VF500F - Top End Modifcations - Tech Questions

The depth of the hardened surfaces has been questioned as well. Basically, after a little wear, the hardness is gone, and things wear rapidly from there.

I'll try to remember to grab some pics of the destroyed top-end of the parts engine (original for my bike) some time.

 

Hey IC have you thought about going with an 86' engine? I read that they have a few advantages over the 84/85 and one advantage being a stronger crankshaft. For the 86' I believe they modified a few things to address some of the probs that the 84/85's were having also, one example being the oil mods, and i bet it would be a safer bet trying to get more power (or reliability at high rpm's). There are a few more mods they did to the 86' engine that I cant think up off the top of my head but i do remember that all of the differences were a fix over the 84/85 design.

As far as the DD oil kit goes I would say that it doesent need it unless you are just going to run the piss out of it. It definately would not hurt as long as the mod doesent starve the engine of oil under low pressure conditions such as idle.

 

Thanks for the post.

I have a very low mileage '84 engine. I would like to give a go at adding upgrades to this - though I wouldn't turn down an '86 engine if one (in good shape) comes up on eBay.

In terms of the bottom end, from what I have read the crank issues are only related to the very early issue '84 engines (ones with a 5-speed transmission). The later issue engines are a-okay.

As noted, there are several changes to the '86 engine - many good and perhaps one not so good. On the plus side is the larger oil pump (larger impellers) and deeper oil pan with extra cooling fins. The caveat with this mod is the you also need to switch out the headers and collector to clear the pan. I'm working on sourcing these parts.

While both the '84/'85 and the '86 were praised when they first came out (articles have been posted here) one issue that the '86 has compared to the '84/'85 is the stock valve spring pressure which increased do to a shorter valve stem. Dave Dodge mentioned this to me awhile back. He use to retrofit '86 heads with '84/'85 springs for this reason.

Dave writes:

"The trick on the VF500 heads is to use a spring with 1985-prior seat pressure in the 1986 heads. The stem height on the 1986 is shorter and has increased seat pressure which caused the valve dropping problem. So finding a spring that provides the lighter seat pressure, but seats at the shorter '86 stem height is the key."

Lots to learn about on these engines,,,as conjoined with the heads are the cam profiles (milder cam in the '86) and carburetor bores (32mm vs 30mm in the '86). See the Dyno charts below for the differences in the torque/hp curve.

My goal for my '84 is to work on modifications that will allow the engine to be content at 10,500 to 11,000 rpm and to get the 10 hp back (right now per JD's recommendation I'm holding to the 9k mark).

I do think a top end oil mod can work but I would tend to want to pair this with the larger oil pump to have the added advantage for more oil/oil pressure in the system.

For reference, here are the dyno charts (orig. published in Cycle back in the day)

1984:



1986:



Overlay:

 

Well noted,,,on this topic - another Dave Dodge tech tip with your morning coffee (or tea)

"First thing to do is keep the oil changed and fresh. I recommend using Valvoline Max-Life 10w-40 which is a mineral/synthetic blend. This oil has good "cling" properties and leaves a good film of oil on the parts when the engine is not running....Next is make sure you have the proper valve clearances. Too tight causes the oil to be wiped from the cam lobes resulting in premature wear."

 

Thanks for the post Stewart.

Would you happen to have a few photos of the install of the kit on your bike?

On a side note - nice to hear of a stock '86 going 30K+ with no issues.

 

True enough,,,this can be rectified with hardfacing the cams and followers à la Megacycle.

Please post the photos when you have a chance. Thx!

 

I'm not sure how much proof is needed, really. If you think sitting at a stoplight on a hot summer day with no oil flow is ok then I suppose you'll never get enough evidence to convince you.

The hardness of the rocker faces is the second part of the problem. Had only one or the other been present we wouldn't be talking about it. Since it's much easier and MUCH cheaper to modify the oiling system rather than re-harden or hardweld and grind the rockers, the solution is easy to see.

 

My 83 750 still has the original cams after 60k miles. Back around 85/86 I put in a different oil orifice fitting that supplies oil to the cams. It was a Honda fix at the time. Notice how much larger the hole in the left one is. The right orifice bolt is the original stock one. I also used Spectro oil in this bike since new. That may be all the 500 needs. I'm sure you can alter your original fitting to supply more oil at idle. Not pressure wise but volume wise. It would be easy to check by running engine at idle with valve covers off. Taking oil away from the mains is not a good thing. IC still trying to track down Keith. I should know more this week.

There are possible ways to find out about your valve spring specs and what you may need if I can't find out from Keith. To lengthy right now to explain.

 

If a top end oiling kit is a fix for the wear on the followers and cam lobes without compromising oil to the main bearings I will say that this would save a bunch versus hardwelding,,,the price really adds up for this service topping out at $598 for the cams and $496 for the rockers.

This said, I would rather invest in a spring kit from KPMI which would run about $500 (if this is a custom order - $400 if a multiple order). The spring kit comes with Ti retainers, and lower collars. Valves would be nice too but these are a bit salty at $50 each and from what I understand, while a serious upgrade, are not required as the stock valves can be re-used - if they are in good shape.

 

Hi Grey, thanks for the post and with putting a call out to Keith. I look forward to hearing his thoughts on this.

On a side note - could you explain a bit more about the orifice mod? If you are increasing the aperture could you run the risk of decreasing the pressure? Also, was there a FSB on this?

Thx!

 

Before people get too excited, this is just a small piece of the puzzle and only applies to the 1983 VF750F. The other models and years had this corrected but it really did nothing to fix the problem. Even with this change the oil flow is inadequate.

 

To clarify, this is the external oil line banjo fitting that goes here?

 

On a side note - do all VF500F cams have these holes? Thx!

 

All of the problems being discussed are easily rectified with currently available technology. Surface treatment of the components is a good first step.

Micropolishing
Cryogenic
Lubricity Coatings
Ultrasonic Impact Treatment

How bad do you want it?


.......

 

The few set that I had ('84 and '85) did.

 

Thanks Michael. I had read that cams issued with the first year VF750F did not have these and that subsequent models did. I looks like all years of the VF500F have them.

Any thoughts on what the holes are for? I read this has to do with how stable the cam is (walking around wise) but I don't know the specifics.

 

Yes, exactly. On the front head you have some clearance issues with the carbs. What I did to solve this was to use a double banjo bolt with a spacer to raise up the banjo fitting. It then can be routed directly out towards the right side in front of/above the intake runner. The 500's are a tight package!