I hope to list the various probs that arent covered by the manuals here

see the Vire7 FAQ pages, which are a bit more in depth...link on the home page

SPARK PLUG PROBLEMS

fit a new Champion L86c plug every year,  (champion L-8/L-10 equiv), this should solve almost everyones breakdowns, 20 thou gap, and i reccomend choosing an old champion over any new NGK/bosch every time - i have had endless misery from other brands that dont make a good Vire plug. Equivalent plugs -Are not! The HT cap is 5k ohm resistive. The spark has to be bright blue on cranking speed.

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I saw this at gosport, we fittes a brand new BP6HS out of the box, and ran the engine for 1 minute, removed the plug - very oily(20:1 oil). Too much oil is silly and going to cause plug fouling. I run my Vire 6 on Carplan 2 stroke oil at 30:1 reliably for 2 years now, and i may weaken it further to prevent sooting. The Vire 7 is 50:1, and it has exactly the same main bearings and piston rings - I really dont think the Vire 6 needs more oil unless you use the original SAE30 oil instead of a modern 2T oil? More oil - more smoke, more smell, more sooting, more cost...

HOW TO CHECK TIMING

remove plug

get crank to TDC(within 2mm), by feeling piston thru plug hole with screwdriver as you turn flywheel

mark/paint flywheel 'T' at exact top - (where dynastart bracket bolt is)

measure 2 inches along pulley circumference to the right (looking from front), mark/paint 'F'

replace plug

attach an automotive timing light (borrowed from mechanic?) to the 12v/earth/HT making sure any advance-knob is set to zero

run engine -  any speed will do

point strobe light at top of flywheel and note 'F' mark should be at top

if 'F' mark is to the right, the timing is advanced, if to the left, too retarded. (2" is 30 degrees).

Alternative: - connect continuity tester/ohmmeter between engine earth and kill wire (points) with kill switch off(run), rotate flywheel past TDC/F, note the resistance changes at exactly the firing point - much easier than using a lamp/strobe etc.

HOW TO ADJUST TIMING

note first you should have points gap correct?? assuming that.....

remove pulley and flywheel cover, not flywheel!

slacken the 3 magneto base plate screws

nudge the base plate clockwise to advance the ignition, anti-clockwise to retard it (by the same angle the timing was incorrect)

re-tighten screws

replace cover, and pulley/belt

re-check

ENGINE DIES

if the carb is backfiring a cloud of smoke, it could be that the exhaust pipe is collapsing - if the water stopped flowing into it, the flexible exhaust hose wont last long!

ENGINE FADES

if the power is hesitant - overhaul/replace carb as the galleries may get blocked or diapragms split inside. Also check fuel system is free flowing, and has inline filter & water trap.

PLUG FOULS

carb overhaul needed, or fuel has too much oil (modern 2T oils can mix @ 30:1) possibly bad fuel if unfiltered

make sure plug has correct gap and type, renew regularly and always carry a spare in good cond with a plug spanner hung up NEXT TO the engine for emergencies

RUMBLING/VIBRATION & slight play in pulley

main bearings have rusted - remove and rebuild asap

KNOCKING VIBRATION

ignition over advanced - check point gap and timing properly

SUCKING sound / poor starting

possibly carb air filter has fallen out

SQUEALING fan belt on starting

loose belt?

if the pulley wont go round freely it could be partial enging seizure due to main bearings / piston corrosion - ensure water intake turned off a minute BEFORE stopping the engine to avoid this

NO CHARGE from dynastart

battery should have over 14 volts at any revs, so if the volts dont go up when the engine runs - look at the wiring - is it secured? check the output terminal on the regulator, and if suspect - get the dynastart checked out by a professional rewinder - new bosch units are avail at about £600! commonly the field coils go so you will be able to start but not charge! if this is so, you could always save money by adding an automotive alternator with some bracketry and longer belt?

good second hand units are hard to find

WATER in the gearbox oil

brownish rust stain on dipstick/filler cap is a giveaway, drain and replace immediately with marinised engine/gearbox oil. if water is left in gearbox, you will end up with excessive transmission noise, then failure such as I had ; the slurry caught on the rear cone clutch and while i was motoring foreward - it suddenly seized the crank because it was now in reverse too! it took a lot of effort to get it out of gear even with the engine stopped

the cause of this problem seems to be failure of the water pump shaft seals, if installed poorly, of the two, at least the outer seal should face inwards(stopping water ingress), and the drain hole imbetween (often blocked or rusted/painted over) should be clear (otherwise pressure build up forces water/inner seal into gearbox rather than dribling out bleed hole indicating partial failure. solution: remove water pump, gears, plate and replace outer seal with tighter 30/14/7 (orig 30/15/7)seal facing inwards, checking bleed hole is open (exits under pump through casting) this job can be done with gearbox in situ! tap in the new seal witha spark plug socket.

EXHAUST FUMES/SMELLY RUNNING

leaking cylinder-to-exhaust is common - remove and reseal using gasket and exhaust cement. another point is where the water pipe goes into the expansion chamber - seal this with exhaust cement while the exhaust is cooling down with balls' of cement.

ENGINE OVERHEATING

normal running you should be comfortably be able to put your hand on the front of the cylinder, but if it is untouchably hot - 2 things come to mind. First , is there adequate water coming out the pump? loosen the pipe while running to see. Second - it could be a blocked waterway in the cylinder itself or a pipe. Check the intake is streaming in if disconnected before the pump, check the outlet is pumping about a pint every 30 seconds or more out the outlet/skin fitting

I recently inspected an unusual instalation on a 1970's Snapdragon cruiser, that used an electric cooling pump.you can see the rusty pump on the left which amazingly was wired between earth and dynamo D+ on the regulator unit- and it worked - effectively pumping several times the designed amount of water through the head,(the vire pump was disconnected and obsolete here). i was very concerned, that this was effectively putting a low resistance to earth at D+, and would be like removing the charging/indicator lamp ., and that might prevent

the dynamo starting up at all because of their self-sustaining/strting design, BUT it actually worked fine, charging, only running the pump when the engine was on, and possibly curing an inherrent overheating problem! Note i expressed concer about the lack of gooseneck height above w/l on this instalation to prevent syphoning/sinking, also the insecure muffler fittings were leaking water badly. Note here the jubilee clip on the head's water outlet was too big a size - this caused a saltwater drip onto the carb linkages and gea parm pivot - which was making the gearstick stick badly (due to inclined shaft as normal) watch out for this as its easy to grease/WD40 the gearstick bearing and very difficult to unseize one in above shows gear stick removed, and the steel stiction/slip ring rusted hard in siitu, preventing gear selection - you may be able to inject white grease or WD40 using the nozzle every year to prevent this - could be a good case for fitting a grease nipple through the lever?.