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Suzuki 800 Intruder Club & Forum

A UK Site Dedicated To The Suzuki C800, VL800, VX800, M800, VZ800, VS800, C50, M50 Model Intruder / Boulevard / Marauder
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 HELP ,Rough Running

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The Civil one

PostSubject: HELP ,Rough Running    Sat Jul 19, 2014 1:05 am

I recently bought a VZ800 , she is a 98 model ,carbs.
  I cant seem to get her to run smoothly , constant spluttering , and not firing on the
  front cylinder .
  I cleaned the tank , there was a bit of dirt in there , i thought this was the issue ,
  but no !.. Cleaned the Carbs in an ultrasonic tub twice ,everything is immaculate ,
  Good spark going to both Cyls , good compression , leads fine ,Valves are fine ,
  timing spot on .Idles ok ,but still has a wee miss.
  Just to add , the bike is used infrequently ,
  She is hard to start , from cold . The Battery now seems to be history from all the
  turning over .

  What am i missing ?
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Mr Intruder Founder ... & ... Senior Administrator

PostSubject: Re: HELP ,Rough Running    Sat Jul 19, 2014 4:24 pm

If your carbs have been cleaned by way of an ultrasonic tub they will probably be as clean as it's possible to get, they are very well thought of. As a very ruff guess, how is the condition of your fuel? As the bike is rarely used do you use a fuel additive such as Redex to stop the fuel from going off?
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The Civil one

PostSubject: Re: HELP ,Rough Running    Sat Jul 19, 2014 4:43 pm

I initially ran "Redex " through the system .
      She ""Maybe "" ran a bit better ,,,but not much.
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captain crash
Mentally Deficient lunatic ..... & ..... Site Moderator

PostSubject: Re: HELP ,Rough Running    Sat Jul 19, 2014 8:54 pm

Fuel additive will help stop fuel from going off or varnishing up but that is when added to good fuel, not already gone bad fuel. Sounds like your fuel needs changing from bad/old to good/fresh
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.. Mechanical Tart .. .. Site Moderator ..

PostSubject: Re: HELP ,Rough Running    Sat Jul 19, 2014 9:17 pm

New plugs? Had a similar problem with my lads 125, everything looked fine  :what1:  I went through all the usual fuelling checks and found nothing  Suspect   Couldn't put my finger on the problem? good spark, good fuel, In the end it turned out the plug was failing under any sort of load.
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The Civil one

PostSubject: Re: HELP ,Rough Running    Sun Jul 20, 2014 12:07 pm

Yep , New Plugs and fresh Fuel . All done , is there any VZ spefic carbs requirements ,
               I have a Suspecy Battery ?
               When you open her up she seems fine
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Mr Intruder Founder ... & ... Senior Administrator

PostSubject: Re: HELP ,Rough Running    Sun Jul 20, 2014 3:21 pm

Battery should be at 12.6 resting, any lower shows a battery that is not in tip top condition.
I am away at the moment so can't think properly at the moment but has your year of bike got the MMM, that can be by-passed that can & does often help. LINK to MMM over-ride/bypass.
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* VZ Guru *

PostSubject: Re: HELP ,Rough Running    Mon Jul 21, 2014 5:11 am

Hello Mr civil one,
Your bike will have the MMM modal as Dave said unless a previous owner has removed/by-passed it, it will probably make a difference and help your bad starting,,, your battery seems compromised,, charge it or replace it mate, these bikes need a good battery. Look under the left side cover and look for a clear or green plastic cover under it is a black box, this is your starter relay ( 3 wires on early VZ`s and 4 wires on later VZ`s) check for dirty or burnt connections fairly common and a cause of bad starting ( I have a list of things ref bad starting ) but the MMM and dirty connections are where I would be looking first.
You say "  leads fine" have you checked with an OHM meter for high readings, it is known,, swap the HT leads over and see if the spluttering/miss firing changes from the front cylinder to the rear ( if it does its the lead if not you`ve ruled it out)
"Good spark to both cylinders" have you checked the plug gaps not always correct straight from the box,
" clean carbs" Have you checked the carb diaphragms mate, not too common a fault but worth checking.
Check and or adjust Idle enrichment screws:-
1) Adjust the screws to 2.5 turns out from lightly seated.
2) Start the bike and let it warm up enough to have the Choke off.
3) connect a tachometer.
4) Chose either carb to start.
5) While running, turn that screw out an additional half / quarter turn.
6) If the rpms go up,  do it again. (Go back to 5)
7) If the rpms go down, turn it in half / quarter of a turn.
Go to the other carb, and repeat 5, 6, and 7.
You can use a vacuum gage instead of a tachometer and adjust the same e.g. [ 7) If the vacuum decreased, turn it in half a turn.]
then set you idle speed to 1100rpm ( idle adjustment screw is under the seat on right hand side just in front of the tool tray), then
Sync the carbs is a must on these bikes,, it is a faff on but well worth it and you get used to it after a while,,, don't skip the adjustment for equalizing the ( pull ) throttle cable ( its a one into two connecter on the left side of the front air filter box) its important and most folk don't do this,,, you can download the service manual from this site.
Good luck and I hope this is of some help mate.
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The Civil one

PostSubject: Re: HELP ,Rough Running    Mon Jul 21, 2014 11:07 pm

Sweet God ....... give me strength .
I thought i was onto a winner with the By-pass ,,,,, Not a Bloody thing.
NOW ,,, Either with or without ,,,,, it wont start AT ALL.

Whilst i was under the Covers ,, I just checked the Fuel line and pump ,all fine.

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* VZ Guru *

PostSubject: Re: HELP ,Rough Running    Tue Jul 22, 2014 2:40 am

Check your fuses, people have blown a fuse doing the MMM by-pass check the ignition fuse number 3.

Here is an exhaustive check system,,, I`ll be surprised if you don't find the fault,,, take your time it`s not as daunting as it first appears.
Thanks to Boydster for collating the tests.




The parts we’ll be dealing with are, in electrical order: battery, ignition switch, ignition fuse (#3), side stand relay, stop / kill

switch, start switch, clutch switch, start control relay, starter relay and the

starter. There are some differences between the years. As far as the starting circuit is concerned,

these differences are for the 97, 98-03 and the 04 side stand relay and how it’s mounted with

other electrical items. These will be pointed out as we go along.

Note: When using jumper wires or shorting out relays, use common sense. Don’t crank on

the starter or jump that relay for excessive periods of time… just long enough to gauge the

reaction of the starter or to check the meter. A few seconds is usually all that is needed.

1. Battery. Make sure it is fully charged. A 12-volt battery that is in good condition and fully

charged will indicate about 12.2 to 12.6 volts with everything turned off, measured across

the battery positive and negative terminals. If you have any question about the status of

your battery, get it load tested. Your battery terminals should be clean, dry and tight. Now

turn the key ON but do not start the engine. The battery voltage should still be about 12.2

volts. If the voltage drops sharply when the key is turned on, suspect a bad or inadequately

charged battery.

2. OK. Battery is in good shape and charged. Remove the LH side cover on your bike. You will

see a funky looking green or clear plastic cover over a small black box. This is your starter

relay. Pull back the cover. See those 2 big red wires? CAUTION: DIRECT LIVE BATTERY


Makesure the transmission is in neutral. Turn the key on, check that the N light is on, and turn the

key off. Double check that it is in neutral. If it is in gear, your bike will take off on its own,

come off the kickstand, fall, damage your handlebars, dent your tank, bust up your front

fender, snap off your levers, break your left wrist and kill the neighbors cat. The jumping

you’re about to do bypasses every safety system on the bike, so be careful, OK? Just make

sure it is in neutral. With the key turned off, use a heavy gauge wire (14 or bigger) or a large

tool like a screwdriver or allen wrench (an allen wrench works well to get around the plastic

blocker between the terminals. Use a big one… ) and carefully short across the two large

terminals that the red wires are connected to. You will see some sparks and hear a loud click.

This puts direct battery power straight to the starter. The starter should engage and the

engine should turn over. If it spins over nicely, go to #5. If nothing happens, or the engine

still turns over very slowly, go to #3.

3. No click? No sparks? Starter does not engage? Engine does not turn over? Engine slow to

turn over as if the battery is weak? Make sure the key is on and use your meter to check the

volts at that inboard RH terminal. Place your meter negative probe on a part of the frame

that is clean and not painted. It should be the same as the battery. If the volts are OK, go on

to #4 now. If there is a big difference between the voltage at the relay and the battery

voltage, you could have a bad battery + or - cable or dirty / corroded connections at either

end of those cables. Carefully inspect the positive and negative battery connections, at both

ends of the cables. Make sure the connections are clean and free of corrosion. Turn the key

OFF. Using the ohmmeter function of your meter, check the resistance from the battery

negative to the bike frame. The battery frame ground is located behind the LH lower

swingarm cover, just below the cover you have already removed. Check from the battery

positive to the live right side starter relay terminal. It should be less than 1-3 ohms. Higher

resistance indicates a bad battery cable.

4. If the volts at the starter relay RH terminal (battery power) are OK, but the starter is still

slow to turn over, remove the cover from the power terminal on the starter. Turn the key on.

Check the volts at the power connection to the starter with the starter relay terminals

jumped like you did before (having a helper would be smart here… or use alligator clips to

attach the meter leads while you short the relay terminals and watch the meter). Bad volts

here indicate a bad starter power cable, a shorted or dirty starter or a ground problem.

Disconnect the power cable from the starter (don’t let the stud turn! Just turn the nut to

remove the cable). Short the relay again and check the volts at the starter end of the power

cable. Good volts = good cable, bad volts = bad cable. If the check with the cable attached

indicated the volts are good, use the ohm function of your meter to check the ground from

the starter motor case back to the battery negative. Good ground = bad starter. Bad ground

= check battery negative cable for corrosion, breaks, etc.

5. So you shorted the starter relay, got some clicks and sparks and the engine spun over faster

than you have ever seen before. Cool! Let’s find out why it is slow when you press the starter

button. Go to the starter relay again. Disconnect the electrical connector that has (1997 = 3

wires, 1998 – 2004 = four wires) in it. There should be either one or two small red wires, a

yellow wire with a black tracer (called Y/B for short) and a black wire with a white tracer (B/

W). Holding the connector in your hand, carefully inspect the connector and socket in the

relay to make sure they are clean, dry and free of corrosion. If there is a section where the

red wires connect that is burned or melted, this is a problem with the charging system and

must be repaired. Plug the connector back into the relay. Connect your meter positive lead to the Y/B wire by sticking the

probes into the back of the connector and the meter negative lead to the battery

negative terminal. Key on, in neutral, clutch in, killswitch on. Hit the start switch and see how

many volts you have on the meter. If it is the same as the battery voltage (within .2 volt),

that indicates that all the starting circuits and grounds are in good shape and you should

suspect a bad starter relay. If the voltage at the connector is lower than the battery voltage

by 1 volt or more, we want to check the ground circuit. Put your meter on ohms and use it to

check continuity from the back of the connector at the B/W wire to the battery negative

terminal. Reading should be less than 1 ohm. If it’s higher, you need to check the wiring

harness B/W wires back to the battery. If the continuity is less than 1 ohm, the ground is

good and we have more checking to do.

6. The MMM: Just behind the starter relay, you will see what we call the Mitsuba Mystery

Module.  We are going to check it because it does affect the starting of your bike.

It is labelled as a "Mitsuba Relay Control". Disconnect the connector. It should have three

wires… yellow with green tracer (Y/G), black with a white tracer (B/W) and yellow with a

black tracer (Y/B). Again, make sure the connector and socket are clean, dry and free of

corrosion. Reinstall the connector. Place your meter positive lead on the Y/G going into the

back of the connector as we did before and the negative lead on the B/W. Key on, in neutral,

clutch in, kill switch on. Hit the starter button and see what volts you get. Now move the

meter positive lead to the Y/B and test again. The voltage readings should be within about .2

volt. Any more significant voltage difference would indicate a failure of the MMM.

If the 2 measurements are within .2 volts, and you’re reading good battery

voltage, you may have fixed your problem by removing and reinstalling the connectors

(cleaning the contacts). Try starting the bike by normal methods. If the 2 MMM readings are

within .2 volt of each other, but you are still 1 volt or more below battery voltage, check the

volts at the Y/G wire with the meter negative on the battery negative. If the volts are now

good, check the ground circuit from that B/W wire terminal back to the battery. If the volts

are still low, the ground is good and we have more to check.

7. Your low voltage problem to the starter relay has been isolated down to one of several

things. At this point, we are looking at a bad fuse connection, bad switches, dirty connectors

or broken / chaffed wiring. We will work on the fuse, switches and connectors first. The fuse

involved is the #3, ignition. The switches involved are the ignition switch, side stand switch,

the stop / kill switch, the starter switch and the clutch switch. We will go over how to locate

and test each one. Make sure all connectors are installed securely. Each time you hit the

starter button, the engine should try to crank. Evaluate how well the bike tries to start as

well as obtaining the voltage readings.

8. #3 fuse & ignition switch: Remove the fuse and make sure the legs are clean and bright. Put

your meter negative probe on the battery negative terminal. Key on. Touch the open

contacts, one at a time, of the fuse box where the #3 fuse was installed with your meter

positive probe and check voltage. One should have no volts; the other should have full

battery voltage. If you have good volts, go ahead to #9 now. If the one reading voltage is

lower than battery volts, suspect the ignition switch. The ignition switch can be tested by

opening the wiring connector to the switch and checking volts at the red wire on the bike

side of the connector with the meter negative on the battery ground. Good volts, but you

had bad volts at the fuse, indicates a bad ignition switch or the orange wire that runs from

the switch to that #3 fuse.

9. Side Stand relay: The side stand relay has a history of being affected by dirty connectors. On

the 97 Rauder, Suzuki installed three separate items (turn signal control, side stand relay and

side stand diode block) with the side stand relay under the RH side cover with four wires

going to it. From 98 - 03, they are all in one unit, under the LH side cover with eight wires

coming out of the connector. It is installed in the same frame as and just behind the fuse

box. Regardless of the year, first make sure you are in neutral (the neutral

light won’t work once you remove the relay, so check it now), then remove the side stand

relay unit from the connector. Check that the contacts are clean, dry and free of corrosion.

You want to install a small jumper wire from the orange/yellow (O/Y) wire socket to the

orange/black (O/B) wire socket. Install your voltmeter in the Y/G and B/W wires at the MMM.

Key on, in neutral, clutch in, kill switch on. Hit the starter button. Check the voltage at the

meter attached to the MMM and check starter reaction. If the starter cranks quickly and your volts have increased, you may

have bad side stand relay contacts. If there is still a problem with the cranking, you have a bit more work to do… remove the

jumper,reinstall the relay and continue on.

10. Kill switch and starter switch: The starter switch has been a source of starting problems on

several MIG bikes. Remove the fuel tank (you might be able to get to the connectors by just

lifting the rear of the tank on a block of wood) and look for the 2 wiring harness’s coming

from the switch boxes along the LH side of the tank and frame rail. You want the one that

has several orange wires in it. Disconnect the connector; inspect it for clean, dry and free of

corrosion. The wires you want are going from the connector to the switchbox (not coming

from the bike’s electrical system). Set your meter for ohms and probe the Orange/Black

(O/B) to Orange/White (O/W) wires (+ and – doesn’t matter). While watching the meter,

actuate the kill switch on and off. When the switch is on, you should see near zero (0.00)

ohms. Anything above 1 ohm, suspect bad contacts in the switch. It is not cleanable, and

should be replaced. If it’s good, probe the O/W to the Y/G wires. Actuate the start switch and

check the meter. It should also be near zero ohms. Note that this is a slider switch, so the

readings may vary while the switch is moving. But once the switch is depressed and held

steady, the readings should be consistent and very close to zero. If the readings are good,

reassemble the connector. If not, you can open the rh switchbox and disassemble the start

switch for cleaning and inspection. Be careful with that tiny spring in there! If your ohm

values are good, assemble the connector and give it a test. If the starter is still slow, we’ll

carry on…

11. Clutch switch: There are several Marauder owners out there that have the clutch switch bypassed and have never had a

starting problem. While I will not suggest or condone by passing a safety

switch, it is an interesting fact. It is known that this switch can be a problem. Locate the wires for your clutch switch. Sitting

on the bike, look under your left switchbox. You should see two wires that come out of the switchbox to the clutch switch. Pull

the connector off and install a jumper wire between the 2 contacts. Key on, in neutral, kill switch on. Hit the starter button

and check your volts (with the meter on the MMM, Y/G to B/W) and starter effort. Good volts and fast cranking indicates

a dirty or faulty switch. This switch is held in with a single, small Phillips screw and can be

removed, disassembled, cleaned and packed with dielectric compound. Be very, very careful

with that little spring in there. Still low volts and slow cranking? Remove the jumper, install

the wires on the clutch switch and move along.

12. If you are at this point and have not fixed the Hard-To-Start problem, your situation is

unusual. Remove the fuel tank. Under the tank, there are some wire harnesses. Follow the

wiring harnesses and look closely at them to make sure there are no spots that are rubbed

through. Inspect the wiring going to all the items you’ve checked. Repair any problems that

you find.

Well that is it. You have checked everything there is to the starting system on the Suzuki VZ800

Marauder. Double-check all your connectors to make sure they are tight. We hope that your bike

is now cranking and starting like it was brand new.

Take your time, be methodical and good luck mate.
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HELP ,Rough Running
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