Bent connecting rod?

Hello gentlemen and ladies,

I purchased a 2002 VFR on eBay. In the past I have owned a 1998 VFR and a 1994 VFR. I did all the maintenance on the VFR's myself, including fork seals and non-VTEC valve adjustment.

The 2002 VFR in question has 22000 miles on it. The previous owner stated in the ebay posting that the engine had a bent rod. In emails and messaging he described the failure event as a loss of power while cruising on a freeway at normal speed, then the engine began running very rough, so he pulled over and stopped. I do not recall if he stopped the engine or it stopped running on its own. After stopping, he was able to restart the engine one time, but it ran very rough and would not keep running. Then it would not start at all. The previous owner was not mechanical, so he had the VFR transported to a mechanic, who checked the engine out and pronounced that it had a bent connecting rod. The previous owner did not ask how the bent rod was detected, nor was he able to recall what the mechanic said about a possible cause for a bent rod.

*My question is "How can I confirm or disprove the diagnosis of a bent rod?"

So far, I have drained the oil. Almost 3 quarts of oil drained from the engine. I did not see any metal particles or gray swirls in the oil. I have not yet removed the oil filter to cut it open for inspection - that is my next step.

Before purchasing a used engine, I thought I'd poke around the bent rod engine and see if it really is damaged internally. A bent rod seems highly unlikely on a VFR with such moderate mileage.

Thank you for any input you can offer.

 

With the plugs out can you turn the motor over by hand

 

Thanks Norm - I'll pull the plugs and try to turn it over.

 

With the plugs out, you can also measure the depth of the piston through the spark plug holes and compare when they peak in the cylinder.

 

I think I bid on that bike. I believe you will find no bent rod, but something else caused it to lose power. I have a feeling you will come out ok on the deal when all is said and done. Just speculation of course.

 

That avatar tho!

 

Thanks, Lint. I appreciate that you noticed my new avatar ...

 

Sorry I know a reply was given but must have missed it due to avatars....

 

let us know what you find. bent rod is unlikely unless it dropped a valve...........but in that case the engine would lock up.

 

I've been a bit slow to replay, what with all the avatar action. I'll read the service manual for electrical troubleshooting procedures, start into the compression check, and post results.

 

I wouldn't be worrying about electrical troubleshooting till you have proven there is nothing wrong structurally with the motor. Once you have established the motor rotates freely, valve clearances are correct, nothing is amiss with the cams then you can think about cranking it over with the starter motor

 

Someone could have hydraulic the motor and bent a rod. Carb drains, fills cylinder and it comes up on the compression stroke. Somethings gotta give...............

Just use a dial indicator or a set of calipers that read .001 or better at tdc in each set. They should come in a couple of thou to each other (2/4) (1/3)

 

Was driving on the freeway and it lost power so unlikely to have hydrauliced the engine

 

No carbs on '02....could possibly have jumped timing due to worn out cam chain and tensioners, etc. If this is the case, attempts to start it multiple times after the event has destroyed the entire top end.

Could be as simple as a failed fuel pump.....

 

I posted this reply before, but as far as I can tell, it's not showing up on the thread [It seems the only option to replay is to use "quick reply"]:

Oil filter element is clean - no evidence of foreign material. Engine turns over by hand [14mm socket wrench through the timing hole] and generates good compression on all four compression strokes.

Question - can anyone confirm that the #4 cylinder is the rear left on my 2002 gen 6? The picture in my service manual really looks like it's rear left, but #4 could be front right...

More to follow after I drop a little oil down the plug holes, turn it over a few times to clear the oil, then do a compression check. Will the preventative oil down the plug well mess up the compression test readings?

 

It should improve them!

 

#4 is front right.

 

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Plug, plug wire, coil, ignition box, fuel pump, fuel pressure regulator, injector are just a few things come to mind. Seeing it lost power when running. Who was the dumbass mechanic? Forget the rod. Didn't see it was running when problem happened. Make sure you have a constant full 12v, without it the ecu doesn't work right.

 

I like the sequence "plug, plug wire, coil, ignition box,fuel pump, fuel pressure regulator, injector. ThanksGreyVF750F.
Plugs out. Engine turns from the timing hole with socket wrench - it's tight for half a turn then loosens up, I presume the tightness is the four pistons going up, looseness is when they go down.

Existing plugs are NGK Iridium, all look practically new except #4 is blackened. No buildup, but the other three plugs have no discoloration.

Drain plug on and torqued, new oil filter on, 3.1 liters of new oil in. 1/4 ounce of oil down each plug hole.*Turned engine through 8 revolutions.

Ready to do compression test.