Cooked Engine

[cabby]

I agree, if the new owner has shown total disregard and blatantly abused the bike then yes, tough titties, however, does the previous owner know that for sure, as by his posting there seems to have been some kind of misunderstanding some way along the line.

[jfc]

Without knowing the bike and witnessing the use of the bike it's all just talk I agree!

Edited January 13, 2014 by jfc

[thats_a_five]

There are so many variables involved that it is extremely difficult to determine what really happened after the fact.

If you feel you represented the bike fairly and honestly when you sold it, then stick to your position that it is not your responsibility.

If you think this will end up in court, you might suggest that the new buyer take it to an authorized GG dealer / service shop for evaluation if he has not already done so.

I do not know about courts in France but in the USA I have learned that the decision making process of the courts often defies any logic that I understand.

Good luck and let us know how it works out.

[ourian]

I'd refer him to the manufacturer of the water pump, (hopefully you have the receipt), if the cause of the problem is due to a manufacturing fault then does not the vice cache lie with the manufacturer.

[jse]

I agree, if the new owner has shown total disregard and blatantly abused the bike then yes, tough titties, however, does the previous owner know that for sure, as by his posting there seems to have been some kind of misunderstanding some way along the line.

" He sent me some pics of the cylinder head which has what looks like a melted hole in it, another pic of the piston which seems to have a piece of metal stuck to it and another pic of the cylinder inside which has a big gouge in it (I think from the metal that is stuck on the piston)."

I don't think I can remember knowing a rider who would continue to ride a Trials bike, with the obvious symptoms of distress the engine undoubtedly exhibited, to the point of this type of damage. I think there is more to the guys story than he is telling you.....

Jon

[vmeldrew]

When you get a second hand bike home, surely the first thing you do it strip it down and see exactly what you have bought?

Check the fluid levels, bearings, breaks, bolts everything,

Taking it for a thrash is tantamount to suicide in my book and as Jon says, Gassers don't just seize and blow up, you really have to hurt them to do that sort of damage. Even without any cooling fluid or a working pump any sensible person would realise a problem prior to the engine giving up like that.

If I wanted to do that to a Gasser, I would fall off and jam the throttle wide open for a minute or two, that should do it.

[phil0925]

Hi All, the young guy who bought the bike did use it the day before, I'm not sure for how long etc. I do feel very sorry that this has happened (a) because I'm a bit sentimental over the bike having had some fantastic times on it. ( because he has this problem. The first time the impeller went I had to push the bike back home through the forrest UMMM OK its a light bike but that's hard work in riding boots up hills and rough ground etc. The local GG dealer (who I bought the bike from) said that the pump impeller was sort of a consumable and implied that they sell quite a few in the course of a year! Like I say I think the origin of the first failure was the inner seal which in a old bike that's a kind of an acceptable failure (10 years old now 8 at the time of the first failure). Thats the reason I bought a complete new pump so as to refurbish the old pump and carry a spare. I spoke with a tech at GG UK to check the fitting procedure just to make sure I hadn't missed something and he confirmed the fitting procedure. I'm a mechanical engineer by trade and in fact measured and checked the end float clearance as well on the pump drive shaft and all was good (in the fitting that's not a requirement as I' bought a new complete unit, I also filled the in and out pipes with coolant an kicked it over to confirm the pump was driving and the flow of coolant), he also confirmed that if the pump was not fitted correct or had a problem then it would not have run for 2 hours on a trials piste without showing a problem. I agree with vmeldrew that the bikes is quite bullet proof, but perhaps the pump could be improved a bit as the plastic thread is "perhaps" a bit of a fragile design but for sure must function under "normal operating conditions". The main point for me is that maybe "IF the impeller is a bit fragile then some of you guys may have had the same problem" if so did it fail under a heavy load / use condition? And was it the Thread that stripped on the impeller due to hard riding?

Thanks again to you all!

[phil0925]

P.S I don't know why but the "b" (but in brackets) automatically change to a half smilly?? Not my intention at all. Genuinely sorry for the guy having the problem!

[phil0925]

If you have a weak heart and love your Gas Gas then don't open the attachments!

[canada280i]

mmmmmmm...strawberry milkshake, my favorite!

I take it the piece of metal on the piston is the piece from the hole in the head?

[blocky]

In my humble opinion, This was the order of failure...

Hot spot developed on the cylinder (Look at the heat mark on the right of the crack in the head)

This in turn led to one or more parts of the head cracking away into the cylinder.

This in turn punched the hole larger forcing shrapnel into the water jacket and probably into the exhaust too.

When the shrapnel worked its way into the water pump this jammed the impeller causing the stripped thread.

So what caused the hot spot ?

You mentioned earlier I think that the engine had recently been de-coked I think. Mostly likely damaged at that point. May have been too small to see with a naked eye.

[jse]

That's a new one for me. I can understand the impellor stripping, actually fairly rare from my experience as usually caused by the rider taking the brass plug out of the pump to drain the fluid and the thrust washer falling off the shaft end and into the housing and binding the impellor to the housing (it also allows the shaft end to sit into the housing too far and the impellor scrapes the inside of the pump housing, and I don't see signs of that here).

Obviously it's hard to see details in the photos, but I don't see any obvious signs of detonation but the rings seem to be seized in the lands (could have happened due to excessive heat, and "after the fact" of the main cause). The hole in the combustion chamber is unique, however, and may have been a surface fracture that let loose and a possible cause of previous overheating issues-chamber gases pushing into the cooling system. I think that's the first one of those I've seen. You could not have normally predicted a material failure of this sort unless you carefully inspected the chamber for cracks while the engine was torn down (not a normal proceedure in my experience other than in high-end racing applications).

It does look like the engine was stopped (locked up) when the chamber wall came apart (and the piece got stuck in the squish area) but it also seems that this engine was run beyond the time it should have been shut off when the first overheating symptoms were noticed.

First rough guess is material failure in the head chamber.

Jon

[big_red_bike]

Hi looking at the colour of the head and piston plus the lack of carbon deposits,also the o ring and markings around the water ways i would say the o ring was letting water into the combustion chamber which then lead to the over heating and head failure.

[phil0925]

Hi All, Again... What a story. For me this is turning bizarre! Went to the garage where the bike is and back today total time 6 hours.... Wanted to know if the carb had some pink (oil and water mix) in it and take some more detailed photos......Because the last time that the pump seal went the engine stopped because of the “pink stuff” in the carb ( for sure it wouldn’t burn) ummmmm! it get’s there I guess by way of the gearbox breather, that goes from the gearbox cover to the carb. Guess its a combination of the added liquid level (coolant with the oil) and the heat pressure in the box with the hot coolant, plus the carb suck? In the clear tube you could see the pink. I wanted to do this as “IF” the pump was the original cause of the problem like last time, then the pink in the carb would have cut the engine in a short time and the head and probably other parts would not have been damaged so drastically if at all, like last time!

Arrive..... the pipe is cut and another pipe is fitted that goes to atmosphere along with the one that’s been cut! So I ask who had changed the pipes? The “!!!!!! MECHANIC!!!!” says it wasn’t connected and that it’s not important and points to a Honda that has a gearbox pipe that goes to atmosphere (......He insisted that it would never of been connected! P.S this guy is NOT a GG service bloke.

I arrive home look at the sales photos taken a couple of weeks ago to advertise the machine and it’s clear that its connected before the bike was taken away.... also in the same photo it seems that the mixture screw is in a different place..........ummm!

I looked at some 07 pro photos and it doesn’t seem connected but on mine (250 TXTI pro 03) (yes TXTI?)it was always connected HELP! When was this changed and does the pipe make a difference to the carburetion mix? ..... guess you know where I’m going! (out of me head) J) Think there’s a call to the nice guys at Gas Gas UK tomorrow. PPS. the bits of metal in the pump photo were found in the water pump but the "mechanic"!!!!! says that the pump was the cause as the threads in the plastic impeller were stripped !!!!!!!!!!!! HELL

[phil0925]

BRB, thanks, the head was decarbed about 6 hours run time ago and the head rings were replaced at the same time and head flatness checked. Today when I saw them they were almost non existant and totaly burnt away from the heat.

BR phil0925