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Crf450r WOT 5th Gear Shutoff

7K views 22 replies 8 participants last post by  punk rock kiel 
#1 · (Edited)
Background info. I bought a 05 crf450r off of a member here. Ended up rebuilding a busted big bore jug with a cylinderworks big bore kit. It already had a HotRods Stroker crank and the HotCams Stage 3 Cam. TokyoMods ignition X10 Ecu. Rode it for a couple weeks then ended up having to replace both crank seals. Then went on another journey...

I went riding with group of sportbikes recently and had it topped out a good amount of the time. I am the a$$hat that was too excited to be on this beast of a bike I didn't pay attention to ride it less hard. Now I'll be paying for it.

I was coming down a long straight and it had 5th gear WOT clicked down into 4th coming up to the intersection and it shutoff on me. I pulled over. Minimal oil was coming out of the back of the head cover like the gasket wasn't tight. Went to kick it over again it felt like the piston had seized up. So I sat there and waited about 5 minutes then rolled it in gear in a parking lot and I could hear and feel that it hadn't seized. I got home let it cool for the week and just pulled it apart. I looked at the spark plug, its somewhat black but not alot and it still smells like fuel and oil level was on the Low mark on the sightglass and this is cold. It did feel like it was running rich previously poppin and snortin and yall could tell me better if that has something to do with it.

I don't see any cracks yet... I took off the valve cover and the back bolt is stripped in the thread which is why it came out. There wasn't alot of oil up there in the head either. Ill post spark plug pics after this post. I'll have to heli-coil the thread or find another camshaft holder.

What should I be looking for on the top end?

Did it simply overheat? Did it lose oil pressure? The coolant is still all intact. It hasn't filled into the oil chamber. I haven't drained the oil yet because I'm afraid to see gold flakes and have to replace a bottom end. I'll do it tomorrow after I go buy more oil.

Someone that has blown these motors or any expertise is greatly appreciated.
I've done forums searches and can't seem to find what I'm looking for.

I know from now on to not ride it all the way out, this bike will take some learning, as I am coming from liter sportbikes I have much to learn. :hmmm:

Thanks
 
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#3 ·
does it kick over Free? Popping and Cackling Is never Good... Usually to me that means you are too lean..
I Dont Want to Sound like *that* guy. but if you are Wanting to Run WOT on a sumo You need to get a Big Bore.. They have much longer Legs and the Extra Oil Capacity To keep the motor cool. Honda 450s Are Not known for their Sumo Reliability AT ALL... especially if They are Ran Wide open..

Im not much of an assuming man But im fairly Certain That your going to need a Full Rebuild.. Low Oil on motors like that Can Wreck a lot of Stuff FAST..

If I were You I would First Check For Shavings In the Oil.. Especially Since you Say its Low Cold.. That will give you a Good place to start Tracking Damage.. :eek:

The Plug looks Fine to me, Especially since you say it was running lean..

And Dont Worry man! It sucks now.. but You have the chance to Build that motor Exactly how you want! Crf450 sumos are Animals and I Envy you for having one! Good luck! :thumbup:
 
#4 ·
updates: its gets worse before it gets better

So I finished pulling apart the top end and its all sort of messed up. melted the piston rings and cracked the cylinder. there are shavings everywhere in there and so I'm looking for answers on what to do properly to clean this. Also I've heard millenium technologies does very well with repairs on the cylinder. Im wondering if the replating is worth it because a brand new kit is $410 (cylinder piston rings and gaskets).
 

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#9 ·
your video -measure rod side clearance with feeler gages -
will be listed in shop manual -

rod should move flawlessly -
Zero up/down movement -

Is there metal shavings in Crank / rod area ?

if there is metal is it magnetic ?

Piston sized for some reason - heat/oil -
Look for what caused that -

Cylinder Liner (sleeve) is Toast -
maybe get used ebay cylinder -

Check valves for leaking-
with sparkplug in place -
fill combustion chamber in head with water or gas -

Zero should leak past Valves -
 
#10 ·
would the tolerances be the same as it being a hotrods stroker crank ? im going to call them in the morning.

there is a little bit of metal down in it but my current magnetic wand is MIA. It does look fresh and flaked and could be part of the rings. theres not a ton that I can see.

it got extremely low on oil from the valve cover coming loose during riding.

I want to keep the bigbore specs and what not so finding a used cylinder isn't going to happen. I'll most likely get a new kit, though I wish I didnt have to.

would you go deeper into detail about checking the valves with water or gas
 
#11 ·
running engine oil low enough
to seize up piston on a 4 stroke engine -
not good at all -

could have Ruined all kinds of stuff -

these engines have just over 1 qt of oil and need all of it -
Drain oil and measure how much oil there is left-
post amount that comes out -

check valves for leak-
place head upside down on bench with sparkplug installed-

fill combustion chamber with water or gas-
Zero water should leak past valves -

water in exhaust or intake port = leaking valve -
simple quick test -
 
#12 ·
Well there's still metal flakes in the bottom end I ran my fingers in there today and it came out shiny silver. The oil was extremely low... like half a quart low.

I checked the valves per your test and it passed. There are no leaks in there. Which is a good sign since I'll be rebuilding the whole motor. Does anyone know anyone local that can test my crank and see if anything is out of spec, Tampa Fl.
 
#13 · (Edited)
Quickly turned into a full rebuild

I started tearing down my bike to clean things and it'll be 100% tore down, every bolt and seal inspected or replaced. I have a friend that has a nice powder coating oven so I figured what the hell why not. I'm going to start doing the major parts and do the little ones accordingly every couple days starting next week. I cleaned the swing arm and prepped it today. We ride year round down here in Florida, so I figured I can have it done possibly by Halloween but more realistically Thanksgiving in time for some cool riding. I still have to get the crank checked out and get a new top end. I am waiting on a flywheel puller tool to come in the mail to further take apart the motor and get it out. And as always something is stubborn, the footpeg bolts are in there so tight its unreal. I'll be getting a punch tomorrow to get those out. This is has turned into a full rebuild woooohoooo:bringiton here are my last 2 nights in the garage:
 

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#14 · (Edited)
I started tearing down my bike to clean things and it'll be 100% tore down, every bolt and seal inspected or replaced. I have a friend that has a nice powder coating oven so I figured what the hell why not. I'm going to start doing the major parts and do the little ones accordingly every couple days starting next week. I cleaned the swing arm and prepped it today. We ride year round down here in Florida, so I figured I can have it done possibly by Halloween but more realistically Thanksgiving in time for some cool riding. I still have to get the crank checked out and get a new top end. I am waiting on a flywheel puller tool to come in the mail to further take apart the motor and get it out. And as always something is stubborn, the footpeg bolts are in there so tight its unreal. I'll be getting a punch tomorrow to get those out. This is has turned into a full rebuild woooohoooo:bringiton here are my last 2 nights in the garage:


CRF's of that year run hot and yours runs very hot with all the mods, not to mention where you live. Heat will be your big killer. You might consider rigging up a fan behind one of the rads or get an oil cooler (which will increase your oil capacity).

Might want to take another look at your gearing too to make it a bit taller, i ran 14/39 but had a lot of chainslider wear (the greenish honda OEM one lasts twice as long as the aftermarket ones), and i'd look at 15/39 for your fast rides, because CRFs don't like being ridden at WOT for very long in 5th. A buddy had one blow up in a wheelie and i rebuilt my old one a few times- once had mine fail similar to yours on a track day years ago. Basically you want to gear it so you're riding it at a much lower rpm as it will last much longer between rebuilds. stainless steel valves is the only way to go; they last far longer than the oem ones.

for that era, if you're riding on the street daily, i'd recommend weekly oil changes, filter every other week, valve adjustment/check once a month, with a piston at most around 100 hours. i miss my crf, but not that maintenance schedule, but oh, that power.... i still get chills thinking about that bike... look to a TTO hour meter as it tracks the hours on the rebuild but can also display RPM so you have a better idea of whats happening down by your nuts.
 
#16 ·
Powdercoating Update

Request to move thread to Project Build Showcase::

I have the majority of the medium sized parts done. Some major parts including crankcases, swingarm, and frame will be done next week. This color is kingsport grey base coat with 2 coats of translucent copper from prismatic powders. My buddy did a good job on these for just getting into major jobs. Its gorgeous in the sun. The bolts and almost all the hardware are ink black also from prismatic.
 

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#17 ·
I've been busy with the rebuild, finished up all the powdercoating and started the reassembly. I went ahead and purchased ACT wide ratio transmission gears(2-5) because my 3rd and 5th are purpleish-blue. Over the weekend replaced all the linkage, swingarm, and case bearings. It's starting to look like a bike again.
 

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#21 ·
I'm not far behind where your at with the build. I had to redo everything cause someone didn't take care of it but I knew the 04-05 trx450r quad so I know what to look for. might be smart to jet a little rich cause the fuel will also help cool the motor down and not run it lean and burn it up again. looks good tho.
 
#22 ·
I will definitely be running it rich after what happened. Thanks for the reminder. It was a fun rebuild, I've had a lot of time to get things done. Everything from case bearings to transmission washers and snap rings have all been replaced. I changed out the countershaft for 07 countershaft because it has a hole drilled in it for oil flow. The wide ratio gears needed a little bit of clearance so I grinded away some of the case. The kits instructions said that some of the 05 cases were like that for 5th gear. I can't wait to see what the difference is for this trans. I'll be putting a whole quart in that side as well to keep it cool. Im hoping on New Years I can fire it up, didn't make the Christmas goal.
 
#23 ·
hope I don't have to clearance for the wide ratio gears. I didn't even get to ride mine before I went ocd on it and ripped it apart. being down at sea level you might wanna up the main jet a little bit. I'm at 500ft to 1500ft in PA but ill rejet, rather have it rich and lose a little power than rebuild another motor. I also run rotella 15-40 oil so it stays a little cooler and runs smoother and less chances of issues from lack of oil. its rare to see or read about crf supermoto so any info is better than nothing.
 
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