GN125H valve clearance troubles (No clearance?)

**h0dgep0dge** · 9th September 2015, 12:40

I've recently scored a deregistered 2012 GN125H (Fixing it up for my girlfriend) and everything has been going smoothly. She got new levers, new clutch cable, new tach cable, new chain, new oil + filter, all bog standard stuff, but the bike has had trouble getting up to speed; when you're in 4th or 5th gear, the engine doesn't want to push you faster than 4000 revs. My first suspects were the carb or spark plug, so I replaced both of those; no joy. I'd decided to take a look at the valve timing (It felt a bit similar to riding a bike with bad timing), and thought that I would check out the valve clearance while I was at it. The internet told me to set it to 0.08-0.13mm, so I whipped out the feeler gauge, turned the engine to TDC and had a crack at it. What I found was that I couldn't get the feeler gauge under the tappet, noway nohow. I thought perhaps I had it at TDC of the wrong stroke, turned it a few times, couldn't get it under, even with the tapped completely removed; the valve is pressing right up against the rocker arm, with no space at all. Anyone got any clues?

**h0dgep0dge** · 9th September 2015, 15:36

So I feel like a right dick. As it turns out the rocker arms are spring loaded. I've only ever worked on my bike (a 30 year old gn250), and if that thing ever had spring loaded rocker arms, it certainly doesn't now.

**Kickaha** · 9th September 2015, 18:35

Originally Posted by h0dgep0dge

As it turns out the rocker arms are spring loaded.

No they aren't

**Trade_nancy** · 9th September 2015, 18:39

Make sure you are checking valve clearances with the motor stone cold..cannot be checked if it has been run.

**Drew** · 9th September 2015, 19:22

Originally Posted by Kickaha

No they aren't

Phew, thought parts had fallen out of the one I've worked on.

The motor shouldn't be at TDC anyway. Point the lobe directly away from rocker, then check the clearance.

If it'sriding the backs of the cams, it'll be well down on power and present with symptoms just like you describe.

**h0dgep0dge** · 9th September 2015, 21:31

Originally Posted by Kickaha

No they aren't

Yes, they are. I took the rocker cover off and saw the springs with my own eyes.

Originally Posted by Drew

The motor shouldn't be at TDC anyway. Point the lobe directly away from rocker, then check the clearance.

At TDC on the compression stroke the cam lobes are facing down.

**Kickaha** · 9th September 2015, 22:36

Originally Posted by h0dgep0dge

Yes, they are. I took the rocker cover off and saw the springs with my own eyes..

I think you need http://www.specsavers.co.nz

Unless the design changed a lot in the later models the only springs in there are valve springs

**ducatilover** · 9th September 2015, 22:38

Hah, I was bidding on that one for a bit. But went to the pub instead.
I may be able to offer a hand if need be, I'm local

It has the same rocker system as your GN250. Only springs on them are to keep the rocker shaft centered

**h0dgep0dge** · 10th September 2015, 00:58

Originally Posted by ducatilover

It has the same rocker system as your GN250

That can't possibly be true, for 2 reasons. The 250 is a 2 valve system, and this particular 125 has great ruddy springs on the rockers.

Originally Posted by Kickaha

Unless the design changed a lot in the later models the only springs in there are valve springs

Maybe they did? idfk. All I know is there are most certainly 2 torsion springs applying a pre-load to the tappets onto the valve stem. Is it an OEM part? Dunno. Should they be there? No clue. But I know with 100% certainty that they are there.

**Drew** · 10th September 2015, 06:37

Those springs might be holding the rockers off the cams, it would be stupid for them to be holding them on it. It would promote heat. That would be followed by the surfaces getting fucked, shortly thereafter you have horrible noises and then failure.

**mossy1200** · 10th September 2015, 06:53

Originally Posted by Drew

Failure.

This sounds likely.

**h0dgep0dge** · 10th September 2015, 18:10

Originally Posted by Drew

Those springs might be holding the rockers off the cams

I fail to see a meaningful difference. All that matters is that there are springs applying a torque that results in a force down on the valve from the tappet, and that is why I couldn't feel the clearance to begin with.

**Drew** · 10th September 2015, 18:16

Originally Posted by h0dgep0dge

I fail to see a meaningful difference. All that matters is that there are springs applying a torque that results in a force down on the valve from the tappet, and that is why I couldn't feel the clearance to begin with.

Ah, I see what is going on now.

Hang on. Why are you not checking the clearance between the cam, and the rocker?

**nodrog:Me** · 10th September 2015, 18:19

Originally Posted by h0dgep0dge

I fail to see a meaningful difference. All that matters is that there are springs applying a torque that results in a force down on the valve from the tappet, and that is why I couldn't feel the clearance to begin with.

is your camera broken too?

**h0dgep0dge** · 11th September 2015, 00:00

Originally Posted by Drew

Why are you not checking the clearance between the cam, and the rocker?

Well, the rocker is attached to the head cover, and to get to the gap between the cam and rocker i'd need to remove the head cover. As to why the engine is designed for checking the valve-rocker clearance rather than the rocker-cam clearance, I dunno. Perhaps so that you can both inspect the valve stem and adjust the clearance through the same inspection cover. But seriously, you'd have to ask someone who actually knows what they're talking about

Originally Posted by nodrog

is your camera broken too?

what does that even mean?