My GX125 doesnt work!

P. · Red Rocket Joined: 14 Feb 2008 Karma :

Hi, its Nemo posting on Paddys account, I cant seem to log in?

G dropped my bike off to Paddys yesterday as there are tools there and Paddy can work on it at the weekends.

There seems to be no compression.
Its definitely getting petrol to the carb, its turning over but I can hold my thumb over the spark plug hole and just feel it hitting with a breath of air. How can I find out exactly what it is?

Ive got some pics as ive found some oil/gunk over the top of the engine.

Also...if I need a new engine, the GX seems very hard to find..If some people here have a GS/EN engine, does this look identical?

Weird oil on engine...kind of oily but dirt at the same time.

https://img35.imageshack.us/i/img0259jq.jpg/

https://img132.imageshack.us/i/img0256rp.jpg/

https://img576.imageshack.us/i/img0257jd.jpg/

https://img696.imageshack.us/i/img0258sa.jpg/

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

N cee thirty · Banned Joined: 31 Jan 2010 Karma :

looks the same as a gs engine.

check one of the valve tappets hasn't come undone,happened on the artists bike i remeber and he had no compression at all.same engine btw
____________________
'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

P. · Red Rocket Joined: 14 Feb 2008 Karma :

Thanks guys

It wouldnt let me add the img tag, it just broke the link Sad

I have no manual, like I said its a hard to find bike Laughing

I'll take top top off and see what I can see, if its a valve...simple. Much better than a whole top end.

I will have a look as soon as Paddy is back

P. · Red Rocket Joined: 14 Feb 2008 Karma :

Well we opened the engine.

Bore looks smooth as, piston doesnt have any movement whatsoever.

The piston is an odd shape though. I always thought a piston was fairly flat on the top... this one isnt, might see it in the pic.. very odd?

https://yesterdaystheory.pwp.blueyonder.co.uk/16.JPG

The valves..look a total different colour.

https://yesterdaystheory.pwp.blueyonder.co.uk/14.JPG
https://yesterdaystheory.pwp.blueyonder.co.uk/12.JPG
https://yesterdaystheory.pwp.blueyonder.co.uk/13.JPG
The rocker arms?? look worn

https://yesterdaystheory.pwp.blueyonder.co.uk/15.JPG

Aside from that, thats all the work we have done.. I just await any info as to what it could be Smile

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

Definitely not the same engine as gs/gn/en/dr.

Clutch different side, oil filter different place. Top end looks the same though.

Pistons like that are common. Valves different colour because one is exhaust and one is inlet although I haven't seen any so different. Not 100% sure on that one.

I would check valve timing/clearances and piston rings. Those valves don't look to tasty either. Maybe not running the right mixture or something.

P. · Red Rocket Joined: 14 Feb 2008 Karma :

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

Weird. To run, an engine needs compression, fuel and spark. You say no compression but from what you just said it sounds like it is a fuel/electrical problem Laughing

First check if it is sparking, simple to check and gets electrical issue out the way.

Can you put your hand over the top of the bore and turn it over to see if the rings are leaking?

MaybeGuy · Super Spammer Joined: 12 Mar 2007 Karma :

regrind the valves
____________________
Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!! Mr. Green

Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

I've just had a 'Ker-Chunk' moment

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

N cee thirty · Banned Joined: 31 Jan 2010 Karma :

https://i825.photobucket.com/albums/zz176/robyarr/DSC00810.jpg

thats a pic of the cg valves i happen to have in my room,you should try regrinding the valves and new gaskets and see if theres any diff
____________________
'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

P. · Red Rocket Joined: 14 Feb 2008 Karma :

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

Clearances are 0.13mm give or take 0.02 I think.

I always forget which one is supposed to be slightly bigger.

The bits of the rocker that contact the camshaft should feel worn as they are always in contact with it and you adjust the clearances to counter the wear.

I would be more worried about the state of the actual valves. If you can, take them out and have a close inspection of the stems and seats.

P. · Red Rocket Joined: 14 Feb 2008 Karma :

P. · Red Rocket Joined: 14 Feb 2008 Karma :

Probably going to have a go at getting the valves out and seeing if its worth regrinding.

Any votes on that being a probable issue?

I suppose to test I could just whip the head back on, reuse gasket and a bit of gasket sealant, bolt it down hard and just see if it has compression without using the valves? My boss was telling me today and I kinda forgot half of it Sad

N cee thirty · Banned Joined: 31 Jan 2010 Karma :

might aswell have a go

me and CHR15 (well him mostly) regrinded the valves on my cg and replaced the stem oil seal and then all the gaskets,must have nearly doubled the compression

only a hours work anyway and £20 tops
____________________
'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

P. · Red Rocket Joined: 14 Feb 2008 Karma :

Suppose while its off, i'll do it.

Where can i pick up the stuff to do it? Ive got grinding paste...but not anything else.

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

I have no idea why you jumped into taking the head off. To do the job properly you need to use a new head gasket, and scrape off all of the old one. Gasket goo is no good for a head gasket, if the goo is strong enough then it'll be horrible to remove.

Now you have the head off you might as well regrind the valves and fit a new base gasket.

If that doesn't fix the problem, I'd look at fuelling. Water in the carb could cause a sudden stop, as could something as simple as running out of fuel or a flat (or low) battery.

So, go a good job of the top end rebuild, strip and clean the carb, and drain some of the fuel from the tank into a clean plastic jug and look for evidence of water or dirt in the tank.

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

P. · Red Rocket Joined: 14 Feb 2008 Karma :

bumpage..

removed the exhaust valve (smaller white one) from the head...
There appears to be a lovely crack running around where we removed it. I didnt think it looked square at all and I think I can see why Laughing

Any idea what head is identical...the GX seems to be one of these hard to find bits.

It cant be to different from a GS, i mean its roughly the same power...

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

Looks pretty much the same as the GS and all its variations.

P. · Red Rocket Joined: 14 Feb 2008 Karma :

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

PM Marki. Top end looks exactly the same, bottom end definitely isn't.