OK it was warm enough here yesterday to get her out for the first real shake down run. Did the M&M to Mikuni conversion on my 96 roadking. These are my findings from yesterday but I need some advice. Idle, throttle response general overall running seemed great. Questions........1.Rocker boxes and nosecone seemed to be warmer (hot) than normal. 2. Starting the engine when at normal temp the first push of the button would always backfire through the exhaust, second push would fire up just fine. 3. Vibration above 3500rpm. 4. Lastly for an engine that NEVER had a leak it started yesterday, yes maybe my run was pushed more than it had before, nosecone and bases. Thought about posting all my questions seperately but I can't help but think the are all related to one issue(timing? timing advance?) Spark plugs looked really good. If anything it was a touch on the rich side but not enough to make a change in my opinion.

 

I am a convert to dyno tuning. Or at the least calling by a local shop that knows Mikunis. There is no substitute for an expert to get things running just right. Better get it sorted out quick, rather than spending weeks or months wondering why the darned thing won't run right.

 

What ignition did you install? Mikuni carb kits are usually happy out of box but a little rich for protection. You can set timing by listening for detonation (marble sound at throttle rollon 45-55 mph) If you can get away with the most advanced setting without detonation go with it, the Mikuni will be rich enough to absorb the advance. If the igniton is retarded it can cause the engine to labor and run hotter plus your backfire in the exhaust at startup which is unburnt gasses igniting, reversion and leaning out is a reason for backfiring when deaccellereating. Usually a vibration in the uppers is a rich conditon and more gas that can be burnt and flat, if it is lean you will hear the marble sound. Advancing the timing in a rich condition will also help as each degree of advanced timing sends air-fuel-ratio towords the leaner side

GR speaks the truth, to be 100% efficient you have to know AFR's in all phases and can make timing adjustments, each timing adjustment also affects AFR's so they work together. Post ignition kit and setting plus if the Mikuni was the new easy kit.

 

I was able to find the stock wiring harness for a carbed road king. So I changed the cam position sensor to p/n 32400-80A and the timing rotor to p/n 32402-83 per the instructions included with the Daytona Twin Tec 1007 EX ignition. I installed this behind the right side cover where the ecm was removed. I set the timing per the instuctions included with the ignition. I did the static timing method. The settings I have on the ignition are, single fire, multi spark enabled, advanced slope setting 5( instuctions say normal pump gas 87-89 octane) rpm limiter set at 5500. The Mikuni kit was the easy kit.

 

"The maximum spark advance curves in the EX versions are more conservative, especially in the lower RPM range"

Checked the website an noticed this, with this EX advance being slow and set on 5 with 87-89 fuel, if you are running 92-93 it will be slower. Technical directions stated that the ignition module can only advance 4 degrees more over stock advance on it's highest setting.

With a stock type engine it would be a positive to get the timing to advance as fast as possible more of a setting for 92-93 octane, detonation will let you know if advanced to far and I doubt if it will detonate on the fastest setting. I'm only attacking the timing because a new Mikuni 42 should be slightly rich on a stock engine and safe to get the timing to come in quicker, 8.5-1 compression needs all it can get help burn the fuel or as GR mentioned use some equipment to know where the AFR's are at which is how I set up engines. Believe it or not but heat is good until too much heat becomes a problem which is detonation, a fine line for performance

 

Thanks. I will bump up my advance setting and take it out for another spin if it ever warms up again here. Bike is stock other than a set of rinehart slip ons. Next project was going to be a cam but I may start on that more sooner than later with my new leak at the cone.

 

Plug pictures from my ride this weekend 50 miles mostly highway. Maybe a touch on the lean side?

 

what do you have for jets in that mikuni?

IIRC, mine had a 25 pilot and a 150 main out of the box, was too lean. running a 160 / 25 before I did the engine work and it was right as rain on the 2nd most aggressive advance curve on the Dyna2000 ignition