|
Post by archloafer on Jun 19, 2021 22:24:12 GMT 1
Hi folks On the motorway doing 70-odd, bike just died. Fortunately very little traffic so was able to coast to the hard shoulder. Tried to start it, engine turned over but virtually no compression. Coolant all down the side of the bike. Wondering how the f*ck I was going to get off the motorway, remembered my insurance has breakdown cover included so started scrolling through .pdf files on my phone trying to find the number. Saw a guy on a Speed Triple on the other carriageway look over at me, 5 mins later he pulls up behind me and asks if I'm OK, do I need any help. I said, jokingly, "you don't happen to know anyone with a van do you?". He said he did, called his mate who turned up 20 minutes later, ratchet straps and everything. Gave me a lift home (fortunately this happened only about 4 miles from where I live), wouldn't take any money for petrol. Total legend. Got the bike in the garage - engine no longer turns over. Started stripping it down, got the pipes off and heard something rattling around, tipped it out on the floor. Uh-oh. Lost the will a bit so will strip down the top end tomorrow and examine the extent of the damage, take a view. Head gasket failed in some way I think - head bolts worked loose perhaps. Hey-ho Cheers - David
|
|
|
Post by firmstools on Jun 19, 2021 22:34:25 GMT 1
Sorry to hear about your engine, sounds like you have a bit of work to do! There are some cracking people out there!
|
|
|
Post by steve h on Jun 20, 2021 0:43:16 GMT 1
There are some bloody brilliant folks out there!! Kindred Spirits...lest we forget!! And thank god for a hard shoulder! Good folks like that reaffirms ones faith in humanity!!
|
|
|
Post by JonW on Jun 20, 2021 2:35:37 GMT 1
Thats wonderful. restores your faith in humanity.
|
|
|
Post by tony2stroke on Jun 20, 2021 11:31:47 GMT 1
It always used to be the case that if a biker came across another biker broken down, they would stop and try to help, not so often these days, but 10/10 for your helper, there are still some good old fashioned bikers out there, hope you haven't had too much damage.
|
|
|
Post by archloafer on Jun 20, 2021 14:42:28 GMT 1
There are some bloody brilliant folks out there!! Kindred Spirits...lest we forget!! And thank god for a hard shoulder! Good folks like that reaffirms ones faith in humanity!! It does indeed restore ones faith. Hungarian lads, both fairly new to biking from talking to them. I was a bit overwhelmed by their friendliness and generosity tbh. Got their phone numbers and said I'd take them out for a good few beers 😁 Re the hard shoulder - if this event had happened a little way further along my intended journey I would have been on the 'smart' section of the M3 with likely much more traffic. Wouldn't have been at all nice. 🍀🍀🍀
|
|
|
Post by archloafer on Jun 20, 2021 15:21:15 GMT 1
|
|
|
Post by donkeychomp on Jun 20, 2021 21:23:27 GMT 1
There are some great people out there. Glad you stumbled across a couple!
Alex
|
|
ajh
Thrash Merchant
Posts: 415
|
Post by ajh on Jun 20, 2021 21:36:49 GMT 1
Wow, never seen a plug like that!!! Any thoughts to as what happened?
|
|
|
Post by chippy348 on Jun 20, 2021 21:47:49 GMT 1
It may be the photos, but the cylinder head looks to have had the chambers reduced volume and squish ?
I take it the engine is not standard
|
|
|
Post by bobon on Jun 20, 2021 21:51:30 GMT 1
Looks like detonation destroying the piston crown and plug.
|
|
|
Post by bobon on Jun 20, 2021 21:57:41 GMT 1
Maybe the changes to the head have generated too much compression. The mixture would be dieseling and gradually destroying the top end.
|
|
|
Post by Tobyjugs on Jun 20, 2021 22:10:55 GMT 1
It may be the photos, but the cylinder head looks to have had the chambers reduced volume and squish ? I take it the engine is not standard I think your right, it's got a copper head gasket and the bottom part of the liner under the exhaust port looks different and the transfer ports look longer than standard. I could be camera angle though.
|
|
|
Post by Tobyjugs on Jun 20, 2021 22:15:30 GMT 1
Looks like detonation destroying the piston crown and plug. Would you not expect to see detonation marks on the cylinder head as well? I would go for the classic meltdown due to lean mixture
|
|
|
Post by midlifecrisisrd on Jun 20, 2021 22:39:53 GMT 1
But what about the coolant everywhere?
Lean mixture wouldn't make it spew coolant
Steve
|
|
|
Post by Tobyjugs on Jun 21, 2021 0:08:37 GMT 1
This might be a bit controversial but my belief is the copper gasket is a poor choice to seal the cylinder head. I feel the force generated by the torque of the cylinder head bolts is not enough to seal the flat copper gasket. If you look at the leaf gaskets or the composite gaskets you will notice the raised area around the combustion chamber. This helps create better sealing. I think there was mention of loose cylinder head bolts as well. If a piece of debris gets caught between the piston and the cylinder head there is usually enough force generated to strain or stretch the cylinder head studs.
|
|
|
Post by 4l04ever on Jun 21, 2021 0:49:39 GMT 1
Looks like someone has adjusted the squish by skimming the head but ended up with too high compression.
|
|
|
Post by archloafer on Jun 21, 2021 21:53:57 GMT 1
It may be the photos, but the cylinder head looks to have had the chambers reduced volume and squish ? I take it the engine is not standard No, not standard. Previous owner raced it for a couple of seasons and had porting / head work done by Bob Farnham (this would have been done around 1988). I took the engine back to Mr. Farnham when I was doing the resto. He looked at the head and suggested that the compression would be a bit high for the road so re-profiled the squish to bring it down a bit.
|
|
|
Post by archloafer on Jun 21, 2021 22:05:15 GMT 1
But what about the coolant everywhere? Lean mixture wouldn't make it spew coolant Steve Yeah, it's a bit weird. When I took the head off the bolts didn't offer much resistance to be fair, particularly the 4 in the middle round the hose joint. I think my theory about air being sucked in through the gasket might be about right. Was thinking though that it would be odd to be drawing in air only - some coolant must have got in too. Dunno what effect that might have had...
|
|
|
Post by archloafer on Jun 21, 2021 22:22:48 GMT 1
This might be a bit controversial but my belief is the copper gasket is a poor choice to seal the cylinder head. I feel the force generated by the torque of the cylinder head bolts is not enough to seal the flat copper gasket. If you look at the leaf gaskets or the composite gaskets you will notice the raised area around the combustion chamber. This helps create better sealing. I think there was mention of loose cylinder head bolts as well. If a piece of debris gets caught between the piston and the cylinder head there is usually enough force generated to strain or stretch the cylinder head studs. Yeah, they seem to divide opinion pretty squarely. I opted for copper originally because I had problems getting the OEM gasket to seal - coolant seeping out of the front of the head. After getting some advice on this forum (a while back) I sent the top end to 4l04ever's engine guy who found one barrel tapered off slightly to the outside edge - right where the leak was. He skimmed 0.2mm off them (as a pair) and also .1mm off the head. That seemed to solve the problem. When I put it back together I annealed the gasket, used a touch of permatex and torqued it up very carefully to a few Nm more than the recommended value. So given this and the above work, no reason for it not to seal properly. I honestly think this is just a case of the head bolts working a bit loose over time. My fault - something I should have been checking regularly. Hard lessons.
|
|
|
Post by archloafer on Jun 21, 2021 22:32:53 GMT 1
So in terms of fixing this, cylinder rebore (both, I guess?) and head re-machining. Given that the engine isn't standard I'm probably looking to a tuner to do this.
And the crank - looks fine but unwise to assume that metal fragments haven't got down in there. So whip that out and send it off to be re-built.
Thoughts?
Cheers - David
|
|
|
Post by tony2stroke on Jun 22, 2021 8:30:53 GMT 1
So in terms of fixing this, cylinder rebore (both, I guess?) and head re-machining. Given that the engine isn't standard I'm probably looking to a tuner to do this. And the crank - looks fine but unwise to assume that metal fragments haven't got down in there. So whip that out and send it off to be re-built. Thoughts? Cheers - David There are ways of getting the stuck alloy bits off the barrel, you could use some emery cloth gently, then get the head and barrels checked by a reputable bike shop or tuner. The crank could be fine, in the old days we would just rinse out the bottom end and hope no alloy stuck to the bearings, its a risk, sometimes your lucky, sometimes your not, problem is you can't see places that could have alloy stuck, its your choice mate.
|
|
|
Post by dougw on Jun 22, 2021 12:38:34 GMT 1
With 0.3 mm removed after Bob Farnham did his stuff compression might be a bit high again , and squish getting tight ?
|
|
|
Post by liffy16 on Jun 22, 2021 13:32:57 GMT 1
Tried a copper gasket on my powervalve but could not get a good water seal,so tried a taiwan made one no problems
|
|
|
Post by Tobyjugs on Jun 23, 2021 18:35:56 GMT 1
Hi David, I'm not sure which permatex you used but it looks like the 300 or 3000 which is a good choice. Similar to well seal. Your post comes over as confident in what you are doing.
If it is a tuned engine then I would say yes re-bore them both unless you can match the weight of the different size pistons? Have you thought about measuring all the engine specifics? It's not that difficult. If 0.30 mm has been skimmed from the cylinder head you could compensate that with a thicker base gasket. It will make a difference with your port timing but it's not that much.
Rob 4l0 can provide different size base gaskets but I usually allow 0.30 mm for compression when fitting a 1 mm thick combination gasket.
One of the basic building rules of a two stroke is the geometric compression ratio. I believe everyone should measure this. It's just as important as squish, a leak down test or removing your brass balls but not so many people talk about it and it is very important. It's not difficult to measure.
Why don't you give it a go. It's written up in one of my threads. You can also pm me for an explanation and help.
I hope you get it sorted without too much hassle.
|
|
|
Post by stusco on Jun 26, 2021 15:17:06 GMT 1
Where’s the pictures I can’t see any
|
|