How many hours last your bottom ends?

I don´t think the R1 and the Honda engines are the best examples, since it´s cranks and rods are set on metal bushings( I think it´s the term) which clearences are filed whit oil on an higher pressurised oil pump, plus, being 4 cilinder engines makes the crank more balanced due to the firing order, opposite to the big stroke on the thumper on just one bearing.but then, it´s just my thought:excuseme:

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.

not exactly flattrack, but supermoto.

maybe i´m riding on a bit stessing conditions and you guys are not so much...

could also help if you tell me how do you ride.

I don´t think the R1 and the Honda engines are the best examples, since it´s cranks and rods are set on metal bushings( I think it´s the term) which clearences are filed whit oil on an higher pressurised oil pump, plus, being 4 cilinder engines makes the crank more balanced due to the firing order, opposite to the big stroke on the thumper on just one bearing.but then, it´s just my thought:excuseme:
The oil pressure is not really any higher within the system, only at the bearing, since rolling element bearings cannot hold any oil pressure. On the other hand, they don't need the pressure, either, and don't even need the volume of oil they get. Look how long the big end in a two stroke holds up on not much more than the smell of oil in the gas.

not exactly flattrack, but supermoto.

maybe i´m riding on a bit stessing conditions and you guys are not so much...

could also help if you tell me how do you ride.

Fast trail rides, MX, desert, flat track when I can find it. Let me know if you think that running down a graded access road at 7-8000 grand for ten minutes at a time isn't stressful for a rod bearing.

My '00 426 has 525 hrs on it now, 1 piston and ring set, hinson clutch basket, no valves (stainless stock) mostly MX, but some trail riding, some fast offroad, never bounce off the rev limiter, mostly use the fantastic midrange, oil change every 10 hrs with 20w50 mobil 1 v-twin oil. The old 426 is heavy but bullet proof. Mike

I've been riding/racing since I was 6. I'm 42 now. Some where along the line, I'm not sure where, I picked up the belief that our MX bikes lower ends/tranny's were designed to run on dirt, which has some give to it, leading to wheel slippage. Thats why I don't really like to even Test my bike on the streets of my neighborhood. With this thought in mind, would the near 100% rear wheel traction on the road portions of supermoto put more strain on the bikes lower end & gearbox than even hard MX use ?

That seems logical at first blush, and it is true that more force is applied to the engine and drive train in high gear on pavement than on smooth dirt. It's also true that SM engines are usually modified to produce more than stock horsepower, exacerbating the situation further. But the momentary forces that occur when the rear wheel leaves the ground at full power and then slams back down and bites, repeated over and over in rapid succession, can be far greater even than that, so I don't think it really follows that pavement is harder on a bike than dirt, no.

But any bike that is exclusively used for racing, of course, will have a generally shorter service life than one that "gets a day off" now and then.

I ride in a lot of sand and hare scrambles and lots of mx riding.and I have raced a little supermoto. Between the months of April and late November I ride 4-5 days a week that is on my dads property where I built a mx track. I also do a hillclimb race once every year mostly all of this with my 03 450. I ride the bike really hard.

I just dont understand how your bike should need a new bottom end after 40 hrs, something is going wrong. How often do you change your oil? Do you ride on the rev limiter all the time?

I just dont understand how your bike should need a new bottom end after 40 hrs, something is going wrong. How often do you change your oil? Do you ride on the rev limiter all the time?

I just feel more relaxed after I do a rebuild, dont even bother about valves, piston or rings. in fact the crank pin looked good those times I did it, but I change it any way. ist just that after that 1st time it got me scared...

oil is changed on a 4/6 hrs average, and its supermoto, allways at the toprange revs, and short time at the midle range.

you stated originally that you have a 400. When you decide to purchase a newer bike buy a brand new one and change oil every 4-6hrs and you will not need a rebuild for 3-4yrs(as long as it is a Yami) I ride in the high rpms ALL the time i still use the clutch like a two stroke, which is very hard on these four strokes. I may be wrong.... but I believe that you are wasting your money and time. If it does not last past 200 hrs then something was installed wrong or something within your engine is severly worn out and you are overlooking it.

you stated originally that you have a 400....
That's a good point in itself. The big end has been revised at least twice since the 400, perhaps 3 times.
i still use the clutch like a two stroke,
Why would you do that?

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