VF500F Cam Spec's '84/'85 vs. '86

Michael your looking at it from the wrong end. Look at it from the valve seat. The valve is "lifted" off the valve seat. Normal position is the valve is closed. Cam bumps valve to lift it off the seat to allow air to flow in to the cylinder. How you lift the valve depends on how you want the air to enter. For example: two cams ground to the same specs ie "lift and duration". One cam will lift the valve lets say .200" in 60 degrees of crankshaft rotation while the other may only lift it .150" in the same amount of rotational degrees. This can be accomplished several ways. 1- by the lobe profile the cam grinder grinds in it, 2-by the rocker arm ratio. Depending on the seat angle 30*, 45* or 55* and if it has a competition grind (3-5 angles) or a street grind of 2 angles depends on how much and when the flow starts once the valve starts to move off the seat, aka lift. The 30* grind is more for more flow at low lift and torque. Where as the 55* is for high rpm high lift racing engines.

the numbers .200, .150 at 60* rotation are just pulled out of my arse and are not actual anything. Just an example for clarity.

 

I don't know, many of my bikes spend quite a bit of time on the back wheel. Since the rear cylinder is actually pointing downward at this time, the valves are in fact being "lifted".

And naturally you could stand on your head when thinking about it.

 

Haha! Thanks guys.

 

Thank you for the post.

So how would you go about describing the cam profile of the '86 vs. the '84/'85 - given that the '86 produces more torque but less HP?

On a side note, the spec's above show the '84/'85 having 230 degrees and the '86 having 225 degrees of rotation at 1mm lift. Does this 5 degree difference in rotation have to do with the smaller 30mm throttle bore?

I'll have to check the rocker arm part numbers - not sure if they changed for the '86 model...

 

"Does this 5 degree difference in rotation have to do with the smaller 30mm throttle bore?"

And the answer is............Yes..No..Maybe. Clear?

It could be any number of reasons. Generally speaking the smaller duration cam the lower the power band is. At the lower end of the PB the slower the piston may be traveling so the lower the velocity if all else is equal. May be the 32mm carbs were to large to begin with and used for higher rpm. Smaller carb should have higher velocity at lower rpms. The only way to know for sure is to talk to the Honda engineers who designed the engine and find out what they wanted to accomplish when they designed it.

JD I'm standing on my head. NOW I get it.:tongue:

 

Okay, got it, I think ;-)

So in describing the '86 cam, the term I've seen used: 'aggressive grind' could be a bit of a misnomer then?

If I want to go with hardfaced cams do you think I should consider matching the stock grind or go for the Megacycle upgrade? This would be for the street.

Thx!

 

This thread is extremely interesting. Honda engineers would be proud to see consumers mulling over data and specifications of a 25 year old machine.

 

Invisible, since I've been on this forum it seems to me you have been very active in preserving you 500's life expectancy. I was just wondering if letting the engine go until it blows it's smooth, sewing machine brains out would be a better and more cost effective option. Let it go, and then buy another engine. I know eBay pickings are slim, and there is an engine up there for an outrageous $750, but there are more out there. I even have an extra one with 7k on it that I was going to sell. That kit is expensive, and I really don't believe it will stop the 500's death clock, possibly extend it though.

If you have an all matching numbers bike, you could take a proactive step and put in another engine to put the miles on and keep the matching engine on a shelf until needed. I also feel like a vf500f with all matching numbers, but after market cams, rockers, etc, will lower the value and collect ability of an all original bike. That's one of the reasons I'm going to sell mine, it's not all original, and I can't make it to be so.

To add: I'm NOT trying to plug a sale for my extra engine, and I don't want to discourage this research into the 500's engine, I would like to see more in fact.

Whatever you do GOOD LUCK!

 

Have you seen his bike? It's like new with super low KM, maybe less than my "new" bike! (Yes, I am jealous)

 

Ferrarone - I can't recall from your mega-thread why you didn't just use the low KM motor in your bike. 7k? I am sure that Invisible will have an offer PM to you in minutes.

 

There were a few steps in my epic learning process that I did not include. At first I didn't understand that a dirty carb could prevent a motorcycle from starting and idling, I thought it just controlled acceleration. Because of this some major parts of my build went something like:
0. (Super clogged carb)
1. Remove Engine A (blown)
2. Install Engine B - No start
3. Remove B
4. Install C - No start
5. Remove C
6. Install B
7. Amateur carb cleaning - Almost start
8. Remove B
9. Install C
10. Super carb cleaning - Starts right over.
(Sprinkle valve tappet adjustments and readjustments throughout)

I didn't post some of this info because I was either hard at work, extremely stressed out, and or ashamed of failure and confirmation of squirrelman's negative predictions.

Had I known what I know now, I would have had a running bike a week after I bought it, and have it in the condition it is now in a month. I thought I understood a lot more than I did at the time. DSkelton also saved my ass with his amazing donation, and I owe all my future motorcycling experiences to him. In fact the frame and some engine components were given to a Montreal member, and some forks to someone in NH I think. Skelton's generosity has reached international levels haha.

 

Thanks for the posts.

Some of this research is admittedly academic. There are some salty birds on here that know their way around an engine and in part I am hoping to glean intel from them.

This said, I have been keeping my eye out for a spare set of '84 heads...

 

"If I want to go with hardfaced cams do you think I should consider matching the stock grind or go for the Megacycle upgrade? This would be for the street."

Seeing I'm a fan of Tim "The Tool Man" Taylor. I always want MORE power grunt grunt grunt!! I'd use the street cam they make. I'd first talk to the cam grinder and see what the characteristics of the cam is. The one I would first ask is this one:

147-20 .360" 254° 110° OK with stock pistons, K.P.M. or R/D springs 17 btc/57 abc .006"are
.360" 254° 110° recommended. Greatly improved top-end power. 57 bbc/17 atc .007"
Good mid-range response. Check all clearances.

My thinking on this would be to ask about the LCA of 110*. Thinking that much is why it's a greatly improved top end. Installing it 108* may lose a little top end but improve the mid range much more. Which is what I would want for street. If there are no valve to piston clearance problems to do that. You will need to go with the valve springs they recommend (even if stock type cam is used). Don't know about the rockers, I'm not familiar with the rocker problems. That would be another question.

Of coarse if you do change cams then you will most likely need to change to headers and do carb work to get the power from the cam. No matter what the carb will have to be dialed in to the new engine config. You might be able to get away with the stock exhaust if you used this other cam:

147-00 .365" 240° 105° OK with stock pistons and springs. Designed 15 btc/45 abc
.365" 240° 105° for mid-range power increase in stock motor. 45 bbc/15 atc
Welded rocker arms suggested for longer wear.

Seeing it seems just to be a little more potent cam like the factory would use. Carb would most likely need some alterations also. Seeing you have the larger carbs that's a good thing. Remember there is no free lunch in any alterations you do to you bike. So be ready to do some tuning.

 

Hi Grey, Thank you for the post.

I think my only choice is Mega's 156-00 (.350" lift, 250 degree duration at .040", 104 degree lobe centers).

The cams you've noted above are for the larger VF700F and VF750F.



Point well noted on the carburetor jetting. I'm planning on installing a Factory Pro jet kit (#108 main jets and adjustable jet needles) .

 

Yea I guess they are. I skipped over that small bit of info. daaaa That's what happens when you get old. Must have rolled the screen to fast and went right by it.

I would still talk to the cam guys about exhaust. It's probably needed to get what the cams are designed for on the top end. You'll have to let us know how it works out.

 

5x5, thanks again for the tech talk.

 

I read through the thread and can offer this if it helps.

The 84' used 107.5 intake-108 exhaust centerlines.

The 86' used 102.5 Intake- 107.5 exhaust centerlines.

Of those two and all else equal the 86' will have broader power range because of the intakes early opening along with less peak TQ and horsepower.

If i read this correctly your looking to warm the 500's output a bit. Suggest spending time and effort cleaning the ports , especially at the valve throat and making a set of adjustable cam sprockets to enable setting the cams @ 106I-108E along with a good exhaust system.

Been there and done it with VTR's and the likes and the increase in VE with race cams can really richen the A/F ratio and without ability to change the carb slides on CV types -- well it can be a problem. My guess without searching is aftermarket Mikuni's for this bike are long gone in terms of availability.

If you do want to pursue camming it up beyond stock , WebCam Inc has a catalog of lobe profiles for the V-4 engines. At only 12.1 compression i'd say easy does it because overcamming is common. Over camming without being able to lean out the midrange easily via carb slide cutaway change is problamatic. That's aside the needle jet and needles.

 

Thank you for the post and welcome to VFRworld!

Adjustable cam sprockets sound like great upgrade. Perhaps this in conjunction with hardfaced cams - following the OEM profile - is the best way to go on my project bike.

On a side note, below is a dyno chart for the '84 VF500F. Source: Cycle, July 1984.



I haven't located a dyno chart for the stock '86 model, as of yet, but I would be curious to compare the two...

 

Thanks for the welcome. I have memories of being smoked on the race track by a near stock 500 Interceptor back in the days. I had double the HP to boot :biggrin:

I just noticed the Megacycle post. The added 14+ degree's of duration does not seem overkill and being able to use stock valve springs to enable longetivity is a plus. The lift would complement any portwork .

As you can see on the dyno sheet, the stock cams had enough to allow additional over run w/o falling off the earth . Depending, i might still opt for stock cams , tighten the quench area with some headwork and a good pipe. That's just me though leaving some HP on the table in effort to reduce cost and tuning troubles.

It's your project though so have fun with it ! I'm wanting to find hidden HP in the VFR1200F. Crazy thing to do, i know. Boys will be boys, right ? :biggrin:

 

Great to have you here.

The VF500F has a bit of a reputation regarding its valve train. While engines that are properly maintained will last a long time - a valve or two has been known to drop from time to time - on less fortunate bikes.

With this in mind I have been looking into options for replacement parts, especially as many valve train parts are now unfortunately NLA.

Perhaps the best place to start though, for my project bike, is with adjustable cam sprockets...I'll see if I can track down a source for these.

Thanks again for your helpful post!