KTM Bottom End Replacement

you have a long way to go before doing a bottom end.

I agree with br8es, u could triple the hrs for a bottom end

You easily be able to get 2-3 top end per bottom end on KTMs. Ive seen guys who race A class at local harescrambles (super fast guys) and they see 200-250hrs out of bottom ends. Which compared to other brand bikes is absurb and unheard of unless you barely ride the bike.

By the book, 50 hours for a top end, 100 for a crank, at least for a 17 FC450. In the end it's your call.

Thank you for replies. Ya my book says 50/100 too, but know that most people are going near the 100 mark for top alone. I just wanted to get some insight about the bottom as i don't recall seeing too much about that.

Use common sense and physically inspect your engine. You should be at least inspecting your top end at 40-50 hours. When you do that you can feel your crank and inspect it against your service manual. When you notice it getting close to the service limits, rebuild it.

Going by hours is just a guide. I used to be strict on going by those hour limits but sometimes theyre rediculous. Replace it when its worn out. Stuff doesnt expire with time like food does.

kb228 wrote:

Use common sense and physically inspect your engine. You should be at least inspecting your top end at 40-50 hours. When you do that you can feel your crank and inspect it against your service manual. When you notice it getting close to the service limits, rebuild it.

Going by hours is just a guide. I used to be strict on going by those hour limits but sometimes theyre rediculous. Replace it when its worn out. Stuff doesnt expire with time like food does.

I will agree. Looking through my KTM manual there are some things a normal weekender is not going to do everytime they ride. My manual says to replace brake pads every 1 race or 3 rides??? They must think im a f’ng pro lol.

kb228 wrote:

Use common sense and physically inspect your engine. You should be at least inspecting your top end at 40-50 hours. When you do that you can feel your crank and inspect it against your service manual. When you notice it getting close to the service limits, rebuild it.

Going by hours is just a guide. I used to be strict on going by those hour limits but sometimes theyre rediculous. Replace it when its worn out. Stuff doesnt expire with time like food does.

Alec138 wrote:

I will agree. Looking through my KTM manual there are some things a normal weekender is not going to do everytime they ride. My manual says to replace brake pads every 1 race or 3 rides??? They must think im a f’ng pro lol.

If you sue them, they are hoping to tell a judge that you didn't change the pads as directed... CASE DISMISSED

My 2005 KX250 manual says new rings every 7.5 hours and new piston every 15. YIKES!

To the OP, I would go ahead and do the top end soon. When you have it open and can inspect things, you should be able to get some idea of how to proceed on the bottom end.

Had new kTMs 2013,2014,2015,2016, 2x 2017, 2018. Most of my bikes has been 100-160h, and after i sold them they have been up to 200+.

There is no chance you need to do one before 200h if you ride easy on the bike. Pro top 5 MX-rider that i know ran 400h on his 2016 350 Enduro.

You need a lot of bad luck if you would have benefited in retrospective to to bottom end earlier than 200-250h.

kb228 wrote:

Use common sense and physically inspect your engine. You should be at least inspecting your top end at 40-50 hours. When you do that you can feel your crank and inspect it against your service manual. When you notice it getting close to the service limits, rebuild it.

Going by hours is just a guide. I used to be strict on going by those hour limits but sometimes theyre rediculous. Replace it when its worn out. Stuff doesnt expire with time like food does.

Alec138 wrote:

I will agree. Looking through my KTM manual there are some things a normal weekender is not going to do everytime they ride. My manual says to replace brake pads every 1 race or 3 rides??? They must think im a f’ng pro lol.

KDXGarage wrote:

If you sue them, they are hoping to tell a judge that you didn't change the pads as directed... CASE DISMISSED

My 2005 KX250 manual says new rings every 7.5 hours and new piston every 15. YIKES!

To the OP, I would go ahead and do the top end soon. When you have it open and can inspect things, you should be able to get some idea of how to proceed on the bottom end.

Ive never looked, but i believe theres a spec for pad thickness... you could say although i didnt follow the 3 hour rule, my pads were still within the specified thickness.

Here nor there tho

Just had my engine rebuilt at 128 hours. I was told the bottom end looked like new but I had it done anyways. I was told that it’s not unusual to go 200-300hrs on a 450 bottom end.

Checking play in a crank with feeler gauges side to side is a piece of cake, but the regular guy trying to "feel" vertical play is a joke. If you can feel it, you just got lucky.

I do wish there was a easy/better way for guys to check bearing play and compare it to manufacture tolerances when it comes to checking the bottom end.

SURFGLOBE wrote:

How many hours until you guys are doing a bottom end? I am at 70ish on my '17 450. I do not ride it hard, change oil and filter every 5-6 hrs, and clean air filter every ride. I'm going to do the top end in the next week or two, should i go ahead and do the bottom at the same time?

What kind of fueal have you been using?