Piston Change At 15 Hours, Why? | Top End Rebuild | Honda Crf 250
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- čas přidán 3. 08. 2024
- Ever wondered why pistons need to be replaced so often in MX bikes?
This video includes a full engine rebuild with an explanation why.
Chapters:
0:00 Intro
0:31 Disassembly
3:25 Explanation
7:15 Rebuild
Let me know what you think and what else you would like to know?
Insta - @abelmotorworks
Website - abelmotorworks.com - Auta a dopravní prostředky
I've got a 2008 KX450F with 278 hours on 1 piston. Gets ridden hard on the limiter all day. Air filter maintenance is key!
It will keep running. You are just causing exessive wear after ~100h
That pretty sick! Full rebuild and another 300 hours fuck it 😂
I believe this 100%, my buddy had a 1996 Yamaha warrior that hadn’t gotten an oil change since 1998, only oil filter changes and oil top offs (if even that). It was running just beautifully with spec compression levels in 2020 and the oil was a slight brown, still transparent with light I swear on it.
Im guessing theres been at least 1 ring change tho. Rule of thumb, piston every other ring change. Agree with ur air filter comment
278 hrs lying like hell 🤣🤣🤣🤣
I find this topic very difficult, I see the sense in how you compare the skirt on the 250f piston to the 125 piston. Sounds right if you think about it.
But in reality the 125 requires piston changes earlier compared to 250f's, according to the manual.
I also find the 15h piston change absurd, when i was still racing i usually got a replacement om my rmz 250 at around 70h.
A well known dirtbike specific local shop used to do the maintenance and also told me the piston was perfectly fine, could do with even more.
Performance never seemed an issue since i could still pull holeshots on a full gate at the end of the season.
as to why i find this topic difficult and confusing, i just see no sense in the 15h interval considering personal experience .
sorry for the long rant
The reality is in the form of high cycle fatigue life - damage and wear to aluminum is not able to be seen. You can google this if you like to get a basic understanding. But when you stress aluminum over and over eventually it breaks - aka the wrist pin can rip out of it - or the skirt can collapse, or the top of the ring land breaks off, or the center of the piston cracks etc etc. While for most users this wont happen because the engineers also design in whats called safety factor - usually the a factor of 3 - aka 15 hours in the manual means 45 hours in reality - in some extreme use cases 15 is actually too many hours. If you fired up your bike, put it on the rev limiter for 15 hours straight - it would need pistons frequently. As a company, they absolve themselves of liability by putting in the requirements the wrost case scenario for replacements. In the serious racing world - what my company deals with - 5 hours on a piston is our intervals. For slightly lessor builds its up to 20. With the racers who hire us - and how hard they are on parts - this is a necessity to prevent failures. It's less expensive to put in a 250 dollar part and garuntee a successful weekend of racing than it is to show up, have a failure at an outdoor national or an amatuer championship or an sx race. Imagine the expense involved of just showing up to one of said races - so in that case a piston is extremely cheap. Same for other parts - vs the cost of travel, entry, training, trainers, and entire lifestyle predicated around doing well on that one weekend.
Yeah every 15h 200 bucks that unnecessary I think and if you trail ride you won’t have to unless they break or you ride it hard
I do casual trail riding will I have to replace pistons for while on a 150r
Good vid but have a few questions. At what hours are you replacing that timing chain and how are you breaking in the new piston? Also if you haven’t already, a video on replacing that timing chain would be awesome thank you
50-60 hours is pretty ok . my 250 had 100 hours piston and timining chain. usually if top end rebuild do but not before 50-60 hours. 15 hours piston replace is 100% maximum power. I am happy over 90% also
Once you get this down, about how long does it take?
thanks Mike
I personally went 100 hr on my first 18 250 but that’s when I wasn’t that fast now I’d probably do it every 40-50hr that’s what matters if you’re riding the piss out of the bike or not
I totally agree, those hours seam spot on for most ‘normal’ riders. I haven’t had any issues with people who change pistons at 50 hours.
Where did you get those graphic they look sick
No idea sorry!
Good video, but tips on how to clean cylinder inside and out would’ve been nice
Does this need to be done at 15hrs if your a C grade rider not an A grade rider. I've got 220 hrs on my FC 450 17 model done 1st piston change at 150hrs.
no. every 15 hours is literarily for the guys you watch race on tv. if your a weekend warrior you can go 100s of hours
do I need to re build my engine after every 20 or so hours if I just trail ride?
No definitely not, for lighter use you can let them go longer!
Frequent piston changes on four strokes help the longevity of the cylinder. While keeping maximum power.
Comparing 2 stroke and 4 stroke piston scirts is useless. 2 strokes need them to be long in order to work.
You did not checking piston - cylinder clearance?
I also checked cylinder ovalization, valve stem straightness, head warp but it’s too much of nothing actually happening to put in a video, its not suppose to be a step by step guide but hope you enjoyed it👍
Looks like you did not deglaze the cylinder. Some say you must others say you don’t have to. What is your take on it ?
Deglazing is basically the cleaning of the hone channels/marks to allow for proper lubrication. Now on a steel sleeve these channels get filled or smoothed because the wall material is relatively soft. Compare that to a Nikasil lining, the material is far harder, and takes a lot longer to get worn down. I have seen 80’000 mile engines with the original Nikasil hone marks clearly visible! So on a steel sleeve, it’s worth running a slight hone through the bore, if not to removing material, to clean the channels. But a hone will not touch a Nikasil bore. You can only clean it. Some use scotch brite, but on a 50 hour Nikasil cylinder, just a good clean with soapy water and re-oil is needed. Which is always done after the gasket surfaces and cleaned.
Deglazing is essential
Is crf250r still a good bike?
Definitely! Good servicing is a part of that.
Comparing 2t and 4t piston, are you kidding?
This new honda engine is similar to ktm 250 sxf
They definitely borrow ideas and are getting closer to the ‘perfect’ blueprint.
Is that the 250 2022?
Unfortunately not! Wish it was though
@@Mike_abel its still a good one sir. Thank for the video
@@olivertan1786 Glad you enjoyed it!
It's mad think ktm say 50hrs
Dude I’ve seen ktm do 100 hours ZERO maintenance no air filters no oil no washing unless it was dunked under water ktm is on a whole other level. The jap bikes just keep getting worse and worse trying to keep up. My buddy has a 21 and a 07 and loves his 07 so much more that the 21 is just a back up bike he uses that only gives him issues. Same with Yamahas having trash reliability long term and suzuki basically said there no point trying to make these bikes better other than spending more money and adding more ridiculous parts to try to make the job the rider is suppose to do easier but ultimately the machine and it’s capabilities are virtually identical.
@Chris Villarreal that Savage I like most brands tbh honda is my favourite tbh but there price is mad yea I think yam have gone down hill my 05 must of had 250+hrs no issue my ktm never had to problems at all that wad 14 only thing battery was shit but run spot on
@@sxfwilson6603 yeah man I got them all literally 125 250 450 two strokes and 4 strokes the best bikes I have are the two strokes they’re just bullet proof and they’re good but these newer 4 strokes have so much shit you just wanna get rid of them after 30 hours cus you know shits going to get complicated down the road
Man getting worse and worse working on these bikes with all the ridiculous electronics they’re adding on my 07 can be stripped to the bone in the time it took him to get the subframe off…
I bought 2 used 05 and 06 crf250r rebuild all and just will not run, honda is junk
or u just dont know wtf ur doing
seems like a you problem buddy haha!
And u had 2 of them man u really screwed that one up guy
i think you are junk xD
Honda is junk
Honda is the best