Tickover when cold

[1340evo]

I wish I could put a video clip on here, but my bike has always done this and maybe you guy's know why?
So when I got it, with a V&H exhaust, after the engine re-build, with a new ignition, swapping the coil leads, with new plugs, with all new internals in the carb, with a new EV27 cam... so whats the problem?

What it does is fire ever spark on the front, but only every second spark on the rear. when its warm it's okay, just whilst on the choke? front bang, bang, bang, bang... rear pop, ..., pop, ..., pop..., take it off tickover and its fine, and runs real strong on both cylinders

I've had the manifold of so many times and now it has new seals so can't see it being a leak.

Got to say, I can hear this in other Evo's but not all... is it a CV thing maybe? or maybe cam overlap...

Don't think I have a fault as such, just curiouse why it does it. the problem it does give at warmup is the rear cylinder does not warm as quickly as the front.. is this why rears can leak on the base?

any thoughts?   

[1340evo]

I'm guessing this is 8 stroking on the rear, so the back pot on choke is getting a lot of fuel.
Also assume the choke probably feeds out the LHS as you look at it from the front so it's literally running backwards in the manifold.
Any thoughts on stopping this at all?

[Hossamania]

Just a thought, but try jumping the battery while starting cold to see if the extra juice helps it turnover better.

[1340evo]

No, it starts and runs fine for the first 10 sec's no problem, then if i leave the choke fully out it start running every 8th stroke on the rear with a pop... front is steady away.
I'll have to try putting the choke in more and holding it on the throttle maybe.
Sounds like the rear is over choking

[Hossamania]

You could try a compression test and leak down test on both cylinders to verify engine health.
Do you have compression releases?
Try swapping spark plugs.
Make sure the coil cover is not touching a plug wire if a Softail.
The choke doesn't feed more fuel into one cylinder over the other by design, if the rear is not firing the fuel it is due to some other factor rather than getting more fuel than the front.
When was the rebuild done?

[Hossamania]

Also, what kind of V&H exhaust? Most have a tendency to run a little off sometimes, especially at idle, low back pressure could cause a little reversion.

[1340evo]

Engine is fine, its just run in and everything checks out as it should. But as I say, it did it before re-build and its still doing it now. I've swapped the coil over, changed plugs, run with no cover on the coil etc.

I'm not sure how the CV carb ports the choke into the manifould, if it's one side and I'm getting slugs of fuel I can see how that might just go into one cylinder. also with a EV27 cam do you get overlap that could mess things up at low speeds?

I've replaced everything in the carb but not sure if anyone has had a go at the choke for what ever reason.

I have the separate V&H pipes straight shots so I know that does not help, but can't see it impacting tickover? I run with the baffles in to give some backpressure.

[Hossamania]

The choke does not favor one cylinder over the other. The cylinders share the common port fed from the carburetor, fuel into the cylinders is pulled by the vacuum created the piston. Technically it is not a choke, but an enrichener, adding more fuel rather than restricting air as a choke does.
Have you changed plug wires? Have you tried a new coil? Is it the stock dual fire ignition? If so, you could swap the leads in the plug wires.
I have a feeling the exhaust is the culprit. If a stock exhaust were installed you may find the issue resolved.

[JW113]

It's hard to tell exactly what you're doing at start up. Here is what I do.

A: Pull choke knob out full - DO NOT touch throttle
B: Turn ign on, hit starter button
C: After bike fires, push choke in about 1/2 way, keep engine speed above 1300 or so with throttle in needed.
D: After 15 sec or so, push choke in until it pinches the tip of my finger against the bracket, maybe 1/8 choke? Keep engine speed high, above 1300 or so.
E: After another 15 sec or so, hit the road, and push the choke in all the way. Keep engine running on throttle until it warms up.

Both cylinders share the same carb/choke, but the dwell time between the front & rear intake cycles is quite different on a 45 deg V twin, 315 deg vs 405 deg, a whopping 90 deg. This means the fuel has more time to fall out of suspension on the 405 deg cycle than the 315, which means that the front one runs leaner than the rear. This is not really a problem at high RPM, but at low RPM, it's a definite phenomenon. Potato, potato, potato of the HD vs. bop bop bop bop bop bop of a Triumph vertical.

 

-JW

[1340evo]

I think thats the problem. On choke its either getting more due to where the CV oulets when on choke, or as you say its that rich its falling out of the air on the rear and needs 8 strokes to get enough oxygen.
Can you adjust in the carb how much a full open choke delivers?.. maybe its been opened up?
I'm not sure I'd keep it running if I did as you say on start up so maybe with the choke in I have it a bit lean.

I think Hossamania may also have a point with the open pipes and may be worth trying some lollipops again but I'm not sure how much they will impact lower revs.

I'll take it of choke sooner and see what happens... still running 180 / 45 with the N65C

[JW113]

What are V&H straight shots? Drag pipes?

-JW

[Hossamania]

What are V&H straight shots? Drag pipes?

-JW

Basically, but a larger diameter I believe, 2" as opposed to 1 7/8" on traditional drag pipes.

[xlfan]

Voltage drop at rear spark plug when cold idle low? I have often wondered if the coil can cause this, or if it just is voltage drop due to too low idle. Å

[1340evo]

yes and no, maybe a middle house.

They have std size headers and open up into the straight tube are with baffles fitted in the end....

But would this cause isses at tickover? obviously there is no link pipe....

[1340evo]

Voltage drop at rear spark plug when cold idle low? I have often wondered if the coil can cause this, or if it just is voltage drop due to too low idle. Å

Dont think its electrical as everything is replaced and I'm sure it would have a harder time as RPM is increased... It ticks over about 1000 rpm and is charging fine

[JW113]

Basically, but a larger diameter I believe, 2" as opposed to 1 7/8" on traditional drag pipes.

OH. Even better.
 

Drag pipe are notorious for running "well" only at full throttle and high RPMs. As in, like, at the drag strip? Getting a carb tuned with drag pipes is almost futile, at least at anything under WFO. I know, I know, some guys claim they they can tune them perfectly for all possible throttle positions and RPM ranges and weather conditions. Not my experience, I gave up and went to more conventional exhaust with mufflers, but who am I? If you're only complaint is at start up, consider yourself lucky.

-JW

[JSD]

What are V&H straight shots? Drag pipes?

-JW

V H long shots are 1 3/4 primary into 2 1/4 with a spiral baffle. they also have a small Equalizer linking the headers. V H short shots are pretty much a drag pipes but not equal length. 

[Hossamania]

What are V&H straight shots? Drag pipes?

-JW

V H long shots are 1 3/4 primary into 2 1/4 with a spiral baffle. they also have a small Equalizer linking the headers. V H short shots are pretty much a drag pipes but not equal length.

My longshots did not have an equalizer crossover pipe. Maybe the newer models do.
I also ran traditional drag pipes for a number of years on my 88" Twin Cam, no baffles. My riding style made them work just fine, no motor lugging, it ran well. But LOUD. They are not for riders that like to putt through town lugging the motor or riding two up chugging through the hills.

[1340evo]

What are V&H straight shots? Drag pipes?

-JW

V H long shots are 1 3/4 primary into 2 1/4 with a spiral baffle. they also have a small Equalizer linking the headers. V H short shots are pretty much a drag pipes but not equal length.

My longshots did not have an equalizer crossover pipe. Maybe the newer models do.
I also ran traditional drag pipes for a number of years on my 88" Twin Cam, no baffles. My riding style made them work just fine, no motor lugging, it ran well. But LOUD. They are not for riders that like to putt through town lugging the motor or riding two up chugging through the hills.

I love the pipes and the way they look, it's how HD used to look so don't want to go 2:1...
I know you can get a dip mid range but got to say I'm more than happy with the rest of the performance, its just the cold start and this issue.. Not a show stopper, just wondered why??

As I say above, I have noticed it on other bikes when people post on you-tube etc... ??

[Hossamania]

As long as it runs good once you start moving, all good to go!

[1340evo]

My AFR sensor kit will be here soon and I can confirm then how close I've got it