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Message started by DrunkenDwarf on 08/29/10 at 17:37:49

Title: Carb Confusion, Pt 2
Post by DrunkenDwarf on 08/29/10 at 17:37:49

I went hunting for intake/exhaust leaks today using my daughters bubbles. Nothing found. It was interesting to feel the pulse of the engine in the rubber cap I used to cover the vacuum port on the carb. I had never noticed that before.

Removing the vacuum tube and running on prime has two pronounced effects. First, the engine idles faster. Second, the pop on shutdown is louder. I'm not sure if that means it's leaner or richer than it was before. Any ideas? General performance is about the same. I'll fill up with gas tomorrow and see what my mileage looks like.

About a week before I removed the vacuum tube I also switched from a 55 pilot to a 52.5. I don't recall that switch having an effect on idle rpm or shutdown pop. If it did have an effect on the shutdown pop, it has gotten worse without the vacuum tube.

When I shutdown after hunting for leaks the was no pop. The engine was warm enough for me to have pushed the choke in, but not fully warmed up. I expected a very loud bang at shutdown. Can anyone explain this?

One last question, I'm not sure if it's related.
How long does it take for your engines to get up to operating temperature? I generally ride about a mile with the choke out 1 notch, then 4-5 miles at 35-45 mph before the lean surging goes away. Is that normal?

I really need to mark throttle positions. The surging I'm talking about happens the most pronounced in 3rd gear at 35mph. I think that's in the 1/8 to 1/4 throttle range.

The reason I'm still poking at the carb is because of the POP I get on throttle close. Same type of pop I get coming off the freeway and engine braking. It happens more often when I shift at higher rpms. For example shifting 2->3 at 20mph generally produces no pop, while 2->3 at 30mph generally pops.

Thanks for all of the advice.

-D. Dwarf

Title: Re: Carb Confusion, Pt 2
Post by justin_o_guy2 on 08/29/10 at 17:44:33

Gotta p[lug the carb where the vac line hooks up when its off the petcork.

Title: Re: Carb Confusion, Pt 2
Post by DrunkenDwarf on 08/29/10 at 20:32:44

584741465B5C6D5D6D55474B00320 wrote:

Gotta p[lug the carb where the vac line hooks up when its off the petcork.

I did. The one on the petcock too.

-D. Dwarf

Title: Re: Carb Confusion, Pt 2
Post by verslagen1 on 08/29/10 at 21:15:00

7871747D677074150 wrote:

I don't think you'll find an intake leak with bubbles unless you can see from inside.

Title: Re: Carb Confusion, Pt 2
Post by verslagen1 on 08/29/10 at 21:18:32

71787D746E797D1C0 wrote:

Removing the vacuum tube and running on prime has two pronounced effects. First, the engine idles faster. Second, the pop on shutdown is louder. I'm not sure if that means it's leaner or richer than it was before. Any ideas?

pop on shutdown says lean.
idling faster generally means air leak.

Title: Re: Carb Confusion, Pt 2
Post by verslagen1 on 08/29/10 at 21:27:58

6861646D776064050 wrote:

The reason I'm still poking at the carb is because of the POP I get on throttle close. Same type of pop I get coming off the freeway and engine braking. It happens more often when I shift at higher rpms. For example shifting 2->3 at 20mph generally produces no pop, while 2->3 at 30mph generally pops.

engine braking it's quite normal to get a grumble pop.
but a shift pop is usually a exhaust leak at either the header or muffler clamp. use a candle to hunt these down. the flame will flicker.
or it could be an adjustment, your idle speed could be too low, and you compensated with idle mixture.

Title: Re: Carb Confusion, Pt 2
Post by DrunkenDwarf on 08/30/10 at 08:27:20

706374756A6761636837060 wrote:

I don't think you'll find an intake leak with bubbles unless you can see from inside.

You don't think the pressure wave in the intake is strong enough to push out if there was a leak? I can feel the pulse in the rubber cap I used to plug the vacuum port. It seemed strong.

2F3C2B2A35383E3C3768590 wrote:

pop on shutdown says lean.
idling faster generally means air leak.

So, by removing the vacuum line and plugging the intake to the carb I created a vacuum leak? Or just increased the symptom?

3F2C3B3A25282E2C2778490 wrote:

I'm not concerned about the engine braking pops. It's the ones that happen when I shift that I'm working to minimize.

I've looked for exhaust leaks, haven't found any. I'll check the idle speed. It's higher than it was before, maybe it was too low.

I figured out why it doesn't backfire when the choke is out. The RPMs don't drop as quickly when I close the throttle.

-D. Dwarf

Title: Re: Carb Confusion, Pt 2
Post by justin_o_guy2 on 08/30/10 at 09:25:32

I figured out why it doesn't backfire when the choke is out. The RPMs don't drop as quickly when I close the throttle.

Well, yea, thers that, but its richer, too, so, thats another variable to consider.

Title: Re: Carb Confusion, Pt 2
Post by DrunkenDwarf on 08/30/10 at 10:05:55

5F4046415C5B6A5A6A52404C07350 wrote:

Quote:

I figured out why it doesn't backfire when the choke is out. The RPMs don't drop as quickly when I close the throttle.

Well, yea, thers that, but its richer, too, so, thats another variable to consider.

Right.

With the choke out it's too rich to idle smoothly, but runs well otherwise. Maybe I need to change the main jet up a size (or reduce washers). I've been avoiding changing jets (more) until all leaks are found.

-D. Dwarf

Title: Re: Carb Confusion, Pt 2
Post by bill67 on 08/30/10 at 10:42:50

Go up on the high speed jet and you'll get more power too.

Title: Re: Carb Confusion, Pt 2
Post by justin_o_guy2 on 08/30/10 at 10:45:27

This is why I call myself an 80% mechanic. Im just not the guy to get that laaaast bit of tuning done. Ill get it running "allright" & call it good. I just dont want to deal with spending the time figuring out what to do next & how to do it. I KNOW Ill waste a ton of time & someone else with the experience to be able to listen to it & look at the plug & know whats the next logical step to take would walk right thru. Im not ready for that learning curve. The electrode on the plug is white & ashen looking, & the ceramic on the outter ring is dark, so IDK if its rich or lean er Wuttt! But, Ive got soot on the brake lever,,, maybe one day Ill take it up the street to the machine & hook it up..Its 100 bux for the first run & 10 for the rest.

Title: Re: Carb Confusion, Pt 2
Post by babyhog on 08/30/10 at 11:03:12

Engine operating temp -- I pull my choke out to start the bike, let it run about 30 seconds, while I put on my helmet, then push in the choke. Takes me maybe another 30-60 seconds to get it turned around in the garage. Then I'm off. Feels fine that way to me, unless its much colder outside, say <55°.

Title: Re: Carb Confusion, Pt 2
Post by DrunkenDwarf on 08/30/10 at 17:18:48

I should just give up. Today into work it was 60 F and 90% humidity. On the way home it was 90 F and 60%. No pop on shift either to or from.

The changes I made from 'baseline' were:
pilot 55 (1 turn out) to 52.5 (1.5 turns out)
removed vacuum tube

It ran better on my way home, so I assume I'm still lean. The bang on shutdown agrees. I'll try 2 turns out tomorrow and see how that does. That puts me back where I started, except for the vacuum tube. I'll have to pull the cap off the vacuum port on the petcock and see if it's collecting gas.

-D. Dwarf

Title: Re: Carb Confusion, Pt 2
Post by DrunkenDwarf on 08/31/10 at 05:25:48

Maybe it's me? 8-)

If I'm heavy on the throttle, I get the POP on shift. If I'm gentle, it doesn't.

Anyway, at least I didn't stop riding. :D

-D. Dwarf

Title: Re: Carb Confusion, Pt 2
Post by ralfyguy on 08/31/10 at 18:38:25

Mine behaves the same way, and regardless of what setting I was trying it never went away. The same with the poofs on shutdown. It sometimes does, and sometimes doesn't. Sometimes a slight very subtle poof, sometimes a louder poof, almost a bang, but not like a gunshot. When i ride to work in the morning, which only 1.2 miles, it does an audible poof when I turn it off. At lunch when I go home, riding almost the same way it doesn't do it. It might have to do with having to ride up a slight hill, and that gets the exhaust hotter than driving with less strain. IDK. It definately changes with weather/temperature/humidity. In summer it's alot more often than in winter. Being easy on the throttle and shifting then doesn't do a pop most of the time. Getting on it and shifting produces pops almost every time.

Title: Re: Carb Confusion, Pt 2
Post by DrunkenDwarf on 08/31/10 at 21:08:08

Thanks ralfyguy. Good to know I'm not the only one.

What jetting are you currently using?

I'm going to try to dial in the 52.5, but I'll probably go back to the 55 to try to reduce the wonkiness at 1/8 to 1/4 throttle.

I'm hesitant to reduce the needle spacer to 1mm. That's the other option.

-D. Dwarf

Title: Re: Carb Confusion, Pt 2
Post by ralfyguy on 09/01/10 at 04:35:15

I run the 145 stock main and the 52.5 pilot, but with bleed holes. I tried the 55 pilot, but it was too rich. I have stock air filter and stock exhaust, but the baffle removed. I tried a 150 main, but it was too rich with plug fouling. I replaced the white spacer with 3 washers from Lancer's kit. Brings it down to 2/3. If your 55 pilot doesn't have bleed holes, try one of those.

Title: Re: Carb Confusion, Pt 2
Post by DrunkenDwarf on 09/01/10 at 07:59:47

I've tried 55 w/ holes and 52.5 w/ holes. I'm currently using the 52.5. It's been hotter than normal this week (it's always very humid) and I've dialed in the idle at 1 1/2 turns (plus or minus 1/4 turns). The shutdown WUMP is pretty significant, but not quite to BANG levels.

I don't want to mess with it too much until the weather cools off. Hate to end up too lean when it's 40 degrees cooler out.

I also need to find someplace to test the main jet. I've had mediocre success with the standard roll-off test.

-D. Dwarf

Title: Re: Carb Confusion, Pt 2
Post by ralfyguy on 09/01/10 at 09:52:10

Maybe 1 1/2 turns isn't enough. Did you try the correct method with were the idle runs the highest? The sweet spot on mine seems to be 2 turns out. And then I turned it out another 1/4 turn, just when the idle wants to start going down again, because I want it a tad on the rich side. When I had the 55 pilot I had to turn it all the way in and it was still too rich. That's why I put the 52.5 back in.

Title: Re: Carb Confusion, Pt 2
Post by DrunkenDwarf on 09/01/10 at 17:17:28

667578726D73616D140 wrote:

I don't know if it's correct, but here's what I did.

Rode to work. About 9 miles total, about of it is 4 highway. Stopped in the parking lot.
Adjusted the screw out until it the engine slowed a lot. 2 1/2 turns
Adjusted the screw in until the engine slowed a lot. 1/2 turns
Adjusted the screw out until the engine slowed a little. 2 turns
Adjusted the screw in until the engine slowed a little. 1 turn

Adjustments were in 1/2 turn increments. The difference between 1, 1 1/2, and 2 turns is very subtle.
It was roughly 70 F and 70% humidity at the time.

Maybe it'll turn it out a 1/4 turn tomorrow and see if there's a response.

-D. Dwarf