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1986 shadow vt750c carb adjustment

7.4K views 5 replies 3 participants last post by  rex1  
#1 · (Edited)
Have a 1986 vt750c Canadian version Honda Shadow.Can anyone tell me the correct number of turns for the pilot screw setting!Have a Clymer service/ repair manual,covers 1983-1987 vt700 but only 1983 vt750.The book states 2 3/4 turns out for 1983 vt750 and 2 turns out for 1986 vt700. Pilot screws at 3 turns now both carbs.
Bike starts up no problem but is idling rough,using manual tackometer,the idle off of 3 of the plug wires is almost the same around (1000 rpm) give or take about 20 rpm between them, but on the forth plug wire rpm is 400 rpm higher! Could this be a problem with 1 of the 2 coils or the pulse qenerator!
Could this be the cause of the rough idle.
 
#2 ·
Will try to balance the carbs with a manometer to see if this is the rough idle problem.I have cleaned the carbs,replaced the air filter,replaced the fuel filter,changed the rad fluid,changed the oil and filter,replaced the spark plugs,replaced the battery,charging system all checks out ok,also replaced fuel with new and added a can of motul fuel system cleaner to tank.
This bike has not been on the road for 7 yaers but was started and ran several times a year over this period.
Bike has been stored in the garage,want to get some miles on it this year,maybe ride with antique plates or sell.
Will check compresion of each cyclinder to see if in spec. bike does start up ok so I think compresion shuold be ok.
 
#3 ·
By manual I'm guessing you mean an analog tachometer. I wouldn't trust those as they are notorious for being off as with any analog meter of sorts. Get a digital as you will be sure as to the readings. Anyways, you shouldn't have one plug firing faster than the others especially on the same side. Remove that plug wire and start the bike and see if the "rough" running goes away. You really need to balance/sync your carbs first, then adjust a/f mix (you can set them at 3 out and then after syncing adjust as necessary).
 
#5 ·
Rex1, these carb. setting by how many turns can be very misleading. Sync. the carbs first, after running the engine and get up to operating temp. [maybe a 15 minute ride] Then adjust each carb after the sync procedure. The age and condition of the carbs is always a question so don't be too concerned about the number of turns in or out. Start by setting the idle speed at about 1000 - 1100 rpms, then start turning either carb. in until it starts to run poorly then turn it out until it clears up and runs the fastest idle. You can use your tac or by ear, you'll be able to tell the difference. Then re set the idle speed back to 1000 - 1100 rpm, and do the other carb. Re set the idle finally at 1000 - 1100 rpm. and you should be good to go. Don't worry if the number of 'turns' is not the same for both carbs. Your bike will tell you when it's right.
Good luck and enjoy the ride.
 
#6 ·
Hey thanks Les.Ill do the idle ajustment as you state.
Took the bike for a 200 km ride last weekend and it seems to have helped with the rough idle.Ran a tank of fuel through with Module fuel system cleaner in it.
Need to replace the fork seals also( any tips)will be doing this tomorrow.