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'96 VT1100 Shadow ACE
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Discussion Starter #1 (Edited)
Hello Everyone,

My bike is idling pretty badly, I've rebuilt the carbs with new jets installed according to the Honda Service Manual, checked for vacuum leaks around the carb boots, and done a few other things to isolate or fix the issue to no avail. So my next option was to check the timing.

I've been following the official Honda Service Manual for my model - as it calls for the removal of the timing cap while the bike is idling at normal operating temperature. The problem is that it begins to spew oil right out the hole while its idling, there's no way for me to check the timing with a gun without getting hot oil all over my face. Can someone tell me how they check the timing on their Shadow with similar specs?
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1983 Honda vt750 Shadow
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Drain the oil out and start it up. NOOO, just kidding.

Actually there is not much point in checking ignition timing since it is not adjustable anyway.
Nothing to change unless you put on some aftermarket timing processor.
And if it is timing chain wear and slack the ignition timing won't tell you that.

Look at your spark plug color.
Maybe squirt a little carb cleaner in each carb throat at idle to see if one will pick up. Still may be a carb jet problem.
 

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If you haven’t been into the engine, and the bike was running well previously, there’s not much reason to suspect timing. Did you clean the carbs completely when you re-jetted? What happens if you adjust your idle speed up?
 

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'96 VT1100 Shadow ACE
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Discussion Starter #7 (Edited)
Drain the oil out and start it up. NOOO, just kidding.

Actually there is not much point in checking ignition timing since it is not adjustable anyway.
Nothing to change unless you put on some aftermarket timing processor.
And if it is timing chain wear and slack the ignition timing won't tell you that.

Look at your spark plug color.
Maybe squirt a little carb cleaner in each carb throat at idle to see if one will pick up. Still may be a carb jet problem.
swifty2014 - Thanks for your reply,
I understand that the timing can't be adjusted, I just wanted to verify that the CDI/ICM is still working correctly by getting the appropriate timing without having to remove the ICM and test it with a Volt meter.
If you haven’t been into the engine, and the bike was running well previously, there’s not much reason to suspect timing. Did you clean the carbs completely when you re-jetted? What happens if you adjust your idle speed up?
The bike was running like absolute crap before I did any work to it. When I removed the tank, I immediately noticed that the rear carb's Diaphragm housing was being held by 1 screw to the point of falling off. Once I managed to remove the carb and start working on it I noticed several things:
1. The Choke plunger needles had different springs on them, and the choke lever on the handle bar was extremely hard to pull down.
2. The rear carb's diaphragm was ruptured because of the poor condition it was in (the housing was loose and held on by 1 screw)
3. The previous mechanic installed wrong Main Jets they were much leaner.(170 Main Jets on both carbs and 42s Idle Jets)
4. Some screws were hex others were phillips
5. Fuel float was way out of spec
6. Had aftermarket Main Jet needles (the needles had several notches for adjustment)

I did a complete overhaul on those carbs and cleaned them on an Ultrasonic Cleaning tank.

When I re-adjust the idle screw one way it begins to rev up consistently
When I re-adjust the idle screw the other way the rpms begin to drop, anything slightly below 1000 the idle gets a lot worse. The speedo spazzes out.
What RPMs?

Too low and it will idle poorly.
Yes, anything around the ballpark of 1100 RPMs, the bike begins to struggle
 

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1983 Honda vt750 Shadow
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Maybe a carb sync will help the strange idle speeds.
 

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swifty2014 - Thanks for your reply,
I understand that the timing can't be adjusted, I just wanted to verify that the CDI/ICM is still working correctly by getting the appropriate timing without having to remove the ICM and test it with a Volt meter.

The bike was running like absolute crap before I did any work to it. When I removed the tank, I immediately noticed that the rear carb's Diaphragm housing was being held by 1 screw to the point of falling off. Once I managed to remove the carb and start working on it I noticed several things:
1. The Choke plunger needles had different springs on them, and the choke lever on the handle bar was extremely hard to pull down.
2. The rear carb's diaphragm was ruptured because of the poor condition it was in (the housing was loose and held on by 1 screw)
3. The previous mechanic installed wrong Main Jets they were much leaner.(170 Main Jets on both carbs and 42s Idle Jets)
4. Some screws were hex others were phillips
5. Fuel float was way out of spec
6. Had aftermarket Main Jet needles (the needles had several notches for adjustment)

I did a complete overhaul on those carbs and cleaned them on an Ultrasonic Cleaning tank.

When I re-adjust the idle screw one way it begins to rev up consistently
When I re-adjust the idle screw the other way the rpms begin to drop, anything slightly below 1000 the idle gets a lot worse. The speedo spazzes out.

Yes, anything around the ballpark of 1100 RPMs, the bike begins to struggle
I see you didn’t mention an idle drop procedure after all the carb work. A must do. Then a carb synch is definitely in order.


Sent from my iPad using Tapatalk
 

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2000 Honda Shadow Spirit VT1100C
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swifty2014 - Thanks for your reply,
I understand that the timing can't be adjusted, I just wanted to verify that the CDI/ICM is still working correctly by getting the appropriate timing without having to remove the ICM and test it with a Volt meter.

The bike was running like absolute crap before I did any work to it. When I removed the tank, I immediately noticed that the rear carb's Diaphragm housing was being held by 1 screw to the point of falling off. Once I managed to remove the carb and start working on it I noticed several things:
1. The Choke plunger needles had different springs on them, and the choke lever on the handle bar was extremely hard to pull down.
2. The rear carb's diaphragm was ruptured because of the poor condition it was in (the housing was loose and held on by 1 screw)
3. The previous mechanic installed wrong Main Jets they were much leaner.(170 Main Jets on both carbs and 42s Idle Jets)
4. Some screws were hex others were phillips
5. Fuel float was way out of spec
6. Had aftermarket Main Jet needles (the needles had several notches for adjustment)

I did a complete overhaul on those carbs and cleaned them on an Ultrasonic Cleaning tank.

When I re-adjust the idle screw one way it begins to rev up consistently
When I re-adjust the idle screw the other way the rpms begin to drop, anything slightly below 1000 the idle gets a lot worse. The speedo spazzes out.

Yes, anything around the ballpark of 1100 RPMs, the bike begins to struggle
Can you explain in layman's terms what the term "the speedo spazzes out" below 1,000 rpm means? What does 'spazz out' actually mean in motorcycle or automotive terms?
 

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'96 VT1100 Shadow ACE
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25 Posts
Discussion Starter #11 (Edited)
Maybe a carb sync will help the strange idle speeds.
I did a bench sync on the carbs then I fine tuned it with a vacuum gauge kit.
I see you didn’t mention an idle drop procedure after all the carb work. A must do. Then a carb synch is definitely in order.


Sent from my iPad using Tapatalk
Edit: I did try to do one but I couldn't get the RPMs to stop rising after every 1/2 turn out, at some point they're suppose to reach a peak but they kept going up. I believe I hit 3 1/2 turns out on each mixture screw, at that point I didn't continue. Figured there could be a vacuum leak somewhere and tried using starter fluid around the boots and intakes... no leak.
Can you explain in layman's terms what the term "the speedo spazzes out" below 1,000 rpm means? What does 'spazz out' actually mean in motorcycle or automotive terms?
I suppose I was being a bit hyperbolic, so the arrow on the tachometer* goes up & down and bike shakes erratically.
*my mistake I meant tachometer not speedometer.
 

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'96 VT1100 Shadow ACE
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Discussion Starter #12
Earlier today I realized that the previous owner mentioned that he swapped the exhaust pipes for Vance & Hines aftermarket pipes. Would this require installing bigger Pilot and Main Jets?
 

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'96 VT1100 Shadow ACE
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Discussion Starter #13
If you haven’t been into the engine, and the bike was running well previously, there’s not much reason to suspect timing. Did you clean the carbs completely when you re-jetted? What happens if you adjust your idle speed up?
I did some tests on the bike an hour ago, as I turned the idle screw up the idle kept climbing more than the rate at which i was turning it. It caught me by surprise, so i let go of the screw and it kept climbing up.
 

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'96 VT1100 Shadow ACE
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Discussion Starter #14 (Edited)
Update!
I did more research into this and decided to re-jett the main jets on the carb with Front -180 & Rear -182 and did 45s on the pilot jets, and shimmed the diaphragm piston needles. I went with 45s so that I could give the screw more room to properly do an idle drop since my last attempt was not dropping even when reaching 3 1/2 turns out. (the RPMs continued to increase after every 1/2 turn out)
warmed up the bike just now and did the idle drop - it took 4 1/2 turns out on each mixture screw but the bike sounds incredible! its stable at 1000 RPMs, i've never heard her so quiet and serene like this!
So my conclusion is that there's a vacuum leak somewhere since it requires more fuel in the Idle circuit to compensate for the extra air.
Will run some more tests on her tomorrow!
 

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You mentioned aftermarket pipes, which would flow more air, though a 180 or so jet is normally where you’d end up at with them... I would almost size the main jets up again, hopefully so that you can bring your mixture screws back in a little. That should be the sweet spot.
 

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'96 VT1100 Shadow ACE
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Discussion Starter #16
You mentioned aftermarket pipes, which would flow more air, though a 180 or so jet is normally where you’d end up at with them... I would almost size the main jets up again, hopefully so that you can bring your mixture screws back in a little. That should be the sweet spot.
Do the main jets in this particular carb have that much of an effect on the idle circuit?
 

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1983 Honda vt750 Shadow
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Watch this video and see the throttle positions and what is providing fuel.

 

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'96 VT1100 Shadow ACE
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Discussion Starter #18 (Edited)
Watch this video and see the throttle positions and what is providing fuel.

That’s a fairly accurate video on how a stock carb works. My carbs have the needles shimmed and larger main jets, I’m assuming the raised needle and wider hole on the jets would allow a small amount fuel to get sucked into the combustion chamber.
 

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'96 VT1100 Shadow ACE
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Discussion Starter #20 (Edited)
If you’ve sized up, and still seem to be lean... It needs even more fuel!
Definitely! I haven't messed with it yet. I did however take it for a spin and it runs incredibly smooth.
Ordered new bottom carb boots, when they arrive i'm going to remove the carbs and replace the main jets with 82 Front & 85 Rear (80 & 82s right now) not sure if I should add another shim to the needle... If that doesn't work then i'm thinking about adding 45 Pilot jets (stock 42s)
 
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