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Suzuki M50, VZ800Z service

Hello Everyone.  If anyone can help compare tips and service issues for a 2008 Suzuki Boulevard M50 (2005 - 2009 VZ800), that would be great.  I recently bought mine used with 20,000 miles.  Maybe you have experienced something and can share your experiences?

1.  Secondary coil resistance was not equal between the front and rear cylinders.  I saw some corrosion inside coil 2, at the spring.  I decided to replace the whole coil assembly, coil 1 and coil 2.  The rear secondary coil 2 was 30k ohms, and the front was 50k ohms.  The primary coils were equal at 3.5 ohms.  (The service manual calls for Primary resistance of 2.5 to 4.0 ohms, and secondary resistance of 24k - 36k ohms) - so I'm out of spec on secondary coil on the front cylinder.  I've ordered OEM replacements.  I'm replacing all four. Have you tried lower resistance aftermarket coils on the 805cc engine? Do you have good performance?  I will update my results when I get the new coils.

2.  Maybe it's related to point 1, but I have pretty high vibration at high RPM, making it hard to drive highway speeds, or anything over 60-65mph for any length of time.  When I pull the clutch in, at highway speeds, the RPM reduces, and the vibration disappears, or at least feels normal then.  So it should be something like:  engine (valves), or spark timing, or fuel/air related (bolts all seem tight), ECU/sensors.  Next I'll move on to doing a compression test, and vacuum test of the intake manifold, and fuel pressure test.  After that might be a carb synchronization test - but is that still done with fuel injection?  Do you have any results for any of these tests I can compare to?  Service technique recommendations?

3.  For the test, the battery was at 12.7 vdc, a little low in my opinion...I think that should be up around 13.5 - 15.0 vdc, according to the manual. So I'll check the peak voltage and determine if I need a new stator or battery.

4.  I took the voltage/resistance/diode readings from the electrical/charging system (stator and reg/rect), except for peak voltage - i'll check peak next week when I have a capacitance meter built up...  Everything was normal, but not very high above the bottom of the tolerances... see below... (Instead of having the suzuki meter, you can use two meters and clamp the probes from meter 2 to meter 1 probes.... HOW:  Have the main probes on meter 1 for testing/probing, set on diode mode (confirm 1.4 volts or higher with meter 2 by measuring meter 1 probes with meter 2 probes - leave them clamped to meter 1 probes), then set the second meter attached to the first meter to VDC. - now you can see the supply of 1.5v on diode on the second meter. - as you test with meter 1, the votage will drop on meter 2, this is what you are reading to compare to the suzuki specs in the manual.)

A.  The reg/rect readings were as follows, with a diode test (which gives a 1.5vdc supply):
B.  Wire B/R1 to (B1, B2, and B3):  all three black wires of the reg/rect at .459 vdc to 0.461 vdc where the toleraces were 0.4vdc to 0.7vdc.
C.  Wire B/R2 to (B1, B2, and B3):  all three black wires of the reg/rect at .459 vdc to 0.461 vdc where the toleraces were 0.4vdc to 0.7vdc.
D.  Wires B1, B2, B3 to (B/W1 and B/W2):  all showed between 0.459 vdc to 0.461 vdc where the toleraces were 0.4vdc to 0.7vdc..
E.  Wires B/R1 to (B/W1 and B/W2):  0.76 vdc where the tolerance was 0.5 vdc to 1.5 vdc.
F.  Wires B/R2 to (B/W1 and B/W2):  0.76 vdc where the tolererance was 0.5 vdc to 1.5 vdc.

Stator readings:  Y1, Y2, and Y3 to ground were all resistance of 0.4 ohms where 0.2 - 1.5 ohms is the tolerance.

QUESTIONS:  From what I understand, failing/worn stator and reg/rec will typically short or show lower readings.  Have you seen this?  Do you have numbers higher than this?  If you replaced the stator or rec/reg with OEM new, what numbers did you read? 

Thank you for you patience and taking the time to read all this - if you can answer partially, that is fine.  Any sharing could mean something, so I appreciate it.  Patrick.




Very first thing,clean all your grounds and then do a load test on the battery. Remember, the charging system is a circuit which includes the battery. A battery is cheaper than a stator and way less work. Then, if it is the battery, replace and retest.
Here's one of my go to resources:
Since the vibration changes when you pull in the the clutch, check the drive chain and then the clutch.
Let us know what you find. A bunch of good people on this site are happy to help.

"You can tell from the sound of the exhaust system, and also from a fluctuating engine idle speed – put simply, the engine no longer runs smoothly. It's time to resynchronise the fuel injection system."
The Louis Technical Centre

Great information - I'll be happy to follow up. I'm doing one step at a time. The secondary coil resistance issue is fixed now... I've got 29.8k ohms on both secondary coils (18.8k ohms to the caps, 10k ohms through the caps), and 4.0 ohms on the primary coils - so both coils are identical resistance now.

If the weather holds, I'll do a test drive tomorrow or Monday, and then move forward with more testing if the vibes are still there. The battery was new last year, so I imagine it's good. I'll follow up with more testing on the charging system though - I currently don't have a load tester, but could run the battery to the auto store for a test. I can feel the vibration in the engine with the clutch engaged, so I don't think it's 'downstream' - I reach down and put two fingers on the head cover, when going fast enough to feel vibes - and the vibration seems to match what I'm feeling from the driver position - the engine seems like the source. I'm waiting for a capacitor in the mail next week, to make my peak voltage tester, but I will come back to this thread and follow up - very much appreciated. Thanks!

UPDATE: the new primary and secondary coils created a slightly better ride and brought the speeds up for each gear, ideal shifting is about 10mph higher, but I still have excessive vibes at high rpm... the hotter it gets, the more vibes... probably still carbon from the bike sitting in storage - or maybe something else... Thanks for the suggestions - i'll try your suggestions and give more feedback to help others as I have it.

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