74 Honda XL 350 - The Turd

irk miller

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advCo said:
A/F is about 3/4-7/8 turns out. I’m using the stock cage in the airbox, just UNI foam to replace the original element.
Oh shit, that's probably your issue. The further in the mixture screw the more rich the mixture. You have that set really rich. It should be about 1.5 turns out.
 

irk miller

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advCo said:
That’s what the manual calls for with stock setup.


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You don't have the stock setup. You have a Uni filter amongst other things, including a rebuild. Use those numbers as a guide. It's clearly rich, so those numbers may be hardly relevant. There are all kinds of specs throughout the motor that have changed. Also, as Trek pointed out, factory numbers tend to be on the rich side anyway for cooling. Also, don't forget things change according to atmospheric pressure, humidity and whatnot. There's no such thing as a universal setting.
 

irk miller

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I assume you have this carb...

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Make sure your air cutoff is functioning properly, is complete, and is assembled correctly. It will prevent air mix if it’s wrong, and low vacuum will fuck it up too.

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1: air from atmosphere
2: valve that allows air to air mix circuit. Normally open by spring pressure.
3: opening to fuel/air mix circuit. There must be a good o ring here.

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4: Opening to intake. Vacuum here closes the valve (2) and blocks air to fuel/air mix.

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5: this nipple must face out. It opens the valve (6) here:

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This system can be eliminated as long as you still provide access to atmosphere.


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adventurco

Nick Ol' Eye
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Yeah. I have that carb. I just rebuilt the ACV (i had it blocked off previously) because I had a hunch that it was screwing with the A/F mixture. When I get a minute I'll pull it off and make sure everything is assembled properly.
 

adventurco

Nick Ol' Eye
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Ok I started with the basics. Cam chain and tappet adjustment. Haven’t touched the valves since rebuild so they were a bit too loose from heat cycling a few times. Cleaned some of the carbon off the plug and she fired up first kick, running strong.

Did a handful of laps around the yard and all seemed good. Once I got it nice and warm I parked it and started to set the mixture. Seemed to be most comfortable at about 1-1/8 turns out. Shortly thereafter heard the same sound as the first time this happened, almost sounded like a quiet backfire. Bike died and started doing the same deal misfiring and won’t idle now.

Possibly coil failing? Advancer malfunctioning? Running out of ideas.


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adventurco

Nick Ol' Eye
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Points were clean as a whistle. I ordered the OEM coil/condenser setup from Honda. It’s a bit spends but should eliminate any questions regarding that bit of the ignition.


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adventurco

Nick Ol' Eye
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cxman said:
mine starts good takes 1-2 in good weather

3-4 in the cold but it starts

If I put a fresh plug in it right now, it would fire up first kick. I need to figure out why it keeps fouling.
 

2strokeTRush

New Member
advCo said:
If I put a fresh plug in it right now, it would fire up first kick. I need to figure out why it keeps fouling.

Retarded timing will foul a plug due to improper burn of the fuel mixture. Worth a shot!
 

adventurco

Nick Ol' Eye
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Today I installed an OEM coil and condenser so I can rule that out of the list of potential issues. I put a fresh plug in and got her fired up.

9ed9d6b003093c9b2113d9f972bbf177.jpg


With the strobe on it, the timing appears to not be advancing correctly, or at all. The strobe flashes at the same exact point whether the bike is at idle or revved up to 4k RPM.

I think that after I clipped one of the springs on the advancer due to it being too lose, it in turn caused too much resistance and is not allowing the advancer to function properly.

I’m going to grab a used advancer and see if that clears up the issue.
 

irk miller

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That makes sense, homie. We've been saying all along that it sounds like retarded timing.
 

cxman

Over 1,000 Posts
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make sure you have the right bolt and belleville washer holding the atu in

if you have the wrong hardware it will bind the atu and stop it from advancing and returning with teh springs
 

adventurco

Nick Ol' Eye
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The hardware is correct.

For whatever reason, I couldn’t get a good reading with the strobe before I replaced the coil/condenser. So that may have been a contributor as well.


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irk miller

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Have you tried to advance it by hand just to make sure it's free and is the cam greased? One coil shouldn't make it that tight, unless you misread how many coils you did and took more.
 

adventurco

Nick Ol' Eye
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irk miller said:
Have you tried to advance it by hand just to make sure it's free and is the cam greased? One coil shouldn't make it that tight, unless you misread how many coils you did and took more.

It’s free and greased. I only took the one coil but it’s pretty damn stiff. Way stiffer than it should be.
 

adventurco

Nick Ol' Eye
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I'm getting closer to dialing it in. Its still fouling plugs but I think the Supertrapp is the culprit. ANYWAYS, I had it out for a romp last week and got some photos. This thing is an absolute hoot to ride.

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