How many hours last your bottom ends?

I own a 400, did it´s 1st season of supermoto back in 2000 and ran about 50 hours on it until the low end seased. ever since then I do a low end/con rod rebuilt every 40hrs, because the 1st time I was lucky that anythig else got thorn apart, but i´ve seen engines totally trashed whith gear box, crankcases, cilinders destroied because of this.

its odd that litlle few people ever mention this, because this seasure happens more than any other part failure( piston, valves,).

in some cases there may be a gear box problem, it depends on the rider/riding style, but sooner or latter the low end will seise.

I´m asking you guys, because seeing few people complaining makes me wonder if I´m not trowing money away money too soon.

running only supermoto might have sommething to do whith it too, but I would like to know how long your bottom end last?

i had my lower end go on my 400 twice, both times it was 3rd gear that seems to explode. It might be the gearing I run in the desert which is 15/44. It might be putting to much load on that gear. What gears are you running? Other than that, the bike has been flawless and I would'nt trade it for anything.

My lower end went once, and Ill be the first to say I was VERY lucky. Nothing else was damaged, including me, as I was going 80 across a dry lake when the engine siezed. Im glad I was able to hang on and not avoid a nasty fall. I estimate the engine had around 150hrs on it or more when the bottom end went.

i had my lower end go on my 400 twice, both times it was 3rd gear that seems to explode. It might be the gearing I run in the desert which is 15/44. It might be putting to much load on that gear. What gears are you running? Other than that, the bike has been flawless and I would'nt trade it for anything.

15/44?? do you ever use your 5th to the top?

any way i´m refering to the low conrod bearing seazing, since the rest of the bike is flawless, exception made to case like yours

just give me a number, guys...

just give me a number, guys...

no way to know. way to many perameters/circumstances. have a customers bike here right now that the bottom end is done on. him and his buddy bought a 250f and a 450f at the same time. they both blew up 10mins apart. (one dropped a valve/the othere seized the crank) :censored:

how many hours on that crank?

He won't know that, because that bike was bought used by the guy who blew it up. I don't want to guess how many hours my '03 has on it, but here's an excerpt from a PM I got that might interest you:

I am doing a rebuild on my 03 yz450 ... I am planning on doing a total head and bottom end restoration. I know it needs it because the intake valves are tight and I have the smallest shims installed also the hour meter reads 709hrs
:censored:

Wow!!!!

oh, ok.

but c´mon... 709hrs on ONE conrod/crank needle bearing!!!???

do you even believe it !?

maybe 70.9hrs...

I don´t want to know how long is it possible to last, just want to make an average based on other people´s exeperiences so that I can be sure that I´m doing the right thing. also from this thread other people can have an idea about this issue

:censored: My '03 has never been apart, and runs up about 70-100 hours per year. I don't know what to tell you.

I have put 100+ hours on two of these bikes. I am at 60 something on my current bike. I never knew they would go 700 plus, but I do beleive it.

My bottom end is original. I would guess it has 600-700 hours on it. I think the bottom ends will last along time when you keep the oil fresh. :censored:

oh, ok.

but c´mon... 709hrs on ONE conrod/crank needle bearing!!!???

do you even believe it !?

maybe 70.9hrs...

While 709 hours is a lot, you make it seem they need to replaced in under 100 hours, which is absolute nuts.

My 02 426 has over 300 hours on the bottom end easy and everything is in tip top shape when I ripped it apart.

Wouldn't you expect the bottom of an R1 to go 10k without a rebuild? At least? At 60 mph average over that distance, that's over 165 hours right there.

The bottom end in a Honda car engine can last over 100k miles, revving decently high. Its not the same, but it shows that bottom ends definately can last.

oh, ok.

but c´mon... 709hrs on ONE conrod/crank needle bearing!!!???

do you even believe it !?

maybe 70.9hrs...

I don´t want to know how long is it possible to last, just want to make an average based on other people´s exeperiences so that I can be sure that I´m doing the right thing. also from this thread other people can have an idea about this issue

I believe it... I am the one that sent him that PM about it. If I remember right it is 709.4hrs. I wrote it in my bike manual last time I ran it. And I did not put the hour meter on until about 3 months after I bought the bike. So it actually has more than 709. I am in the middle of rebuilding it now and the crank has no real wear and the rod is still tight on the crank, no slack out of spec. I change my oil a LOT!

Keep in mind here that most of the guys on this forum dont race. Some dont even do any mx. When you are not being super hard on the motor it will last a long time. You said you were dirt track racing right? Personally I think that is one of the hardest things you can do to a dirtbike motor except maybe running it on road america with stock gearing.

After owning 7 YZFs nd 2 WRs...I have never done a bottom end on any of them.....my 03 has probably 200hrs on (2)450 top ends and now -20hrs on 470 top end still no problems with bottomend....

Not sure why this is even being asked.....:censored:

I bought my son a new yzf250 in December, It now has 45 hrs on it, mostly from practice, he races Motocross, and the Motos usually last less than 8 minutes, 4 races at 2 moto's each, thats 1 hour and 4 minutes race time. I have checked the valves and they are perfect, I plan on running all year before rebuilding. The oil gets changed at minimum, once per week, maybe twice if it is a race week, and the air filter cleaned after every ride. I keep 3 airfilters ready to go, in plastic bags that way i just clean and oil them once a week, all at the same time.

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