KX450F vs. KX500

[bigbellybob]

i have one of the most expensive 2t dirt bikes there is for parts KTM380. if a bomb went off in my motor and i needed everything cases, crank + bearings and rod, new cylinder, head, piston and gaskets. it would be under $2,200

Item # Description Your Price Quantity Subtotal
54730018500 CRANKSHAFT. BEAR STROKE 77  $830.54    $830.54 
54730006100 CYLINDER HEAD  $103.07    $103.07 
54730005244 CYLINDER CPL.W.FLANGE 380'98 $456.00    $456.00 
54730007200 II PISTON II CPL. 78,0MM 380'98 $106.99    $106.99 
54630000944 ENGINE CASE CPL.W.TRAN.BEAR'98
original partnumber 54630000844
superceeded by 54630000944 $522.89    $522.89 
Your Total  $2,019.48
+ gaskets.

now put a bomb in a 4t and see how much bigger that list of parts gets.

lets say the 2t and 4t will need a fresh top end at 70 hours, with my expensive KTM its under $150 for piston kit and gaskets, if the cylinder is good
can someone tell me how much it will cost to freshen up a 4t if the cylinder is good?

[don46]

This is totally out of hand, how often do 4t's blow up and need everything from cases up, not many that I've seen. Heads, yeah I've seen them crater, but again, most can be traced back to the maintenance or lack of. Knock on wood, I have not had 1 problem personally with any of my 4t's. These are not for everybody, but for those that race seriously, they are a must. I have both and like each for the application they are used, the other issues and it doesn't matter whether it's 2 or 4 stroke a person should learn how to repair them.

[don46]

i have one of the most expensive 2t dirt bikes there is for parts KTM380. if a bomb went off in my motor and i needed everything cases, crank + bearings and rod, new cylinder, head, piston and gaskets. it would be under $2,200

Item # Description Your Price Quantity Subtotal
54730018500 CRANKSHAFT. BEAR STROKE 77  $830.54    $830.54 
54730006100 CYLINDER HEAD  $103.07    $103.07 
54730005244 CYLINDER CPL.W.FLANGE 380'98 $456.00    $456.00 
54730007200 II PISTON II CPL. 78,0MM 380'98 $106.99    $106.99 
54630000944 ENGINE CASE CPL.W.TRAN.BEAR'98
original partnumber 54630000844
superceeded by 54630000944 $522.89    $522.89 
Your Total  $2,019.48
+ gaskets.

now put a bomb in a 4t and see how much bigger that list of parts gets.

lets say the 2t and 4t will need a fresh top end at 70 hours, with my expensive KTM its under $150 for piston kit and gaskets, if the cylinder is good
can someone tell me how much it will cost to freshen up a 4t if the cylinder is good?

Your right you do have one of the most expensive brands of bike to repair.

[Texas Champ.]

Not everyone is mechanicaly inclined....I've seen guys that are A class riders but can't use a pair of pliers. They are left to pay shop rate for repairs. A guy I race with in the vintage class rides a KX 450 in the +50 modern class also, he had 9 hrs. on his 450 and the crank broke. Good rider and is good about maintenance...Factorys have whittled away at iron and aluminum to the point where they won't last as long as a 2 stk. and all in the attempt to make us content with 4 stroke perfomance. Just look at the shirt-less pistons in a 4 stroke for instance, You could do it to a 2 stk. or a Chey 350 but the reliability goes out the window in lieu of performance....km

    KXcam22 ; We are just grown men having a grown man debate here..Don't fear we mean no harm..we'er just stating facts and discussing observations made......km

[don46]

The bottom line, and I think we will all agree the 4 stroke is more expensive to maintain, the only debate is how much it will cost and what is likely to break. The 06 KX's did have piston pin issues, kawi stood behind those.

Texas champ, I wpuld of contacted kawi if I was the guy you raced with, they have been very good about repairing failures.

big belly bob, I just put a piston in my 450, with gaskets it cost me less than $100, but we have a deal with Wiesco, retail prices are about $150 piston and another $35 for gaskets.

[Texas Champ.]

Don , My friend rides for a Kawasaki house in N.W. Houston...They hooked him up and it didn't cost a penny except for service items like oil,filter and coolant.
My Husky 400 has won me 3 Texas vintage titles in 4 years in those 4 I've been through 2 piston/ring and bore jobs...I did replace the clutch because a the plates were aluminum and it required an oil change after every race..I have a full steel unit now and I can go 2-3 races on the same oil..the bottom end hasn't been opened in 4 almost 5 years now....Ahhh the good ol' days....km

[BDI]

KXcam I hate to burst your bubble but crf450 and 250 and most modern 4t motocross bikes need valve adjustments all the time 100 hours is an astronomical amount of time expect your modern four stroke bike to go with out an adjustment. a lot of them need the valves adjusted as soon as they are broken in. I do valve adjustments on these bikes for people all the time. I did one yesterday it was an 08 crf250, it is the first bike this guy has owned in twenty years he's not exactly on the rev limiter all the time. The bike had three tanks of gas through it, IN valves were .003 and .005 EX valves were .009 and .009 spec is IN .005 and EX is.011 pluss or minus .001. Yamaha recomends a new piston and rings in their 4t every thirty hours alot of people put in new valve springs at the same time do to the fact they lose tension. Titainium valves like to lose their heads after so many hours regardless of how well you maintain your bike and should be changed out as prevenitive maintenance like two stroke pistons. I had valve seats cut by a local shop recently(Baker cylinder head) the guy was happy the head was not desroyed by valve failer like nine out of ten heads he does, that was his words. A lot of you will think I'm full of it and want to argue about the things I have stated and there will be no convincing you until the day it happens to you, alot of things in life are like that.

[kaw rider]

on the yzf motor after 10 hour if you have to adjust the intake more then .002 you better get those valves out of the motor now. i never blow my yzf but i changed the oil evry race day and geared it right and it had 50 hour on it when i sold it and it was due for new valves.

[GDubb]

A lot of you will think I'm full of it and want to argue about the things I have stated and there will be no convincing you until the day it happens to you, alot of things in life are like that.

How very true that statement is.  I guess we are all like that to a certain extent.


-G

[BDI]

I don't think that cleaning your air filter or changing your oil regularly can make any of us immune to these sorts of failures.

                                                   http://met-tech.com/motorsports.htm

[don46]

I agree with most of whats been said, 4t are much more labor intensive and more expensive, what I don't agree with is the statement that after 35-70 hrs of use it's going to cost me 1/2 the cost of my bike to repair it .

Knowing what I know, I accept the fact that it's going to cost me more money to maintain and more time doing pm's, in return I have a bike that runs really well and can be competitive.

Even if we weren't using our bikes for MX, I'd still have one for a playbike as well as the the 500's, it is easy to go fast on the 4t.

[Good]

Not everyone is mechanicaly inclined....I've seen guys that are A class riders but can't use a pair of pliers. They are left to pay shop rate for repairs.

Tell me about it! 

[bigbellybob]

This is totally out of hand, how often do 4t's blow up and need everything from cases up, not many that I've seen. Heads, yeah I've seen them crater, but again, most can be traced back to the maintenance or lack of. Knock on wood, I have not had 1 problem personally with any of my 4t's. These are not for everybody, but for those that race seriously, they are a must. I have both and like each for the application they are used, the other issues and it doesn't matter whether it's 2 or 4 stroke a person should learn how to repair them.

how often do 2t's blow up, i just put some numbers out there for comparison. my bike is a 98 and its only on its second piston still stock jug, head, and bottom end. and it gets rode hard, only seeing the upper RPM's most of the time. so the cost for 10 years of riding, it has had a couple air filters replaced, normal oil changes, 4 sets of rings, and 1 full top end with a new piston. and if my 368cc 2t @ 221lbs had 08 suspenders it would be very competitive agents the 450's and it would still give the 450 a big advantage in cc's. as the cc advantage comes down i think people will start racing 2t's, especially the amateur guys that don't have that factory money

[hughes]

I don't own a 4t at this moment, but have ridden a few YZ450F'S and I'll be buying my first YZ450F this year. I ride and work with a group of guy's and all they ride is 4t and they never complained nor have I seen any failures on their bikes. I know 4-5 bikes is a small sample but I ride with these same guy's most weekends. My boy's 2004 Yamaha TTR-90 is going strong with no valve adjustments or top end failures.     

[bigbellybob]

My boy's 2004 Yamaha TTR-90 is going strong with no valve adjustments or top end failures.

i don't think that helps. the old style 4t's were very reliable, xr650's and stuff. i had a 200x that ran forever but that stuff don't count. its the new style 4t racing motors that have every part as small as possible to save weight, and pumped up passed the point of reliability in question.