Trying to confirm motor on 86 VFR750?

Hello,

Picked up an '86 VFR750 and starting to go through the bike looking for things that need some TLC and noticed that it has the black side covers, not gold as I have seen in other pics. Any of you veterans have an idea of ways to determine if this is the original motor or not? I have also read somewhere that the 86's had the half moons on the cylinder heads (from a machining process) and my motor does not have those either so I am not sure if there is some variation depending on when it was built or other characteristics that will confirm this is the original motor?

The ODO just topped 24K miles on it so I would think that is relatively young but I have no history on this bike at all. I just finished dialing in the carbs so that it runs well and have started to ride it more; I notice a small "tick" in the motor at idle but I have read many posts of others with the same sound so let me know if there is anything I can do to identify any signs that that motor was changed. It runs very nice and I have put a few hundred miles on it in mildly hot weather with no signs of overheating or anything unusual besides the ticking sound but that may be normal so let me know...?

 

Does it have a steel frame or aluminum?

 

86 motors have a timing sensor with a wire on the back of the front cylinder. Then you can look at the casting marks on the cylinder portion of the crankcase to see which one, 698 or 748.

87 motors (all 698cc for the U.S.) have digital ignition and do not have the timing sensor.

 

It has the aluminum frame and I will take a look for the sensor and casting marks when I get home.

Thanks, this bike is like a box of chocolates with no history it so I am trying to get an idea of what I am working with...

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Is this (circled in red) the sensor you are referring to?

do some bikes come with the gold side covers and others not? Should I have the half moon covers on the cylinder heads or does that indicate something other than the year?

Sorry for all the questions..

 

That's the sensor, yes. All U.S. 86 had "gold" covers. Somebody has installed 87 covers or they have been re-finished. How many cc's is the motor?

Half moons you refer to deal with 1st gen motors.

 

Ok, i took a closer look at things and the Vin tag says VFR700F but the casting marks on the motor say 748. What other ways would I have to determine if this is the original motor?

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You just verified it's not.

 

how so? the displacement? I thought they sold both 700' and 750's during the same year? If it is not, is there an easy way to determine what year motor it is?

I read somewhere that all VFR's say VRF700F on the VIN tag and that both 700's and 750's were produced so I am confused... I guess it is not that uncommon for the side covers to be changed/modified as well.

 

They sold both 700 and 750 in 86.
The 700 was made to beat the high tariff on motorcycles over 700CC.

A 750 will say "VFR750F" on the tag.
Does the VIN say "JH2RC26..." or "JH2RC24..." ?

26 is a 700
24 is a 750

Your motor has to be an 86 because of the sensor.

 

ah, it says JH2RC2617xxxxxxx so if I am reading this correctly we can assume that someone put a 750 motor in my bike then?

 

It appears that would be the case.

 

I checked the engine number and it is RC24E-2011099.

Is there a database somewhere that will help me understand more about this motor?

One thing I have noticed is that it does not have that strong "whine" that I hear with other VFR's associated with the gear driven cams.

I guess if someone went to all the trouble of replacing the motor then who knows what other changes have been made to it?

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The early gear driven cam engines have more mechanical noise than the later ones in my opinion, covering up some gear whine. The later ones (90-93 & 94-97) have a more pronounced whine.

The "tick" you describe at idle is probably normal (mine have it to some extent with properly adjusted valves), but not being there in person, hard to say. If it was my "new" bike, I would be checking valve lash and inspecting the valve train.

 

Thanks for all the great information. I have a friend with a late 90's VFR and it has that strong whine so I figured they all sounded that way. Mine has the 4-1 Yoshi so the exhaust is the dominant sound but I love the way it sounds.

I will be checking the valve train next and sure wish I knew the true mileage nor rhat I know it is not the original motor. It sounds like we know it is an 86 motor at least.

again, thanks for all the great information, it has been very helpful since I am new to this bike.

 

Mileage on these engines is almost a moot point. If it sounds good, runs strong, and doesn't smoke... Enjoy your 750 motor. I have personally seen and serviced 2 that were ran hard and had over 100K with zero engine issues.