T3-850 issue getting running correctly with VHB30C

[katit]

Spent some time this weekend messing with a bike and trying to get it running properly.

PO claimed it had "carb issue". What it was - it would run mainly on right carb. Those are Dellorto's VHB 30 carbs.

What is not stock about the bike:
a. 950cc cylinders
b. Dyna ignition
c. Some aftermarket coils
d. K&N filters
e. Exhaust

I did verify/adjust valves
I did check compression (pretty much equal slightly below 150psi measured cold)
When checking spark I noticed left plug was sparking on a side, incorrectly, barely. Spark plugs were wrong. New spark plugs spark correctly.

Then I went about carbs rebuild:
New larger mains (130 instead of 120)
New floats and needles
New main needles and needle jets. Needles were incorrect V5, installed new V9
New adjuster screws (per Guzziology)
New #60 slides (per Guzziology). MORE ON THIS LATER
Flipped choke rubbers, verified they seal correctly
Floats (one specifically) was sticking to float cover, had to shave off some plastic moulding to make it move correctly.
Float levels adjusted. Float needle sealing verified.

Once all that was done I went for test rides. Default carb adjustor settings, adjusted throttles to idle.

Ride #1. Running on both cylinders, but not "nice" Feels sluggish on take-off, 1/4-1/2 throttle. But runs and rides. Just doesn't feel right.

Went about adjusting carbs per manual (similar how airheads done). Right carb was good on screw adjustment as-is. Left one - I had to turn needle in full turn (lean) to make it run best.
When adjusting for running on one cylinder (per manual) - need to lift left slide more to make it run. When adjusting using TwinMax - it's different and once adjusted it wouldn't idle just on left. But left cylinder does run once right one helping.

Ignition timing verified using timing light. Good.

Ride #2. Runs crappy. Popping from a carb (I think).

Reset left to correct default needle setting.

Ride #3. Running, no popping but it doesn't run correctly in 1/4-1/2 throttle.

Replaced slides with stock #40s

Ride #4. Runs and rides great for the most part! So, #60 slides were waste of money
Spent some time riding, liking this Guzzi more

Checked spark plugs. Right one - lean. Left one - black, wet inside.
So it is NOT correct

Now my line of thought was why? Carbs good (ultrasonically cleaned, visually verified all passages and blew every hole and ject with carb clean and pressure air)

Maybe bad coil on left side? Anyways..

I decided to swap carbs L<->R and see if problem stays on L side.

Ride #5. Runs about the same. I didn't adjust anything.

After 15 miles or so - R plug is black and L plug is white.

So, it's not timing, not ignition. IT IS carbs. But what?

Any ideas on what to look for? Plug being "white" is not bad, I think slightly bigger pilot jet will fix it. But I need to figure out what the H is wrong with left carb.

My next steps:
1. Get carbs back into correct spots. I will double-check floats move freely (not sticking) and float levels.
2. Run and see if problem persists.
3. Swap choke plungers L/R and see if problem migrates to other side.
4. ? Ordered colortune, want to visually see what is going on, but not sure it will help me any if I will have all the basics checked..

 

[Raven]

I would thoroughly clean the problem carb again. Pass a thin guitar string or similar though every passageway. I doesn't take much to mess it up. Then do the full set up and balancing.

 

[john zibell]

Is that the carb that you trimmed the float? If so, float level may be too high as it will be lighter. Also what Raven said. Those white floats are a bit lighter than the originals. I set the float level a few mm less so they stop fuel flow further from the carb base.

 

[katit]

Is that the carb that you trimmed the float? If so, float level may be too high as it will be lighter. Also what Raven said. Those white floats are a bit lighter than the originals. I set the float level a few mm less so they stop fuel flow further from the carb base.

Yess.. I will need to check weights. They are 8.5g. I actually trimmed both and set them both the same.

I almost tend to check left carb again, clean thoroughly and then start moving parts one by one.
Swap chokes, then swap floats/needles, then swap accelerator tube with jet, etc to see if problem migrates. Does it sound right?

 

[john zibell]

Yess.. I will need to check weights. They are 8.5g. I actually trimmed both and set them both the same.

I almost tend to check left carb again, clean thoroughly and then start moving parts one by one.
Swap chokes, then swap floats/needles, then swap accelerator tube with jet, etc to see if problem migrates. Does it sound right?

Trying individual component swaps one at a time is a logical step(s). Hope fully you may find the issue. Again clean passages are a must. I didn't look that closely at the kits you put in, did it include float needle and seat? Sometimes I just burnish the seat with a wooden chopstick that I sharpen like a pencil to improve the needle sealing. In addition, if memory serves me correctly original floats are around 10-12 grams.

 

[katit]

Trying individual component swaps one at a time is a logical step(s). Hope fully you may find the issue. Again clean passages are a must. I didn't look that closely at the kits you put in, did it include float needle and seat? Sometimes I just burnish the seat with a wooden chopstick that I sharpen like a pencil to improve the needle sealing. In addition, if memory serves me correctly original floats are around 10-12 grams.

I got all parts from Harpers. I didn't replace float needle seats, just needles. I use those on a picture mounted in a drill with bit of polish applied to gently clean/polish seats. Blowing in with carb upside down show no leaks, but thats not 100% reliable. On other carbs I use those clear tubes to see actual levels but unfortunately VHB carbs don't allow for this

 

[motomatt]

Trying individual component swaps one at a time is a logical step(s). Hope fully you may find the issue. Again clean passages are a must. I didn't look that closely at the kits you put in, did it include float needle and seat? Sometimes I just burnish the seat with a wooden chopstick that I sharpen like a pencil to improve the needle sealing. In addition, if memory serves me correctly original floats are around 10-12 grams.

Original floats are (nominally) 14g.

 

[Grahamgrot]

Spent some time this weekend messing with a bike and trying to get it running properly.

PO claimed it had "carb issue". What it was - it would run mainly on right carb. Those are Dellorto's VHB 30 carbs.

What is not stock about the bike:
a. 950cc cylinders
b. Dyna ignition
c. Some aftermarket coils
d. K&N filters
e. Exhaust

I did verify/adjust valves
I did check compression (pretty much equal slightly below 150psi measured cold)
When checking spark I noticed left plug was sparking on a side, incorrectly, barely. Spark plugs were wrong. New spark plugs spark correctly.

Then I went about carbs rebuild:
New larger mains (130 instead of 120)
New floats and needles
New main needles and needle jets. Needles were incorrect V5, installed new V9
New adjuster screws (per Guzziology)
New #60 slides (per Guzziology). MORE ON THIS LATER
Flipped choke rubbers, verified they seal correctly
Floats (one specifically) was sticking to float cover, had to shave off some plastic moulding to make it move correctly.
Float levels adjusted. Float needle sealing verified.

Once all that was done I went for test rides. Default carb adjustor settings, adjusted throttles to idle.

Ride #1. Running on both cylinders, but not "nice" Feels sluggish on take-off, 1/4-1/2 throttle. But runs and rides. Just doesn't feel right.

Went about adjusting carbs per manual (similar how airheads done). Right carb was good on screw adjustment as-is. Left one - I had to turn needle in full turn (lean) to make it run best.
When adjusting for running on one cylinder (per manual) - need to lift left slide more to make it run. When adjusting using TwinMax - it's different and once adjusted it wouldn't idle just on left. But left cylinder does run once right one helping.

Ignition timing verified using timing light. Good.

Ride #2. Runs crappy. Popping from a carb (I think).

Reset left to correct default needle setting.

Ride #3. Running, no popping but it doesn't run correctly in 1/4-1/2 throttle.

Replaced slides with stock #40s

Ride #4. Runs and rides great for the most part! So, #60 slides were waste of money
Spent some time riding, liking this Guzzi more

Checked spark plugs. Right one - lean. Left one - black, wet inside.
So it is NOT correct

Now my line of thought was why? Carbs good (ultrasonically cleaned, visually verified all passages and blew every hole and ject with carb clean and pressure air)

Maybe bad coil on left side? Anyways..

I decided to swap carbs L<->R and see if problem stays on L side.

Ride #5. Runs about the same. I didn't adjust anything.

After 15 miles or so - R plug is black and L plug is white.

So, it's not timing, not ignition. IT IS carbs. But what?

Any ideas on what to look for? Plug being "white" is not bad, I think slightly bigger pilot jet will fix it. But I need to figure out what the H is wrong with left carb.

My next steps:
1. Get carbs back into correct spots. I will double-check floats move freely (not sticking) and float levels.
2. Run and see if problem persists.
3. Swap choke plungers L/R and see if problem migrates to other side.
4. ? Ordered colortune, want to visually see what is going on, but not sure it will help me any if I will have all the basics checked..

I had a similar problem with a rebuilt, left side choke wasn’t clearing properly causing similar issues to yours

 

[katit]

I had a similar problem with a rebuilt, left side choke wasn’t clearing properly causing similar issues to yours

Can you elaborate? Currently I have individual chokes.

 

[Grahamgrot]

Can you elaborate? Currently I have individual chokes.

Mine has the two cables running to the chokes and the left hand side choke cable was sticking leaving the choke partly on.
Not sure if this can happen with separate chokes, but the symptoms sound similar with the popping and wet plug etc.