Red Sparks Coming From DT 125 (Help) :(

[Stuster]

Morning all.

I was riding along the expressway lastnight on my Yamaha DT 125 when my friend i was riding with comes up along side me screaming to pull over haha

I turn around to look what its all about and there is red hot sparks bouncing from under the bke. When i pulled over a fair amount of steam came out of the exhaust ( not sure if thats anything to do with it )

The only thing i could think of was, the front brake binding a little, but also there is a few little holes at the front of the exhaust.... could some sort of carbon bui;d up be coming out of there???

Thanks for reading
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Yamaha TZR125 x 3 Lifan LF125 14-F x 3 Jinlun 125 x 1 Honda CBR 600 F1 Honda Varadero 125cc I am now starting my Honda VFR400 NC30 Project (Still ongoing 27/02/18) Daelim Roadwin 125R

[chillyman0]

Did anything feel abnormal?
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preivious : 2007 Skyjet 125 (died), 1991 gsf400 (problems, rotting in garden)
1996 gsf600n (sold)
current : 1996 VFR750 for sale, PM for info! 2000 E1 ZX-9r

[Stuster]

no, nt that i can think of, the engine didnt miss a beat, didnt loose power.

I wouldnt have known if it wasnt for the other guy i was riding with shouting at me haha.
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Yamaha TZR125 x 3 Lifan LF125 14-F x 3 Jinlun 125 x 1 Honda CBR 600 F1 Honda Varadero 125cc I am now starting my Honda VFR400 NC30 Project (Still ongoing 27/02/18) Daelim Roadwin 125R

[Teflon-Mike]

Holes in the exhaust aren't good.
On a Two-Stroke they are very not good.
Depending on where the holes are, sparks could have been anything from bits of exhaust packing, to bits of piston.....
Either way, fact that they were hot and glowing, and 'clouds of steam' suggests weak running due to lack of back pressure and possibly HGF....
Or in other words..... majot attesnion.
If sparks were coming off your brake, it would be becouse the pads were down to metal on metal, and even then, only when you pulled the lever in unless it was so siezed it never came off, and it would be accompanied by a fuck-horrible scraping / ringing noise you would NOT fail to notice!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Stuster]

[Stuster]

Just looked at the bike a little closer, it has 2 very very small holes, its where it has been repaired by the prevouse owner. i will try add some pics a little later, also there is quiet a build up of gunk/oil at the front of the engine and where the exhaust connects to the barrel. doesnt look like it should be there.

any suggestions guys i would really appriciate
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Yamaha TZR125 x 3 Lifan LF125 14-F x 3 Jinlun 125 x 1 Honda CBR 600 F1 Honda Varadero 125cc I am now starting my Honda VFR400 NC30 Project (Still ongoing 27/02/18) Daelim Roadwin 125R

[Stuster]

is nobody willing to help..... could do with your suggestions people
____________________
Yamaha TZR125 x 3 Lifan LF125 14-F x 3 Jinlun 125 x 1 Honda CBR 600 F1 Honda Varadero 125cc I am now starting my Honda VFR400 NC30 Project (Still ongoing 27/02/18) Daelim Roadwin 125R

[mysterious_rider]

You need to ask your friend where they came from!

The exhaust, go take it to a welder. It'll cost about 45 quid to patch up. Mine split 5 inches on my ns125r and had a hole the size of a two pence piece in it. Rode around for 3 weeks like it.


The front brake pads, check them over?? If they don't have any wear left replace them.

I've run a brake with one pad in before, the otherside of it was hitting metal. I never got any sparks even under braking. But then again it was just an offroad pitbike....


Check brake pads. Patch up exhaust.
You can always use that shit from halfords exhaust repair kit.

[Pete.]

[skatefreak]

Hey,
Whilst you have the exhaust off i would strongly reccomend looking up the exhaust port and pushing the bike a little to see the piston, would be worth inspecting tbh.

-Jvr

[Stuster]

[mysterious_rider]

Maybe it's just hot carbon from the exhaust or something. The bike runs fine does it not? If your piston is breaking away you wouldn't of made it home! I wouldnt worry about it, you have probably changed the mixture or whatever the bike runs at by having holes in the exhaust, maybe its spitting unburnt fuel out or something.


why dont you start it up and have a look tonight?

[Stuster]

i hope thats all it is, i will fire it up in a mment and take it for a quick run and see how it does. hopefully it will be ok.

i think the mixture is a little rich because there is a build up of oil at the front of the barrel where the exhaust is. (or is this somthing else) ?

Again thanks for your help and advice.
____________________
Yamaha TZR125 x 3 Lifan LF125 14-F x 3 Jinlun 125 x 1 Honda CBR 600 F1 Honda Varadero 125cc I am now starting my Honda VFR400 NC30 Project (Still ongoing 27/02/18) Daelim Roadwin 125R

[Teflon-Mike]

If your exhaust has holes in it, effect is usually to make the motor run 'weak', from reduced back-pressure during the 'over-lap' period when the inlet and exhaust are bothe open to the cyclinder.
On a foru-stroke this can be farily bad, but on a two-stroke its pretty bludy critical, as the two-stroke is reliant on the back-pressure and shock waves from resonance tuning of the exhust to keep everything in order, as the fresh charge being forced through the transfers washed the exhaust gasses out the exhaust port.

A weak mix or effective weak mix from a holed exhaust has the effect of making the motor run hot, and prone to pre-ignition.

This can lead to head-gasket failure as the water-jacket simply cant take away the heat made by the hottur combustion fast enough, particularly if its a bit weak to begin with.

However, more critical than over-heating issues, weak mix and pre-ignition cause localised hot-spots in the combustion chamber.

This can melt metal, particularly the piston crown which is usually aluminium, so has a lower melting point than steel, and isn't directly cooled by the water-jacket.

In worst cases, the piston crown will melt very quickly, and its common for the piston to actually 'hole'.

The old DT's and RD's were actually rather prone to this, and didn't even need the encouragement of a holed exhaust to burn through their slug.... plenty of lads managed to do it simply removing the baffles from the tail-pipe or fitting an all-speed, and not re-jetting the carb to suit.

Mate of mine when he was 17 actually had a row of RD pistons on his windowsill, half melted half new in the box, ready for when the one in the motor went, pratting about looking for more power!

Anyway, in less severe cases, the piston wont always hole through, like it had been hit with an oxy-acetaline 'gas-axe', but will deform like a beer can chucked on a bonfire.

And often they sort of bow in the middle, and they frequently 'dip' around the exhaust port, where the thin section of metal between the piston rings will often bow and 'nip' the rings in so they can move in the groove and seal properly.

Incredibly, in some cases, engines can run for a lot of miles with deformed pistons, and in some more bizzare ones, where they dip around the exhaust port, they can actually run rather well.

Another mate with an RD reckoned that his bike was 'horrible' after a rebuild and fitting of a new spannie, but it 'loosened off' quite nicely and made 'shed-loads' more power... then inexplicably just 'stopped working'...

Piston had slowly deformed, and the piston skirt around the exhaust port was slowly drooping. Timed by the piston falling beneath the holes in the cylinder wavy, the effect of the 'ramp' where the pistion drooped, was to open the exhaust port earlier, the same as a porting job raising the port..... hence it was 'self tuning' lol!

The drooping of the piston crown was also lowering the compression ratio, which was to some degree, compensating for the weak mixture, to some degree, so apart from horendouse fuel consumption and really rough low speed running, the thing actually worked reasonably well for a long time, and it was only when the rings snagged in the exhast port that it actually gave up the ghost.

Moral.... Get it sorted!

Exhaust off, and inspect, repair replace. NO! Dont run the thing until its sorted out, it wont get better on its own, WHATEVER the matter is!

Do inspect the piston from the exhaust port, and look for signs of deformation on the piston crown and skirt around the port area, damage MAY have been done, and it needn't have stopped the engine working all together....
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Stuster]

cheers for all the advice, i have fell lucky today as my cousins friend has offered to take the bike, strip and rebuild the engine for me for FREE as he likes doing this kind of thing for a hobby, all i will have to pay for is the re spray.

how lucky is that, he said pretty much what you have said. thanks so much for all your help guys.
____________________
Yamaha TZR125 x 3 Lifan LF125 14-F x 3 Jinlun 125 x 1 Honda CBR 600 F1 Honda Varadero 125cc I am now starting my Honda VFR400 NC30 Project (Still ongoing 27/02/18) Daelim Roadwin 125R

[skatefreak]

Sounds good,
i wouldnt mind rebuilding bikes for a hobby but alas i barely have time to rebuild my own heh.

Best regards

-Jvr