104 hours on piston and still going!

[KPRacing]

CamP, my apologies if you took the response as rude or a personal attack on you. It was not meant that way at all.

I was simply explaining the differences between the cylinder reed port lacking support & the lack of cylinder skirt support in the case reed engine & that the lack of piston support is the real problem for the cylinder reed engine. It was nothing personal in any way.

Anyway, the case reed is better but still lacking support. On the case reed engine, the rod angle is more inline as the piston starts to lose the support of the cylinder so the "unsupported" side load on the piston is less in this engine than in the cylinder reed design.

The cylinder reed is a twofold problem since there is less piston skirt & a huge intake port for the piston to get mashed. This engine is constantly beating the piston on the power stroke & wear is much higher.

[thirdgenlxi]

Yikes...... y'all don't even want to know what kind of hours I've got on my KDX      I'll just keep quiet on that one, lol 

[KPRacing]

Tame engines can go longer.

Smaller ports (more piston/ring support), less compression, less rpm, less power, less stress=longer service life.

Edited June 8, 2016 by KPRacing

[MX450R]

Tame engines can go longer.

Smaller ports (more piston/ring support), less compression, less rpm, less power, less stress=longer service life.

and chances are less aggressive rider, not saying that's always the case but If I pass 2 riders in the woods and one is riding a CR250 while the other is rider a KDX220 Im just going to assume the CR250 Rider, riders harder

[Becykagaz]

Yikes...... y'all don't even want to know what kind of hours I've got on my KDX      I'll just keep quiet on that one, lol 

My friend had an old '85 3-wheeler tecate 250-2t.... last year the engine seized. He told me: damn i don't understand why it happens, the bike runs great since i'm 13.(he was 28 at that time)   ?

never did any top or bottom end or whatsoever. Rode the bike all year round, winter and summer, never re-jet the carbs.....man that is dumb !

 

So he dumped 1500$ in rebuild, let the carb jet settings as is and seized the engine again on the second ride !! dude was pissed ! That's the price to pay for being dumb and let an around-the-corner jobber guy rebuild his motor. 

 

so he said &%$#@!-off and bought a '14 raptor 700 

[thirdgenlxi]

and chances are less aggressive rider, not saying that's always the case but If I pass 2 riders in the woods and one is riding a CR250 while the other is rider a KDX220 Im just going to assume the CR250 Rider, riders harder

 

Yea I don't ride that hard...... most of our trails here are slow, steep, rocky technical stuff, so not really anything where you're wide open. I do ride it on the road though as both a dual sport and a supermoto as well, so it does see some higher RPM stuff still. Compression is at 170 psi and it starts first kick every time hot or stone cold

[BillDirt1]

Figured I'd share my experience with my 06 cr 250. Little about me been riding dirt bikes for about ten years had many bikes all different sizes colors both 2 and 4 stroke and this is by far my favorite. I bought the bike from a AA mx rider in decent shape. After owning the bike for a few rides sucked some sand in needed a new piston but cylinder was fine believe it or not. So since I've installed a weisco piston I've got 104 hours on it and still runs strong with 185lbs of compression I know it's starting to get low. I'm a mid pack b woods rider and have used this bike for everything and all conditions big sand pits, ice riding, mx and mainly woods. Used nothing but bel Ray h1r and mix between 36:1 40:1 never really precise on mixing. I'll continue to run this till it pops as everything motor wise is getting worn out anyways. And I don't mind replacing what ever is needed. All chassis and suspension bearings have been replaced a couple times. Anyone else getting lots of hours on there Hondas

Didn't do any engine work on my 1989 CR250 till the year 2000.

[2bitsamile]

duplicate post

Edited July 2, 2016 by 2bitsamile

[2bitsamile]

Rings have a small bevel/chamfered edge to prevent snagging on ports. Rings that are worn past service limit reduce that bevel , thus greatly increasing chance of ring snagging exhaust port and also accelerates cylinder wear. Rings can beyond service limit and still give good compression test result. A forged piston maybe good for 100-150-200 hrs but i doubt rings are in service limit after 50 hrs. I wouldn't let a cast piston go past 50hrs even if dimensionally in spec, as they may fracture.  Rings are like $30(?) and 1 hr to replace.  You don't even need to take the head off.    It's beyond silly to leave rings in too long.  Also, at least measure piston to cylinder clearance.  Use new circlips and make sure circlip opening is at 6:00 or 12:00,  not 3:00 or 9:00.....,,,  Alex

Edited July 2, 2016 by 2bitsamile

[Pigsfly]

i've always done 1200

[terrobelone]

Yea I don't ride that hard...... most of our trails here are slow, steep, rocky technical stuff, so not really anything where you're wide open. I do ride it on the road though as both a dual sport and a supermoto as well, so it does see some higher RPM stuff still. Compression is at 170 psi and it starts first kick every time hot or stone cold

That is very low compression time for a new top end

[thirdgenlxi]

That is very low compression time for a new top end

 

Ummmmm..... I really don't think 19 psi higher than spec is considered 'very low compression'....... just sayin'. A little carbon buildup but that's about it 

 

[terrobelone]

Ummmmm..... I really don't think 19 psi higher than spec is considered 'very low compression'....... just sayin'. A little carbon buildup but that's about it 

 

 

 

Well, That is the specs for a KDX200, not a CR250. Mine typically test around 190-200 with a new top end and i replace the rings at anything under 185psi