I've searched the forum but haven't found an answer so I'm hoping someone can help. I noticed a ping when I was riding with my wife on the back. (she's only 112 lbs..so it's not her) It would happen when pulling out from a stop. I realize it was detonation due to increased load. The ping isn't as bad when I'm alone but will still happen when I'm pulling out from a stop, predictably enough it's worse the warmer the bike is. As the exhaust was modified by the PO without any changes to the carb I thought it was due to a lean condition. I'd had to back out the idle screw about five turns after drilling out the plug to get rid of carb farts when I bought the bike last September so I know it was lean in the low speed circuit and that the carb hadn't been touched. I have a S&S jet kit and swapped the 42 pilot for a 45 and the 170 main for a 175. In the midrange it seems to have more power but at full throttle it pings and still has the ping pulling out from a stop. I'm not sure if it would have had the full throttle ping before or if I just noticed it because I was testing for it. Anyway...should I go with bigger jets or look elsewhere? The bike is a '99 1200, stock cv except for the changes mentioned above, stock ac, radius sweepers with baffles, stock engine. 24k miles. No smoke of any color, runs strong, no carb farts now, minimal deceleration pops. Sorry this is so long, just wanted to include all pertinent info. Thanks for any help, Tom

 

What octane gas are you running? I will have to pull a carb manual to check on the procedures on which jet to go after first. This will take a day. It's just been since last century I dealt with this.

 

You could try dropping a couple of heat ranges on the plugs to a colder plug; may help. Sounds like a timing issue that an adjustable ignition could deal with by pulling out some timing in the ping rpm range. Five turns out on the A/F screw indicates a larger pilot jet is required. Get the A/F rignt first, then tune for the midrange (pilot and needle) and then tune for WOT (main). Take plug cuts; that's the most accurate way to read lean/rich conditions at certain rpm ranges. If you haven't taken plug cuts; Google and read. Time consuming and you will need severa sets of plugs but best way to tune a carb.

 

Sorry, one thing I forgot to mention, I run 91 only. It's the highest available in my area and I've never put in anything else.

 

The plugs in it are NGK R DCPR7E. Front shows white/Lean and the rear is slightly tan...I'm thinking it's lean and I should bump up the pilot to a 48. Lost a little faith in the PO as the plugs were just finger tight, something I should have checked myself obviously but never though anyone would forget to tighten their plugs.

 

I run 9Es in both my 95" and my 107" engines; two heat ranges cooler. You will never get the same read on both plugs, one will always read a little more lean/rich than the other. Going up on the pilot is worth a looksee. Don't disregard the needle; it is often overlooked when tuning a carb.

 

Tom, be sure you do not have a vacuum leak at carb or intake seal before you start other changes.

 

I think I have it right, it's a bit cooler now than earlier so I'll have to take it out tomorrow to be positive. For anyone going through the same thing I'll recount what I came up with and how I got there. First I went to a 45 pilot, still pinging so went to a 48. It still wasn't right but was better. I switched the main from a 170 to a 175. I then decided to change the needle for the one in the kit which helped quite a bit but I noticed the throttle was a bit sluggish off idle and I lost some power at wide open throttle so I figured I was now too rich since the needle change. I switched the main back to a 170 and went to 45 on the pilot. With the needle change, the 45 and the 170 it seems right. No pinging and plenty of power and no stumble or hesitation. I'll run it and check the plugs to be sure. I'm also going to check for leaks just to be sure, I know..should've done that first. It's running right but I noticed one of the bolts is missing from the front cylinder intake port. That doesn't necessarily mean it's leaking as far as I know, but I want to be certain. From what I know the jets it now has aren't all that unreasonable for a 1200 with modified exhaust so I'd be surprised if it is leaking...but I've been surprised before.

 

Ahhh, that pesky needle; so often overlooked but the lynch pin of carb tuning. Always good to hear about progress. When you think you have it right, take some plug cuts to confirm.