675 Will Only Partially Crank Not Enough To Start

Hi Spikey and welcome to the forum, first off these engines are pretty much bomb proof, however what you describe does not sound good, take off the cover to access the bolt for the timing check, and try turning the engine over very slow using a good socket and break bar, that way you will see if the engine is turning freely, the story given to you by the previous owner may be of being "economical with the truth", and it may be the person knew more than they are letting on. Before going into more detail of what may be wrong, try turning the engine by hand and come back and let the forum know the result of that. Hope this assists.

 

They symptoms you describe sound like hydrolock. Try it with the plugs out.

 

Never heard of that. How does that pan out ?

 

It's when fuel or coolant seeps into a cylinder. The massive increase in compression means the starter motor can't turn the engine over. I'f you force it, you usually bend a con-rod

 

It used to happen a lot with early 2 stroke Suzuki's, the problem was the fuel tap drained fuel from the tank to the crankcase, then when you tried to start it the engine was effectively Hydro locked, the result was damaged conrods, it happens in more modern machines when the head gasket fails and leaks water and oil to the crankcase, the engine then effectively becomes locked with pressure.

 

I have had similiar in the past with a supposedly good, just purchased, secondhand Transit DI engine. The seller stated in good order when in actual fact it must have been stored somewhere damp and corrosion had set in. Being a diesel the clearances were tight and getting over TDC on that cylinder proved difficult so giving one tight spot per revolution. I took the head off and all was revealed, promptly returning the scrap unit.

Turn over as @Iceman suggested and report back on the resistance experienced, noting the crank angle if anything untoward is felt ( marker pen on the flywheel). Then repeat with the plugs out and see if the resistance is similar or resolved

 

Not sure if starter relay/socket was mentioned but it could be that if corrosion on the pins or burned cables?

 

Lots of fail safes in the starter circuit, for example clutch and sidestand switches. There should be a wiring diagram/service manual available online to help find them. By jumping the solenoid from the battery you are effectively bypassing them, locating them and bypassing each in turn might throw up a faulty sensor (some are located in areas where the contacts/connectors will corroded and/ or get dirty).

The CPS connector is another potential culprit, its connector is hidden on the crankcase below the injectors and is a pig to get to.

Still on the electrical side, a broken or partially broken wire is another possibility if the jerk of the starter causes it to break contact. The wires running to the side of the headstock are particularly prone to this type of damage. Bridging suspected areas with a jump wire and using a multimeter or test light to check continuity should help.

If you can't find a wiring diagram, I might have one but would need to check to be sure.

 

Have you tried another solenoid? Sounds like high resistance across the contacts to me, as you said it spins over if you bypass the solenoid.

 

All symptoms of hydrolock on a modern bike.

 

Head for the oven

 

The gas bill will come some time later so as long as you are effective........
just saying

Fuel pump relay?
Is electrical supply getting there at all to do the "initializing" ?

 

Oh god, electrics, the devil's work. Good luck.

 

Did you find out what was causing the issue? Have a similar problem with mine. Only getting a partial crank