Starting on 2-3 Cylinders, Fine After That

[D0wn5h1ft]

So I've got a peculiar problem. When I got to start my bike I throw the choke out all the way and I have to open the throttle about 1/4 to get it to start. When it does I leave it idling (still full choke) and it take about 15-20 seconds before all the cylinders start firing. It seems like on initial start up I'm missing at least one (either #3 or #4) because not only is it an audible change when it start firing but the exhaust pressure changes (held my hand next to the right hand side pipe).

I'm rocking the 4-2 headers with now baffled pipes. After those initial 15-20 seconds it purrs right along and I don't have any issue with it. It even behaves like it's supposed to on choke (full choke RPMs increase, then down to half until they increase, then no choke for normal idle once it warms up a bit). It's just weird having it only start on 3 cylinders almost every time from a cold start.

The carbs have been cleaned VERY thoroughly. All new jets, seals (butterfly seals included), idle screws + washer + o-ring, everything has been gone through (if any of you remember from previous threads).

I'm not really sure what the deal it but I'm guess once of the cylinders is starving for fuel for a second and then after that everything goes fine. Also, these have been vacuum synced.

[CaptonZap]

Are the plugs new?

CZ

[oldyam80sg]

When you start the bike-spritz the pipes-even on choke-when they sizzle that will give you an indication if all 4 are firing.

[trbig]

Didn't read the carb cleaning thread you speak of, but I'm betting the little jets that are in your carb BOWLS are plugged on a couple.

[jjz28]

Didn't read the carb cleaning thread you speak of, but I'm betting the little jets that are in your carb BOWLS are plugged on a couple.

This is what I was thinking. I had the same issue and it was the little hole in the bowl itself that was plugged up. That is where the enricher (choke) gets its fuel for initial startup.

[Eastcoaster]

I am with you both on the small holes in the bowl that feed the enrichners.
They can be tough to clean out lots of compressed air a few I needed a wire. I always blast with carb cleaner with the small red hose not satisfied till its blasting through the bowl

[wingnut]

When you set up the carbs were your float levels dead even with each other?

[D0wn5h1ft]

Are the plugs new?

CZ

Pretty new, less than 400 miles on them. VERY strong spark on all with the dynateks I have. It can jump a 3/4" gap when holding them away from the engine.

When you start the bike-spritz the pipes-even on choke-when they sizzle that will give you an indication if all 4 are firing.

Unfortunately, the problem doesn't persist long enough for me to do that. It only happens for 15-20 seconds and that combine with my header wrap makes it difficult to do a heat test. I'm thinking if I pull one of the #3 or #4 spark plugs that if the bike goes dead it's the other cylinder because that will be the one that is firing vice versa.

Didn't read the carb cleaning thread you speak of, but I'm betting the little jets that are in your carb BOWLS are plugged on a couple.

I'm not sure I'm familiar with the little jets you're speaking of. I have late model 1980 carb bodies on this one. Are you talking about that little brass tube that protrudes out of the carb body and into the bowls? Also, I'm not sure how they could have gotten plugged. The carbs were dipped and completely broken down and cleaned when I did them. The nets are all still intact on the float seats and the gas tank has been completely refurbished (de-rusted and sealed). It's only been 2-3 months since the carb overhaul and it hasn't sat for more than a week without running. I will blow some carb cleaner through there even though it was just done about 2 weeks ago when I bumped up my mains.

[D0wn5h1ft]

I pulled the #3 plug cap while it was in this "weird" period and that's definitely the cylinder not firing on start up.

[GLoweVA]

I'm not sure I'm familiar with the little jets you're speaking of. I have late model 1980 carb bodies on this one. Are you talking about that little brass tube that protrudes out of the carb body and into the bowls? Also, I'm not sure how they could have gotten plugged. .

The brass tube goes down into the carb bowl and at the bottom of the hole in the bowl is a little orfice that can get clogged and that's where the choke circuit gets its fuel.



Just be careful when spraying carb cleaner in there. IT WILL SHOOT BACK AND GET YOU IN THE EYE! DAMHIK. BTDT.

[D0wn5h1ft]

The brass tube goes down into the carb bowl and at the bottom of the hole in the bowl is a little orfice that can get clogged and that's where the choke circuit gets its fuel.



Just be careful when spraying carb cleaner in there. IT WILL SHOOT BACK AND GET YOU IN THE EYE! DAMHIK. BTDT.

I have known few pains like getting hit in the eye with a stream of carb cleaner while wearing contacts. The best part is all you can do is wait for it to evaporate and hope the tears clean it out...

[flyingdakota]

My bike, after sitting a long period will do this. I have now since turned it to PRI on the fuel selector and let it sit a few seconds before I attempt to start. Seems to start easier. I was thinking that it needed to get the fuel to the carb because it evaporated out of the bowl(s)....I could be wrong...haven't cleaned the carbs in forever either. She starts every time though!
Cheers!
Tim