View Full Version : Engine seized - Aprilia rs250

25th March 2008, 08:03
Hi all,

Had a breakdown on the Southern Motorway on Sunday. It lost power, the temperature shot up, and then completely siezed - the kickstart lever won't budge. It's a 1996 Aprilia RS250 with 12,500 km on it, I've had it since 9,500km

(As an aside - I'd like to say cheers to the cop who called the towtruck and the two cages who stopped to offer help (no bikers stopped) )

Anyway, all I've done so far is stick it up on paddock stands and remove the fairings. I'm keen to open up the engine, but would like a bit of advice before I do so. Can someone please suggest what to do next? Do I need to remove the engine from the frame?


25th March 2008, 09:37
Take off the fuel tanks and all the fairings, if there is good access to all the cylinders then you shouldn't need to take the engine outta the frame. Pop of the cylinder heads, have a wee squiz, see whats up, may just need a decent thwack and a rehone.

If you decide it ain't worth it, PM me, i want the frame

25th March 2008, 22:11
It lost power, the temperature shot up

$2 on headgasket failure leading to a cracked piston which then seized, no idea how to check for sure on a two smoker... *waits for ixion to enter the thread*

26th March 2008, 19:03
Ah, two smokers, yes, they do that. It's why we luvs them . :love:

Seized, reason could be anything. Did the sun go behind a cloud just before?

Head gasket , possible (it's water cooled). Or base gasket. Or carb popped loose. Or sun behind cloud.

Pull the top end of off (pretty easy), ask Mr GiJoe to send round Mr Block and Mr Mallet. And buy a bit of emery paper.

It'll be as good as new.

26th March 2008, 19:15
(As an aside - I'd like to say cheers to the cop who called the towtruck and the two cages who stopped to offer help (no bikers stopped) )

So much for a "biker helps bikers" :oi-grr:

I heard two strokes are way more complicated than the 4 stroke bikes.
Compare to a FXR, I must be the fortunate son...

Anyways, good luck with the rebuilt :)

27th March 2008, 21:47
ask Mr GiJoe to send round Mr Block and Mr Mallet.

+1, mr block and mr mallet seem to solve most things

@EJ, nah, not complicated, just different... seeing as they don't follow and sort of logic what so ever!

28th March 2008, 06:15
Two Smoker and I saw it up on the tow-truck at spag junction. Nice bike, hooray for Conti's.
If you want, you could drop the bike at mine, and I'll take a look inside 0122517356

1st April 2008, 14:32
Thanks for the offer mate, might take you up on that. It's going to be a bit tricky for me to find the time for this as I've got a lot of other things on my plate, but hope to make a start this weekend.

1st April 2008, 16:55
Bummer bout the engine probs.
I can help if you need it.

2nd April 2008, 17:38
welcome to the sieze club, this is where you become a true 2-stroke rider :D

do as said above drop the cyclnders and un-seize the cyclnder,

then find why you sized, temperature can rise quickly with insuffient lubrication
im guessing its oil injected so make sure you..

a. had oil in it,
b. check condition of oil pump, seals orings, shaft etc

check condition of spark plugs, so see how the engine was in its last state.

if the cylnder has scuffing (which it will), you can get it cleaned up at

"taylors automotive, in auckland city, then get a new piston and rings, and off you go, jack your oil pump up to the max, to ensure maxximum lubrication

dont pay a mechanic to rebuild it for you as 2-strokes are easy as hell to work on..

good luck!

if you need help with rebuilding your engine pm me,

3rd April 2008, 15:50
Luckly your in luck it does sound like a top end! hopefully you can give it a smack and rebore as said before.

Piss easy to work on!

7th April 2008, 13:56
OK I've had a look at it. I've removed the cylinder heads from both cylinders (it's a v-twin for those who don't already know). In the bottom right cylinder there was a bit of metallic grunge which I have removed. Not sure about the cylinder, there may a small amount of scuffing. I've included some photos. Apart from that there is very hardly any carbon on piston and on cylinder head.

The top left cylinder looks structually very good, but there is a lot of carbon on the piston and on the cylinder head. I really need to take out the pistons to clean them and the cylinder, but I don't know how to do this - can someone please help? The manual says that I should be able to remove the pistons without taking the engine out, but I've got no idea how to do this.

The good news is that I have been able to turn the engine over using the kickstart lever.

Photos attached. Should I remove engine from bike? If I leave it in, how do I remove pistons? Thanks?

7th April 2008, 14:50
You may not need to remove the pistons. But you do need to remove the barrels. "bit of metallic grunge which I have removed" is a BadThing, and must be further investigated.

You may find damage to the piston wall or lands. I don't like the look of that piston crown at all.

To remove the barrels remove any nuts/bolts holding them down (not sure if there are any on an RS once the head is off), and carefull pull them off. Be ready to catch and support the piston as the barrel comes off, don't let it bang around.

Check the piston and rings carefully and report back

If you do need to remove the pistons themselvs, it's dead easy.

Each piston runs on a gudgeon pin, a short shaft through the middle of the piston. The gudgeon pin is held in palce by a circlip at each end. Remove circlip (DON'T LET IT FALL IN THE CRANKCASE !!!) and GENTLY press out the gudgeon pin

8th April 2008, 08:45
OK it looks like I will be able to remove the barrels, but they're attached to the exhaust pipes and also attached to what looks like a pulley system for the exhaust shut off valve?

The top barrel is quite difficult to access, might have to remove the carbs and the splitter box, I'm a little worried about being able to put it back together right, especially if I have to undo the throttle wires and the oil pump wires in order to get at the top barrel.

8th April 2008, 09:32
Yes, you'll need to drop the pipes, and the carbs, and the power valve actuator. And any remaining hoses etc.

It's easy enough to get off and put back, just Meccano stuff, no skills needed. Unbolt, pull off, reverse to put it all back.

Pay enormous attention to gaskets when reassembling, especially cylinder base gaskets. And of course , correct torque on head bolts, and retighten after a couple of heat cycles.

11th April 2008, 11:29
OK thanks I'll have another go this weekend, following Xions instructions. I've got some work to catch up on, as well as prepare for an interview on monday, so hopefully I'll have enough time to do it.

If anyone wants to help out, let me know your contact details and I will get in touch (the bike is in birkenhead, north shore).

13th April 2008, 22:25
From the photos, it looks a lot like the piston on the right hand side has heat siezed, caused by a large amount of detonation meaning piston temps got far to high. What would cause the detonation? At first guess I would say it is most likely a lack of fuel. The hose to the carb blocked, of the float valve no opening. I'd almost put money on that.

Second is A very very serious air leak in the intake letting air get in and not enough fuel, causes very lean running, leading to detonation.

Third but highly unlikely, ignition timing out. but I would suspect that it would affect both cylinders if that was the case. But, while were on ignition. check you spark plug numbers. are they both the same?


13th April 2008, 22:29
Crankcase seals will cause lean detonation (though usually other symptoms also). Most common cause , IMLE, is a carb not securely attached, causing a leak between the carb and the manifold (loosly expressed). Ignition timing is rare in these days of solid state ignition . though it can be caused by a dud coil or CDI unit.

Water in the fuel is another possibility, though unlikely to affect only one cylinder.

13th April 2008, 23:31
I reckon it looks like the headgasket has been leaking?? Or maybe the head has warped and caused that crap around the head surface??

EIther way, the right cylinder is stuffed and the left one is fine. Don't take the left one off, if it ain't broke, don't fix it. They are supposed to be black, it isn't a 125GP bike. Black is good. See how much a new piston is and take the cylinder into the bike shop for them to check it out. If its ok (i'm pretty sure those barrels are nikisil so you might be lucky) then you can throw a new piston in there and you'll be away laughing. Assuming it isn't a bung crank seal etc. Not sure if those bikes can suck air in with a bung crank seal. Do they have a dry clutch?? Pretty sure they don't. So one side is oil, that only leaves one crank seal as a possible culprit.

14th April 2008, 09:25
Thanks for suggestions. When I get the cylinders out I'll have a proper look at it. I'll concentrate on the right one first. The cylinder heads were on pretty fucking tight on both cylinders.

The fuel hoses to the carbs look fine to me. Haven't taken the carbs off yet, but they seem to be attached fine. A couple of times I've had the fuel cock turned off, then forgotten about it, following which I've had trouble starting it after its stalled a minute later. I know that probably wasn't too good for it. But the last time I did that was a while ago, and I always check the position of the fuel cock now before I start it.

The air filter foam was stuffed - could that have led to too much air not enough fuel? Anyway, I've ordered a new one. Spark plugs were both the same. Anyway I've got new ones to put in because they're dirt cheap. Sorry for the lack of progress - will try again this weekend.

14th April 2008, 21:19
The air filter foam was stuffed


Stuffed in which manner? as in blocked? or falling apart

If falling apart, you have the chance to

1 - Let too much air through, but I would think that would affect both cylinders.

2 - debri foam to easily block one of the air tracts in the carb, then not letting fuel through..

No matter what the out come, just pull apart the carbs while you are there, and clean them with compressed air..

28th April 2008, 10:03
OK it looks like the piston in the right cylinder is broken. I've removed the cylinder and you can clearly see that on side underneath the head there is a whole chunk missing.

I've had huge problems removing this piston though. I removed one circlip, no problems. But I could not remove the circlip on the other side because the gap in the circlip is right where the hole is to put your screwdriver in, meaning I could not push it out using a screwdriver.

This shouldn't matter because I thought I'd just push out the gudgeon pin through the side where I have removed a circlip. But it won't budge. I've tried using a screwdriver and hammering with a mallet on the screwdriver handle, and that moved it a little bit, but not any more. Plus I'm worried that I might move the piston out of alignment if I keep at it like that.

I've tried using a clamp but that doesn't work either. Can anyone tell me the best way to remove the gudgeon pin. Is there a tool that would make it easier?

(There's no danger of bits dropping into crankcase because the piston is hanging downwards out of the engine).

28th April 2008, 10:11
I've started a new thread on this http://www.kiwibiker.co.nz/forums/showthread.php?p=1540195#post1540195