Broke down out of no-where

RS2MATRIX · Spanner Monkey Joined: 03 Apr 2008 Karma :

Ok, so pushed the bike home about 2 miles after trying out my new settings for the new air filter. I was riding up a hill when it lost power, so i dropped a gear and it continued losing power and eventually died at the side of the road.

It was very hot and no matter what it would start, so i gave up and pushed it. The plug was black when i got home and i was fed up with messing around with the pod filter and stuck the old one back on.

When i tried to start it, it felt as though no fuel, when i held full revs on it stayed on but just barely if i let the revs go it would die again.

So, now ive got the old filter back on and took it out for a short run, the plug is now a dark brown colour but sounds a bit clogged and sticky Confused

any help appreciated, nick.

Trixie · World Chat Champion Joined: 27 Jul 2005 Karma :

From what you describe, the bike is running rich (i.e. too much fuel, not enough air). You need to change the mixture, so you need to revise what you've done with the air filter.

When you rev, it might sound like it's got no fuel but the opposite is true - there's too much fuel and the engine is flooding.
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Dead nobodies in company cars...

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

Sorry to say it sounds like you have run it lean and over-heated or melted the piston, causing it to nip the rings and losing the compression. I take it this is a 2-stroke? Expect to find significant damage to the piston by way of deep scoring and damaged rings and probably the barrel too.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy

RS2MATRIX · Spanner Monkey Joined: 03 Apr 2008 Karma :

Oh no!

Is there any way to know of this damage, without of course taking the top end off.

Would the fact it still starts and runs (if a little badly, clogged up like) mean the damage is minimal or will it just happend again now that i have reverted back to my original filter?

Thanks guys

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

You could drop the front of the exhaust off the barrell and look up the exhaust port. Get the piston so you can see the rings in the top of the port and take a pic.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy

StealthDJ · Nova Slayer Joined: 21 Apr 2008 Karma :

If it had seized, the plug shouldn't be black - it should've been white and quite possibly whiskered with bits of melted alloy from the piston.

To the OP: Taking it as read that the air filter experiment didn't work, it sounds like the plug well and truly fouled afterwards. Before ripping the top end off the bike (looking up the exhaust port will only tell you anything if that's the side it nipped up on), have you tried a new spark plug in there? If that gives you full power back, you may well have got away with it.
____________________
Current garage: VFR800 FI-W | RD500LC YPVS | SV650 K2 | MZ TS250/1 | MZ ETZ251 | BSA WDB40
Previous notables: H100 S2 | CB250NA/B | CB250T | GT250X7 | Z650 B1 | SR650
Still owned, but long gone: RD250LC | CB750F2 SOHC | C50

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

StealthDJ · Nova Slayer Joined: 21 Apr 2008 Karma :

RS2MATRIX · Spanner Monkey Joined: 03 Apr 2008 Karma :

Thanks for the replies guys..

Im guessing the fact it starts and rides means there is no serious damage *yet*?

Ive just got back from work and this morning i was debating wether to take the bus or not, i ended up taking the bike and it was *fine* there was a noticeable lack of power (probably due to original filter back on) but it felt pretty similar to before, maybe a little bit more underpowered. What could this mean..

Im going to wait for it cool down and get the plug put and inspect it, what should it be looking for?

I have a day off tomorrow, is there any tell-tale signs i should note for damage before i whip the top end off

Thanks nick

RS2MATRIX · Spanner Monkey Joined: 03 Apr 2008 Karma :

Ok, bit of an update, i took the plug out and it was dark brown with black threads. So, i decided to have another go at it seeing as i have the day off tomorrow and dont have much to lose.
Dissassembly of the carb revealed i have a 72.5 main jet, (standard is 70) Only other jets i could find were a 90 and a 200 Shocked

(didnt fit anyway) So i cleaned up the 90, put it in and put the filter back on.

Went for a run, and the plug is brown still with black threads. What else should i do apart from upjet, what else needs changing or adjusting.
Now for pics. *apologies for appaling quality of my camera Embarassed

*

https://i290.photobucket.com/albums/ll275/RS2Nick/SUNP0008.jpg

https://i290.photobucket.com/albums/ll275/RS2Nick/SUNP0005.jpg

Thanks nick

StealthDJ · Nova Slayer Joined: 21 Apr 2008 Karma :

Blau Zedong · Banned Joined: 26 Jun 2006 Karma :

Cone filters cause midrange flatspots on reed valve strokers which can be very difficult to eliminate. On MZ's and other piston port tat they aren't so bad but do need a fair bit of fannying with jets etc. Hence why the trick for big power on RD's etc is to use a 2-1 manifold from the carbs (sourced from an old A/B model) and stick a big single K&N on it. Gives you the resonance of an airbox (i.e. good drivability) with the ability to flow lots more air (top end power).

Trust me, I know what I'm talking about.
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Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

I still say it's damaged from heat-seizure. Up a hill...losing power...down a gear...comes to a stop...red hot & won't start. That bike has leaned out and seized.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy

RS2MATRIX · Spanner Monkey Joined: 03 Apr 2008 Karma :

Is it possible for it to have siezed and it still run and ride *normally*, or am i defining 'seized' in the wrong way?
the position im in now, is ive change the jet from 72.5 to 90 and put the pod filter back on and its back to normal, decent speed and not cutting out. Apart from once when i started it and put it in gear, then it took ages to start again? But the plug is just black with white on the bit where the spark goes from metal to metal

Have i damaged it Evil or Very Mad

Nick

StealthDJ · Nova Slayer Joined: 21 Apr 2008 Karma :

It is possible for it to nip up and then free off again. Generally speaking, the harder you're thrashing it when it goes, the worse it'll be.

You mentioned that after it came to a stop, it wouldn't start again - was the engine turning over freely? If it did seize and free that quickly, I personally wouldn't even bother taking the barrel and head off, but it's up to you.

Out of interest, don't think I've seen mention of what bike this is?
____________________
Current garage: VFR800 FI-W | RD500LC YPVS | SV650 K2 | MZ TS250/1 | MZ ETZ251 | BSA WDB40
Previous notables: H100 S2 | CB250NA/B | CB250T | GT250X7 | Z650 B1 | SR650
Still owned, but long gone: RD250LC | CB750F2 SOHC | C50

Cigaro · World Chat Champion Joined: 28 Mar 2007 Karma :

Surely overfuelling can also cause overheating, too.

It may be damaged, it may not. I'd definitely change that spark plug, though - if it's pretty much back to normal after that, dont' worry about it. A good plug is improtant on a two-stroke and it can't hurt to change it, can it?

RS2MATRIX · Spanner Monkey Joined: 03 Apr 2008 Karma :

Well i pulled to the side of the road, checked anything obvious, all seemed ok and it turned over fine. but wouldnt start, took my glove off and the engine was realllly hot. I had to wait a while for it to cool and then i tried again, when it only stayed on when i had it on FULL revs and it felt like it was idling.. badly!

Cigaro · World Chat Champion Joined: 28 Mar 2007 Karma :

Without taking the head off you'll never know.

Could it have been a vapour lock in the engine stopping it from starting? Especially if it was overfuelling prior to this?

RS2MATRIX · Spanner Monkey Joined: 03 Apr 2008 Karma :

Cigaro · World Chat Champion Joined: 28 Mar 2007 Karma :

RS2MATRIX · Spanner Monkey Joined: 03 Apr 2008 Karma :

Ah right,dont think it was flooded to be honest although im not totally sure,

Ill get a new plug tomorrow if it gets me to the shop Laughing

thanks, nick

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

RS2MATRIX · Spanner Monkey Joined: 03 Apr 2008 Karma :

Just done a compression check if that tells me anything? It was 130psi

Cigaro · World Chat Champion Joined: 28 Mar 2007 Karma :

Don't know about your bike but that doesn't sound too bad.

The thing that you should be worried about is more that your rings will suddenly fail, if they did seize and then free up again.

As I said though. I'd get a new spark plug in there and stop worrying. If it goes pop, it goes pop. There's nothing you can do about it.