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Suzuki GZ125 - Cylinder Head Compatibility

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Ambergnat
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PostPosted: 22:53 - 04 May 2013    Post subject: Suzuki GZ125 - Cylinder Head Compatibility Reply with quote

Hi People,

Complete noob at this, so apologies in advance if I'm doing it wrong. You can prolly skip the first bit - as this is a bit of a long one

The Situation:


I Recently passed my CBT (at 47) & bought a lovely little Dark Blue GZ125 (k4) - she runs beautifully (given what she is) and as my first foray into biking I couldn't ask for more. She pulls well (I'm 90+ kg) handles slow traffic beautifully and will do 65 on the flat quite happily (I even got 73 on a long downhill but the vibration scared the shit out of me so I'm not trying that again!)

I've just started a 58 mile roundtrip commute to work (properly in at the deep end!) and on my 8th day I committed the cardinal sin of relaxing, as I thought I'd got the hang of handling the Bike

Overtaking a lorry on a hill - (which in itself wasn't a massive issue, but...) dropping from 4th to 3rd to accelerate past, left my foot on top of the gear lever and instead of going back up to 4th, dropped to 2nd - panicked and dropped further into 1st...at 40mph... Embarassed (yeah, ouch! - proper screamer!) After recovering quickly I overtook the lorry and the bike took me to the top of the hill before cutting out...

The Problem:

I took it to a local bike garage and It turns out I've damaged the valves and cracked the head. So I need a new one...

so what you ask...just get one then, right? Wink

The Garage quoted me 507.00 for a new part from Suzuki Shocked - but I only paid 900 (delivered) for the bike in the first place! Rolling Eyes

Sooo, I looked online and just missed a 2nd hand K4 head on eBay for 75 (mutter mutter grumble grumble) but I also saw quite a few 'pattern' heads, (with valves) going for similar amounts (circa 75) but they all seem to be for different years ('92 - 98' or 98 - 02' or '01 - 03' '06 - 07' etc but no '04 - 05' which is bloody annoying!).

However there are a couple of pattern heads which claim to cover the whole age range, which worries me greatly as they all have the 'don't blame me if it doesn't fit' disclaimer on them

I have been in touch (online) with an intermediary bike breaker contact website (who claimed to contact over 200 breakers on my behalf) but I've only had one reply and that was for 180 for a (complete) k4 head - that with the 170 quoted for the fitting by the Garage makes for a hefty bill! Sad .


The Question (s)

(1) Has anyone had any experience with 'pattern' cylinder heads - and given that I have no way of QCing them or the retailers, should I just leave them well alone, bite the bullet and get the used part (New is way off my radar)

(2) Also I am aware that the engine design has changed very little over the years, but I thought that since there see to be so few GZ k4 heads about maybe a Head for a '04 GS, GN or DR might fit, as the Haynes manual has them all in the same book with 'minimal' differences?

(3) Has anyone out there come across a GZ125 (k4 or k5) cylinder head for less that a ton () they can point me at?

I know I should probably wait for another one to come up on eBay or something but every day I'm without the bike I'm back to using the train and cycling 25miles a day (which lost any appeal it had a long long time ago!) and the weather has finally got decent!

(4) As I'm reasonably competent physically and know which end of spanner is which - is it worth thanking the garage, paying for the diagnosis and doing the repair myself (saving ~120) or is it too much of a risk for a novice to take on... I'm not sure if I would need to eff around with the timing and the carb etc... (proper noob - see Smile )

5) Is there a pattern head which will fit on all versions of the GZ or is that just opportunistic bullshit from the sellers?

I Think That about covers it - Sorry to write a bloody novel, but there's a lot I don't know /need to know - or can't seem to get straight answers to.

Cheers
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moonzoomer
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PostPosted: 23:12 - 04 May 2013    Post subject: Reply with quote

507.00 quid my arse
http://www.ebay.co.uk/itm/NEW-Cylinder-head-SUZUKI-GZ125-Cylinder-head-GZ125-/390294188805?pt=UK_Motorcycle_Parts_13&hash=item5adf58b305

http://www.ebay.co.uk/itm/Suzuki-GZ125-GZ-125-Marauder-98-00-Cylinder-Head-Assembly-Read-Description-/380602504782?pt=UK_Motorcycle_Parts_13&hash=item589dad564e

http://www.ebay.co.uk/itm/UK-Stock-SUZUKI-GS125-GN125-DR125-GZ125-Cylinder-Head-/221222317593?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item3381e0ae19
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Spudly
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PostPosted: 23:25 - 04 May 2013    Post subject: Reply with quote

There is also the point that even if you buy off ebay, if it turns out the head doesn't fit and it was advertised as doing so, the distance selling regulations state that the item was advertised incorrectly and as such, you can return it.

Just buy from an established ebay shop and you'll be fine Thumbs Up
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moonzoomer
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PostPosted: 23:27 - 04 May 2013    Post subject: Reply with quote

Spudly wrote:
There is also the point that even if you buy off ebay, if it turns out the head doesn't fit and it was advertised as doing so, the distance selling regulations state that the item was advertised incorrectly and as such, you can return it.

Just buy from an established ebay shop and you'll be fine Thumbs Up


DSR regs apply to all BIN ebay sales and since the business contact details are available from ebay business sellers there is no need to buy via ebay, just click on contact details and buy directly from the supplier with the same DSR rules applying. DSR rules only apply with in the U.K
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Ambergnat
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Joined: 21 Apr 2013
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PostPosted: 23:49 - 04 May 2013    Post subject: Reply with quote

Hi Chaps,

Thanks for the quick replies.


I had actually looked at all of those listings earlier today - the first two are for the earlier models (98-00 and 01-03) the last one claims to cover 2004 but it's from Ireland (I'm not sure if the DSR still counts if it turns out to be crap?) but thanks for pointing me at them anyway.

You're right about the 507 quid though Smile - I've found complete heads myself for 470 brand new and a whole (2nd hand) k4 engine for 420!
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moonzoomer
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PostPosted: 23:55 - 04 May 2013    Post subject: Reply with quote

Ambergnat wrote:
Hi Chaps,

Thanks for the quick replies.


I had actually looked at all of those listings earlier today - the first two are for the earlier models (98-00 and 01-03) the last one claims to cover 2004 but it's from Ireland (I'm not sure if the DSR still counts if it turns out to be crap?) but thanks for pointing me at them anyway.

You're right about the 507 quid though Smile - I've found complete heads myself for 470 brand new and a whole (2nd hand) k4 engine for 420!
forget about the flat piston nonsense, that only applies to the restricted low compression models. I f you want a cylinder head go to the manufacturer which is Hyosung and not suzuki, the engines are not japanese but korean.
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Ambergnat
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PostPosted: 00:10 - 05 May 2013    Post subject: Reply with quote

moonzoomer wrote:
forget about the flat piston nonsense, that only applies to the restricted low compression models. I f you want a cylinder head go to the manufacturer which is Hyosung and not suzuki, the engines are not japanese but korean.


Cool Smile I'll go have a butch
Cheers
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humanbeing
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PostPosted: 03:13 - 05 May 2013    Post subject: Reply with quote

Find the compatible in cmpo.co.uk. It's used on K157FMI (Dafier / Sinnis...)
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Spudly
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PostPosted: 10:13 - 05 May 2013    Post subject: Reply with quote

On a different note, how did you get your Passive Aggressor to an indicated 73mph?

I just recently managed to get my 2006 GZ125 to an indicated 61mph while going down a hill with a very strong tailwind. The engine was howling like a banshee at the time.

I love that little bike, but I can't wait to get on something bigger.
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Ambergnat
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PostPosted: 15:16 - 05 May 2013    Post subject: Reply with quote

Spudly wrote:
On a different note, how did you get your Passive Aggressor to an indicated 73mph?

I just recently managed to get my 2006 GZ125 to an indicated 61mph while going down a hill with a very strong tailwind. The engine was howling like a banshee at the time.

I love that little bike, but I can't wait to get on something bigger.


To be honest, I have absolutely no idea how - it was on the A287 heading towards Basingstoke, there 's a couple of very long hills with dual carriageway which (if the wind isn't in me face) lend themselves to some bone rattling speeds... and I was going full chat on the crest Smile done it two or three times and got 69/70 the first two - 73 the third but as I said the vibration was a bit freaky for me.

As far as the bike itself goes it looks like, and was sold to me as a stock GZ125.

I've done nothing in the way of tweaking (wouldn't know how!) but I have no trouble at all of getting it up to 60mph and 65 is easily attainable, but admittedly a bit slower to reach on the flat.

Having read the advice on these forums I have just been letting it get up to the higher rev range (but not screaming) before changing gear and making good use of 5th, which (despite some comments) is a proper gear at speed and an excellent overdrive gear in town.

The (indicated) speed ranges I have been using per gear are something like this.

1st - up to about 12-15
2nd - 12 - 25 odd
3rd is good from 20 up to ~40 before getting too noisy
4th from 35 to 50+
5th from 45 upwards and a slow climb to 60+

... after about 20-30 seconds I'm maxing out at anywhere from 58 - 67 depending on wind...which is a complete bitch and will slow the bike down horribly - in fact it's pushed me back to the low 50's on the flat sometimes (dead frustrating!).

That's about as much as I know I'm afraid.

I have no idea why your (newer) GZ is not behaving as well as it should - and you should definitely be getting more than 61mph from a windy downhill screamer. But... I have noticed some disparity between different owners of the same model & year - dunno why - too many variables to work out a pattern yet, but I'm looking... Smile
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Ambergnat
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PostPosted: 15:23 - 05 May 2013    Post subject: Reply with quote

humanbeing wrote:
Find the compatible in cmpo.co.uk. It's used on K157FMI (Dafier / Sinnis...)


Looks good Smile - cheers

Just ordered something similar on eBay (just hope it fits Neutral )

But if it don't - that looks pretty damn close.
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humanbeing
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PostPosted: 16:17 - 05 May 2013    Post subject: Reply with quote

Ambergnat wrote:

Just ordered something similar on eBay (just hope it fits Neutral )...


The old type had minor difference (Bigger valves/ 12mm spark plug):
http://www.motorfans.com.cn/bbs/t_17250767_1.htm

If jammed it directly on the "newer engine" , the compression ratio maybe too low. Solution: dome shaped piston as the good old Suzi / thin gaskets ...
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Spudly
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PostPosted: 18:58 - 05 May 2013    Post subject: Reply with quote

I have a feeling it may have a bit to do with the weight the bike is carrying. I'm six feet tall and only just on the correct side of 25 stone.

I find a headwind drops me back to 40mp/h and as I said, a tailwind can push me up to previously unheard of speeds. It's a grand little bike. Just a tad slow.
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Ambergnat
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PostPosted: 01:21 - 06 May 2013    Post subject: Reply with quote

Spudly wrote:
I have a feeling it may have a bit to do with the weight the bike is carrying. I'm six feet tall and only just on the correct side of 25 stone.

I find a headwind drops me back to 40mp/h and as I said, a tailwind can push me up to previously unheard of speeds. It's a grand little bike. Just a tad slow.


Aaah yes, that'd probably do it.

I'm just over 5ft10" and 14 stone - so your bikes got an extra 65kg to cart around and you've a larger frame to stop the wind with - double whammy (as the yanks would say) Wink - I guess that's the main disadvantage of the low power.

Ideally, if you could get your hands on a GZ250 it would probably be perfect for you - just a bit more grunt in the places which need it (circa 18-19hp) - problem is they're rare as rocking horse shit in the UK Sad - and you'd need a full license...
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Ambergnat
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PostPosted: 01:23 - 06 May 2013    Post subject: Reply with quote

humanbeing wrote:
Ambergnat wrote:

Just ordered something similar on eBay (just hope it fits Neutral )...


The old type had minor difference (Bigger valves/ 12mm spark plug):
http://www.motorfans.com.cn/bbs/t_17250767_1.htm

If jammed it directly on the "newer engine" , the compression ratio maybe too low. Solution: dome shaped piston as the good old Suzi / thin gaskets ...


Thanks Smile I'll bear that in mind if it turns out to be a dog after the fix.

On this occasion only - I'm going to let the mechanics fit the part (and pay through the nose for it) and after that, keep an eye out for old k4/k5 heads on fleabay to replace it myself when I'm a bit more GZ savvy.
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