Two Stroke Motocross
Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: TMKIWI on May 16, 2011, 09:08:59 PM
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Before you all get wound up check this I found on another forum.
Even some 4 stroke guys have a few brains. ;D
http://www.dirtbikeworld.net/forum/showthread.php?t=80976 (http://www.dirtbikeworld.net/forum/showthread.php?t=80976)
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This is nice to see :)
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I only read the first page of the thread but it brings up another question.
When you rebuild a 2T, it stays rebuilt for the regular life of the parts. My experience with modern MX 4$ has been that you rebuild them but they go off again like a roman candle about half the time of the original.
Is that just my local builders and competitors or is that normal for thump-thump-thumpers?
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In my experience 250F's are so highly stressed I'm not really sure if they can be rebuilt.I won't go near them because how can you guarantee that the rebuilt engine will last more then a few weekends?You can't.
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the only four stroke off road bike I would own is an XR or DR the rest are time bombs
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for me, if it doesn't burn oil, it sucks! (4$ with worn piston rings doesn't count)
you can go for a 2s with 5yrs or 10yrs, if it's in a decent shape, a brand new piston will bring it back to life and will be a reliable bike.
i don't understand why do i see lots of adverts selling 4$ as brand new bikes or such as 08 or 09 models! thats almost brand new, but they might so destroyed that they rather sell it than rebuild it.
my friends can't stick with a 4$ for more than 3yrs, they trade they'r bikes too often.
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you can go for a 2s with 5yrs or 10yrs, if it's in a decent shape, a brand new piston will bring it back to life and will be a reliable bike.
That is not usually the case and we should not be spreading misinformation if we want to be taken seriously. Any motor will fail with time. 2T's are not an exception. In 'many' cases you can just replace piston and rings but in most 5 or 10 y/o bikes, 2T or 4$, you 'll need more - a lot more.
Cylinder walls ware out and most if not all are nikasil now. That means replating and that is not cheap. Rod bearings, crank bearings, crank seals all are most likely beyond end of life by 5 years. Of course, you need to do that with both 2T or 4$ but with the 4$, there are a lot more parts and those are much more expensive.
To give you an idea - and by no means is this an average, parts for my 2006 Honda CRF250X - top and bottom were $1500. Parts for a '73 Husqvarna, '71 Bultaco, or a '98 YZ139 are between $350 and $550 (the YZ needed replating).
All this and that is just the motor. Of course there are chains, sprockets, tires but costs that are overlooked are wheels, wheel bearings, spokes (they get stretched and loooose!), suspension bearings, shock bushings, shock recharges, fork seals, cables. The list to bring a 5 or 10 y/o bike up to par is just as expensive to restore any old vintage dirt bike. And often, the parts are even harder to find!
Also, there are plenty of people that are quite happy with their 4$ and have not (yet) experienced a catastrophic failure. Those people properly maintain their bikes and replace parts as needed or recommended before '$61+ hits the fan'. You have to marvel at the technology employed to get that much power out of a 4$ design - even if it is 85% to 100% larger than a 2 stroke.
I concede the point though. "2T's are cheaper to maintain than 4$". We should just be careful though not to give the impression that they are trouble free.
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before i bought my bike all engine bearings were replace because o water pump not sealing correctly. i saw the engine parts and they were in decent shape, including the barrel.
in a 4S if the head parts tend to fail, there are more parts to replace than a complete 2s engine and is way more money to rebuild it.
now that i read your comment, your totally right, it's not only about the engine, other parts do fail a lot, that's why my linkage is all fcked up.
my uncle has a 08 kxf450 and in 1 year as a weekend rider, he allready spent a 1000â?¬ (1250$) replacing piston, rod, crank, oil pump and new valves. it's also the second time that he replac shock seals and the suspension is leaking again.
do you think that nowadays parts don't last as long as they use to in older bikes?
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As always,quality really varies.The Kayaba shock on one of my Suzukis was a nice unit,but it blew up all the time.The Rieger shock on my 500 Maico is also very nice but is also extremely durable,there is no comparison.
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Most people don't even start with a rebuild for a race-designed 4 stroke.
They just sell it...
That's why, in my view, the current race-designed competition 4 strokes
are already the joke of this century.
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This may be a repost, and I may not agree with all of it - but I like what Eric G. says on the subject.
http://www.eric-gorr.com/fixing4strokes.html (http://www.eric-gorr.com/fixing4strokes.html)
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This may be a repost, and I may not agree with all of it - but I like what Eric G. says on the subject.
http://www.eric-gorr.com/fixing4strokes.html (http://www.eric-gorr.com/fixing4strokes.html)
Thats a pretty straight up way of explaining it. :)
No BS.
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Yikes! :o
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do you think that nowadays parts don't last as long as they use to in older bikes?
That is a good question but I think it is a complicated answer. On the one hand, everything for the American (and the rest of the developed countries) is basically "throw away" and/or "planned obsolescence" design. Meaning, it is cheaper to build it than it is cheaper to repair it or they want it to fail after a pre-described point so you have to reinvest. That is my feeling with the 4$. The Big 4 need to sell huge numbers of motorcycles each year to fit their business plan. With the number of new riders shrinking each year - not growing, they have to 'somehow' get those of us who continue to ride to want new motorcycles. The 'old' way to do that was to provide something new, but to do that your company must invest in R&D and that takes away from the bottom line. In most cases, simple refinements and BNG's (bold new graphics) serve to get 'the kiddies' to want the latest gizmo. In the '70 and '80's we saw distinctive changes in motorcycle design. Except for the 4$ engine, what has changed since...oh '91? Very little I'm afraid.
All that said, we have come a long way since the '70 in metallurgy, computers, and flow design. In theory, that should make bikes lighter-stronger-faster but in practice, just seem to have aided the manufacturers in creating obsolescence. That '68 CZ was meant to be rebuilt and raced for the next 5 years and then used second hand for 5 or 10 more! That 2011 Suzuki DRZ450 was made to last 1 season, with 2 rebuilds and then into the parts bin.
AMA and the FIM are culprits as well. Racing rules have hindered development. Nowhere is it more true than in motorcycles that "Win on Sunday, Sell on Monday" moves product. Rules meant to provide stability and lower the cost to the privateer have only raised the cost of racing and took away any chance for a privateer to come up with a mechanical advantage. No new shock designs, brakes, engine modifications, custom frames. No changes worth speaking of. Can it be that shock technology has gone virtually unchanged in 20 years? Why are bikes still minimum weighted at the same levels as the '70's!?! We all have aluminum frames for crying out loud! What incentive does Yamaha have to make a stronger, lighter bike when the rules won't let you race it?
Of course, this is true for 2T's and 4$'s alike but back to your comment about other parts failing more often. I have a theory and only my own experience to back it up - no hard data. That said, I believe ALL modern MX'ers are not built for the dirt. I know that statement doesn't make much sense but follow me here. These bikes are built for Supercross, not Motocross. They are built to run in clean stadiums for two 8 lap motos and one 20 lapper, not the original qualifiers plus two 45 minute motos. Parts are easier to inspect for failure between races and motos. Bikes are not built to endure a season plus the ISDE! Weather, mud, sand, dust are all the enemies of the modern bike. Don't agree? Where are the fork boots? By 1990, almost all bikes had gone to the 'upside down' forks. An advancement in technology to be sure but now it put those delicate fork tubes down in the dirt and all they got was a sliver of plastic to protect them from rocks, roots and trees? No, they were not meant for rocks, roots and trees; they were meant for 70 foot triples, clean whoop sections and groomed corners. A simple solution to fork seals was the neoprene "Seal Savers" but are they on ANY new motorcycle as standard equipment?
So your uncles Kawasaki gets 'used'. It goes to the track or the trail and is exposed to the 'elements'. As with most riders, he takes care of his equipment; he brings it home, washes it off with the pressure washer from Home Depot, sprays it down with WD-40 and lubes the chain. Then he puts it away until the parts he has to order on Monday arrive so he can go riding again on the following Sunday. Nice life and the perfect customer. Except that bike was meant for more attention. Read the owner's manual and see just how frequent the chain needs to be tightened and replaced. How often you should adjust the valves, how often you should change the shock oil. You need your own full time mechanic to ensure your bike is prepared for the weekend - or plan on giving up family, friends, etc. There is just not enough time in the day. And that is what they want. Ride it until it goes pop and buy another one.
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Stepping into the conversation..
I hear what' you're saying VBS. I can't vouch for the big fours intentions behind the design of their modern 4-stroke MX bikes, but, my thought is that more than likely they're all under pressure to crank out the latest and greatest - fastest, strongest, bestest bikes each year. In that pursuit, the have the bikes so high strung and so hotly tuned that they're overly fragile and require a lot of maintenance to keep them from grenading.
More HP, higher rev's and new lightweight figures are so much more sexy than reliability and low maintenance..
Someone said it recently: "Quality, Performance, Price. Pick two..."
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The latest Kiwirider magizine has a comparison between Shane Kings 1996 factory KTM SX360 ( The actual bike he won the worlds champs on ) and the new KTM SX350F.
It is an interesting read.
If some one can tell me how to post a PDF file i'll put it up.
Or I can e-mail to Charles or Coop or ACMX ?