this and forgetting the gauges just to get a known baseline, when it’s running great, use the gauges once again if you wish and record the difference.

Personally, on old Brits, I have never used vacuum gauges of any kind. Just getting the slides to be perfectly synchronised has always produced great running and starting (assuming all else is good). And it’s actually quite amazing just how much effect a little out of synch difference can make.

Out of synch slides have the biggest noticeable effect at very low openings / speeds and can convince you that you have something dreadful wrong with the bike!

As can fouled plugs. ALWAYS, ALWAYS, ALWAYS start a poor running / poor starting problem solving process with NEW plugs (not old ones you took out for some reason before and kept, but NEW ones).

I must have wasted months of my life chasing issues by not following the above! But I’ve learnt. And I’ve learnt that you can get dodgy new plugs too. I now buy plugs in boxes (ie 10 at a time) from a known good supplier (ie not freakin’ eBay).

Always start with new ones when problem solving, always try a second set of new ones if the first didn’t work, and always throw suspect / high mileage plugs away. If you leave a dodgy plug in circulation it will appear and torpedo your problem solving at the most unhelpful times !

“But they’re expensive” I hear you say. No they are not! And they are much cheaper than wasting hours / days / weeks chasing potential ghost gremlins.

Sermon over. Carry on.

Some background:

I hear the wisdom of the experienced. I was previously setting up my carbs as per those procedures, using drill bits and checking lift off and full open positions were as close as possible. This did work for me, got bike running fairly well. At some point I started getting an occasional slow return to idle rpms while out riding. Tried all kinds of things to resolve that, full carb strip and blow out pilots, new plugs, checking for free moving cables and slides etc etc. Even bought new premiers thinking my original sleeved carbs were the issue. Welp, the premiers would also occasionally hang at a higher idle. Got my carb tune guage and found one side had more vacuum than the other, despite being as close as I could make the slide opening/movement. So dialing in the vacuum balance via cable adjusting seems to have cured the return to idle issue. I guess the lesson here is the mechanical movement/opening of slides is not an exact way to achieve balanced vacuum/air flows. All kinds of other variables could affect flow rates through carb/manifold/combustion chamber, exhaust etc.
If may well be that I'm just not experienced enough to do the mechanical balancing effectively enough. The guage takes a lot of the mystrey out of what is happening. At least for me.

There is one problem on old twins using gauges: The crossover tube is not connected.

The pilot circuit starts near the bottom/rear of the bowl, goes up to the bottom up the body, makes a greater than 90 turn towards the engine, goes across the body to the front, makes a 90 turn to the center, goes though the pilot jet, then up into the throat. The gas doesn't want to be there due to gravity and the only thing that causes it to be there is vacuum. Without the crossover tube there is one vacuum "maker" for every two engine resolutions. With the tube, there is some vacuum every revolution which helps keep the pilot circuit full.

So, gauges can help you see if things are even, but they must not be connected when finally setting the idle mixture and speed.

marshg246 said:

There is one problem on old twins using gauges: The crossover tube is not connected.

The pilot circuit starts near the bottom/rear of the bowl, goes up to the bottom up the body, makes a greater than 90 turn towards the engine, goes across the body to the front, makes a 90 turn to the center, goes though the pilot jet, then up into the throat. The gas doesn't want to be there due to gravity and the only thing that causes it to be there is vacuum. Without the crossover tube there is one vacuum "maker" for every two engine resolutions. With the tube, there is some vacuum every revolution which helps keep the pilot circuit full.

So, gauges can help you see if things are even, but they must not be connected when finally setting the idle mixture and speed.

Click to expand...

Yes, this is my experience. When I'd set the off-idle balance on the gauges (by adjusting the cable lengths), then dropped to idle, I could tweak the idle balance (via stop screws), a bit. This at least gets the slide stops at an even air flow. But once off the gauges, the idle would then be higher than wanted, likely from the effect you describe...so I just touch up final idle from there without the gauges. Not been making mixture adjustment with gauges.

Fast Eddie said:

As can fouled plugs. ALWAYS, ALWAYS, ALWAYS start a poor running / poor starting problem solving process with NEW plugs (not old ones you took out for some reason before and kept, but NEW ones).

Click to expand...

And, check the gap! Norton specifies 0.023" to 0.028", Triumph specifies 0.025". I believe that the plugs specified always came set to 0.025" but some today come larger. A NGK set I recently opened were 0.035" - that's too much for Lucas coils. NGK plugs ending in -9 are gapped at 0.035", ending in -7 are gapped at 0.0275", they don't have 0.025" gapped plugs although -7 is within Norton spec.

Tornado said:

I didn't use a ColourTune, I used a Morgan CarbTune, which is a vacuum metering device using a solid slider pins for comparing vacuum btwn inlets rather than dial guages or fancy digital readouts.

View attachment 85694

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One of the best separate cylinder syncing tools I've seen. but still dependent on the ID of the tube diameter and the OD of the metal indicator slugs. Simple enough to take the reading, reverse the rubber tubes and see if there is a difference, in which case split the difference.

Best.

RoadScholar said:

One of the best separate cylinder syncing tools I've seen. but still dependent on the ID of the tube diameter and the OD of the metal indicator slugs. Simple enough to take the reading, reverse the rubber tubes and see if there is a difference, in which case split the difference.

Best.

Click to expand...

Yup, I did do this swapping hoses left/right in the past to convince myself the two metal rods were giving equivalent readings. They were the indeed. The older version of this carbtune device was setup with mercury instead of rods, just like a blood pressure meter in a doctors office. That had to be discontinued for environmental reasons, but the rods are a nice way to do the same thing. I believe this tool is essentially like the one MotionPro sells (perhaps that one used fluid though?), at more than triple the $80 I paid for the CarbTune Pro (two cylinder version, a 4 banger is also available).

Checked coil connection and added a ground line to head from the ign ground point on coil mounting bracket. Frame has recently been powder coated and not convinced that location is a good ground point to frame. Will run a direct line to battery soon.
Out riding today, three starts so far, first took 7-8 kicks again until I cracked throttle open then it went. Next start, semi warm, fired with 3 kicks, no throttle, third, cracked throttle and fired up first try.

Will get some more data points and report back.

OK two more starts, one with throttle cracked and immediate first kick fire up. Next start, two kicks no throttle and nothing, not even a pop. Cracked it and off she went.

In that case I'd crack the throttle every time and forget about it!! Do what the engine wants to do, not what people think it SHOULD do. If it's running well otherwise...

Tornado said:

OK two more starts, one with throttle cracked and immediate first kick fire up. Next start, two kicks no throttle and nothing, not even a pop. Cracked it and off she went.

Click to expand...

Sounds like you found the sweet spot. You can’t fix it if it ain’t broke.