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…Getting forked – 40.5 Hrs.
16/05/2010 | 22:25
Started on the forks tonight, popped the caps off with my newly acquired special KTM tool and drained the main bulk of the oil out, I’ll let the rest seep out overnight and then continue to strip them tomorrow, after stripping, greasing and reassembling the rear suspension to make it nice and smooth, it’s only fair to do the front’s, one of the forks needs a seal anyway,the bike should be nice and soft once this is done, I’m very much looking forward to getting in some jump practice on all newly serviced suspension… Think I’ll have to get it on track for that though…
…Throwing it together – 40.5 Hrs.
21/05/2010 | 12:59
I’ve been busy over the past few days so updates have been lacking but I’m back!! The best way to stay up to date on what’s happening is to follow me on FACEBOOK. So what’s been happening i hear you ask, well the bike has been back together, ridden and is now in parts again lolFirst off i finished stripping the forks, replaced the seals, built them up, filled them with new oil and fitted them back onto the bike, this all went as planned with no problems at all…
Their was still quite a lot of work to be done at this stage, refit wheels, subframe, plastics, fuel tank, lights etc etc
I gave all the plastics a good clean, built up the subframe and bolted it back on, it makes the bike look more ‘bike like’ almost instantly, then the fuel tank and radiator shrouds, once the exhaust and wheels were on she really started looking like a bike again…
Not many jobs left to do, the front light is missing a bulb (must get one of those lol) but it was fitted anyway so it ‘looked’ like their was a light in place, coolant was filled, wheels aligned ready for the first start and running in, she looks semi naked without her skid pan in place…
And then it was time to start her up, this is always nervous/exciting no matter how many times you do it, she kick’s into life on the second kick and purrs onto a nice idle, she’s smoking oil but that’s to be expected when the engine has been in pieces so i let her warm up while i gear up, i believe in a fairly hard break in with lots of closed throttle building up slowly from small throttle openings to full throttle, probably takes 30 to 45 minutes and has always given good power for me in both bike and car engines in the past, after 45 minutes she was still burning some oil, i had topped her up as running low can be fatal but she was burning far more than she should be, she was making great power but burning far too much oil and after an hour of running and topping up she was still burning it making me think that their was something else wrong besides the worn piston rings, so back in the garage, it takes under an hour and a half to take her from a full bike to this…
And then not much longer until she looks like this on the bench again…
For the sake of a couple of gaskets their is no reason NOT to pull her apart and look inside, you’d feel pretty stupid if faced with a £1.5k rebuild because you were worried about pulling her apart, if you find nothing it costs £20 worth of gaskets, £20 well spent in my eyes, anyway, everything that had been done previously was fine and exactly as I’d put it in, i was worried a ring may have broken, not so, or that i’d been stupid and put the ring on upside down but i hadn’t, i feel slightly better about it now i know I’m not to blame, i really did have that sinking feeling that i may have f****** up but that wasn’t the case.
What now i hear you ask, well I’m currently thinking of 2 different possible reasons, 1 being that the increased compression of new rings is sucking more oil past a dead valve stem seal or out of tolerance valve, i will be stripping the head to measure up and will replace the seals regardless, the other thought is a strangely worn piston/bore and the new rings not fitting in a round peg/square hole kind of way, the piston showed very little signs of wear originally, i now have a micrometer and some cylinder telescoping gauges on hand so i can measure everything spot on in multiple places and get an accurate picture of what’s going on an then go from their…
Paul hasn’t updated the blog to the latest findings so when or if he does (I think he is quite disheartened by the whole thing now unfortunately as what was supposed to be him being able to ride a dirty bike has turned into a mammoth rebuild so fully understandable that he may be a lil miffed)
Very generous of you to lend him your bike. Shame about the problems wit the engine. Interesting read Pete, thanks for posting. Some good tips and pics too.
Pete, I have just read this whole post through again and wanted to say what a great job you’ve done with it. Pics and text are as obsessive-compulsive as your bike maintenance (in a good way!). It’s sure to help someone who is doing the same thing.
Anyway, hope you get the oil problem sorted. Valves seals are likely to be the culprit if the bores are not scored aren’t they? Sorry to ask if obvious but did you offset the gaps in the rings? Is the coolant clean or contaminated?
its not me thats done the work or the blog, its my mate Paul to thank for that but it is great to know the work is being done properly and is a good read too
I am sure he did offset the gap, apparently due to the mismatch from new between the barrel and piston it has worn the cylinder oval, will ask him about the valve seals tho when he gets back from his holiday
quote:
KTM have accepted no liability saying that a size 1 piston can indeed be assembled into a size 2 cylinder, in some cases that’s correct, but in this case it couldn’t be more wrong so i have taken more measurements and photos explaining EXACTLY what i have found and forwarded them on in an Email so it can be sent on to KTM and hopefully they will step up and see their error.The Email…
“All specs are taken from section 5-7 of the KTM 250f 2005-2010 repair manual.
The manual states that a size 2 cylinder should be between 76.013-76.025mm and that a Size 1 piston should be between 75.960-75.970mm.
It also states that the piston clearance should be between 0.030mm and 0.055mm depending on the piston/cylinder fitted and that the MAXIMUM wear limit should be .070mm regardless.
The piston fitted to this engine was a size 1, it is used so ‘as new’ measurements cannot be taken, but for all purposes we will assume it was of maximum size (being 75.970mm) when new.
The included image SDC10856a.JPG clearly shows the piston to be stamped with a ‘1#8242; indicating it’s size.
The cylinder fitted to this engine was of ‘Size 2#8242;, in some cases a ‘Size 1#8242; piston could be used with a ‘Size 2#8242; cylinder, however measurements taken from the unworn top and bottom sections of this cylinder are 76.04mm even if this was to be taken as 76.035mm, it would still have been .010mm OVER the specified maximum size for a new ‘Size 2#8242; Cylinder.
Taking the measured cylinder size of 76.04mm and subtracting the largest ‘Size 1#8242; piston size of 75.970mm leaves a piston to cylinder clearance of 0.070mm which means this cylinder/piston combination would have been assembled with a clearance which the KTM manual states to be the wear limit, if not more if the ‘Size 1#8242; piston was of less than maximum size!
The included image SDC10848a.JPG shows that the cylinder was clearly marked ‘2#8242; and the included images SDC10839a.JPG, SDC10841a.JPG, SDC10843a.JPG and SDC10846a.JPG show that the ‘Original Bore’ shows the same measurements both front to rear and left to right on both the top and bottom of the cylinder.
It’s not like we need them to do the work or supply a full set of parts for the rebuild, gaskets etc would have need to be purchased anyway so their is no claim for them, simply a replacement piston and cylinder as should have been fitted from day 1, KTM’s response will play a large part of which bike i look for when the time comes for me to get a machine of my own, hopefully they will step up and allow me to keep a high opinion of them, if not I’m not sure which manufacturer i would turn to for a good spec, almost race ready enduro machine, with good UK parts availability…
My break away has only made me more determined to get competitive, all i could think of while out in Spain was taking something like KT round their mountains…at speed… everything lies out of my hands at the moment though, hopefully KTM will come through providing a cheap and easy solution to a problem they originally created…
…Good head – 41.5 Hrs.
06/06/2010 | 22:02
No point sitting round not doing anything while waiting for an answer from KTM so i started stripping the cylinder head to give it a refresh…Quite a simple job really, remove the valves…
1 out…
Not the cleanest valve I’ve ever seen, baked on oil is just another indication of what we already know, she was burning it, this could be drawn past one of the seals but both of the exhaust valves are like it and the inlet valves are spotless so it’s very unlikely, she’ll be getting new seals anyway…
2 out…
3 out…
4 out…
Nice clean inlet ports, dirty horrible exhaust ones…
The valve train components laid out ready for cleaning…
Valve seals have been ordered and should be here Tuesday, the valves and springs have been checked and are fine, so the head will be getting a good scrubbing and the valves will be all cleaned up, maybe a light exhaust port polish during clean up and then reassemble with new seals…Easy and free power
She will be so different once all this is done, i may need to factor in some jetting changes to account for the higher compression of a piston that fit’s it’s cylinder and a nice clean free flowing head…
Nice to see the job being done properly, I hope KTM respond.
Is it just me or is that cylinder head really cute?
The 250 is back with me now. It may not be hanging around for long tho as I am hankering after somit a lil more powerful but lighter! [
]Not ridden it yet, going to take it to the jet wash tomoz tho so will ride it there. From what Paul was saying its a totally different bike now with loads more umph, am really looking forward to riding it even if its on tarmac just to see for myself how different it is now. If I get the 200 then I’ll prob strip the rolling chassis down and grease everything up properly as soon as I get it
] lol (but yes, very very cute lolz) [- You must be logged in to reply to this topic.