Engine noise...Valve timing? CCT? Camshaft?

*Long post, Sorry*
Hello everyone,

I'll start by saying that it is an '84 VF750F with about 34k miles on it. It is up to maintenance and has been running great as my daily driver on a 70 mile R/T. This problem seems to come out of nowhere and I'm hoping someone can shed some light.
Symptoms - After about 15 miles of a freeway ride and nearing my exit, I hear a brief top end sound, like a slap rattle I suppose. It lasts all of 2 seconds and I think nothing of it. After I exit and have to accelerate, I'm sure it's me, the sound doesn't dissappear this time and performance suffers simulataneously. I pull over and before I can shut her down, the idle dies down and off. I start her back up after making sure there are no leaks and oil is full only to hear the same noise and idle dying off. Being 20 miles from home, I roll down a hill, lucky me, with the engine off, top speed 45mph and get to a friends house where I take her apart. Hoping I had not tightened a valve adjuster locknut, I take off the covers and check them. They are all on tight and adjusted properly. However, what I do notice is....

At TDC 1.3 both the 1 and 3 cylinders should be at TDC where both exhaust and intake valves are closed and noted by freeplay in the rocker arms. However, when I put it at T1.3...
the 1 cylinder has both intake and exhaust open to the point the rocker arms are stiff.
the 2 cylinder has both intake and exhaust closed and freeplay is observed.
the 3 cylinder has both intake and exhaust closed and freeplay is observed.
the 4 cylinder has intake open and exhaust closed where one set is free, the other stiff.

At TDC 2.4 both the 2 and 4 cylinders should be at TDC where both exhaust and intake valves are closed and noted by freeplay in the rocker arms.
However, at T2.4...
the 1 cylinder has intake open, exhaust closed, one free, the other stiff
the 2 cylinder has both intake and exhaust closed and freeplay is observed.
the 3 cylinder has intake closed, exhaust open, one free, the other stiff.
the 4 cylinder has both intake and exhaust open, where they are both stiff.

A bit more data -
I believe it is the alternator that you turn to manually turn over the engine in order to do the valve adjustment that has the timing marks on it? Well anyways, while turn it the counter-clockwise as described, I noticed that I come upon a noticeable change in resistance just before T1.3 and as I pass T1.3, the resistance lets off and it turns like nothing. I don't remember noticing this when I did the valve adjustment last month and was wondering if anyone could tell me if this is normal or suggestive of a problem.

I fiddled with the Cam chain a bit and noticed that it is a bit uneven in slack, but I'm not sure what the measurements should be.

Number 1 cylinder's intake rocker arm also had what appeared to be a deep scrape? Looks like it was gripped by pliers if you can picture that kind of effect. The rest look alright.

So I've heard cam chain tensioners go out on these, but I would like to isolate the problem before I begin buying parts. Anyways, I would appreciate more than you know if someone could get back to me soon. I have alternative transportation, but with traffic, it will take me 2-3 times as long. The bike is at a friend's house and I'd like to get it home soon. Thanks for any help in advance.

 

sounds like what happened on my friend Bobcat's '85( 25k miles), a clean, well maintained bike that suddenly, at about 40mph, windowed the crankcase after loosing a rod!! But it worked out ok.....he bought an '86 VFR 750, a MUCH better bike.

good luck.

 

Sounds like the cams have gone to s*** just like most do eventually. My '84 750 had a similar course of events that is leading me to replace the cams, I was cruising down the freeway and a tick began to emerge and grow over about 40 miles.

Judging by what you described with the rocker, significant damage has occurred. Here is what I believe happened to both you and me. The cams on these bikes are soft. After adjusting the valve clearances, the lock nuts were not tightened enough. I've heard that this will cause the gap to shrink. The smaller gap allows less oil for lubrication and the subsequent eroding of the cam/rocker interface.

Although my bike continued to run, I found a rocker on the intake side that was so worn it probably wasn't even opening the valve. I found a clean, complete set of cams and rockers for $150 from a salvage yard. Installing these along with the Dave Dodge top-end oil mod should fix my problems for a reasonable price.

If you wore an exhaust rocker to the point it was barely opening, the spent fuel/air charge could be traveling back through the intake and this could cause the bike to quit. Otherwise you could have some other problem. Hope this helps.

 

Just re-read your post and saw it was the No. 1 intake valve. Funny, that is the same one that went on mine. I think that cam is the most starved for oil.

 

Brothers, are you listening??
get rid of these early, problem-plagued beasts.
the VF bikes aren't old enough to be antiques, not good enough to be classics!


look in the for sale section....i have posted the fix for all your VF problems!
1986 VFR 750, clean, maintained, perfect, $2500.
maybe alot of money?? well, it's alot of bike and will maintain value!!

 

Sounds like she may have jumped time. The cam chain tentioner may have stuck, allowed too much slack in the chain then she jumped. A little scaring on the rockers isn't the end of the world. Try turning the engine over 1 revolution and recheck your findings. Any chance you are checking it 180 out? I think the 1st gens are worth the trouble if you want it as a toy and not so much for everyday transportation. I love mine!

 

do you like to be plagued by constant maintenance issues?? you love yours???? is that the best bike you've ridden???
the world has moved on since '84-'85, so why not join it??the best bike you can ride is possibly the NEWEST bike u can afford...riding time is so short, so why not go 4 the best??

1986 VFR 750 $2500.......STEP UP!!!!!!!

 

Take a look at my list of rides under my name on this post. You'll find several newer bikes in there. Including an '07 RWB!! Newer bikes are great, but so is riding around on a classic sport bike, not just a classic, but the grandfather of all VFRs!! My '83 is not "plagued" with anything except for my lack of time to ride it as much as it would like. I would feel just fine riding it anywhere in the country, and turning the heads of all those who wanted, or had one back in the day. :biggrin:

 

Sorry to jump in but this thread might have affirmed my worst fears. Ahoyboyhoy's bike problems sound just like the problem I am having with my 1985 VF700F. I thought it was a carburetor problem but the problem persisted after I throughly cleaned them. When I took the carburetors off again I saw oil through the carburetor intake near the valves of my number four cylinder. Looks like I am going to be ripping into my valves as soon as I can as well as looking at my cam chain and timing.


Thanks this tread has been great,
James