No Compression

[iowgav]

I have been offered a 2011 X Evo 125, to replace my ageing X9 125, for next to nothing. However, I have been told it has no compression. I am a fairly competent mechanic, but would this be something I could do on my own.

What are the likely problems and replacement parts I would need? I am guessing anything from piston rings to a full new cylinder head.

Is it worth taking on as a project.

Thanks muchly for any help or suggestions.

[roadster]

If you would enjoy the challenge of the mechanical work then by all means take the gamble. But as practical alternative transport I don't think the Evo would be a great improvement over your X9 unless you are fairly sure that the X9 isn't going to go much further anyway. In terms of cost then as soon as you start buying expensive engine parts that is money that you will never recoup so if you just want a replacement scooter buying a non-runner can only make sense if you also buy more used parts ( a write off that has a good engine for example).

[unchained]

Could be anything; rings, valves, gaskets, piston, barrel, timing chain or simply timing.

At the right price (next to nothing) it would be a worthwhile project but until you strip it down you will not know the cause of the problem. A replacement engine from a donor would be the easiest option.

Bob

[Dave Milnes]

If all that is really wrong with your current X9 is general wear and tear on the frame, suspension and electrics, then swap out the motor from the X9 to the Xevo as unless the mileage is astronomical there will be nothing wrong with your X9 motor.
No compression is a swine to sort as it isn't always something obvious by just looking, you usually end up changing several gaskets, lapping valves, replacing rings or even pistons, and when sorted never really know what it was that cured it. Only if it's damage caused by a failure or misuse is it usually fairly clear where the fault lies.
You could keep the external ancillary parts from the Xevo like the later carb and exhaust, engine mount and transmission components, just use the short motor parts from the X9.
A weekends work should see it done.

[iowgav]

My engine is on about 20,000 ish but still pulls well when the carb isn't playing up, so I might consider this option. My bodywork, frame and electrics are all showing wear and tear though, few crashes have led to a fair bit off glassfibre repairs, and a lot of the plastic has faded, and have a cracked screen.

Def will look into the engine swap.

[Dave Milnes]

You can also then sell on the decent bits from the X9 and probably cover costs. The wheels and tyres will fit the Xevo, battery, switches, some bulbs, so the X9 is a bank of spares as well.

[Mike H]

"I have been told it has no compression"

This might be taken with a pinch of salt, is only prev owner's diagnosis? How was it done? With a compression tester?

[iowgav]

Well, I've brought it, delivered tonight. My only concern is the swap between carburettor on my old X9 and fuel injection on the XEvo. Will the fuel injection be a straight swap onto my old engine.

Are there any engine removal guides on here that I could follow, both the XEvo and X9.

Thank you all very much.

[Dave Milnes]

The manifolds will need swapping and should have the necessary tappings for injectors and such. Conversion to Fi was mainly a bolt on job to the same basic motor casings. The X9 125 Evo was originally going to be injected but for some reason it remained carb.
I would remove the Xevo unit and see what you can find wrong first job as you never know, it may turn out to be a simple fix that is more cost effective to repair than bothering to swap motors over, if not you can at least do a close side by side visual to confirm that the older motor can be upgraded.
If there is no compression it could be a stuck valve or bent or broken rocker, or just a blown head gasket and a simple fix.

[roadster]

Can I suggest that you don't assume that the no-compression diagnosis is correct. Remove the spark plug, reconnect it to the HT lead and place it in contact with bare metal. Then spin the engine over. It should spin really quickly and you should also see a healthy spark. Then take a softish object such as clean stick with a rounded end and hold it tightly on the spark plug hole (on not in), you can use your finger if you can get it over the hole to make a good seal. Turn the engine over again and if you cannot prevent some air forcing its way past the plugged hole then there is probably enough compression for the engine to start. If you can feel very little pressure the diagnosis is correct.

[Dave Milnes]

True, I remember someone else on here not able to start a 125, claimed no compression on the 'thumb test' but having changed the coil it ran fine. Compression at starter motor revs is minimal but once revolving at 1000rpm plus it goes up a lot. Less time in the revolution to leak away.

[iowgav]

Turning the engine over it does spin fast as though the plug is out. Will try the method above though to check then remove the engine for a better look.

[roadster]

Turning the engine over it does spin fast as though the plug is out. Will try the method above though to check then remove the engine for a better look.

Also make sure that the crankshaft is actually turning.

[Dave Milnes]

Yes the outer variator pulley has been known to shear it's splines so the starter motor isn't turning anything but the pulley.

[iowgav]

Piston is def moving when turning engine over, can see it through the spark plug hole. Should have the engine out and cylinder head off today. Will report back later, with a photo possibly.

[iowgav]

Had to laugh when I took the head off, no idea how it got like this but it has. Pics on links below.

https://drive.google.com/open?id=0B7juGGkzjYcPV2lnS2Y2RGI4Szg

https://drive.google.com/open?id=0B7juGGkzjYcPanktQ0o4YllXMzA

[Mike H]

Bluddy hell both exhaust valves' heads broken off and gone AWOL down into the sump 

[Dave Milnes]

That's the biggest issue, where have the bits gone. If the oil strainer caught the smaller swarf and it hasn't gone round the bearings, then a new piston and head will fix it but you need to clean out the sump thoroughly. The previous owner must definitely have known what had happened, it is not wear and tear loss of compression.

[roadster]

A second hand engine must be the only realistic option then. I can't come up with any explanation for as much damage as this before the engine stopped unless it was running on a rolling road or down a very steep incline.

[Dave Milnes]

Timing chain tensioner failure? Jumped a few teeth at speed so piston hits inlet valves? Definitely a failure you would know about.
Best bet is to compare the two motors you have and see if the X9 one will swap over. As far as I know the 125 remained pretty much unchanged in it's basic casings, just slightly different bolt on parts used in each application so it should swap over.

[iowgav]

Have been comparing them this morning. The cylinder head does have an extra port just above the exhaust port, see pic above. Attached to this was a metal pipe that runs to something mounted just above the water pump. As far as I can tell the extra port on the Xevo head goes straight into the exhaust so I am assuming it is something to do with emissions. Do you think I can just leave the metal pipe unattached as there isn't the same port on my X9 head. Apart from that, all looks good to go.

[Dave Milnes]

Later engines had a small air bypass pipe that bled inlet air into the exhaust stream for emissions test. It often corrodes away and is removed and a blanking plate fitted with no effect on running.

[iowgav]

Found most of the big bits of metal and valve heads in the exhaust manifold, just small bits in the sump. I guess that is lucky as less likely to have done any internal damage. Am just waiting for gaskets to be delivered now so it can all go back together.

[Dave Milnes]

The oil pickup strainer and filter should have got them but it might be an idea to use some old but 'known good' oil and filter, say off your X9 as a flushing oil then if it all seems OK put new oil and new filter before use.

[iowgav]

Good idea. My X9 had a fairly recent oil change so will use the oil and filter from that and maybe some flushing fluid.