Bog of Idle when choked won't run without choke

[gooch]

I have a 79 Special that I'm building. It's almost done just can't get it to run correctly.

A guy built a wiring harness for me and cleaned my carbs up really nice. So I know that's not an issue, my petcocks seem to be flowing pretty well, I even pulled one to make sure the screen wasn't clogged just for shits and giggles.

I'm running stock needle height, one over stock pilot and 2 over stock main with pod filters and straight pipes with some small emgo mufflers welded on.

Suggestions?

One thing I've read is there are good pod filters and bad pod filters, These were clean and newish when I got the bike from the PO but he doesn't remember where he got them from he said "probably Mike's"

 

[5twins]

If the pods resemble the K&N pleated style element, they're not what you want. Your needles should be leaned a step with the jets you're running. You think your carbs are clean but it sounds like they're not. It sounds like the pilot circuit is plugged. If it won't idle without the choke, that's the usual problem.

 

[gooch]

That's what I had been reading that the pilot was dirty but I've taken them out and cleaned them even after the guy that did the work for me cleaned them. I can see through them pretty well. But I'll hit them again.

The filters are cone shaped silver and pleated, like you said like a K&N. What's wrong with them?

 

[5twins]

The pleated style element disrupts the air flow and causes tuning problems. The foam UNI pods work best.

There's more to cleaning the idle circuit that just doing the jet. You have to make sure the passageways leading from the jet into the main carb bore are clear. If you remove the float bowl, on the bottom of the carb body next to the needle jet is a small pilot inlet hole. This is how the fuel/air mix from the pilot jet gets into the carbs .....

It comes out 4 little holes in the main bore. Three are clustered together around where the butterfly plate closes. These flow the mix directly from the pilot jet. The 4th is off to the side and comes from the mix screw. Some of the mix from the pilot goes to the screw then out that hole .....

Remove the mix screw then blow carb cleaner through the inlet on the bottom of the carb and make sure it comes out all 4 holes in the main bore. Cover the mix screw hole with a finger while doing this so the cleaner is directed out the hole in the bore.

 

[gooch]

awesome thanks!

 

[Rush]

Great, clear directions, 5twins. I'm going to go do that just to be on the safe side. Definitely can't hurt & it seems like such a common issue, might as well do it before trying to run the bike.

 

[5twins]

If you find any blockage, you can come at it from different directions by alternately blocking off different holes. Block off the mix screw hole and it's outlet into the main bore, and cleaner will come out just the 3 holes. Block the 3 holes and the mix screw hole and cleaner will come out only the mix screw outlet hole. Block all 4 holes in the main bore, blow cleaner in the mix screw hole, and it will come out the inlet on the bottom of the carb body. By alternating like this, most blockages can be cleared without the need to resort to poking or probing the holes.

When you're done with the carb cleaner, blow WD40 or some other mild solvent like kerosene through to flush the remnants of the cleaner out. If you're not sure you even have any blockage, like in your case, just use the WD40 1st to "test" the circuit. That will save you the flushing step if it is already clear.

 

[gooch]

Everything seemed to flow out as 5twins said it should. It should be all clean but still the same. Half choke idles ok with some popping, no choke dies, full choke races.

I'm so close to having this bike road ready after a year and this is the only hold up.

I appreciate all the help.

 

[Toast]

I had the same problem on an old honda...for me it was the air filters. Like 5 twins said...if they are attached directly to the carb, those K&N style filters disrupt the air flow. poor flow = lousy performance. there is a ton of info on them here. Velocity stacks, or different elements will likely help a ton.

Oh...and 5twins....AWESOME instructions

 

[gooch]

anyone think it could be valves?

which set of numbers do I use? I'm not sure which model number a 79 special is.

Tappets - model...inlet...exhaust
...XS1-B.....0.003"(0.076mm)...0.006"(0.15mm)
...XS2-650..0.006"(0.15mm)....0.012"(0.30mm)
...XSB........0.0024"(0.06mm)...0.004"(0.10mm)
...XSC-on...0.0024"(0.06mm)...0.006"(0.15mm)

 

[weekendrider]

The filters are cone shaped silver and pleated, like you said like a K&N. What's wrong with them?

These are the small round cones or the larger oval cones?
The small round ones have rubbers that block the air hole on the carb bell.
Pics help.

 

[5twins]

Yes, check your valves. Your model is an "SF" so use the last settings (.003" intake, .006" exhaust). Also make sure your mix screws are set at the proper spec. Starting point for your model is 2.25 turns out. Fine tune from there. Also make sure the idle speed screw is turned up enough. It could be something as simple as that - having that adjustment turned too low. Idle speed should be 1200 RPM when warm.

 

[gooch]

small round cones

 

[gooch]

Thanks everyone, mix screw has been adjusted, as has idle screw I've been wondering about these filters for a while. I had read when i first got the bike about how the rubber boot can block off inlets on the carb and spent some time trying to see if they do or not but could never really tell.

 

[5twins]

Yep, those are the junk ones, the worst of the worst. Try a quick test run without them and the bike just might run OK. Use those as pencil holders on your desk, that's all they're good for, lol.

 

[gooch]

I needed pen holders for my desk....I did run without them and it didn't make a difference. Like I said I had been wondering about them and tried without them

 

[gooch]

Deleted.

 

[gooch]

Carbs off and on, cleaned again, mix screw turned out to 4 full and in to 1 full. idle screwed dinked with, taped off the filters to see if it was too much air getting in and checked the valves for clearance. Still no progress.

 

[gggGary]

At least half of all carb problems are ignition problems tell us about that side.

Are the vacuum barbs capped off? if they are connected to the petcocks, take em off block em and use prime for running. see if anything changes.

 

[5twins]

Yes, I'm out of carb ideas, maybe it is something else like electrical.