250-500cc When to rebuild bottom end WR300

[Sandgroper]

Hi Gents,

My 09 wr300 has about 80hrs on it since new. Mostly open desert and soft sand
riding so gets a good work out. Also had the hi compressionhead since new.
Last weekend I made the mistake of not checking the coolant before
I headed out. At the first gas stop approx 20mins into the ride I checked it and then had to put
in approx 800ml ! She was running hot but didnt miss a beat before or after the ride. Yes I know
Im a goose for not checking it.

Question is based on the 80hrs and the low coolant running time should I be looking at changing the
bottom end bearings soon or is this totally unecessary?
If I do need to change the bottom end what parts need to be done whilst the case is open? Ive never rebuilt a smoker before so bit new at this. Plus because none of my local shops have parts I need to order them myself and have the shop do the job. Im the sort of bloke who always has a few screws left over when building something so I prob shldnt touch it

Im about to buy a few parts from Halls Cycles in the US as they were the only guys who have been helpful
with my email requests but this isnt a cheap exercise :s

Any advice?
Cheers
SG.

 

[Terrence R]

I would just check the crank and rod for free play and listen for any howling noises while spinning the crank by hand. You are prob fine, but it's always good to check. I've heard of these bottom ends taking a lot of abuse well before a bottom end rebuild is needed. I just bought my 04 WR250 and I feel a slight vibration on deceleration. Meaning, it could be a bit of rod bearing play, or it could just be how the bike is supposed to feel. I've felt worse deceleration vibes before where the rod bearing has been tight though. Just check out the bearings/noises/vibrations. I'm sure with 80hrs on your bike, it's fine though.

 

[shrubitup]

remove ignition cover and move flywheel up/down. If no movement the crank bearings are fine.

 

[Sandgroper]

Thanks gents. Will help me get started. Bottom end parts arent cheap so hopefully she is all good.

 

[juicypips]

The fuel cools the bottom end so personally i think your worrying needlessly. If topends fine where all the coolent actually reaches then bottom will be too.
80hrs on a bottom end is no cause for concern yet but thats just me.

 

[Tinken]

You'll hear it when it needs tlc. It's the rod bearing that will go first.

 

[gwynfryn]

I'd be more concerned as to where all your coolant went,looking for external and internal leaks. Check the trans oil.

 

[ajaxauto]

Watch the end of my video from round 7 of the AMa National Hare and hounds You will hear the rod bearing on my WR 300saying we have had enough The bike and the lower end was running perfect and after 4 years of racing broke My WR 250 broke a rod bearing after about 4 years also My Cr 125 went 4 years before I changed it but it was still working

 

[Sandgroper]

Thanks. Seems these engines are more bullet proof than I already thought
Cheers

 

[icebergstu]

I've gone for miles with my bike sounding like a truck. Next to 0 liquid in rads. Got 150hrs out of the top end.

 

[juicypips]

Was that an air-cooled diesel the military use icebergstu?

 

[icebergstu]

Was that an air-cooled diesel the military use icebergstu?

No my 2011 WR300 - Yep...lol...sounded just like that though! So you have heard it too then?

Stu

 

[ray_ray]

I've ran my 08 WR250 hot till it knocked and pinged more than once ... ... Just let it cool, filled the radiator back up with water and no problems ...

remove ignition cover and move flywheel up/down. If no movement the crank bearings are fine.

This sounds simple enough

 

[Motosportz]

Question is based on the 80hrs and the low coolant running time should I be looking at changing the
bottom end bearings soon or is this totally unnecessary?

That. Run it. The bottom ends on these motors last forever. Regardless of the coolant the bottom end gets a nice clean splash of cool gas and oil all the time. Buddy with an 07 WR250 has over 500 hours of hard technical riding and the bottom end is still perfect. The worse thing you can do to a two stroke bottom end is let it sit way to long and let the bearings get surface rust on them. Short of that they last a ridiculously long time.

 

[justintendo]

80hrs isnt even enough to hardly worry about the piston, let alone the bottom end..unless you are a pure racer you can get 200 plus hours on a piston, as long as the motor is fed clean air and jetted close

 

[juicypips]

200 hours on a piston yes but how many on a set of rings???

 

[justintendo]

depends on how hard you rev it how many times i guess, lol