4 stroke maint vs 2 stroke

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#1
Ok I'de decided to seel my kdx and get a kxf250 4 stroke(better mx bike) what kinda of maintenance can I expect with the 4 stroke ? Mainly the valves,how ofter do they get checked and shimmed ? How about overheating ? These bikes are getting great reviews.
 
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#2
Well, you are going from a very reliable 2 stroke, to an unknown (relaibility factor) 4 stroke. I am not sure anyone can truthfully answer the question.

Valve adjustment is easy, inexpensive and I consider it routine maintenance. Cylinder head overhaul is a more difficult process and can be quite expensive. The hope is that the 4 strokes will last a long time between overhauls.

In a previous discussion, we determined that a CR500 was less expensive to operate over a long period of time, than some of the current crop of 4 strokes.

I'll bet you already knew everything I have mentioned.

Chris
 
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#3
With a 4 stroke I'm not sure you can accurately predict when maintenance will need to be performed, Where with a 2 stroke you can come pretty damn close to knowing when you are going to be maintaing your bike. But then again any thing can happen at any time.
 
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#4
Originally posted by MONKEYMOUSE
With a 4 stroke I'm not sure you can accurately predict when maintenance will need to be performed,
Why is that exactly?
 
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#5
Honestly Rich I'm not positive on that like I stated I'm not sure. But because there are many more parts and variables to the 4 stroke motors I figured it would be much harder to predict. . .I'm sure you have more to add to this. Allthoe if by maintenance he means like changing the oils, cleaning your filter, oiling your chain and such then I wouldn't think in those aspects that its any different then a 2 stroke.
 
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#6
Once a four-stroke engine is out in the field for a season or two the maintenance requirements are fairly predictable. As cujet pointed out, the KXF is a brand new engine with no track record. Only time will tell how closely you have to adhere to the factory service recommendations. This would be pretty much the case regardless of whether it was a two-stroke or four.

So far the KXF hasn't exactly been a model of reliability, but hopefully that is nothing but early teething problems.
 
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#7
Well, in my dirt poor past, I would overhaul 4 strokes by doing a valve job, piston and rings. However I always overlooked some worn out component or other. I would leave in: worn cam chains, worn cam bearing races in the head, recut old valves, worn valve guides and of course the crankshaft. (like I said, a dirt poor overhaul).

This did result in less than preditable reliability. A fact which could have easily been predicted:)

SO, I believe that engine life is predictable with new parts, whether 2 or 4 stroke. An hourmeter and a compression gauge will help provide the method to achieve the predictability. For instance, 25 hours and compression drops by 3%. 50 hours and compression drops by 10%. 45 hours might be a good time to renew the rings/cylinder/piston/valves. A careful measurement of worn parts after disassembly will help the evaluation.

Chris
 
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#8
You don't have to drain the coolant and remove the water-pump housing to change the oil filter on a 2-stroke, but you do on a kxf.
 

biglou

#10
MrLuckey said:
Wow, you really have to drop the coolant just to change the oil filter?
That's what I hear. One-piece oil filter cover/water pump cover. There are aftermarket 2-piece replacements available, or very close to being available.
 

CR Swade

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#11
Yeah, its true. The one piece was supposedly done for lower weight, damn the maintenance. The KXF is also prone to overheating, although there is some work being done on oversized radiators.

As far as general maintenance for non-specific fours, its no big deal, about the same as a two stroke. I change my oil and adjust valves every 15 hours. The last service I did took about 1.5hours and I adjusted the valves, changed oil & filters, cleaned air filter, changed rear pads. This about the same time I would have spent on the CR250, unless I had to clean the power valve and it would have taken longer.

The only added cost is the oil filters, but I don't spend as much on piston/rings and chipped reeds.
 
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#12
2-piece cover

Pro Circuit has the 2 piece cover out now. Unfotunately I cannot find the price on any site. Boyeseen is also seling, but it comes with some other stuff. check this out - here. This is my first time with a hyperlink so it might not work. The boyeseen setup keeps the temp. way down. If the link does work look at the 2nd graph.
HOPE THIS HELPS! :) :thumb:
 
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#13
Muzzys also has a really nice CNCed two piece cover for the KXF. click here
 
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#15
Four-Strokes are very reliable. In fact, the current crop of Four strokes are the most reliable and maintenence free four-strokes ever produced. Aside from changing the oil and filter every few rides maintenence is basically nill if you follow the factory prescribed maintainence intervals. You will rarely have to replace pistons and rings, and valve adjust ment is a once in a while type of thing , and is no more than a 1-2 hour proceedure. As for the Kxf, having to drop the engine coolant in order to replace the oil filter is one disadvantage of that bike. However there are two other manufactureers out there who offer 125 class four strokes, that do not have to empty the coolant to change a filter, and also have much more proven track records as far as reliability. So shop around talk to some knowledgable people and compare bikes before you sell yourself on green.