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Author Topic: Engine/tuning issues  (Read 1957 times)

LarsBloodbeard

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Engine/tuning issues
« on: October 29, 2012, 02:17:06 AM »
When I slowly crank over my engine it blows a fair amount of air out the carb right after intake.  It does close fully and has good compression (can stand on the kicker and it supports my 250lbs).

ace.cafe suggested the cams might be off a tooth.  Pulled the timing cover.  Looks fine, except some rust and the oil in there was really watery and green for some reason...

I'm wondering if maybe the intake pushrod is getting hung up.  Don't know where else to look, really.  The pushrods are adjusted right.  When cold they will rotate by hand, but not move up and down (checked 4 times).

Edit: changed title to match how this thread progressed.
« Last Edit: November 04, 2012, 08:58:54 PM by LarsBloodbeard »

ace.cafe

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Re: Intake not closing soon enough?
« Reply #1 on: October 29, 2012, 02:09:00 PM »
If it's doing it just during the very slow kicking procedure, that isn't necessarily indicative of a real problem because the engine activity is too slow. Any closing of the intake valve after BDC could cause that in a very slow engine rotation, and all engines close their intake valve after BDC.
It only matters if it's doing it during running.

The other possibility you might see during idling is exhaust related. If you have an exhaust pressure wave reflected back up the exhaust pipe, that arrives at the cylinder during the overlap period when the intake valve is open, it can cause a reversion up the intake tract like that. Typically you can see this reversion as "stand-off", which is a little mist cloud of fuel-atomized vapor standing still outside the mouth of the carburetor during idling. This is commonly seen when people run "straight pipe" exhausts.
Usually you can cure this with a wave-breaker, such as a muffler with baffles, or a megaphone, or something like that. Preferably one that changes the overall length of the exhaust system too.
« Last Edit: October 29, 2012, 02:14:39 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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Vince

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Re: Intake not closing soon enough?
« Reply #2 on: October 29, 2012, 04:27:52 PM »
      Check your ignition timing.

LarsBloodbeard

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Re: Intake not closing soon enough?
« Reply #3 on: October 29, 2012, 04:48:07 PM »
I have the stock exhaust.  It actually idled really, really nicely without the silencer on (only the header) when I briefly started it for testing purposes.  So it could be that it's too restrictive.

How do I adjust the ignition timing on this bike?

2002 Bullet 500 ES (now 535), btw.

barenekd

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Re: Intake not closing soon enough?
« Reply #4 on: October 29, 2012, 05:41:55 PM »
See PM
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LarsBloodbeard

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Re: Intake not closing soon enough?
« Reply #5 on: October 29, 2012, 06:02:34 PM »
Don't know if you got my PM, it said it had a server error when I sent it.

Anyway, I will check whether it's 180 degrees out and adjust the ignition timing/gap.  I have a TDC finder, so it makes that fairly simple.  Timing cover is still off too, so I can see where the cams are at.  I will try this tonight and see how it goes.  I just wasn't sure where to set the gap.  I'm used to adjusting ignition timing with a timing light.

Spark did look slightly weak (though acceptable), so I think I'll buy one of those Bosh coils from nfieldgear just for the heck of it.

Here's a vid of it.  I had the throttle open, then backed down so as to capture it sneezing without it just dying.  http://youtu.be/4d36ZX4BRnw

Excuse the poor quality, I sprayed wd-40 in the carb to help start it (jetting was too lean --now fixed) and kicked it, while filming.  I really needed 3 hands for that.  Then when it died I tried the ES, which sucks, before finally kicking it again... didn't realize the camera was still rolling.

ace.cafe

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Re: Intake not closing soon enough?
« Reply #6 on: October 29, 2012, 06:12:44 PM »
If it was 180 out, it wouldn't be running.

I think you just have a tuning issue.
You have a very restrictive exhaust silencer on there, which is about like a potato in the pipe. If it ran well with the open pipe, then it's going to run like shit with that muffler on it.
Try unscrewing your air bleed screw a half turn, and see if that helps it.
I think you're just too rich with that muffler on it.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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barenekd

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Re: Intake not closing soon enough?
« Reply #7 on: October 29, 2012, 07:41:33 PM »
Yeah, seeing the video, the timing isn't that far off. Go with Ace's recommendations. Pull the muffler first and see what happens.
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LarsBloodbeard

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Re: Intake not closing soon enough?
« Reply #8 on: October 29, 2012, 07:57:44 PM »
If it was 180 out, it wouldn't be running.

I think you just have a tuning issue.
You have a very restrictive exhaust silencer on there, which is about like a potato in the pipe. If it ran well with the open pipe, then it's going to run like shit with that muffler on it.
Try unscrewing your air bleed screw a half turn, and see if that helps it.
I think you're just too rich with that muffler on it.

Sorry, meant 360 degrees. 
I didn't say it ran well without the silencer.  Any amount of throttle would kill it... but it did idle very smooth and consistently.  Heck, I'd leave the silencer off if the header would stay put without it and I wasn't afraid of damaging the valves.

I've adjusted the hell out of that carb with the exhaust on now... including changing jets.  Haven't messed with the needle position though.  I really should check the timing anyway, so I'll give that a crack tonight.

I still think it's really bizarre that the intake stays open so long, but if you guys say that's nominal, then I trust you.

ace.cafe

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Re: Intake not closing soon enough?
« Reply #9 on: October 29, 2012, 08:31:35 PM »
The spec for the intake closing is 60 degrees After Bottom Dead Center.
That's not really a very late timing.
We use 78 degrees ABDC for the  Fireball, and it NEVER spits back. That's 18 degrees later than stock!

The problem with the Bullets is that they OPEN the intake too early, when the exhaust pressure is still high and the piston is still coming up on the exhaust stroke, and it pushes back up the intake system. The overlap triangle is way to wide on the stock bike, for it's state of tune. It's always been a problem.
« Last Edit: October 29, 2012, 08:33:58 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

Please visit my new website:
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LarsBloodbeard

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Re: Intake not closing soon enough?
« Reply #10 on: October 29, 2012, 09:29:39 PM »
That gives me more peace of mind.  Thanks.

Is the idle mixture purely controlled by the two screws on the outside and not any jets?

ace.cafe

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Re: Intake not closing soon enough?
« Reply #11 on: October 29, 2012, 10:03:49 PM »
That gives me more peace of mind.  Thanks.

Is the idle mixture purely controlled by the two screws on the outside and not any jets?

The idle mixture is set by the pilot jet and the air bleed screw, together. The pilot jet sets the amount of fuel and the air bleed screw sets the amount of air, for the idle mixture.
The large-headed thumbscrew is the idle speed adjustment, and all that does is lift the slide by small amounts to get the idle speed where you want it.

If you unscrew the air bleed screw, it lets more air in, making in leaner. If you screw the air bleed screw in, it lets less air in, making it richer. You have about 3 turns allowable movement from all-in to 3-turns out, with that screw. Outside that range, you need to change the pilot jet.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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LarsBloodbeard

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Re: Intake not closing soon enough?
« Reply #12 on: October 30, 2012, 03:42:30 AM »
Thanks for the tips, guys.  I adjusted the timing and it made a world of difference.  It now runs fairly decently, though it does need more tuning.  It could be smoother, and if I open the throttle quickly it will die. 

Check it out: http://youtu.be/N_RJs2u6RNA

After I get the higher flow silencer I might just take it to an expert for tuning, just to get some peace of mind.

baird4444

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Re: Intake not closing soon enough?
« Reply #13 on: October 30, 2012, 04:08:45 AM »
Timing seems still off a bit....  try opening the points just a bit. In the old country they often fine tune the timing by opening or closing the points. to open advances....   close = retard...
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« Last Edit: October 30, 2012, 04:38:59 AM by baird4444 »
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Vince

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Re: Intake not closing soon enough?
« Reply #14 on: October 30, 2012, 04:19:42 PM »
     If it dies when you open the throttle quickly, that is indicative of it being a big, long stroke single. At low engine speeds a quick blip of the throttle will drastically change engine vacuum, but there isn't enough air velocity through the carb for the carb to work. Gas won't be picked up through the jets so it runs lean and stalls. Learning to roll the throttle on will eliminate most of this.
     This feature is why car carbs had an accelerator  pump to pump in more fuel at low engine speed/large throttle openings. You can tune some of it out, but eliminating it requires an accelerator pump or jetting it so rich that you almost instantly foul plugs.
     When properly jetted you will never notice this issue with proper throttle technique.