I'm doing crank seals (stator side leaks) and wanted your guys' feedback on how it looks. 140psi, cold engine and 7,000' elevation seems pretty good. I've got 45 hours on it since I bought it and supposedly the engine was rebuilt shortly before then. So I was thinking about leaving the piston as is, is that dumb to try and save a few hundred bucks?
I've yet to check out the power valve components.
The bike is trail ridden, a lot of low speeds, not raced.
87 octane ethanol free, lucas semi synthetic and Maxima 927 used.
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Re: Looking for input on my engine... pics and video.
Posted: 12:17 am Nov 13 2023
by SS109
I would replace the piston since you're in there but that's just me. Those vertical lines on the cylinder and piston are from dirt getting in there. Make sure you're servicing your air filter regularly and getting it seated correctly. It's also a good idea to wipe out the air box with a tacky rag, or even a paper towel with some oil on it, to keep dust from falling in when R&R'ing the filter.
Oh, btw, you are jetted way too rich from what I see. You can tell by the piston wash on the crown and on the head chamber. It should be more uniform across the surfaces. Clean areas with thick carbon areas tells me you're too rich.
Re: Looking for input on my engine... pics and video.
Posted: 09:00 am Nov 13 2023
by jaunt
Thanks for the input!
Re: Looking for input on my engine... pics and video.
Posted: 12:40 pm Nov 13 2023
by John_S
With it being that far taken apart, I would put a new piston in it if it were mine.
Re: Looking for input on my engine... pics and video.
Posted: 07:46 pm Nov 13 2023
by jaunt
Yep, Pro-x piston inbound.
It also looks like i've got a steel sleeve in the cylinder, good to give it a hone? It measures out at 65.85mm
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Re: Looking for input on my engine... pics and video.
Posted: 08:15 pm Nov 13 2023
by kdxdazz
i know americans seem to replace things more often as they have access to cheaper parts but i am a little more old school. i would do what has been done since engines began and just inspect the piston and measure with a micrometer to determine wear and check the piston to cylinder clearance with feeler gauges, you are running a cast pro x piston which may last more than 1000 hours with light trail riding so 45 hours is near nothing,especially since its run in to the cylinder as are the rings.
i don't understand how the flywheel can remain on there without the nut,maybe its been loctited on, only my guess on repairing the broken thread,it could be welded up and a new thread machined on or drilled and tapped and a threaded extension put on, remember to inspect the surface area of both parts for nicks and scratches,file down if neccessary then lap together with valve grinding paste then clean,clean,clean again with acetone, the mating surfaces have to be absolutly spotless, i know as i had a flywheel come loose lol, previous owner did none of what i wrote and used a regular nut rather than the factory flanged nut
Re: Looking for input on my engine... pics and video.
Posted: 09:27 pm Nov 13 2023
by jaunt
I've also got another cylinder that came with the bike, it's not sleeved but needs replating bad. I'd prefer the non lined cylinder but it's like $400 these days for a replate...
Re: Looking for input on my engine... pics and video.
Posted: 10:14 pm Nov 13 2023
by bufftester
If your piston to cylinder clearances and ring gaps are within tolerance I would reuse the piston IIWM, especially if you're just trail riding. As kdxazz said, the cast unit will last a while under moderate usage as long as you do your regular maintenance, although I don't know where he gets 1000 hours since Pro-X recommends 12 hours, but certainly you could get 100-200 hours out of it as long as the rings last. They also don't recommend running their cast pistons in a chrome plated cylinder, so hopefully your sleeve is not. If you were to replate your other cylinder you're still looking at a new pitson/rings...unfortunately our hobby is not a cheap one anymore Also as SS109 pointed out, you could stand to run through the jetting process once it's all back together. As for your crank...ouch. You could probably get it to a competent machinist and have the missing piece welded on and then turned down and threaded. They would also need to notch it for the Woodruff key. Not surprised it is still on the broken shaft as it is a tapered interference fit, but am surprised you haven't spun the flywheel as the keyway appears to have departed with the missing part of the crank. No way you put it back together and ride it that way safely as there is no way to torque it down. Best bet is to find a crank either on Ebay or elsewhere, cheaper than buying an OEM one (though you can still get crankcase halves and have a competent crank reman build it back up).
Finally, the whole "I know [insert race/country/sex]..." generalization has no place on this or any other enthusiast forum and does nothing to further all of our members enjoyment of our collective passion.
Re: Looking for input on my engine... pics and video.
Posted: 10:37 pm Nov 13 2023
by jaunt
bufftester wrote: 10:14 pm Nov 13 2023
If your piston to cylinder clearances and ring gaps are within tolerance I would reuse the piston IIWM, especially if you're just trail riding. As kdxazz said, the cast unit will last a while under moderate usage as long as you do your regular maintenance, although I don't know where he gets 1000 hours since Pro-X recommends 12 hours, but certainly you could get 100-200 hours out of it as long as the rings last. They also don't recommend running their cast pistons in a chrome plated cylinder, so hopefully your sleeve is not. If you were to replate your other cylinder you're still looking at a new pitson/rings...unfortunately our hobby is not a cheap one anymore Also as SS109 pointed out, you could stand to run through the jetting process once it's all back together. As for your crank...ouch. You could probably get it to a competent machinist and have the missing piece welded on and then turned down and threaded. They would also need to notch it for the Woodruff key. Not surprised it is still on the broken shaft as it is a tapered interference fit, but am surprised you haven't spun the flywheel as the keyway appears to have departed with the missing part of the crank. No way you put it back together and ride it that way safely as there is no way to torque it down. Best bet is to find a crank either on Ebay or elsewhere, cheaper than buying an OEM one (though you can still get crankcase halves and have a competent crank reman build it back up).
Finally, the whole "I know [insert race/country/sex]..." generalization has no place on this or any other enthusiast forum and does nothing to further all of our members enjoyment of our collective passion.
Thanks for the input. After doing some reading I feel like I should really get my other cylinder replated, seems as though they last longer and have much better cooling, which is something i've often needed on slow, rocky hill climbs. I've already ordered a ProX piston kit.
Also after more research it seems as though these E series KDX's use a crank that takes a bolt, not a nut. So my crankshaft is not broken but the bolt inside is, once my flywheel puller shows up i'll get that bit removed amd continue moving forward. The woodruff key is intact.
Re: Looking for input on my engine... pics and video.
Posted: 11:08 pm Nov 13 2023
by jaunt
So I went out to the garage to inspect that other cylinder I have, it actually doesn't feel bad, I wish I knew the story behind it. I don't think I trust it enough though to run it as is. Still looks beat up to me but i'm new to all this.
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Re: Looking for input on my engine... pics and video.
Posted: 12:05 am Nov 14 2023
by kdxdazz
1000 hour number was just a round about number as there have been reports of 1500 plus hours on stock piston and cylinder under moderate use or used as a daily ride around and as you may recall from one of my videos the pro x is a direct copy of the stock piston. kr150 engine here which is closley based on the kdx e series engine quite often sees 100k kilometres but admittely thats all road use
as for your comment about my comment on countires, you are trying to find something that is not there, most people on this forum are american and as such you have access to a greater number of choices at a lower price,that is the nature of large populations ,in australia pistons are expensive due to low population and low demand and high cost of living and not thrown away willy nilly, in thailand a new kdx piston,rings,pin is the equivalent of 3 weeks work at minium wage and possibly 5 months of savings, my statement was simply given because people on here recomend throwing pistons away at very low hours with no mention about using a micrometer to check for wear.
2+2 is 4 but maybe i should have changed that to a non binary gender fluid 4
Re: Looking for input on my engine... pics and video.
Posted: 08:52 pm Nov 15 2023
by jaunt
Well I've been told by a man named Jeff that running my steel lined cylinder will be just fine for trail riding, so yeah I'm going to pass on the $400 replate on my other jug.
Flywheel puller showed up today so now I can move forward.
Also as SS109 pointed out, you could stand to run through the jetting process once it's all back together. As for your crank...ouch. You could probably get it to a competent machinist and have the missing piece welded on and then turned down and threaded. They would also need to notch it for the Woodruff key. Not surprised it is still on the broken shaft as it is a tapered interference fit, but am surprised you haven't spun the flywheel as the keyway appears to have departed with the missing part of the crank. No way you put it back together and ride it that way safely as there is no way to torque it down. Best bet is to find a crank either on Ebay or elsewhere, cheaper than buying an OEM one (though you can still get crankcase halves and have a competent crank reman build it back up). 