TOPIC:

Hello Everyone,

I have my bike together and running after the top end rebuild but I'm having trouble dialing it in. The bike starts right up and accelerates powerfully and smoothly while riding but when I check the plugs I'm getting a different story. Also the fuel consumption is terrible ( maybe 20mpg) These are symptoms the bike had before the rebuild and I was hoping that the issues would have been resolved at this point. I'm assuming the issues are in the carbs but I'm here to ask your opinion on the matter.

Firstly, I realize there are many threads concerning these carbs and I have done my best to read through them and try to fix my situation with the information provided. but I'm still stumped. Here is my current set up with the Carbs and what I have tried.

Mikuni Vm 29 Smoothbore
Individual Pod filters
4 into 1 delkevic Exhaust system
new pingel petcock
Main Jet - 120
Pilot Jet- 17.5
Air Jet- 0.9
Slide- 1.5
Needle 5Dl31 with clip in Middle position (3)

Here's what's been done

-Ultrasonic cleaning with carb dip then compressed air (twice)
- new o rings on the air mixture screw, and choke plunger
- removed and cleaned the air jets
-bench synced the carbs
- set float heights using the clear tube method
- changed my pilot jet from 25 to 20 and finally to 17.5
- I have set timing both statically and dynamicly with a timing light
Tried both b7es and b8es plugs
- air mixture screws seem to want to be only a 1/4 turn out anything more and the rpms will get hung up around 3000 rpm in neutral.
- About 200 miles on the Top end rebuild ( new valve seals, valves lapped,new piston rings,honed cylinders, new o rings and gaskets, new timing chain tensioners and gears, switched cams from Andrews .410 lift to GPZ750 intake and Kz650 Exhaust, cam's degree'd and valve clearances set.)

Here's what's going on with he plugs

This first picture is after putting in fresh B8es plugs and riding about 10 miles mostly at highway and freeway speeds top plug is 4



traffic.

This second picture is what the same plugs look like after another 30 miles with a little bit of freeway but mostly in town stop and go city top plug is 4



Like I said the bike starts right up. When cold I start it with choke on but only leave it on for a split second as it revs super high. After I turn the choke off the bike will hold an idle at 1100 rpm. It holds but sounds a bit loping (not a consistent purr) The bike seems to run really well. the idle may get less smooth as that number 4 plug gets more carbon fouled but I've been cleaning them often. I know this is a lot of info right out of the gate but I'm losing my mind on this one.

I'm thinking it's not the carbs.
Steve

If it's the carbs they're too rich for some reason. Your main and pilot jets are in the ballpark. Needle position too.

If you have another (old) set of carbs you can try putting them back on and see if the problem goes away.

Any idea what I should look into swest? I wish I had another set of carbs Kapahula but these are the ones the bike came with so I was hoping to make them work.

Sounds like the carbs are close and judging by some of the plugs. Coils, wires or caps?
Steve

I will check them out. The wires and coils are new from Dyna but maybe something isn't hooked up properly.

Dirtyhands wrote: . . . fuel consumption is terrible ( maybe 20mpg) . . . .

As 29's have no overflow circuit. if not already done, would check for possibility of gasoline intrusion into the crankcase, to rule out a potentially disastrous condition.

Good Fortune!

After thinking about it for a while I'd do this. Recheck valve adjustments. I know it's a new top end but the valves may have been misadjusted due to grit or something holding the valves open. When they freed up they became too tight. If they check out and the coil wires/caps are good, I'd check the emulsion tubes in the main circuits. I'm suggesting this because I went through mine and found the PO had munged them up. Compare all four. and note what sizes they are.
jetsrus.com/a_jets_by_carburetor_type/needlejet_jets_mikuni.htm
jetsrus.com/carburetor/carb_mikuni_VM29_...loded_view_parts.htm
You said you have pods. Have you tried to run the bike without them yet?
Steve

Thanks swest that's a good check off list. I'll bring the bike into the work area and start going over these points.
Patton, I have since corrected the float heights but they were initially too high and I fear I may find gas in the oil. I"m going to do an oil change pronto but wonder what the "potentially disaster condition" would be.

I'm back to work on the bike today. I warmed it up drained the oil . I could indeed smell some gas in it but there was no metal or other debree in there. I decided to double check the float levels using the clear tube method. When I set these off the bike I had the carbs as level as I could get them but I'm noticing that on the bike they are slanted toward the cylinders. What side of the carb should I be measuring from? Things look good on the air side but high on the cylinder side. Or should I measure from the center of the carb body?

P.S. The bike is on it's center stand

Measure in the center. Why are your carbs slanted?
Steve