Valve clearances

So with the 84-85 engine requiring 0.16mm clearance and the 86 Engine requiring 0.15mm clearance....

What if you take an 86 VF500 somewhere and they don't know there's a difference so they set it to 0.16mm. Would the 0.01mm difference matter?

 

You do however have to make sure your feeler gauge is centered on the contact patch of where the rocker arm meets the cam, if not then it can get cocked sideways.

found my mysterious tick, turns out I had the clearances adjusted too tight for that valve set, it was the same clearance as all the others but for some reason on that one part it was too tight, loosened the gap up .002 in and it seems to be fixed. I did however replace the rocker arm/rocker arm shaft/ that spring that holds the shaft/ and the tappets on the rocker arm at the same time. Under close inspection all the parts pass the honda manual's specs but maybe somewhere in there something was wrong also.. who knows, Im just glad its fixed!!!

 

You would be suprised as to how small of a difference matters with these things, an 1/8th of a turn on the tappets can cause the valves to tick alot louder than normal. However I do not think that the 84-85 engine requires .16mm, I may be wrong because thats not what I have but I believe that engine calls for .12mm intake and .13mm exhaust. And the 86 does call for .15mm for both.

 

Agreed - the Factory specification in my '84 in my manual is .12mm intake and .13mm exhaust.

 

Any chance to cajole you to get out your sketch pad? Thx!

 

If one valve is more worn than the other, the tappet on that side will just be screwed in alittle further when you are adjusting them. When you put the feeler gauge in between the rocker and cam, you are setting you gap to 1.5 times whatever feeler gauge you use, you then tighten the tappets down till they both touch the valve tips which gives drag on the feeler gauge. As long as you tighten both tappets down till they cause drag, once you remove the feeler gauge there will be an equal gap on both sides. Help any? I know alot of that you probably already knew but putting it all together like that is what helped me understand it. Ill try and draw alittle something...

**valve thats not worn**
_ <-- rocker
l
l <-- tappet
( gap)
_ <-- valve tip
******************************************
**valve thats worn**
_ <-- rocker
l
l <--- tappet
l
( same gap)
_ <-- valve tip


sorry for the extremely primative drawing!

 

Thank you for the post. It's a very clear explanation.

Regarding the 1.5 to 1 ratio - does anyone know if this is applicable for all VF engines - i.e this is the same ratio on the 500, 750 and 1000cc engines?

 

I checked my 85 owners manual and my 86 owners manual and they do call for .12mm intake and .13mm exhaust for the 85, and the 86 does call for .15mm for both.

Any ideas why the change?

 

That's what the Clymer's amnual says as well.

I wonder if the looser clearance would help or hurt the valve float issue? Well, not that it would make the float any different, but maybe the damage from the floating. Jamie, paging Jamie Daugherty to this thread...

 

Seems like the extra clearance would hurt the floating, maybe the cams on the 86 are more/less aggressive and that is affecting the clearances??

 

Actually I did hear somewhere that the 86 has more aggressive cams.

????

 

In looking around for other info, I ran across this link, which give a reasoning for them changing the spec, from Dave Dodge, THE early VF guru.

Explanation of top end oiling problem

The answer is at the end of the second paragraph.

 

1986 VFR500FG valve clearance spec

My 86 VFR500FG has a factory honda sticker under the seat specifying .15mm clearance both intake and exhaust.