Seized 2-stroke

[Alastair]

This has to be the most embarrassing thing ever, especially as I've only just got the bike but;

I managed to let the oil run out on my TDR (I don't think the warning light works properly) so obviously the engine seized.

Is this repairable or going to need a replacement engine? Is it the same as a hot seize? The kick start is solid but the bike did go into neutral. I'm no wizard with a spanner but can attempt most things and can manage things with the help of a Haynes manual.

I'm really hoping I can sort this out as being on the bus again today was MURDER!

Any advice appreciated, thanks.

EDIT - Just to save face a little, it really doesn't seem that it did run out of oil now, not sure yet what did cause it though.

[Kickstart]

Hi

It will be rapairable, although depending on how un/lucky you are a 2nd hand replacement engine may be cheaper.

First thing is to find out what has seized. For me the top end has always freed off shortly after seizing, so it might be the bottom end that has gone.

Drain the coolant and try taking the top end off and take a look.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[stinkwheel]

Depends. Probably the same as heat siezing as there is often a fair bit of oil floating about in the bottom end which would keep the mains and big-ends lubed for longer than it takes to dry sieze the bore.

Only way to find out is pull it apart and have a look.

At a minimum it will need a rebore/plate and new piston/rings (may as well replace the small ends while you are at it).

At worst the mains and big end will be gubbed which would mean a service exchange crank, new bearings, conrod kit, piston and rebore. Might still be cheaper than a new engine though, especially if you fit the parts yourself. The only real biggy would be the crank...and the barrel if it is nikosil coated.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Dischord]

try bump startin it first, it might unseize and ride away, it happened to me twice! but they free'd up within 2minutes of seizing, so if you left it seized chances are it will need a rebore!
____________________
2012 KTM EXC 250

Check out my vids - https://www.youtube.com/user/KTMSparky/videos

[DM]

I seized a 50cc Runner's piston around 10-12 times (out of oil) and it still ran fine. Of course, opening it later revealed a sickeningly scored piston/cylinder, yet the compression stayed at a very acceptable level so I never told my friend when I gave it back .

[Alastair]

Been at home today trying to sort it out. have got the head cover off, piston out, cylinder and exhaust off too.

Seems the piston exploded rather than just get wedged so there is a lot of debris in the bottom half of the engine. Any idea what I could try next to get it all out?

[stinkwheel]

Probably safer to split it. Although I have flushed the crankcases in 2-strokes before. What we did with my mates H100 that was in a river for a few days before we bought it (cheap) was to flush all the silt out with diesel.

Just repeatedly filled the crankcase with diesel, swooshed it about, spun the crank in it then turned the whole engine upside down and emptied it out. When we were happy it was clean, we flushed it again with 2-stroke pre-mixed petrol to make sure the bearings had plenty of oil then banged it back together again.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Alastair]

[Kickstart]

Hi

That doesn't sound like it has run out of 2 squeak oil. Not certain about the TDR but it is rare that road bike 2 stroke oil tanks take less thanb a litre in size.

It is possible to get air in the 2 stroke oil line (leave the bike running on its side for a while might do it, but likely to cause other problems first), but not common.

If it has destroyed the piston in style as you say then it is possible that it has cold seized (were you thrashing it when cold?) but most likely it is just bad luck as to when it has failed.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[John C]

[Alastair]

Do I win any prizes for the most spectacular piston failure?

I'm not too hot on how long to leave it warming up to be honest, I left it standing (upright) for about 2 mins, then rode easy for another 5-10 before giving it any welly. I did thrash it before it blew up but when it actually went I was only at mid revs.

Starting to think it was bad luck more than anything and I'll have to chalk it up to experience and just pay to get it sorted. Will get the pump and reeds checked out though so it doesn't happen again as soon as I put it all back together!

[lilredmachine]

nice one

certainly does not look like a lack of oil seize TBH.
____________________
Bikes: too many, too much for one man to maintain anyway.

[John C]

ace

Looks like you've been feeding it ball bearings.

[Kickstart]

[stinkwheel]

Guy up the road from me has a Z650 piston with a valve embedded in the piston crown so firmly you can't pull it out.

I have a Jawa 350 piston somewhere with the skirt ripped off, gudgeon pin ripped out and three needle rollers from the opposite side small end embedded in the crown.

EDIT: looking at that picture, it looks like the piston crown is 'dinged over' at one point? Has it hit the head? If it has, this would suggest one of the main bearings or big end has let go.

It will need pulling apart and the crank spinning up with a dial guage, if there was enough force to rip the gudgeon pin out through the bottom of the piston, there was enough force to make a bent crank a possability. The conrod is almost certainly gubbed.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[satans_BIG_helper]

I seized my old TZR250 pretty badly before.... some little pikey on my estate had cut the oil line... no amateur really but it still happened... rode fo about 20 miles at about 25 MPH cos it wudnt pull.. then it died n pissed petrol n coolant everywhere....

the left hand piston had gone all the way throough on the top and the rings had melted into the barrel... and the right hand one looked like a rat had been in the barrel chewing at it....


end result pair of new barrels, pistons, n a crank rebuild as it done the main bearings too etc... very messy

[Alastair]

Right, nothing has changed since my last post as I couldn't do anything over the xmas break.

Am starting to look for replacement engines now though, is there anyway of knowing what engines will fit? Is it as simple as any TDR/DT/TZR engine or are there other things to consider?

Would frame numbers help me determine which to buy etc?

All help much appreciated as I really want to get it back on the road as soon as I can now.

[Knowlsey]

[faith183uk]

Ebay has a few TZR engines on there at the mo.

This one looks very clean for the year, but obviously id get more info from the sellers before making a decision.

https://cgi.ebay.co.uk/TZR-125-ENGINE_W0QQitemZ8027366536QQcategoryZ10490QQrdZ1QQcmdZViewItem

[Alastair]

Thanks so much for the heads up - had missed that one with all my searching.

Got outbid on sat night by someone using software to snipe auctions on a DTR engine that looked great.

Will the TZR engine def fit is my only concern now as it looks a bit different to the DT and TDR engines I've seen.

[Alastair]

I'm still in exactly the same situation and but had decided to get it rebuilt. I have been let down by a mechanic twice that was going to come and pick up the bike though. If he doesn't want my money, fine, someone else will get it.

Have had time today to take the engine out but I've spotted something that to my untrained eye looks pretty terminal. See the bit inside the red circle on the attched pic, that shouldn't be bent should it!?!

Does it look like a replacement engine is the only way to go now?

[Gazdaman]

No, I don't think that should be bent.

But with that much crap in the bottom half of your engine, I'd be looking for a new lump anyway.

Engines for a bike of that age are pretty cheap, splitting crank cases is /not/ fun.

Gaz

[cagiva gezzer]

Way too much crud in that bottom end to even consider using it without stripping it. The crankcase shouldn't be bent, it's taken a hell of a whack from the con rod.
____________________
"because one stroke isnt enough and four strokes waste two"

[ancientd]

Judging by that bending in the case it looks like one of 2 things has happened, either the reeds have been sucked into and through the engine, (you haven't taken off the air filter have you?) or the big end failed.
____________________
I ride 3 bikes, a Thundercat, an FZRexup 1000 Streetfighter and a Jawa 350 Combo, something for all seasons.

[Alastair]

Wasn't going to try and use that engine without a full rebuild don't worry. If it is fixable it'll be a full strip job

Air filter is still in place and the reeds actually still look pretty decent (to my eye and it's the first time I've ever seen reeds), so it probably is the big end but i wont know till I split it and I don't know if I'd ever get it back together!