Anybody have an extra KLX250 cylinder?

H

heilong

Member
Joined
Jan 9, 2012
Location
Pran Buri, Prachuap Khiri Khan, Thailand
Bikes
"Macera" 2009 Kawasaki KLX250
Doing a top-end rebuild on my 2009 KLX250 with over 70k km on the odometer. Got a new piston and rings, took off my cylinder, had a mechanic deglaze/hone it, then I measure the cylinder/piston clearance and it's over 0.50mm! Way past spec. Checked the ring end gaps and they are way past spec as well. I suppose the cylinder bore is quite worn out (and therefore the nicasil plating gotta be gone as well).
Was wondering if I put it back together like that, will it run, how well, and how long will it last? I'd rather go big bore with the 300 route, however got no cash for that right now. Anybody has a good condition KLX250 cylinder you don't need anymore?
Thanks.
--Gene
 
Gene, you could try and find a shop to get the cylinder recoated with Nicasil or alternatively find a shop that can give you a Cobalt based APS (air plasma spray) or HVOF (high velocity oxygen fuel) coating. For applicators that do this regularly it wouldn't cost too much, shouldn't be more then 500-1,000baht, then you can re-hone it to spec measure. Alternatively you can have a hard chrome coating applied but if you're that far off you will need a filler base coating in between (usually copper) which would increase the cost a bit but should still be a lot less then buying a cylinder. Good luck with that rebuild.
 
Thanks!
Aren't those coatings really thin? Anyway, I'd love to try and visit such a shop, but where/how could I possibly find one? I can't find anything good on google. I figured I should ask a mechanic, so I talked to a Kawasaki mechanic in a dealership in Kui Buri (nearest dealer from me, a 50km drive), he told me "Thai people would use this cylinder just like this", and he didn't know any place to recommend about re-coating.
I figure big cities such as Bangkok (250km from me) for sure should have some shop like this, but how do I "try and find it", no idea.
Basically I'm hoping to be directed to a particular shop somebody used in the past.
Do you think I can just put the bike together and it will work for a reasonable time like this? I will eventually get a 300 cylinder and piston, so I just need the bike running reasonably well until that point.
 
Why not get the existing cylinder bored and sleeved for a 300 piston?
 
Hey Matt, if I get a 300 now, I will need a PowerCommander or similar juice box, I'm really tight on cash at the moment, just want my bike up and running without any extra spendings which are not strictly necessary (boy I wish I could get that 300 kit now!) I was thinking about bore&sleeve for my new stock 250 piston (unless it's indeed possible to get back into spec with some kind of coating). Either choice, my only question is - where is the shop that will do this for me? Anywhere in Thailand would be ok since EMS is pretty cheap.
 
I understand your situation. I put a 350 cylinder on my KLX and that was sleeved, so having it bored and sleeved should be no problem.
Are you sure you are measuring the piston bore clearance correctly? I'm no expert, but we came across a similar issue a few months ago. Pistons are not round, they are oval. We thought the clearance was too big, but it was actually spot on. That nikasil coating is very hard wearing.
I wouldn't bother progressing coatings if I was you. I've not heard of anyone having any success over here with it. When mine needs doing I'm going to take it to the UK and get it done.
There are shops in Chiang Mai that can do the bore and sleeve for you. However, there must be people closer to you that can do it.
I'm sure some people from Chiang Mai know the names and addresses of the machine shops here and will post them for you.
 
I'm not measuring the clearance correctly, as I don't have the cylinder bore measurement tool. I put the (new) piston in and visually the gap is pretty significant (standard clearance per the manual is "0.035 - 0.062 mm", "if only a piston is replaceed, the clearance may exceed the standard slightly"). The biggest feeler gauge that can bend enough, could easily slip between the cylinder and piston inside.
I heard about "oval pistons" as a rare special feature, never thought regular pistons could be anything but round, however rotating the piston 90 degree inside the cylinder I can see the fit is much better (tighter) in the correct front-to-back orientation. I've heard before (and the manual mentions this) that the cylinder wears unevenly in different directions (usually wears more front-to back and becomes oval due to the movement of the piston and the conrod), is that why the piston (even new) is slightly oval?
Anyway, the manuals specifies that the cylinder bore should be checked both front-to-back and side-to-side at three locations (close to top, middle, close to bottom of the bore), and the piston diameter should be measured at the bottom part, at right angle to the piston pin direction - this supports the idea of different wear of the cylinder and/or piston.

I did measure the piston ring end gaps with feeler gauges, top and second rings were 0.48mm and 0.58mm, service limit is 0.6mm for both, and standard end gap should be 0.20-0.35mm per the manual. So basically the new rings are close to the service limit.
I guess that means my cylinder is still usable, but is pretty close to the service limit.

I'm wondering how much would be a bore&resleeve job for my 250 piston in one of those Chiang Mai shops? I'd prefer a shop in Bangkok but whatever, EMS post is cheap and fast in Thailand. However I'd be rather happy to put it back together (unless it's a really bad idea) and ride like this until I got cash for a big bore.

Appreciate your time, Matt!
 
Gene, I believe in Prachuap there must be at least a couple shops that can do that...I know there is at least one huge metal working company, a subsidiary of a British company my GF's cousin worked for but I can't remember the name, I'll try and get the name if they do coatings and let you know.

In BKK there is a shop under the industrial ring bridge on the south-east (sukhumvit) side, as you get off the bridge onto Phuchao Saqming Phray road turn right at the light and the shop is on the right hand side about 150-200m from the intersection. Pretty sure it hasn't moved as it is a pretty big shop. When I was looking for a shop a couple years ago I was also told that there is a shop doing all types of coatings in Pack Chong but I have never been there.

Personally I would take the time to apply a coating and bring the measure back to spec. It's the cheapest and best way. Of course if you are certain that your monetary situation will change shortly and you only will ride a few kilometers...and don't mind possibly burning your rings and damaging your cylinder bore and piston (possibly irreparably) then just go ahead and use it like this...
 
Great info, thanks! Prachuap would be most awesome as this is just 100km away and a real nice place to visit anyway. If you can find the name/contacts of this company, would be brilliant!
I'm not that familiar with BKK but I will ask my friend who lives there if he can visit that place and find out if they can do that. Hopefully they speak English!
I agree with your personal opinion, it does feel very wrong to do a major service on the bike and then reassemble some of the most critical parts in less that good condition.
Appreciate your help!
 
It's most likely to be the piston and rings that are worn if the cylinder is not visibly damaged, they are a lot softer than the Nikasil. If the cylinder is worn you shoulf be able to feel a ridge. A piston is slightly oval to compensate for uneven heat expansion. We often used to just change the rings in 'the old days'.
I saw an engine specialist at a motor show and he said recoating or sleeving with a coated sleve was specialised even by UK standards so I would forget it in Thailand.
 
I asked about having a bore coated with nikasil and was told by a few places that theres no where in Thailand who will do those recoats.. When I pointed out it was kinda essential and how could a rebore be done without one I just got a grin and "we dont bother with that in Thailand"..

Posting a barrel out to the states with all the shipping and import duty hassle when it comes back was easier to just buy a new barrel..
 
Gnasher, as I mentioned that I have a new OEM piston and rings.
I see, so recoating might be next to impossible to find in Thailand. Boring and fitting a steel sleeve, though, sounds to me like a pretty common machining operation, though. I figure a proper machine shop should be able to do so.
I decided to put it back together as is, as it still seems to be within service limit (coming very close, though) and with any luck I'll be able to get a low-mileage second-hand cylinder, or get the cash for a 300 or 331 big bore kit.
Thanks guys...
 
Sorry for the delay. My suggestion would have been to be put it back together again as is and see how it runs. I'll bet it runs fine.

Wait until you have the bits you need for the 300 conversion before you do anything else. Bore the existing cylinder, sleeve it and add the rest of your bits. 300cc piston, etc. Will not cost too much.

Good luck and I hope it comes out well.
 
I'm putting it back together like this, cylinder and head already on. Had to replace exhaust valves and cam, kept the intake side, lapped the valves. Got all new cam chain tensioner parts, cam chain and cam sprockets. Gonna do the Marcelino mod.
Bikesncats, that's a very good deal, thanks! I'll try to contact that guy.
 
he's selling to upgrade to a 300cc kit, he may have additional info for you. Good luck!

btw...from what you're doing sounds like you've been running low on oil or with a defective/clogged oil pump or conduits...did you check that before putting everything back together
 
Yep, I noticed, will ask some more questions I reckon.
I have changed the oil every 2000-3000km, and checked the level often. The last few months of use the bike was eating oil, I kept adding between changes - more than 100ml per 1000km, that's quite a lot.
I had the pump disassembled, it looks perfect. And I did clean / check for blockage all the oil holes and passages and the oil pass pipe (outside tube), haven't found any. Coolant pump mechanical seal was leaking, but the drain hole between that seal and the oil seal in the engine cover was blocked, oil seal was still intact so coolant and oil weren't mixing. I'm replacing the mechanical seal, oil seal and the ball bearing in there. Also got a new coolant pump impeller, old one had some pitting.
 
Did you check the top (cylinder head) passages? I recall my DR750 had a clogged passage when I bought it and the cam shaft started grinding before I even got home:fan:. The wanker :GFthat sold it to me forgot to mention that he just replaced the cam and rockers (but obviously never verified why he had the problem in the first place). I wanted to redo the engine anyways but was planning to make it home first :mad:
 
The camshaft cap (which sits on top of the cams and bolts onto the head) has a bunch of small oil holes which I checked, I don't remember finding any passages like that in the head (or maybe there were just two in the cam journals), I did blow into every bolt and whatever other hole with compressed air.
So, did you have to replace the head on that DR750?
 
Under normal circumstances I would have probably had to but I opted for a different route since I was tuning it up to increase low and mid range torque. I actually machined all the seats (besides intake and exhaust ports) and applied a CoCrAly coating on all structural places and a Moly top coat on the friction seats, TiN coating on the valve stems and added new roller rockers and a new camshaft with sharper intake opening and exhaust overlap timing which allowed to increase the power to 55HP (at 5,000rpm) but most importantly give low end torque with 60Nm already at 2,200rpm and reaching 70Nm at 3,600rpm and keeping it up till 4,800rpm...though redline was accordingly lower at 5,000-5200rpm. That one was a beast with only 160Kg after the diet it went through...but never matched the handling and reliability of the XT600.

Since the engine is already open I would take the time to inspect and wash with a proper cleaning solution rather then just blow air through the passages. It's well worth the time in the event that something is restricting oil flow or drainage...
 
Hat's off to your skill and expertise, man! Wish I had the knowledge and tooling to do this kind of stuff. One day, maybe...
So what is the proper cleaning solution and technique? The holes I'm talking about (in the camshaft cap) are maybe 1mm in diameter, they all go into the camshaft cap, where they join a perpendicular "tunnel" which was machined in the cap then closed off on both sides by plugs. So I guess one of them is an inlet hole and the rest are outlets, I don't see any way to poke the holes with a piece of wire or anything like that because of the 90 degree bends and no access from the sides. Anyway, cam journals and cams don't show any signs of overheating.
 
There are plenty of methods and fluids to properly clean your head and engine components. Personally I do prefer ultrasound cleaning - there are many shops that do carry ultrasound cleaner baths (Red Baron on Ramkamheng road in BKK is one of them, though not the cheapest their service is really good). There are plenty of petroleum and water based mixes available on the market but simple varsol and diesel or kerosene do the job.

Personally when I do not have access to a an ultrasound bath I just prepare a bucket and soak my parts in a Kerosene solution (adding 20-30% mineral spirit improves residue issues, you know...paint thinner) for a day then brush everything thoroughly and use pipe cleaners to clean all the passages through. Subsequently clean with air and then rinse with Isopropylic alcohol. This is in my opinion the best way when doing things at home. Whatever you do never use caustic solutions on your Aluminum engine parts.

If you want to keep things environmentally safe this is a decent cleaner that goes well with ultrasound as well:
ULTRASONIC CLEANING SOLUTION ENGINE PARTS FORMULA 5LT: Amazon.co.uk: Car & Motorbike

...and this guy shows how to improvise a cleaning bath:
DIY Parts Washer - YouTube
 
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