GSX750F engine - cannot manually crank

[Gnome]

Hello gents,

So after taking the side cases off the Teapot motor, I found a rounded off Timing rotor. 

I've got a replacement and fitted it, but I have found that upon trying to manually turn it, it's started to round off because everything seems seized. 

I tried putting some oil down the spark plug holes a few days ago, in the hope it might help lube everything up, but it doesn't seem to want to budge (plus this rotor will be mullered if I try and force it anymore). 

So I suspect the rounded off rotor I originally found was a sign of something - A potentially seized engine?

I'd like to strip it down to investigate, but I can't crank it so the cams are in the right position before I remove them and the head.

 

Does it matter if it's not in the correct position if I'm pulling the head off anyway? 

(First venture into pulling an engine apart, so forgive me if it's an obvious question)

[Dezza]

Is it in gear and/or is something in the transmission preventing the engine from turning over? I have heard about dropped screws getting in between gear teeth and locking motors up before. Double and triple check it's in neutral first or remove the clutch, then go from there. It sounds like you'll have to do this anyway.

[Gnome]

1 minute ago, Dezza said:

Is it in gear and/or is something in the transmission preventing the engine from turning over? I have heard about dropped screws getting in between gear teeth and locking motors up before. Double and triple check it's in neutral first or remove the clutch, then go from there. It sounds like you'll have to do this anyway.

FFS, why didn't I think of that! 

It's missing the sprocket cover and a clutch cable, but the foot lever is in the spares I believe. Assume I can just "crash" it into neutral?

[Swiss Toni]

Dezza might have a point there, in that 'something' may be in the g/box, clutch/crank pinions and locking it up. If you need to get the head/barrels off, there are certain positions for the crank to be in, to facilitate an engine strip. But ... if it's definitely siezed, you don't have this luxury! Just strip the top end as per the manual (RTFM) But, be aware, as you can't put the crank where it's meant to be, there will be valves open, creating pressure on the cam(s) as you're loosening them. Do it gradually along the length of the cam, and if you can, find some way of holding the cam down in the bearings a few threads before the cam caps are off. This will prevent the last few threads in the lower cam bearing getting stripped out by the cam pushing against the cap! Head off, then hopefully followed by the barrel. Try the neutral thing first though! 

Edited June 10, 2020 by Swiss Toni

[Captain Chaos]

18 minutes ago, Swiss Toni said:

as you can't put the crank where it's meant to be, there will be valves open

on an inline four there are always some valves open, whichever position the crankshaft is in. So this does not matter.

Just remove the camchain tensioner and unscrew the cam caps evenly and it will be ok.

Edited June 10, 2020 by Captain Chaos
spelling

[Dezza]

1 hour ago, Gnome said:

FFS, why didn't I think of that! 

It's missing the sprocket cover and a clutch cable, but the foot lever is in the spares I believe. Assume I can just "crash" it into neutral?

Turn the shaft that the front sprocket is attached to by hand. If it's in neutral it should turn freely. If it does turn freely, then the cause of the engine lock is further up the drive train. If it doesn't turn freely, then it could be one of several problems. If you remove the clutch and the engine is still locked, then you're going to have to look at the top end. If the engine is not locked then the problem is somewhere in the transmission. If so, part of the transmission can be inspected without splitting the cases by removing the sump.

 

Also, does the engine still have the aternator and starter motors attached? Many tight-arsed breakers remove these so if anything's dropped down inside it may have jammed some gears.

[Captain Chaos]

But first remove the clutch as said to be sure it's not the gearbox which is blocked. In that case a complete engine stripdown is not necessary (although it would be wise if it's an unknown engine), the crankcases can be split with the top end in place.

edit - Dezza beat me to it

Edited June 10, 2020 by Captain Chaos

[Gnome]

Thanks Gents. Will hopefully get chance to take a look this evening!

Hoping it's just sat in gear, fingers crossed, but as mentioned, I'd like to strip it down to check everything anyway as it's probably been sat for a while and is a bit of an unknown quantity. 

[Gixer1460]

If its in gear - you should still be able to turn the motor over. An it takes some sort of ape to muller the ign rotor hex - please don't try and turn it over using the 6mm cap screw!

[Gnome]

9 minutes ago, Gixer1460 said:

If its in gear - you should still be able to turn the motor over. An it takes some sort of ape to muller the ign rotor hex - please don't try and turn it over using the 6mm cap screw!

Don't worry, I know not to do that. Although I fear the replacement rotor I've purchased may also be destined for the scrap pile (FFS).

[clivegto]

Can be taken to bits in any position but needs to be put together in the correct position. 

[Gnome]

37 minutes ago, clivegto said:

Can be taken to bits in any position but needs to be put together in the correct position. 

Well, seeing as this will be my first stripdown (calm down back there, I meant in terms of engines!), then I'll be probably asking for some guidance on that! 

[Captain Chaos]

buy and read the fucking manual.

[Dezza]

OEM Suzuki manuals freely available for nothing on the interwebs, so for those of us that have bits from multiple models on a single bike, we don't have to buy multiple fucking manuals, which would be fucking expensive otherwise

[Gnome]

28 minutes ago, Captain Chaos said:

buy and read the fucking manual.

 

Just now, Dezza said:

OEM Suzuki manuals freely available for nothing on the interwebs, so for those of us that have bits from multiple models on a single bike, we don't have to buy multiple fucking manuals, which would be fucking expensive otherwise

Oh yes! GSX750F manual was downloaded the other day. Currently browsing it. 

[Gnome]

Found the first problem. No left-hand pushrod!

[Gnome]

2 hours ago, Dezza said:

Turn the shaft that the front sprocket is attached to by hand. If it's in neutral it should turn freely. If it does turn freely, then the cause of the engine lock is further up the drive train. If it doesn't turn freely, then it could be one of several problems. If you remove the clutch and the engine is still locked, then you're going to have to look at the top end. If the engine is not locked then the problem is somewhere in the transmission. If so, part of the transmission can be inspected without splitting the cases by removing the sump.

 

Also, does the engine still have the aternator and starter motors attached? Many tight-arsed breakers remove these so if anything's dropped down inside it may have jammed some gears.

So starter and alternator are still attached.

Removed clutch and everything now moves freely!

[Swiss Toni]

3 hours ago, Captain Chaos said:

on an inline four there are always some valves open, whichever position the crankshaft is in. So this does not matter.

Just remove the camchain tensioner and unscrew the cam caps evenly and it will be ok.

Correct!

[Gnome]

So timing is lined up now. 

@Dezzawhat should I be looking for now with regards to the transmission? 

[Dezza]

I would turn the engine upside down, remove the sump and examine what can be seen of the gearbox and selector mechanism carefully. It will help to have a gear lever so you can operate the gear shift mechanism to make sure everything is moving as it should. Check for the obvious first: is there metal debris inside or is there a loose screw or washer jammed between some gears?  Clean the engine first as having bits of crap drop into the gearbox isn't that good for it. As CC says if you cannot see obviously why the transmission is locked then you'll have to remove the bottom case. This can be done without disturbing the top end.

[Gnome]

On 6/11/2020 at 10:15 AM, Dezza said:

I would turn the engine upside down, remove the sump and examine what can be seen of the gearbox and selector mechanism carefully. It will help to have a gear lever so you can operate the gear shift mechanism to make sure everything is moving as it should. Check for the obvious first: is there metal debris inside or is there a loose screw or washer jammed between some gears?  Clean the engine first as having bits of crap drop into the gearbox isn't that good for it. As CC says if you cannot see obviously why the transmission is locked then you'll have to remove the bottom case. This can be done without disturbing the top end.

So I've updated my project thread, but I'm yet to fully pull the bottom crankcase off - got a couple of stubborn bolts (namely the 2 allen ones at the front of the block, and the screws that hold in the ignition timing plate) so am awaiting a delivery of tools for the job.

However, I've found a few chunks of metal, so chances are something has definitely broken. Can't see what just yet though, although I can see one cog on the gearbox with damage to the teeth by the looks of it.

https://oldskoolsuzuki.info/forums/topic/14026-project-gnome-2-get-to-da-chopppeerrr/?do=findComment&comment=161524

[Dezza]

All is explained: the technical term being 'your gearbox is knackered.'