time between top ends

[bulldog71169]

I am moving my son from an XR80 to probably a KX85, and I am a bit concerned as to how often I will be doing top end jobs.

Number one... I've never done it and dont know whats entailed, and number two... it can get expensive with the seat time my son gets.

In the past 9 months on his XR he averaged 14 hours a month. If most are doing the top end every 15-20 hours... this may not be in the budget.

How often is it neccesary for an aggressive rider... both race and practice. And what is actually done in a top end job... ie. parts and prices.

Thanx in advance,
Matt

 

[crkid]

i'm not really sure how long it should be, no one's is the same. but i average a lot more than 14 in a month and i have yet to do one on my bike. also, is 15-20 hours what the manual says? cause mine says every 7.5 hrs and at that rate i would never get to ride. my friend on a yz125 waited a long time to do his and he had very low compression and the bike would cut off occaisionally. don't wait that long, when he took it apart it was nasty looking.

 

[GaryKTM200]

Hi Bulldog,
It seems I am replying a lot. My son's KX 80 went over a year of very regular riding before a top end. And even then the compression was not low. I just wanted to clean the power valve. For a top end job you will need a piston,rings,gaskets,radiator fluid, and a manual. The power valve has to go back together a certain way. The manual will show you how exactly. Total job I think is about 90.00 dollars or so.
One thing that will get a top end quicker than anything is a dirty air filter. Keep your filter clean at all times and you should be able to go for a good while between top ends. I have 3 filters for my sons bike and 3 for mine. I ride a KTM 200 mx/c.

Gary

 

[bulldog71169]

Thanx for the advice Gary... maintenance is a must in this house... even his XR was gone over after almost every ride. The deal was for my son to ride he had to learn how to work on it. So he does the filter after every 1-2 rides and oil changes every 15 hours or so.

I know my questions have been vague but I'm not sure what I'm getting into with 2-strokes, other than limited seat time here in CA soon.

the 90% rider and 10% bike thing... I agree with and he has learned that, since on a tighter track with little or no straights he is very competative, but cant handle the big tracks we've recently ridden with huge straightaways.

Sounds like most of the big 4 are evenly matched... he rides his XR wide open most of the time but thats because of the lack of power. He is going to want to be able to trail ride and do some singletrack again.

Are the RM and KX lacking power or speed on the top end? I would imagine if they are strong low and mid then he can always grab another gear.

 

[GaryKTM200]

"Sounds like most of the big 4 are evenly matched... he rides his XR wide open most of the time but thats because of the lack of power. He is going to want to be able to trail ride and do some singletrack again.

Are the RM and KX lacking power or speed on the top end? I would imagine if they are strong low and mid then he can always grab another gear."

They are all 80's or 85's and that is true. Like I said before the CR and YZ likes to be ridden on the upper ranges of the RPM range. The KX and RM have good top end speed also but with the addition of the power valve the two models have good low end power too. I think by having good low end power it really helps coming off of a turn and get good speed quickly to make the jump right out of the turn. And the RM and KX low end power really helps on the trails. From what I have read the YZ and CR caters to the more advanced rider that can twist the throttle more and quicker. As for top end speed I would say that all of the bikes are close. But as we both know on most tracks and especially trails top speed is not that much of a concern. Unless maybe your Ricky Carmical or James "Bubba" Stewart. With those two names mentioned they rode KX's all the way through their ameture years.
In my opinion the average rider will find it easier to ride a KX or RM. KX is my first choice. BTW. We have had really good service with my sons KX80.

Good luck,
Gary
:cool: :cool:

 

[bulldog71169]

Thanx Gary...

We have pretty much decided to go with a new KX85. Its just a matter of selling his XR to help pay for it first now.

He's still in a full leg cast for a couple more weeks anyway. Hopefully by then we'll be ready to buy. There are only a few in my area.