Very nice. Big or small wheel? I had the big wheel version back when I used to ride dirtbikes. Absolutely LOVED it. I wish Honda would fuel inject that engine and put it in a street bike. Check for recalls, I believe early 2007 models had a camshaft recall, and certain 2008s(?) had a swingarm recall.
My only gripes with the bike was that the gearing was a little too short for longer tracks, and it was quite prone to bogging down low. It really doesn't like running below 4000 RPM. Allegedly has a rev limiter of around 14700 RPM, incredible for a single, but I like the 17200 RPM my MC19 does better The intake noise of that CRF was quite glorious.
Mine was ridden for several years as a trail bike and never rebuilt. I did not skip valve clearance checks however.
Btw why do a lot of dirtbikes have this hose (?) like things at the tank lid? Is that just something to prevent the lid from getting lost or has it another purpose? I've never seen something like that on a non dirt bike.
If you have the shop manual, look at the fuel/fuel tank chapter and note that the tank has an extrusion for the attachment of an air line. This is normally near the top of the tank, the hose is "hidden" under the tank, so that it is out of sight.
Dirt bikes do/did not have as stringent antipollution rules. Honda street bikes from the 80's had vented fuel caps which were functionally the equivalent of the dirt-bike fuel caps with a vent hose.
My son was home from college and was anxious to see what was going n with the new CRF150R (that doesn't run), so we started ripping it apart.
First thing we found after removing the cam assembly and lifting off the spring were the valve retainers and tiny shims laying loose in the head (some visible in the right lower corner in the photo) -
The tappet or lifter had a hole punched through it from the valve stem -
One of the intake valves was bent and jammed open -
Where the valve hit the piston -
We did figure out that when the cam slipped and the timing went off the intake valve stem got punched up thorough the tappet and into the cam, where it ground the cam lobe down. Not sure why the other intake valve didn't do the same, but everything there looks fine.
The kid that sold it to me probably knew things were a lot worse than he let on, but I did get it for about 1/2 of a regular price so I can't complain too much.
Ordered a new piston, pin, rings, cam, gaskets, valve, tappet, and a few other pieces that should be here in a week or two. Spent about $400 so far including the factory service manual (which is absolutely required for working on it - IMO)
Overall not as bad as it could have been (but it ain't running yet...).
Had to order another intake valve, both intake springs, and have the seats cut, but the head is now good as new. Installed the new piston and rings and have the head torqued down. Waiting to have the new cam and sprocket hub pinned before installing the new cam to prevent this from happening again.
Also installed this in the garage to make working a bit more comfortable -
Assembled the engine and fired it up the other day, and it ran, but not well. We ran it a bit and pulled the valve cover to re-check the valve adjustment. 3 of 4 valves had changed, so we needed to get the proper shims and reset them.
When I purchased the bike the owner (kid) said it "had been sitting a while" and wouldn't start - which was a half-truth to say the least. After pulling the carb and not finding debris or varnish in the floatbowl, I gave it a quick cleaning and reassembled it. After checking it closer today we found the Pilot Jet was obstructed. Removed and cleaned it, set the valves, and it fired up first kick and idled decent. It still needs a few more parts, but it's together and ride-able.
Spent about $700 on parts and machine work to get it going, and it still needs a chain/sprockets and a few other parts. Overall I'm going to have about what it's worth in it. No deals here...
It just left in the back of my son's pick-up. He is planning to ride it on the dirt a bit and eventually set it up for Supermoto competition.
Ready to install a new crank and high compression piston. Cam and bore look great. Crank replacement is more preventative maintenance considering how the engine was/wasn't taken care of before we got it. If you wait too long you'll end up with a hole in the cases.
I'm impressed with these little engines. It spends most of it's time at the track near the rev limiter, and after a season of trackdays shows almost no wear on the internals. Probably could have gone another season without much of anything.
My son is designing a velocity stack for the carb to have 3D printed. The airbox looks like a big compromise, as it has a stiff rubber boot that jogs awkwardly around the shock spring and makes jetting changes difficult.