VF500F - Top End Modifcations - Tech Questions

Hollow core camshaft and lubricating the journal it runs in.

Switching the spring and seat cup/retainer assemblies completely out to another OEM style thats still available and ditch the multiple spring base seats Honda was using is both the most logical and suitable solution. Kibblewhite offers some good parts but you don't need or want heavier springs than necessary even with hardweld rockers, unless it's a max effort engine which it's not.

There's just no getting by not hardwelding the rocker followers.

Increasing the sump capacity would be a good thing with or without the 86' oil pump. You will need to use the 86' pickup because of the extra depth. Blueprint the oil pump by simply closing up the rotor clearance. The pump must be in much better starting condition than either of the two pumps you posted photos of. You might even rework the oil bypass on the 84-85 style pump. Easy enough thing there but i would also entertain the idea of actually overdriving the oil pump by aprox 10-15%, only if using the larger oil pan and smaller 84/85 oil pump. Hold that thought for later though.

Next up is giving the rocker pad a direct shot of engine oil using the existing over head oil tubing with minor redirection. That looks to be as the second largest issue aside the soft rockers and lack of NEW OEM valve spring availability.

I have some questions . Are you going to cam the motor up or leave cams stock? Can you give me both valve spring diameters and installed height ? Free length on both? If not, a trip to a local machine shop will be needed and then there will be more that needs be checked at that point. That being both open and close spring pressures.

Without that no need to start looking for springs.

 

Thank you for the post. I think you may be a few classes ahead of me on this ;-)

I hope it is okay if I ask a few questions.

Regarding the inner and outer valve springs,,,as noted the VTR250 shared the same part number as the '84/'85 VF500F (the '86 has a different valve stem and valve spring design) but unfortunately both are NLA. I think the only option at this point is to send a spare head to R/D Springs or KPMI for some R&D but I would be interested to hear your thoughts on this.

Also, could you please go into a bit more detail on 'ditching the multiple spring base seats'? Are you recommending to only use one spring instead of the double spring design?

5x5 on the followers - hardwelding is pricey ($60 each) from Megacycle though - any thoughts on other sources for this service?

Interesting point about keeping the stock pump and using the longer '86 pick-up in conjunction with the deeper '86 oil pan. I hadn’t thought of this. How would you go about overdriving the '84/'85 oil pump?

Redirecting the overhead oil tubing also sounds interesting. What the are the caveats to this and how does one go about modifying these?

Regarding the cams, I am planning on keeping them stock.

I do not have the valve spring specs you requested but I do have a spare set of '85 heads. I could look into getting this data but as you suggest I will need to send a head to a machine shop to accomplish this. Do you have a machine shop that you can recommend?

Again many thanks for the post! I appreciate the interest in this project.

 

Here you go IC. I installed this kit back in 2003 and I believe it came from Mark Douglas. As stated, this bike has given me no problems and my brother's is bone stock with 30K+ miles. Both bikes are properly maintained as this could be the whole key to the problems that people have with this bike.

 

Thanks Stewart!

It is very helpful to see this kit from Mark Douglas. It looks like he made a quality product. Glad to hear that this is working well for you.

I agree that the VF500F benefits greatly from a conscientious owner.

Besides careful maintenance (I've recently read that a factory rep suggested to one owner that the valve lash be checked every 4,000 miles for example) one the most important things you can do is let the engine properly warm up to operating temp before riding. I have a hunch that a lot of wear and tear was caused by improper revving on a cold engine.

 

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Hardening

Brycoat Advanced Metallurgical Coatings - BryCoat Titanium Nitride (TiN) Coatings


......

 

FYI - Mark made the Dave Dodge (DRP) kits for a number of years before he fell off the map and Dave had to find someone else to make them. I believe that Dave used different lines to the heads though. The banjo fittings at the head on Dave's kits had more restriction., if memory serves me.

 

I found this on one of the endless resources there are for information on old V4 Honda's and it seems to have a lot of valid points for the oil flow being insufficient, etc. (From v4honda.com)

"Since the beginning Honda has made many upgrades to the materials, hardness, etc., but the problem can still occur at any time. The stock top-end oiling system is low pressure, low volume and unfiltered. One thing that most people overlook is that the top-end is getting it's oil supply from the low pressure side of the oil pump that also feeds the
transmission.

To build the pressure to an acceptable level the oil passes through a nozzle with an .080" hole which equals less than 25% of the ID of the metal hoses it feeds. If the oil is not changed regularly, debris can also be passed through to the heads which can cause cam journal gouging. Also, when the engine is at idle the pressure can sometimes drop below 8 psi meaning that sustained idle time can cause wear that progressively gets worse.

The stock top-end oil system has no provision to stop back-flow, which means when the engine is not running the lines that feed the heads drain back into the crankcase causing a dry start-up situation in the heads. Proper valve clearances are also important because the stock oil system feeds no substantial volume, tight valves can actually wipe the oil from
the lobes and rocker surfaces causing even more wear or cam pitting.

This is why Honda increased the clearance spec from .004" to .006". When the engine is at running temp., valve clearance is reduced as much as .003" from part expansion. The entire surface of the cam only gets lubricated at the point on the heel of the cam where you have clearance. There are even occurrences where an engine and cams will be fine for 30K or more miles then all of the sudden cams fail. This can be caused by the last valve adjustment being too tight, or a weakened oil pump. An oil system that is barely good enough to begin with, can cause problems as the pump loses it's full pressure from wear. "

 

I don't know if I've ever seen a definite specification for the oil pressure to the top end, Only for the pressure at the oil pressure switch.
I think it's kind of a piece of mind modification just as extra insurance for the top end. Personally I want to do the adapter mod but there's no way i'll be able to torque the banjo bolts with the carbs on the bike and tha'ts a damn hassle to take the carbs off and on.
Personally I think with good synthetic oil and taking care of the bike (very vague but you get my point) it PROBABLY wont fail prematurely. My bike has 11k miles and i know for sure it was abused and it seems to be pretty solid.

 

I've posted a link to the web article for reference. The author is Dave Dodge.

Explanation of top end oiling problem

On a side note DD does not recommend installing a top end oiling kit on the VF500F:

We have determined over the years that the VF500 does not work well with an oil mod. The pre-86 models had weak cranks* and a stock oil system that would not support the addition of the mod. The 1986 model has a strong crank and rods, but were prone to drop valves due to mechanical issues more than oiling issues.

We recommend and make oil mod kits for 1982-1988 VF700, VF750 (V45), VF1000, and VF1100 (V65) models. On these engines we can feed filtered oil to the heads at twice the pressure and volume vs. the stock system, plus we get 3-5 psi oil pressure increase at idle.

*From what I have read the weak crank issue was only on the early VF500F engines - these are identified by having a 5 speed transmission.

 

By his own admission Dave doesn't have much experience with the 500's. I think if he'd seen the damage from inadequate oil flow, as myself and others have, he might change his mind. I interpret his statement as a reason why he doesn't offer one for the 500's, thus keeping people from asking. Just a hunch.

 

A bit more intel - from DD - The 1984/85 rods were soft... only 14.5 c-scale for hardness. In 1986 the 500F, VFR 750, and 1000 had stronger rods 42 c-scale hardness, which is a hardness spec we always used for high RPM and race engine use.

I haven't heard of connecting rod failure on '84/'85 engines but if the Rockwell Scale specs, as noted, are correct there is quite a difference between the '84/'85 and the '86 models.

 

How does this data correlate to the strength of the rods? Hardness really isn't a very good way to look at it. In fact, a higher harness value means it's more brittle. This would also mean that cracks propogate easier through it. Hardness can be an indication of the carbon content in the material. The carbon content will determine how hard you can get in a heat treatment process. For example, a low carbon steel can't reach the same hardness of a higher carbon content grade. You also need to know the percentage of other elements like Nickel and Chromium before making a judgement on how "good" the material is.

Besides the extremely early 84 5-speed engines, which you won't ever find since they were recalled before hitting the dealerships, I've not heard of any bottom end failures on the 500's. I probably wouldn't advise trying to put nitrous or a forced induction on a stock bottom end though!

 

Well noted, thanks for the post.

 

Keep us updated IC I would like see what you get.

 

I need to subscribe to this post. Lot's of good info here. Thanks

 

Have got one of these in the UK that has been stood for 7 years. Needs loads of work given myself a few years to get her up and running any totally renew of paint etc. Looking forward to it but used to super reliable CB250rs sinlge and CBR 600 have enjoyed some of the help from the forums, will post any info as looks like this ones been run hard before it was left to the weather. TY Rich

 

Hey Rich. Welcome to the board. Everyone here will help out as much as possible. You should consider setting up a thread to introduce yourself and your bike and post your progress. We love this stuff. Post lots of pics! Good luck.