Motorcycle Repair: Carburetor calibration, compression tester, engine stall

Question
Mr. Shively:

Thanks for the quick response.  To answer your questions.

Mark: More intel on exactly what the engine does. Does engine bog and stall? Does engine stall immediately? etc...

Rman:  The engine will idle properly, I did have to open the fuel screws from 2.5 turns to 3 turns to idle properly with the choke off (perhaps I never had it properly warmed and it would idle good at 2.5 turns but I did run it for a good 5 minutes sitting still).  Upon rolling open the throttle the engine just stops at 4 to 4.5k RPM.  Kind of like a rev limiter, hits that RPM and off like a switch.  If you slap open the throttle, total kill at 4 - 4.5K RPM.  If you gently open you can get it to rev up to 4-4.5K and hold it there but if you attempt to go any higher it dies.  If you close the throttle it will return to idle, even if it had "died", if you close the throttle before the engine spins down to stop it will catch and run at idle.  If I put the choke all the way on, even after it is warm I can raise that "kill RPM" to about 6K but it acts the same way only with a new 6K RPM "off switch"  This was all conducted under zero load.  I did not notice it bogging, sounded fine until I changed the throttle position and then off like a switch.  I have a compression tester and will check.  I'm fairly certain that I will be low or out of spec low.  My oil comes out black as ink after 3K miles.  With the high miles I expect the rings are nearing end of life and I am getting some blow by at the high R's.  When that data is taken I will pass it on for interpratation.  The bike isn't really stored over the winter.  I'm a fairly avid cyclist so I go long in the fall and early in the spring.  I run the machine once a month in the shop over the winter.  Long enough to get everything warm then pull the batter and keep it inside where it is warm.  This allows me to have the bike rideable on a 5 minute notice.  No gas stabilizers used.  I like to keep the tank tip top full in the winter to minimize the "breathing space" from warming and cooling over the day.

Before we really dig into this I want to make sure I was moving the needles out (richer) instead of in (more lean).  Every adjustment I have done in the past is to lean things out, smaller mains, needles in (currently two clip slots BEYOND the last adjustment slot, there is a spacer on the bottom of the slide that I removed that lets the needle sit even lower to try and lean back the warn emultion tubes)  By force of habit i may have actually been "leaning" the needle clip adjustments when I thought I was "riching" them.

More info Monday

Respectfully

Lohman D. Hafenrichter (Rman)
Rifleman@hotmail.com

Answer -
Hi Rman,

Rman: ... I have had a significant drop off in gas mileage (45+ down to 23-24) with progressively "rich" mixture indications. I have tracked this down to what I think is "Emultion tube" wear in the carbs and have ordered and received new emultion tubes for the 38mm Mukuni's on the machine from Factory Pro.

Mark: Needle jet/Emulsion tube wear is directly related to excessive fuel consumption due to the jet needle "bell mouthing" (normal wear) at the needle jet Venturi opening. New tubes will cure that problem. Good diagnosis!


Rman: The engine would idle but would die above 4-4.5K RPMs.

Mark: More intel on exactly what the engine does. Does engine bog and stall? Does engine stall immediately? etc...

If possible, check cylinder compression and do a leak-down test while you're working on the MC. Advise on the readings.  

Was the MC stored over winter? Any stabilizers used? Any additional intel is helpful. Great description narrative. Include your email addy so I can return info files.

Respectfully,
Mark Shively  

Answer
Again, great descriptions and narrative. You keep the MC well maintained and you have above average mechanical knowledge.

Instead of leaning out the fuel, try working with the air. Is there any obstructions of the airbox, filter, ducts, or air jets? I've found wallets placed over airbox intake openings, insect & rodent nests, and a variety of other air restricting obstructions causing rich air-fuel mix.

Do you have access to inside diameter gauges?

Check fuel levels in float bowls, too high (too rich).

I'll send some ifo files via email.

Mark