Engine Noise

I just left an intro with video of my VF750FD, when I first got her running.

I've since done just over 400 miles on her and she's developed an engine noise.

I'm gonna have the rocker covers off tomorrow to investigate - I think (hope) it's just a loose valve adjuster - she starts up right away, runs fine and still pulls like a freight train. All the downpipes are hot, so it's obviously firing on all cylinders, so I'd suspect it's not a dropped valve - maybe I'm wrong? I dunno..

I have a video of the motor running. Anyone experienced this noise? As I say, she starts right away and revs cleanly. The noise isn't there all the time - it'll quiet down for a few seconds then start chattering/tapping again. Doesn't seem to have adversely affected the bike's performance - still sets off like shit off a shovel. Anyway, have a listen, and I'd be grateful if anyone has any pointers.

[video=youtube;oDyZPo-lg4M]http://www.youtube.com/watch?v=oDyZPo-lg4M[/video]

 

Sounds like timing chain tensioner did on mine last year.

 

Thanks for the response. I've not had one of these bikes before - If it is that, is it replaceable without too much engine disassembly? I assume the camshafts have to be removed, but does the cylinder head need to come off? I think it's the rear cylinders that the sound is centred around but it's hard to tell.

 

I'm not sure on the 750. I changed the one on the front head of my 500 with the engine in the bike, then I realized the heads needed to come off fo some valves. On second though, I guess it could've been the valves being trashed that was causing the noise on mine, since I replaced them and the chain tensioner at the same time. It really does sound like the chain slapping around in there to me, and I believe the chain tensioners are yet another weak link on the VF's.

 

Yes sounds like chain tensioners. I changed both of mine this past winter. Second time in 60k miles. It's easier taking both cams out on the front. The rear you can get by with just taking the intake cam out. There are some good write ups on the web. Just do a search. If you don't find what you want, I have some just pm me and I'll try and help.
I bought mine from these guys. Fast shipping.

Honda Yamaha Suzuki Kawasaki Sea-Doo Can-Am Ski-Doo Motorcycle Parts ATV parts Scooter Parts personal watercraft parts Accessories

 

Thanks for the advice, and the link. I'm based in the UK so I'd have to find out what they charge for international shipping.

These guys are based in the UK and have an excellent reputation for supplying NOS OEM parts among the UK Jap classics community, the prices seem reasonable and the shipping will be cheaper : David Silver Spares

I took the top off the rear cylinders this afternoon. I don't think the cams look bad - very slight pitting to one lobe. I took some pictures but they are not clear enough to see the detail, so I won't post them here. Other than that, everything seemed pretty much correct and secure. Further disassembly might reveal otherwise, but for now it looks ok. Here's one picture that does show something I found:

One of the camchain tensioner bracket retaining bolts has at some point sheared off - the bracket being held by the remaining three. It seems tight and secure, but for all I know whoever broke the bolt might well have dropped it down the camchain tunnel and left it there. Maybe it's that that's been rattling around? It could easily be the tensioner as you both suggest, but I reckon I should strip the motor completely for my own peace of mind.

At that point I stopped disassembling that motor and took the lid off the rear cylinders of the other one - I might need some parts, and I'll know a little more about what I'm doing when I strip the other motor.

The bike's been stood for 15 years - some of the time with the carbs off. The intakes were full of water when I collected the bike. I fully expected it to be seized solid - but it isn't. I only turned the motor over enough to remove the camchain gears but it did turn over. Everything seemed reasonably clean and fine in there considering it's history, and the cams don't appear to have any pitting.

Anyway, I've ordered a full gasket set, and I'm off on Friday so... the serious disassembly begins.

 

That sucks...might want to pull the oil pan and see if there is any debris

 

..........

you gambled and lost, sorry.


Cam chain tensioners are well known failure item on VF series 750 and 1000 bikes, and, along with the top-end oiling problems, are a good reason never to buy one.

 

Don't be sorry on my account - I wanted an old, cheap jap classic to play around with and rebuild - now I have two, and for far less money than I expected to have to part with. They'll both be fixed - they'll both be having top end oiling and tensioner mods - They will both run again. An update on the broken bolt issue - I contacted the original seller of the bike before I started disassembing the motor any further and he confirms that the broken bolt - the head of the bolt is still stuck in a cheap socket he was using when he refitted the tensioner! I've been busy since, but I'm expecting to be able to replace the tensioners next weekend - I'm modifying the tensioners and fitting new slippers. I've therefore got a full gasket set for the other motor, which I've started to disassemble. The heads are off - there is very minor pitting to one exhaust cam in the front head, but all the others look perfect. There was approximately half an inch of rusty looking paste in the cylinders - and a nice topping of pale blue coolant. I thought they'd be a real disaster area, but I carefully cleaned out the rusty paste from the tops of the pistons, and the bores are perfectly smooth and free from marks and corrosion! I've turned the engine over carefully using the alternator rotor bolt and it's nice and free - I expect the piston rings will be history, but everything else so far is looking far better than I expected.

 

Unexpected commitments prevented me doing the tensioners the weekend after the last post, but I did get time to tackle the job over the last two days.

The bike is now running modded tensioners, though I haven't performed the oil mod yet - the cam bearing journals on all cams were perfect = not a mark on them. The bike is much quieter, revs more cleanly and the tickover is more stable and slower than it was before. It ticked over at about 1100 rpm, but varied slightly, rising up to maybe around 1300 then dropping again. Now it's ticking over at about 1000rpm, smoothly and cleanly.

One thing I can't understand is that when I took both heads off, I'm sure the cam index marks in the rear head were facing up at T 1-3 while those on the front head were facing down? That would mean the cams in the front head were 180 degrees out...

Maybe I'm mistaken? would it even run like that?

I'm really not sure any more - I've read so many writeups and the clymer manual, and I think I tried to assimilate much too much information such that I made a simple job extremely complicated - in my own head, and the front cams ended up going in and coming back out again multiple times...

The rear cylinders were piss-easy to set up - I only removed one cam, but I couldn't figure out the front cams, both of which had to come out. In the end it was so f'kin easy just to line up T 1-3 with the rear cam indexes pointing upwards then chuck both front cams in both with the indexes pointing up and the sprocket marks level with the head surface - then bolt everything down.

Every time I tried to turn the motor over from T 1-3 to T 2-4 without tension on the chain the front exhaust sprocket would skip a couple of teeth, then I'd set about lining everything up again.

In the end I set everything up entirely on T 1-3, bolted everything down then released the tensioner before I even attempted to turn the motor over. Turned the motor over a few times using the alternator bolt - nothing seemed wrong, so I spun the motor using the starter a couple of times. Set the tappets - spun the motor a couple more times then put everything back together.

She fired up first stab of the starter and ran smoothly and much quieter than before. A few circuits of the neighbourhood later and everything seems fine.

In the end I didn't need to use the new slippers I'd bought - I'll save those for the other motor, so I've now got a quieter motor for zero financial outlay, and I'll know more about what I'm doing when I rebuild the other bike's top ends.

I'll post a pic of the modded tensioners when I can find me usb cable - and maybe a video of the quietened motor.

 

Easily one of the top 10 responses in all of VFRW. Total props from this reader.