GN125H - Piston, exhaust valve, exhaust port, completely caked in soot?

[h0dgep0dge]

My partner and I recently picked up a 2012 GN125H on the cheap for her to get her licence on (It's just been a scooter for her until this point). As soon as I rode the thing I knew it needed work, but one oil change, one new spark plug, one carb cleaning, one timing adjustment, and 2 valve clearance adjustments later, the problem was still there. I decided to get serious with it, and I removed the cylinder head to take a look (ended up buying a new socket just for this; as it turns out, 1/4 inch drive shafts don't play nice with head nuts. go figure.). Not fifteen minutes ago, I got around to taking the valves out to inspect them, and as it turns out, the exhaust valve is fouled to crap (I've suspected a compression problem for a while), along with the piston, combustion chamber, and exhaust port. The exhaust port has a layer of carbon 1 or 2 mm thick, crazy.

Cleaning out the carbon is no big deal, but the question remains, what's likely to have caused this? Is there anything I should do to prevent this happening in the future?

[Drew]

The seating portion of the valve? 1-2mm?

That seems...unbelievable frankly.

Only way to build that much crap, is to be getting a shit load of oil in the combustion chamber. Go another step, and whip the barrel off.

Have a sniff of the oil, you're checking for petrol in it.

[h0dgep0dge]

The seating portion of the valve? 1-2mm?

1-2 mm in the exhaust port, the valve seat is substantially less than that.


Go another step, and whip the barrel off.

I'm reluctant, because I've never dealt with the business with the piston rings and oil rings, and I'm not confident I wouldn't fuck it up. I might get in the gear I need to replace the rings and lap the cylinder, then have a crack at it. I'll take a look at the oil when I get a chance.

[Grumph]

Was there still a seal on the exhaust valve guide ?
Before you pull the barrel off, tell us if there are any marks on the bore...long deep scratches would indicate a broken ring.

[ducatilover]

Check the valve stem seals haven't been typical Chinese shit and leaking.
Then pull the barrel, shit on it, put it in the bin, go drink a beer

[Akzle]

run premum fuel.

Pics. Help. Cos, like. Stuff.


A leak down test woulds done. A'fore the head was off.

[nodrog]

All that carbon is probably making it run better due to increased compression.

[h0dgep0dge]

I have pictures!

They include, picture of the top of the piston, pictures of the bore from both sides (i also ran my finger around it; it feelts smooth all the way around), picture of the valves, picture of the valve seats, and picture of the oil seals. No clue if that last one was necessary, but oh well.

[Drew]

You've got a burnt out valve. Simple to fix, problem solved.

[h0dgep0dge]

You've got a burnt out valve.

Is that to say the valve is damaged? Or just covered in combustion products? I ask because it doesn't look damaged, so does that mean I can get away with just recutting+lapping the valves?

[Akzle]

Pics.



I have pictures!


You've got a burnt out valve. Simple to fix, problem solved.

yw .

[Drew]

Is that to say the valve is damaged? Or just covered in combustion products? I ask because it doesn't look damaged, so does that mean I can get away with just recutting+lapping the valves?
That's the action alright.

[husaberg]

My partner and I recently picked up a 2012 GN125H on the cheap for her to get her licence on (It's just been a scooter for her until this point). As soon as I rode the thing I knew it needed work, but one oil change, one new spark plug, one carb cleaning, one timing adjustment, and 2 valve clearance adjustments later, the problem was still there. I decided to get serious with it, and I removed the cylinder head to take a look (ended up buying a new socket just for this; as it turns out, 1/4 inch drive shafts don't play nice with head nuts. go figure.). Not fifteen minutes ago, I got around to taking the valves out to inspect them, and as it turns out, the exhaust valve is fouled to crap (I've suspected a compression problem for a while), along with the piston, combustion chamber, and exhaust port. The exhaust port has a layer of carbon 1 or 2 mm thick, crazy.

Cleaning out the carbon is no big deal, but the question remains, what's likely to have caused this? Is there anything I should do to prevent this happening in the future?

The fact that the valves look like that at bugger all km's suggest it at one time likely had zero valve clearance.
PS buy a new valve they are cheap enough

[Kickaha]

PS buy a new valve they are cheap enough

Fuck off they are, either $80 or $120 for OE cant remember which is exhaust and which is inlet, although cheaper than a motor

[h0dgep0dge]

PS buy a new valve they are cheap enough

I think we might, I'm looking into it.


OE

Hah, OE parts? That's funny

[jellywrestler]

I think we might, I'm looking into it.



Hah, OE parts? That's funny

yip and when the last owner replced the valves in one of my beemers with aftermarket parts it lasted three rides for me before dropping a valve....

[husaberg]

Fuck off they are, either $80 or $120 for OE cant remember which is exhaust and which is inlet, although cheaper than a motor

I will translate that to should have brought a Honda.

I think we might, I'm looking into it.

[h0dgep0dge]

yip and when the last owner replced the valves in one of my beemers with aftermarket parts it lasted three rides for me before dropping a valve....

That's a completely different beast. A large displacement BMW, made in Germany? Sure. This is a 125cc commuter bike, made in China. We paid $600 for the thing, I don't think I'm going to be losing sleep over putting cheap parts in it.

[husaberg]

That's a completely different beast. A large displacement BMW, made in Germany? Sure. This is a 125cc commuter bike, made in China. We paid $600 for the thing, I don't think I'm going to be losing sleep over putting cheap parts in it.

Try TKRJ
http://www.tkrj.co.jp/product/m-engine-valve.html

[h0dgep0dge]

Try TKRJ

It's not there

[husaberg]

It's not there

Gs125 is the sporty (looking) version GN125 is the custom, DR125 is the trail bike.
Kickaha will know for sure if the valves are the same in all models.
but either way they have the measurements on the right.

[h0dgep0dge]

Gs125 is the sporty (looking) version GN125 is the custom, DR125 is the trail bike.

Learning something new every day.

[Kickaha]

Hah, OE parts? That's funny

Not as funny as using aftermarket valves and having them fail in a fraction of the time of OE as has happened to me

Although my usage was a bit more extreme


Try TKRJ
http://www.tkrj.co.jp/product/m-engine-valve.html
Yeah try TKRJ, they lasted one meeting comapred to OE lasting 12-14 meetings


Gs125 is the sporty (looking) version GN125 is the custom, DR125 is the trail bike.
Kickaha will know for sure if the valves are the same in all models.
but either way they have the measurements on the right.

All the same going from the mix and match engines I have, currently have DR200 valves in the 125 head

[husaberg]

Not as funny as using aftermarket valves and having them fail in a fraction of the time of OE as has happened to me

Although my usage was a bit more extreme

So are the heads the same between them all Kicka? One had closer ratios or was it more gears?

[Kickaha]

So are the heads the same between them all Kicka? One had closer ratios or was it more gears?
Heads on the 125 seem to be all the same, DR125 is a six speed but the ratios aren't closer

That's a completely different beast. A large displacement BMW, made in Germany? Sure. This is a 125cc commuter bike, made in China. We paid $600 for the thing, I don't think I'm going to be losing sleep over putting cheap parts in it.
Same principle applies regards of brand, pay your money and take your chances

[h0dgep0dge]

Same principle applies regards of brand, pay your money and take your chances

Is it really the same? Obviously there's going to be a big difference between OEM german made parts and aftermarket chinese made parts for a BMW, but it's not the same thing as the difference between a chinese made OEM part and a chinese made aftermarket part. The chinese made OEM parts obviously aren't that great, they're the reason we're even here right now.

[ellipsis]

...why are you asking?...it sounds like you know it all...

[h0dgep0dge]

...why are you asking?...it sounds like you know it all...

I don't claim to know it all. Just claiming to know that different brands have different quality standards, and that the chinese made suzuki GNs are shithouse.

[Kickaha]

I don't claim to know it all. Just claiming to know that different brands have different quality standards, and that the chinese made suzuki GNs are shithouse.

Anything built to a price regards of the country of origin will have those problems

[h0dgep0dge]

Anything built to a price regards of the country of origin will have those problems

Is it not true that modern low end suzuki bikes are built down to a price? If so, why have they gotten gradually shittier over the last 30 years?

[Drew]

The chinese made OEM parts obviously aren't that great, they're the reason we're even here right now.

I doubt it. It's not something I've heard of them doing.

I think the clearance was too tight, and has caused this. After all, you measured the gap as being fine...but the valve wasn't actually closing.

[h0dgep0dge]

burnt out valve

I took it into a bike shop (bikeworx in onekawa, if anyone's wondering) and the guy there said that the valves and oil seals look fine to him. I'm having him lap the valves to make sure, but he reckons that's not the issue.

[husaberg]

I took it into a bike shop (bikeworx in onekawa, if anyone's wondering) and the guy there said that the valves and oil seals look fine to him. I'm having him lap the valves to make sure, but he reckons that's not the issue.

Well there is something up with the original seating or the oil seals or as me and about every else as said with zero tappet clearance at sometime because 2000 km engines ex valves and seats and ports shouldn't look like that.

[h0dgep0dge]

zero tappet clearance

I'll make sure to keep the tappets in check, plus the rocker arms have these weird springs that keep the tappets pressed onto the valve stems. I'll remove those for good measure.

[F5 Dave]

Cam timing out a tooth. Havent read most of the post, but that'd do it.

[husaberg]

I'll make sure to keep the tappets in check, plus the rocker arms have these weird springs that keep the tappets pressed onto the valve stems. I'll remove those for good measure.

I remember now, did you ever post a pic of them?

[h0dgep0dge]

I remember now, did you ever post a pic of them?

I didn't, I haven't had the head cover off since the last time I posted, I'll go grab one now.

[husaberg]

I didn't, I haven't had the head cover off since the last time I posted, I'll go grab one now.

Hard to tell but it looks like those springs are arranged to be pressing the rocker in contact with the valve is that the way they are pressing?
It seems perverse.

[h0dgep0dge]

Hard to tell but it looks like those springs are arranged to be pressing the rocker in contact with the valve is that the way they are pressing?
It seems perverse.

That's exactly what's happening. It gave me some trouble when I tried to adjust the valve clearance, no matter how far I loosened off those tappets it was still tight against the valve. It was such a strange modification, no one would believe they were actually what I said they were, and I have no idea why someone stuck them in there.

[husaberg]

That's exactly what's happening. It gave me some trouble when I tried to adjust the valve clearance, no matter how far I loosened off those tappets it was still tight against the valve. It was such a strange modification, no one would believe they were actually what I said they were, and I have no idea why someone stuck them in there.

I didn't. But there they are.

[Grumph]

Take those bloody springs off and toss them as far as you can...Totally unnecessary, someone's added them.
If springs are used there, the idea is to take load off the valve springs - not add to it.
IMO they could have been a contributing factor to the ex valve problems - all the carbon.

[Drew]

That's really weird man. Would have been a really queit motor though.

[pete376403]

If those springs kept the rocker in contact with the valve stem tip, then there would have been clearance between the other end of the rocker and the cam (when on the back of the lobe). Just moving the clearance from one end of the rocker to the other.

Maybe someone thought they were making a desmo out of it

[husaberg]

If those springs kept the rocker in contact with the valve stem tip, then there would have been clearance between the other end of the rocker and the cam (when on the back of the lobe). Just moving the clearance from one end of the rocker to the other.

Maybe someone thought they were making a desmo out of it

The Spaniards did built some desmo Ducati singles under licence with coil springs. They had a very poor reputation for reliability even compared to the std ones.
Someone brought one and took it to bits and it turned out they used the std non desmo springs but had them preloaded to half there free length. No wonder they trashed the cams.
When the guy removed them it actually allegedly bent his spring compressor in half.
Can't remember what they were called trans something

edit after google Mototrans.

[Katman]

The springs are clearly just there just in an attempt to quieten the motor.

[Drew]

The springs are clearly just there just in an attempt to quieten the motor.

I thought that, but I'm nearly always wrong about these things.

I didn't think the head noise was that bad on the 125, they're not overly quiet and they are a cunt when the cam sinks into the bearing surface, but not at such low k's one would think.

[Cheesy]

While you are playing with this you wouldnt be able to measure the diameter of the starter motor body for me could you?

[h0dgep0dge]

While you are playing with this you wouldnt be able to measure the diameter of the starter motor body for me could you?

60mm

(Seems like you can't submit a post shorter than 10 characters, go figure. Adding this for padding)

[Cheesy]

60mm

(Seems like you can't submit a post shorter than 10 characters, go figure. Adding this for padding)

Thanks for that.
Since the gear ratios were mentioned earlier and I couldnt find them on the net Ill add them in here too

GN125
11:33
14:26
19:26
21:23
23:21

DF125
11:33
12:27
16:24
21:23
23:21
25:19

[husaberg]

Thanks for that.
Since the gear ratios were mentioned earlier and I couldnt find them on the net Ill add them in here too

GN125
11:33
14:26
19:26
21:23
23:21

DF125
11:33
12:27
16:24
21:23
23:21
25:19
So that makes them
GN125
3.00
1.86
1.37
1.10
0.91


DR125
3.00
2.25
1.50
1.10
0.76

[Cheesy]

So that makes them
GN125
3.00
1.86
1.37
1.10
0.91


DR125
3.00
2.25
1.50
1.10
0.91 < This one as well
0.76

I tried putting those numbers in but for some reason the forum kept on taking all my spaces out

[Kickaha]

DR125
3.00
2.25
1.50
1.10
0.76

DR manual I have says

3.00
1.85
1.36
1.09
0.91
0.80

GS125, the same first 5 ratios with no 6th

[Cheesy]

DR manual I have says

3.00
1.85
1.36
1.09
0.91
0.80

GS125, the same first 5 ratios with no 6th

I just double checked the ones in front of me and I did count them correctly, apparently it was a DF and not a DR though, maybe the farm version had lower 2nd and 3rd to help drag sheep around the paddock.

[husaberg]

DR manual I have says

3.00
1.85
1.36
1.09
0.91
0.80

GS125, the same first 5 ratios with no 6th


I just double checked the ones in front of me and I did count them correctly, apparently it was a DF and not a DR though, maybe the farm version had lower 2nd and 3rd to help drag sheep around the paddock.

whoops missed that gear and just assumed the df was a typo.:spanking: