"crunchy" valves, GSX750E

[prutser]

Long story short: the katana-styled make-shift all-road GSX750E ejected a con-rod through the crank case recently, so I bought a similar replacement engine of a local bike shop. It had been laying dry on the shelf for god only knows how many years, so the first thing to do was to clean the outside of the head, then pour a bit of oil in the plug holes and over the cams and valves, and then crank it by hand. It turned over alright, without any noticeable hard or rough spots, but it made a rather "crunchy" noise every now and then, which seemed to come from the valves.

So to rule things out I lifted the cam-shafts to move pistons and valves independently:
- as expected the pistons go up and down smooth like butter, no weird noises at all.
- some of the valves make a "crunchy" sound sometimes when seating again after being compressed.

Of course, during the storage years some debris could have easily have gotten in there, that now gets trapped under the valves. Or could it just be some carbon deposits that got loosened up?

I tried blowing whatever could be in there out of the cylinders by pushing down individual valves and blowing compressed air down the plug hole. Unfortunately, stuff is sticky in there because of the well-intended dose of oil.

I'm thinking to re-install the cams to hold the valves open, and have a blast with brake cleaner or some other solvent and more compressed air.

Or do people have other smart ideas?

 

Here is a picture of the cute kat in merrier times, just for the sake of it.

[Swiss Toni]

You’re never going to be sure until you lift the head. 

[FJD]

If the engine has been on the shelf for ages, and you dont know milage, you are better off taking head off.

That way, you can clean up valves, and install new valve guide seals, as the old ones will definitly be hardened out.

Edited November 2, 2022 by FJD

[gsxwill]

Yeah head off and check properly it will be worth it in the end 

[prutser]

I was afraid  of these answers, but it does make sense.

As matter of fact I happen to have a third lump laying around, with a thrashed head, but a decent lower end. If the head of the con-rod ejector is still usable, these two could make one solid engine after a proper reassembly.

I was hoping to cut some corners and get back on the road in little time, and then have a nice relaxed winter project with the two cripples.

Any other specific wear-points to check while the cams are out? I always take a measurement of the camchain stretch. The chain guides look a bit worn in already.

[prutser]

Well, in the end I decided to not take the head off (yet) but try cleaning it first.

Instead, gave it another blast with brake cleaner first, trying to get the sticky oil out of there, so any dirt would be blown out easier with compressed air. Then another round with carb cleaner. (People say it works on carbon deposit as well.) Eventually, valves didn't sound crunchy anymore! Funny thing is: once I poured some new oil down the plug hole, some crunchiness came back here and there. I suspect the 'crunchy' sound might have been some oil being squeezed between the valve and seats. (?)

But whatever: after having adjusted the valve clearance, mounted the whole lump, carbs, exhaust, etc back together and gave it a shot. It fired up straight away at first try. Immediately running smooth on all four cylinders. Sound is comforting. (The previous engine use the have a light, mysterious, erratic, 'tinging' sound that used to come and go, which I never managed to trace, but which just might have been an unhappy big-end bearing ?)

Have ridden it a couple of dozen of km's by now, runs smooth, can idle below a 1000 rpm, so far so good. Haven't rev'd it above 5000k rpm yet, though. Gave the outside a good clean today, to keep an eye on any oil seeping out of old gaskets and O-rings in the coming time. No major oil weepings so far.

[Swiss Toni]

Sounds like you’ve been lucky! Might pay to do a compression test though. Just to settle your mind. 

[Captain Chaos]

and to be sure, change the oil & filter after a few hundred km