My "new" 84 750, loud tapping and hopeful restoration

Answered an add 2 weeks ago regarding a non-running 84 vfr750 (i get these models mixed up...it is an 854 Interceptor). Bike had been running fine, started running rough and owner parked it 2 years back. Unfortunately, outside for much of it so weather did take some toll on shiny stuff.

In anycase, I had only inquired out of interest and when the owner wrote that "he had some interest but no-one followed up and the scrappers would only give him$50 so I could have it free", I accepted but gave him $75 out of respect. I did not expect to get a running bike for $75 but figured something might be swappable to my 85 500 model (probably not) and had little to loose.

My son and I went to pick it up....three of us had to push it onto my trailer ramp, as the front tire was flat and the brakes were seizing, this was not too easy to do.

The bike came with an extra fairing and shield, lower scoop, side covers (front-body ones not under seat ones) so simply selling these will make up for the $75 purchase price and $25 flat repair.

A day later, my other son and I started to breath life back into it. We changed out the honey-like gas, sprayed the carbs from inside of the airbox after draining the floats, changed the oil, cleaned and gaped plugs, squirted some fresh oil onto the pistons and rotated a few times slowly, tightened everything up and punched the button...stated right up after a slight stumble. Idle was fairly smooth considering and the rear bank had a lout tapping noise. I figures these were out-of speck valve clearances. The clicking sped up as the rpm sped up.

Yesterday, we opened the rear cover and checked the valve clearances. 3 of 8 were a bit tight. We used the 2 feeler method to adjust and tighten, .005 for all valves and rechecked with .006 (no entry) to be sure. Buttoned things up again but noise remains.

It is quite loud. The cams had some pitting but no grooves.

We hope to do a compression check today to see if thee is any evidence of valve-piston contact. I am not familiar with these engines so will pose a few questions:

If the valves are adjusted but the cam lobe has some pitting (no grove), will this cause noise?
If a lobe is slightly worn, the valve would not open fully (as the worn material means the lobe would not push down as far) so would adjusting the valve clearance by the same amount minimize the effect by essentially taking up the slack?

I hope those questions don't sound too novice but better I ask than don't. I would really like to. bring this bike back to life. Then again, 90,000km so not expecting decades of riding fun.

Thanks

 

I don't know what the correct valve clearance is for the first gen. However, for the fifth gen the intake and exhaust are not the same value. Someone with the service manual will chime in soon.

In the mean time, some suggestions that you may have already addressed.

Before trying to start the non-running / neglected engine you should always make sure that there is no rust in the tank that could be pulled into the carbs and plug up the many ports and jets in the carbs.

The same check should be done in the air box to make sure that the local rodent populaton has not set up house keeping in the intake.

And.......while we are on the subject of mice, look over all of the wire harness for missing insulation. I have no idea why, but they like to chew on them. Find the problem before turning on the electrical power and you will save yourself much larger headaches later.

On the pessimistic side, the first gen VF750's were given the title "chocolate cam" because Honda failed to desgin sufficent oil lubrication to the cams and they became discolored. Your "tapping" may be a result of this known flaw.

I hope that you are able to sort it out.

 

if the valves are in spec then the noise may be the cam chains - I bought a 750 with around 64000km on it and it made a lot of noise and after checking the valves, both front and rear chains were loose.

fairly easy to deal with but I swapped in a low mile motor instead.

I would also recommend opening up the valve clearance slightly to 0.006" as from what I've read, 005 is a bit tight, far more experienced folks than me will likely chime in on this however

either way, congrats on the purchase and best of luck, post some pictures when you get the chance!

Tony

 

another hopeful optimist in the face of troubles

the noise won't be going away anytime soon.

 

Not expecting miracles but might as well go through the list of "maybe" stuff before I coffin the brave machine. Will adjust to .006 as per Honda update and check chain tension just in case. If those don't work, will explore "trading" some hard to find body parts for supply and install of a good, used rear cam. You just never know.

 

Hopefully it is top end noise and not lower end.... yep, proceed as planned and see how it goes.

 

Adjusted valves on 1 and 3 to .006 and checked for loose chain. Seems fine. Pitting is on short side of lobe on #1 mostly and none noticed on long sides of either. No noticeable grooving or marks on the long side either. Posting a link to a youtube video I took after adjustments... may make it easier to identify cause.

Thanks in advance.

 

cam noise judging from the frequency. maybe i'm wrong but i think exhaust valves should be set at .008"

that is LOUD, and you were taking a huge gamble to buy it, not so much for the $75, but now you gotta figure how to get rid of the damn thing.

the only possible hope to fix it is to find exactly where the sound is coming from.

 

.008? was that from a revised service bulletin? The manual claims .005 (Clymer) and the revised setting I have read about calls for .006.
Yep but for $75 ($100 now that I had the front tire repaired), I can get that back by selling the plastics and some parts. I really don't want to go that route but there is a limit to what i will invest in mechanical fixes for a bike this age. My 500 runs well enough.

 

Clymer is "a" manual, not "The" manual. Trust Clymer less than a "fine" from your wife.

 

^^cap, what's your opinion on the tapping ?

 

With the noise that loud id say either Cam failure or Cam Chain. Seems to be too loud to be a valve clearance issue, and IF its definitely coming from the top end, I'm thinking the chocolate cam's may have melted.

 

Well, they had the cover off to do a valve lash adjust and didn't note anything catastrophic.

If all the adjustment screws are in approximately the same spot (meaning a pair didn't have to be moved a lot to make up for a worn cam and/or follower), then I'd say the cam chain and/or tensioners are toast? Maybe a valve stem is mushroomed from valve float?

Sure sounds like cam/follower failure though.

What are the miles on the bike?

 

99k, which is why I will limit what I invest but the next step may be to remove the rear cam, check the specs and inspect the chain as well. Maybe one or the other. Maybe both. I will report back. Thanks y'all.

 

O.k. Thought I would check the tensioner for damage. Removed it safely and found the tensioner spring is fine, lever is fine and hole that the lever goes through is not damaged in any way as to bind things. Removed the cam and found that the lobes are worn (profile changed) and the #1 follower is cupped. I think the "clank" is the cam lobe smacking into the flat of the follower. So, the search begins for a good exhaust cam and followers (after I look into the spak plug hole with a borescope to see if I can spot any damage).

 

Well, shit. Not surprised, it's exactly what it sounded like. But still... shit.

 

But doctor....can it be saved?

 

Decent condition replacement cam and follower and you "should" be in good shape, problem is going to be finding a suitable replacement.

Best of luck and let us know how you make out, hopefully you can get it back on the road in short order!

 

Looking through the Honda FSM and I don't see any reference to part numbers, just the limits on the cam lobes. Are the front and rear or intake and exhaust cams t same on this bike? I did find some part numbers and they do change but I expect Honda would have different part numbers for the front and rear intake and exhaust cams, even though the front or rear should be the same. I ask as i may have found a rear intake cam but not certain if it will also fit the exhaust (worn) one.

 

Different part #'s beeton, see the link here to parts fiche local to us. you can look up any year, I chose 1985

https://partsfinder.onlinemicrofiche.com/snowcity/showmodel.asp?Type=13&make=hondamc&a=32&b=6&c=0&d=1985 VF500F INTERCEPTOR 500 CAMSHAFT AND VALVE


BTW, are you by chance located in Beeton, Ontario ? between Tottenham and Alliston ? I used to be in Gilford (just north Bradford), but now im up in North Bay.