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General Category => General Discussion => Topic started by: Perazzimx14 on March 08, 2019, 02:37:33 PM

Title: Dellorto popping when cold
Post by: Perazzimx14 on March 08, 2019, 02:37:33 PM
Got the SP tagged and insured and out for a test run yesterday. Bike starts and idles great but when cold pops through the carbs and had no power upon takeoff. It bogs, stumbles, pops then once at about 4,000 RPMS clears up and runs well. After a few miles when the motor is warmed up the popping is 99% gone.

Carb jetting (stock VHB's) 130 and 50
New Euro a/f screws set at 2-1/4 & 2-1/2 turns out. 
New needles clip in the middle setting
K&N 2:1 air filter
Dyna 3 ignition
Carbs sync'ed
Timing checked and is good

So do I raise the needles one notch and try again or is there something else to try?
Title: Re: Dellorto popping when cold
Post by: Antietam Classic Cycle on March 08, 2019, 03:00:37 PM
On my Convert, I raised the needles up (clip in bottom notch). Adjust the mixtures screws for the fastest idle or just turn them out 1/4 turn, go for a ride, repeat as necessary. You may need to go larger on the idle jets. It has Bub mufflers as well as K&Ns IIRC?
Title: Re: Dellorto popping when cold
Post by: pete roper on March 08, 2019, 03:06:56 PM
Go to a richer slide.
Title: Re: Dellorto popping when cold
Post by: Furbo on March 08, 2019, 03:08:58 PM
On my Convert, I raised the needles up (clip in bottom notch). Adjust the mixtures screws for the fastest idle or just turn them out 1/4 turn, go for a ride, repeat as necessary. You may need to go larger on the idle jets. It has Bub mufflers as well as K&Ns IIRC?

What Charlie said - it's a bit lean. raise the needle. If that doesn't work, go with a 55 pilot.
Title: Re: Dellorto popping when cold
Post by: Perazzimx14 on March 08, 2019, 03:52:55 PM
Needles were raised one notch and in the driveway the popping is diminished. Test ride tomorrow :thumb:

Thanks to all
Title: Re: Dellorto popping when cold
Post by: Antietam Classic Cycle on March 08, 2019, 03:54:09 PM
Go to a richer slide.

IIRC, it already has a #40 (or should have) so already has about as "rich" of slide as is available for VHBs.
Title: Re: Dellorto popping when cold
Post by: travelingbyguzzi on March 08, 2019, 06:00:44 PM
Check the seal (gasket) between head and intake runner.
Title: Re: Dellorto popping when cold
Post by: Chuck in Indiana on March 08, 2019, 06:08:07 PM
Good replies.
Quote
. You may need to go larger on the idle jets.
Is all I had.
Title: Re: Dellorto popping when cold
Post by: Perazzimx14 on March 09, 2019, 05:34:56 AM
Check the seal (gasket) between head and intake runner.

They are newer but upon warm up today I'll spritz little carb cleaner around the gasketed areas to see if there are any breeches.
Title: Re: Dellorto popping when cold
Post by: Two Checks on March 09, 2019, 06:38:30 AM
Depending on your altitude you may want to fatten the main. You will feel the difference at a wfo. Both my SP II and Cal III came with 130s and spit and sputtered. 142s cured it. Now with E10 they might like 145s.
Title: Re: Dellorto popping when cold
Post by: Charles in Lake Charles on March 09, 2019, 07:35:18 AM
Also check the float levels. If the fuel height is too low, the engine will display a lean running condition, where the engine typically hesitates before accelerating or surges as the throttle is opened.
Title: Re: Dellorto popping when cold
Post by: Perazzimx14 on March 09, 2019, 07:35:40 AM
Depending on your altitude you may want to fatten the main. You will feel the difference at a wfo. Both my SP II and Cal III came with 130s and spit and sputtered. 142s cured it. Now with E10 they might like 145s.

617 feet above sea level. With most riding between 200 and 1200 feet.
Title: Re: Dellorto popping when cold
Post by: SED on March 09, 2019, 10:49:16 PM
Posting this because it's a different solution. 

My LMIII would bog on takeoff and sometimes pop through the intake.  changing jets and slides and float level never quite solved it.  Solution was to replace the distributor advance springs and reset the timing.

Also put the stock airbox back on, but the advance springs really let if come off the line better.