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Think I've killed my XR250

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Sad day, my 1999 XR250RX acted like it was running out of fuel, then started to make rattling noises. It felt tight when I kicked it over, but loosened up after cooling for a couple of minutes, so I am guessing I have a partial seize.

I did a top end rebuild and de-coke to try and stop it smoking on start up, but this did not resolve the problem and recently it has been smoking when running. Only upside was it was much easier to start and ran better after the top end rebuild.

I feel a bit stupid because I had not checked the oil before going out today, so I recon it has been burning more oil than I thought, and probably seized due to lack of oil.

Anyway, before I strip it down, any advice:

1. Will I need to strip all way down to check big ends, or can this be done without splitting cases?

2. What do I check for? What is normal damage caused by seizure?

3. Assuming the barrel/piston are standard, can the barrel be re-bored and are oversized pistons available?

4. Apart from worn rings, valve guide seals and leaks, is there any other way of losing oil?

5. Any other advice?

I am in UK, I have looked on e-bay, but most piston/barrel spares seem to be from USA. Is there anyone in UK?

Thanks

Gary

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If you have run it completely out of oil, there will be significant damage throughout the engine which will be very costly to repair. If it is just the top end (cam & rockers), still a little pricey but not bad. Oversize piston kits are available up to 78mm. Best thing to do is a complete teardown, assess the damage and cost of replacement parts and go from there. Sometimes a used engine is the less costly way to go.

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Thanks Creeky

I got the top end stripped, found why it performed so well, it was bored to 77mm, I thought it was stock 249cc.

Anyway, damage so far:

Camshaft

Centre journal where camshaft runs in aluminium:foul:. (anyone know - is there anyway to bush this? otherwise it's a new head and rocker cover required)

Cam followers.

Piston and sleeve.

Big and small ends seem OK but I will strip it further to check the big end journal.

When getting a re-bore, is it normal to remove the sleeve from the barrel? If yes, do you heat barrel, and to what temperature?

I ask these questions as I am trying to determine if it is viable to rebuild. Hope so as I love this little bike.

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no need to remove sleeve for a rebore,

78mm is as big as you can go on the stock liner,you can get oversize liners and go up to about 300cc,but you,d have to machine the crankcases to make it fit,

try vic eastwood for 78mm wiseco piston and oversize head gasket

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just remembered this , and thought it was worth mentioning,

when i was ordering my piston from vic eastwood,i asked how much they were,when i got the answere,my reaction was "jeez,not cheap are they"was really just thinking out loud,not haggleing for a better deal,but the guy on the phone offered to knock 10% off, so i would suggest asking if thats the best pricewhen ordering, if you decide to use them,

vic eastwood 01322662426

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Thanks Nick, very helpful.

I will give him a call in the new year. Do you know if he also does re-bores?

Just looked at cams and followers more closely, I think they are actually ok. A light touch up with wet and dry and they look fine. Just not sure how hot they got tho, so may have lost hardness.

Cheers

Gary

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no vic eastwood wont be able to do the rebore for you,

i use these guys,http://www.pjme.co.uk/

they are only 15miles from me so i can pop them in personally,

they are 2 stroke specialists,but they will rebore any bike,they fitted my new con rod too

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Could you post pics of the cam and rockers? It is not uncommon to find the center cam journal on the head and the cover galled somewhat, even in an engine that shows no other damage. Use some emery cloth to polish it smooth and don't worry about it. Measure the piston pin hole in the top end of the rod carefully and make sure it is not galled. You can buy complete piston kits from Wiseco, link attached. As said, you don't need to remove the sleeve for a bore job. Be sure that the machine shop that does the bore puts a chamfer at the bottom edge of the sleeve, otherwise it will be difficult to install the jug over the piston and ring assembly.

http://www.wiseco.com/ProductSearch.aspx

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Pics of cam and followers. As you may be able to see, there are a few small scratches on the cam lobes and followers. These are pretty shallow and could be polished out with a diamond sharpening stone, but I am concerned that the cams/followers may be case hardened and not hard all the way through.

I couldn't find my bore gauge to check the small end, but there is no visible damage, and the gudgeon (piston) pin is a nice running fit.

I was going to make a split phosphor bronze bush for the centre journal, but it is not too easy to machine the head and rocker cover to accomodate a bush, so I will see how it cleans up. Rocker cover journal is not too bad, the head is the worse.

My other question:

How reliable is an XR when bored out to maximum 78mm? Any other watchouts?

I didn't have any real problems when it was at 77mm, apart from high oil consumption. I am considering the alternative of buying a new piston and liner for 270cc if I could find one in the UK.

Thanks

Gary

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IMAG0243-1.jpg

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While the cam and rocker contact surfaces do not look the best, judging from the photos, they look usable. XRs Only in the past offered a center cam journal bearing modification, but I'm reasonably sure that it is no longer available. The 78mm bore is very reliable, good as stock, just that at 78 there is no overbore left. Have you measured the bore to make sure that an overbore is necessary?

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i wouldn't have any worries about going to 78mm,however if for some reason you just dont fancy it,then you dont have to order a new liner from the states,that shop that i gave the link to,a couple of posts back,can make you a new liner any size you want,i recently talked to them about a new liner for my old dt250,to take it out to 320cc,think they said about £70 and that includes the complication of cutting all the ports,

probably as easy to find a used barrel on ebay and get that bored

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Thanks all for your help and advice.

I will go with the 78mm rebore. I don't suppose 1mm will make any difference to the jetting.

Gary

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While I am waiting for my new 78mm Wiseco piston, gasket and re-bore, I have another question:

Before I realised my bike had been bored to 77mm, I did a top end rebuild to replace the valve seals and de-coke. As I didn't realise it was bored to 77mm, I used a standard head gasket when I put it back together. Could this be the reason I lost my oil? What other effect would using the standard gasket have?

The bike started better after the rebuild and appeared to have plenty of compression.

Thanks

Gary

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when you say you lost oil, where were you losing it? Consumption typically happens either by poor ring seal or valve seals. Might want to replace valve seals while you're doing the top end if you have consistent smoking at start up but diminishes after heating up. Installing the correct gasket size for the bore is important as well.

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The bike was burning oil on start up, so I stripped the top end and replaced the valve seals and de-coked at same time. Following the re-build, it smoked worse but started better with what seemed like more compression.. This is why I was asking if the wrong sized head gasket could have caused the extra oil being burnt.

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xrs only still dose the cam jurnal repair i think its $125 for the head and the valve cover is extra pretty sure but u should call them or email to be sure

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Thanks all for your help.

Bike is back together and running fine. Plenty of compression now! I went for the 78mm Wiseco piston. Also I managed to pick up good second hand:

Crank and rod, standard bore barrel in good condition, head, cam, rocker cover and all tappets etc for £140. Thought that wasn't too bad. My crank and head were ok, so have spares now.

Only managed a 10 min ride after re-build as it is dark and -4degrees C by the time I got finished.

There is oil leaking somewhere, but will take a look tomorrow as it is too dark and cold at moment. Think I may have overfilled the oil. I put 1.6 Litres in as I thought it was pretty much empty.

Anyone know, would oil overfill cause an oil leak, and where would it leak from?

I still find checking the oil level on this bike a bit hit and miss.

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Overfilling can cause oil to blow out the crankcase vent. When the bike sits, especially overnight, the oil drains from the frame reservoir into the crankcase and an accurate oil level check is not possible. To accurately check the oil, the engine must be run at least 10 minutes, preferably riding it rather than fast idle. Shut down the engine and immediately check the oil. Checking the level immediately when you are done riding it is a good idea, don't have to worry about for the next ride.

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