engine running rough and smokine

[edszuk]

Hello all, I just picked up a lone bed 65 for my son. The engine runs but blows lots of black smoke and runs really crappy. It's going to be his first vehicle and figured him and I can work on it, but didn't want to put alot of money into it right away. I would like to keep the straight six in, but will have to come up with something else if I have to rebuild it. I do have a buick V6 3.8 with an automatic trans that I could put in it the truck but don't know if I have to modify the motor mounts.

So, the straight six cranks right up, sort of idles blows black smoke and sort of pops.
Suggestions?

Thanks,
Ed

[aerotruk63]

Black smoke, is the choke on? A 1 barrel carb kit is cheap and easy.

[edszuk]

Nope the choke isn't on. I'll pull the carb off and rebuild it and put fresh fuel in it. So black smoke = maybe bad carb? I'm good with that. I don't want to pull the engine this early in the project.

Ed

[Slow Build]

It's running rich.

[edszuk]

Makes sense. I should have also mentioned that the truck sat for a year or so. Should I be concerned about the engine at all?

[62gmc910]

the engine should be fine , if the carb is not leaking you could disconect the fuel line from the suctionside of the fuel pump , plug it and then run the enfine dry of fuel , if there is a piece of crap in the needle seat it may fall out and solve the problem its self , also change the filter at the carb inlet

[jchav62]

Also clean or change the plugs. Running rich like that tends to foul the plugs pretty good.

Does the carb get wet with gas? Possibly, the floats are getting stuck. Sometimes, a quick tap with a screwdriver or something can fix this problem. Things tend to get sticky when a vehicles sits for a long time.

Another suggestion. Drain and clean out the fuel tank and blow out the fuel lines. Old gas and crap in the lines will cause a lot of problems like this.

[MacAttack]

Yep - same, same / those 6's are hard to kill.

You may be pleasantly surprised with how little work it takes to get it up and running.

Mac.

[1Bad62Pro/Street]

Also check the Ignition Timing.
Probably just needs a tuneup.
Those Stovebolt I6's are pretty tough motors, and will last as long as you take care of them.

Other Engine Troubleshooting Tips:

Trouble-shooting.


__________________________________________________________________________________________
Engine will not start.
• Attempt to drain float chamber
o If there is little or no fuel in chamber:
 Clogged fuel line, filter behind float valve, main filter, fuel tank breather hole.
 No fuel in tank or fuel tap turned off.
 Sticking float valve or faulty float.
 Loose or disconnected fuel pump or relay wire.
 Faulty fuel pump relay.
 Faulty fuel pump.
 Clogging within carburettor body.
• If there is fuel in float chamber then check spark plug.
o Wet plug:
 Mixture too rich
 Carb flooded
 Choke valve stuck open
 Cylinder flooded
 Dirty air cleaner
• Perform the spark test
o Weak or no spark: See rough idle
• If there is a good spark then do this
o Pour 1-2 cc of fuel into cylinders thru the sprk plug hole,
reinstall spark plugs and try to start engine without choke applied,
with full throttle
 If engine starts:
 Faulty choke system
 Fuel comtaminated
 Carb incorrectly adjusted
 Intake pipe leaking
 Clogged carb passage or jets
• If engine does not start perform compression test on each cylinder, see rough idle.
o Low compression:
 Valve stuck open
 Damaged cylinder head gasket
 Improper vlave timing
 Improper valve and seat contact
 Worn cylinder and piston rings
 Damaged piston
• If compression is normal:
o Improper ignition timing
 Fautly pulse rotor
 Generator with ferrous burrs

__________________________________________________________________________________________
Engine is hard to start or soon stops.
• Check fuel supply to carb as above.
• If fuel supply is good then try to start with choke on
o If the engine starts:
 Clogged carb jets
• If engine does not start, check plug as above
• If no problem at plug perform spark test as above
• If spark is good then perform compression test
• If compression is good check valve train
o See valve clearance
o See cam chain replacement for valve timing
o Worn camshaft
o Loose valve adjuster and lock nut
• If valve train is good check ignition timing
o If ignition timing is out:
 Faulty pulse rotor
 Generator with ferrous burrs
• Clogged carb passage or jets

__________________________________________________________________________________________
Engine lacks power with normal loading.

Note:
• Check engine oil level and condition. Be sure the oil is not contaminated
with coolant or metal burrs.
• Start the engine and warm it up to operating temperture, then check to see
if the temperture gauge reading is abnormal.
• Check for engine mechanical noise: Cam chain and cam chain tensioner; improper
valve clearance; worn camshaft and rocker arm sliding surfaces; broken piston rings,
worn piston pin and connecting rod small end.
• Check that the wheels spin freely, check for brake drag, faulty wheel bearings,
incorrect drive chain slack, bent fork, bent frame.
• Check exhaust smoke at half throttle
o Blue smoke
 Engine oil leaking into cyclinder
o Gray smoke
 Rich mixture
 Worn piston rings
 Incorrect ignition timing
• If exhaust smoke is normal check for surging during acceleration.
o Causes of surging
 Incorrect adjusted pilot screws
 Incorrect synchronization
 Intake pip leaking
 Clogged crankcase breather
• If there is no surging check the spark plug
o Wet plug
 Loose connection between spark plug caps and wires
 Dirty air cleaner element
 Improper float level
 Rich mixture
o Cause of a light gray or white discoloured spark plug
 Improper heat range
 lean mixture
 Improper float level
 leaking intake pipe
• If plugs are good check the specified fuel flow capacity
o Under the specified
 Dirty fuel filter
 Clogged fuel lines
 Faulty fuel pump
• If fuel flows good check cylinder compression (above)
• If compression is good heck ignition timing (above)
• If ignition timing is good check valve train for surging (above)
• If there is no surging check for clogging in carbs
• If carbs are good
o Seized cylinder and piston
o Seized connecting rod bearing
o Damaged main bearing

__________________________________________________________________________________________
Poor engine performance at slow and idle speed.

Note:
• Check engine oil level and condition. Be sure the oil is not contaminated
with coolant or metal burrs.
• Start the engine and warm it up to operating temperture, then check to see
if the temperture gauge reading is abnormal.
• Check idle speed: specified 1,200 +/- 100rpm

• Check engine condition with choke applied
o Better
 Intake pipe leaking
 Improper carb adjustment
 Clogged carb slow jet
 Improper float level
• If it does not improve remove air cleaner and check again
o Better
 Dirty air cleaner
 Improper carb adjustment
 Clogged carb air passages
 Improper float level
• If it does not improve do spark test on all plugs (above)
• If spark is good check carb synchronization (carb overhaul)
• If synchonization is good check cylinder compression (above)
• If compression is normal check ignition timing using timing light with "F" mark
o Abnormal
 Improper ignition timing
 Faulty spark unit (CDI)
 Pulse rotor
 Generator
• If ignition timing is normal check valve train
o Problems
 Improper valve and seat contact
 Valve stuck open
 Improper valve timing
 Damaged cylinder head gasket
 Worn cylinder and piston rings
• If valve train is good clean carb air passages and jets
o Better
 Clogged air passages or jets
• Does not improve
o Seized cylinder and piston
o Seized connecting rod bearing
o Damaged main bearing

________________________________________________________________________________
Poor engine performance at high speeds

Note:
• Check engine oil level and condition. Be sure the oil is not contaminated
with coolant or metal burrs.
• Start the engine and warm it up to operating temperture, then check to see
if the temperture gauge reading is abnormal.
• Check idle speed: specified 1,200 +/- 100rpm
• Check that the wheels spin freely
• Check for spark plug (above)
• If plug is good check exhaust smoke at half throttle (above)
• If exhaust smoke is good check engine performance with choke applied
o Better
 Lean mixture
 Intake pipe leaking
 Improper carb adjustment
 Clogged jet
 Improper float level
• If performance does not improve check performance without air cleaner
o Better
 Dirty air cleaner
 Rich mixture
 Clogged carb air passages
 Improper float level
• If performance doesn't improve test specified fuel flow
o Under the specified
 Dirty fuel filter
 Clogged fuel lines
 Faulty fuel pump or relay
• If fuel flow is good check cylinder compression (above)
• If compression is normal check ignition timing using timing light with full advance
o Abnormal
 Faulty pulse rotor
 generator with ferrous burrs
• If ignition timing is good test ride bike and check for valve surging
o Valve surging
 Improper valve clearance (too small)
 Weak valve spring
 Worn camshaft
• Check for clutch slippage
o Slipping
 Improper clutch lever free play
 Faulty clutch lifter system
 Worn or warped clutch discs/plates
 Weak clutch springs
• If clutch is good clean carb air passages and jets
o Better
 Clogging
• Does not improve
o Seized cylinder and piston
o Seized connecting rod bearing
o Damaged main bearing

________________________________________________________________________________
Common faults on the Bros
• Stater motor does not work
o Starter relay switch
o Worn carbon brush terminals in starter motor
o Open circuit in stater button wire on right hand switch gear
• Hard starting
o clogged carb
o Incorrect carb adjustment
o Vacuum in fuel tank caused by clogged breather hole
o Faulty fuel pump
• Engine stalls as if it were out of petrol
o Clogged breather hole in fuel tank
o Faulty fuel pump
• See rough idle

________________________________________________________________________________
Ignition timing


_________________________________________

Ignition advance for Bros 400 J/K
10° BTDC, "F" mark, at idle (1,200 rpm)
32° BTDC at 9,000 +/- 200 rpm, full advance

_________________________________________

Ignition advance for Bros 650 J/K
10° BTDC, "F" mark, at idle (1,200 )
31° BTDC at 7000 +/- 200 rpm, full advance

_________________________________________

[edszuk]

Thanks for all the info. Just out of curiosity, what is acceptable cylinder pressure? I'm off to the parts store for a carb kit and filter.

Ed