Rebuild soon: Ideas, suggestions

Hey all..

Long time since last post.. Thought this would be the best place to ask

Ive gotten back into racing again loving it

Running a 2010 Crf450r which im slowly getting sorted

Very little mods

Gearing 13:49

Suspension revalved and springs for my weight

Fat bars and non-rubber mounted clamps

Ive been considering rolling the bike over at the end of the year and i thought to myself why bother this bike actually suiting me alot now

So its almost to 80hrs now without opening the engine. Willing to accept being flamed for that. Im an ex 250 rider and i know running that long is asking for trouble but the bigger bike is still running strong.

Gets air filter every ride (a given) Got plenty of got twin air filters

Oils every 5-7hrs

always running on good 98 octane fuel

Anyways 80 hours i was planing to get it rebuild at 100hrs (am i pushing it too much?)

im going to keep it till end of next year i hope so going to get it done properly.

What will i be looking at.


valves? replace or adjust

should i be looking at getting bottom end looked at so i dont have any issues till next piston.

Everything is running great starts easy as always. Doesnt burn oil.

No Metal Shavings anywhere (Oil Filter and in Oil)

Next thing

With my rebuild that will be happening soon i was thinking maybe some performance mods

Make some more bottom end power mainly or more power everywhere then id gear it back down even.

Was thinking a High Comp Piston maybe or cams or a Yoshi Slip on or remapping or yeah im open to any ideas. Wont be doing everything just one or 2 things

Another Question the backfire screen can it be removed. i know it made a good difference to my old carby crf250. Should i remove it without worry or yeah ideas would be great. Any other cheap mods that can be done?

Any help would be great

Cheers Hayden :ride:

What level racer are you A,B,C? With the 250f I would say you are pushing it. The 450's last much longer as most are not hitting that rev limiter. If you are a pro and your ringing out your bike on some rough outdoor tracks, then yes I would freshen it up. I would say a fresh top end. And since you have it opened up replace the valves and have the seats cut. Look for wear, cam etc. and go from there. As far as mods go, unless you are a fast A racer, I see engine mods as a waste of money. You will not get the same life out of that engine when you start doing engine mods. I have friends that are pro level racers (Privateers) running stock bikes engine wise and doing well. Most people are not using everything a 450 can give but think they need mods. I see kids around here that get brand new bikes and start asking what ca I do to get more power yet they are mid pack C racers, what a joke. Good luck with rebuild.

Im a midish B Rider

So i should just wack in the piston from in the spares kit.. new valves and ride it like i stole it

Bottom end should it be done now?. Had a big end go in my crf250 did not end pretty

Cheers Hayden

I don't want to give you the wrong info since by no means am I an expert in this field. In the past I raced 2 strokes and that is what I am familar with. I am still learning about 4 strokes. I race 40 plus vet. I have slowed down in my older age from when I was a teen but I feel that I am a much smarter racer. I also race 450's. I don't get out that often anymore but I have an 08 RMZ 450 and I cant immagine needing more power. I don't know when the correct time (hrs.) is for a rebuild. I guess it depends on the type of riding and how hard you are on the bike. I would guess you are ready for a top end like I said. I would search for other threads that are experts in the area. On a 2 stroke I would do a top end every 15 hrs of hard racing. Some did it after every couple of races. These bikes are much mor costly and more complicated to do it. I just read a thread that said high compression mod does not mean less longevity. So, I dont know. Good luck, let us know how she looks when you open her up.

I would reach out for Ron Hamp, He is a engine expert and can give you the most reliable information. I've seen bikes go a couple of hundred hrs. before a tear down, but I'm sure they are trail riding and not mid level B racers. But comparing your 250 to the 450 is apples and oranges. The 250 f's dont have much life in them compared to a 450.

I think I'm in the same boat:

My 09 has 90h (all MX). Never changed anything in the engine. I can feel the lack of power compared to my almost new 11. The engine makes a different noise too, sounds more like an old engine.... more mechanical noise and slightly vibrates when I rev it up.

If I keep the bike I will go trough the whole engine. I would even check the transmission too. At this point, I see it very risky to get only the top end sorted out.

Yeah mines just on 80 hrs.. thinking running it too 100hrs and getting it completely checked over... keep her running strongly to the end of next year

thanks for your help fellas

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