CRF250X Mega Thread

[North ride]

I clicked on the fastheads link and thought the stainless $499 option seemed like a good way to go for trail riding requirements.

Do you think a valve adjustment with thinner shims will get you through this season of riding? Then go big with the head work over the winter? Your bike looks low hour in those clean pics. My '08 was hammered, in spec and running great as a trail machine. Dropping a valve can be catastrophic but if there's life left for another adjustment, it's something to consider.

I wouldn’t do it, If you run that bike until it comes apart. It will be a write off not worth fixing.

 

[Bearcat]

You gotta good point there, can't argue that! The bike just doesn't look high time, but looks can be deceiving.

 

[Bitingdog]

I checked the valve clearance…

Exhaust was slightly over spec. The intake was 0.000. I couldn’t even fit a piece of Starrett 0.001 tape in there!

Anyone have suggestions for a good machine shop?

I found some people like this place:

Fastheads - dirt bike cylinder head service

Fastheads deals exclusively in dirt bike cylinder heads and valve train components for all brands. New and service options available. 435-668-7776

fastheads.com

I can't believe that pressure washed it hard enough to wear out the intake valve. Yew animal!

Get the stainless steel valves, and you're golden forever

 

[DJ_MI]

I can't believe that pressure washed it hard enough to wear out the intake valve. Yew animal!

Get the stainless steel valves, and you're golden forever

Yeah, just a coincidence it turns out.

 

[jwaller]

Yeah, just a coincidence it turns out.

Gotta hate those coincidences with pressure washers!

 

[DJ_MI]

So I pulled the cam last night and measured the shims and buckets.

The buckets are just over the diameter service limit. Top to bottom taper was about 0.0001".

I don't want to sink a bunch of time and money into the head only to find out that the piston and rings need attention too so I've decided that I'm going to shim the valves and get it running again so I can get some compression and leak down test numbers and see how the rings are sealing. If the numbers are decent I'm going to put a few hours on it and then recheck the valve clearance. If they show a lot of change then I'll tear it down and get the machine work done. If they remain consistent then I'll probably run the bike until winter before tearing it down for valve replacement. I understand the risk and am willing to face the consequences if I have a catastrophic failure.

While having problems isn't ideal, I've been learning a lot about working on motorcycles and having fun doing it.

 

[Bitingdog]

OEM pistons are pretty cheap iirc. I'm with you, run it for now, and build it thoroughly over the winter. These things don't shed piston skirts like a deranged two-stroke, probably because the pistons don't have any skirts

 

[DJ_MI]

OEM pistons are pretty cheap iirc. I'm with you, run it for now, and build it thoroughly over the winter. These things don't shed piston skirts like a deranged two-stroke, probably because the pistons don't have any skirts

I'm sure I'm missing some parts here but it's looking like ~$194 in parts for piston replacement. Not including ancillary gaskets and all the other stuff that should be replaced while it's torn down.

Name	REF#	NmMod	QTY	MSRP	SubTotal
RING SET, PISTON (STD)	2	RING SET, PISTON (STD)	1.00	$52.40	$52.40​
PISTON	3	PISTON	1.00	$86.20	$86.20​
PIN, PISTON	4	PIN, PISTON	1.00	$25.13	$25.13​
CLIP, PISTON PIN (16MM)	5	CLIP, PISTON PIN (16MM)	2.00	$1.71	$3.42​
KEY, SPECIAL WOODRUFF (25X14)	6	KEY, SPECIAL WOODRUFF (25X14)	1.00	$3.45	$3.45​
GASKET, CYLINDER HEAD	4	GASKET, CYLINDER HEAD	1.00	$23.44	$23.44​

I know it has to be done at some point but I'd rather do it in the off season if possible. The bike has only run for four days so far since I've owned it, I'm itching to ride it some more!

 

[Bearcat]

Off CRF topic.

Speaking of piston and rings. My neighbor has one of those Hyosung V-twin 250 cruiser things. He doesn't take good care of his bike and shoves it in a musty old shed or leaves it parked outside. He wanted to get it running after it sat for the last three years. I cleaned the carbs and the jello out of the fuel pump and the other usual things that go with corroded old junk. After fiddling with the jets, float heights and airscrew adjustments the bike started but was a dog, it made no power, it didn't smoke yet could barely hit 45 mph on the flats. He says it now runs better... It was a hard starter too.

Long story short I found out he had been running the bike for the last 8,000 miles with the choke on... He didn't understand the choke lever direction and got it backwards. I knew something was up when he argued about the choke lever position and I had to show him in the owners manual. I don't know how that thing even ran decent enough without him not noticing it. The cylinder walls were getting washed down with raw fuel and wearing out the rings. Out comes the compression tester: Front cylinder 49 PSI, Rear cylinder 35 PSI. The valves were in spec on the tight side. I didn't bother with a leak down, just adding air it was the Leaky Tiki everywhere!

Now back to CRF's

 

[DJ_MI]

Off CRF topic.

Speaking of piston and rings. My neighbor has one of those Hyosung V-twin 250 cruiser things. He doesn't take good care of his bike and shoves it in a musty old shed or leaves it parked outside. He wanted to get it running after it sat for the last three years. I cleaned the carbs and the jello out of the fuel pump and the other usual things that go with corroded old junk. After fiddling with the jets, float heights and airscrew adjustments the bike started but was a dog, it made no power, it didn't smoke yet could barely hit 45 mph on the flats. He says it now runs better... It was a hard starter too.

Long story short I found out he had been running the bike for the last 8,000 miles with the choke on... He didn't understand the choke lever direction and got it backwards. I knew something was up when he argued about the choke lever position and I had to show him in the owners manual. I don't know how that thing even ran decent enough without him not noticing it. The cylinder walls were getting washed down with raw fuel and wearing out the rings. Out comes the compression tester: Front cylinder 49 PSI, Rear cylinder 35 PSI. The valves were in spec on the tight side. I didn't bother with a leak down, just adding air it was the Leaky Tiki everywhere!

Now back to CRF's

It’s always interesting diagnosing problems. Frankly it sounds like he’s safer with an inoperable bike!

 

[Bearcat]

It’s always interesting diagnosing problems. Frankly it sounds like he’s safer with an inoperable bike!

Dude! you just nailed it. That thing couldn't get out of its own way and is dangerous in traffic. It would run out of power going up a slight hill that normally isn't even noticed! He's better off on a bicycle...

 

[MVI]

Off CRF topic.

Speaking of piston and rings. My neighbor has one of those Hyosung V-twin 250 cruiser things. He doesn't take good care of his bike and shoves it in a musty old shed or leaves it parked outside. He wanted to get it running after it sat for the last three years. I cleaned the carbs and the jello out of the fuel pump and the other usual things that go with corroded old junk. After fiddling with the jets, float heights and airscrew adjustments the bike started but was a dog, it made no power, it didn't smoke yet could barely hit 45 mph on the flats. He says it now runs better... It was a hard starter too.

Long story short I found out he had been running the bike for the last 8,000 miles with the choke on... He didn't understand the choke lever direction and got it backwards. I knew something was up when he argued about the choke lever position and I had to show him in the owners manual. I don't know how that thing even ran decent enough without him not noticing it. The cylinder walls were getting washed down with raw fuel and wearing out the rings. Out comes the compression tester: Front cylinder 49 PSI, Rear cylinder 35 PSI. The valves were in spec on the tight side. I didn't bother with a leak down, just adding air it was the Leaky Tiki everywhere!

Now back to CRF's

subscribed

 

[Bearcat]

subscribed

Okay, well here's the rest of the story:

I don't know how that Hyosung even starts with those low compression numbers. Granted I have a new inexpensive HF tester and the gage calibration could be way off. Even at TDC with just adding compressed air it was roaring out the airbox, exhaust pipe could blow dry your hair, and air was coming out of the oil fill cap hole. The valves were still in spec but on the tight end. The valves must be gunked-ed up and the oil washed off of the cylinder walls and wore out the rings form running full choke for the last 8000 miles... Before checking all of that I was wondering if the CDI had issues. I don't know how he didn't notice, probably that frog in a slow boiling pan of water story. He would crank and crank that thing. I noticed the low float heights and adjusted that. When he started arguing with me about the choke lever position that's what aroused my suspicion and thus doing the comp test.

The fact is the bike is a pile of corroded scrap at this point and unsafe to ride. After researching it, parts are harder to find and those things aren't worth much to begin with. I was honest with him and told him to park it for safeties sake. It's a reason I'm not a fan of the cheaper buy-in no-name bikes. You're kind of stuck with them. He's 5' tall and liked that bike because of the low seat height. I gave him some used replacement recommendations such as the Honda CMX 250 Rebel and various scooters.

MVI, that's the rest of the story!

 

[MVI]

I suggest you remove the starter gear from the bike and stuff an old gym sock down the intake manifold for his own safety.

then offer to haul it off to the scrap yard.

 

[DJ_MI]

Okay, well here's the rest of the story:

I don't know how that Hyosung even starts with those low compression numbers. Granted I have a new inexpensive HF tester and the gage calibration could be way off. Even at TDC with just adding compressed air it was roaring out the airbox, exhaust pipe could blow dry your hair, and air was coming out of the oil fill cap hole. The valves were still in spec but on the tight end. The valves must be gunked-ed up and the oil washed off of the cylinder walls and wore out the rings form running full choke for the last 8000 miles... Before checking all of that I was wondering if the CDI had issues. I don't know how he didn't notice, probably that frog in a slow boiling pan of water story. He would crank and crank that thing. I noticed the low float heights and adjusted that. When he started arguing with me about the choke lever position that's what aroused my suspicion and thus doing the comp test.

The fact is the bike is a pile of corroded scrap at this point and unsafe to ride. After researching it, parts are harder to find and those things aren't worth much to begin with. I was honest with him and told him to park it for safeties sake. It's a reason I'm not a fan of the cheaper buy-in no-name bikes. You're kind of stuck with them. He's 5' tall and liked that bike because of the low seat height. I gave him some used replacement recommendations such as the Honda CMX 250 Rebel and various scooters.

MVI, that's the rest of the story!

So he’d start it by turning the choke off?

My wife ran our snow blower once with the choke on the whole time. It still runs ten years later but an old Brigs is probably more tolerant than a Korean motorcycle.

 

[DJ_MI]

Update on my 250X:

The intake valves had 0.000" clearance with 1.600mm shims and wouldn't start. I ordered the two closest sizes that RMATV had in stock (1.450 & 1.400).

I popped the 1.45s in there released the tensioner, rotated the engine by hand a few times and remeasured... still 0.000" on the intakes. Pulled it apart got the 1.40s in there, same deal, measured and got 0.102mm (spec is 0.120mm (+/- 0.030mm) so the target is between 0.150mm and 0.090mm). That's on the tighter side but I don't have any thinner shims so it'll have to do for now.

I put it all back together and sat back just staring at it wondering if I'd forgotten anything important. After a few minutes I was satisfied that I'd done my best and figured it was time to put some gas in the tank and give it a try. I've never dug into a bike this far and was full of doubt and question. When I hit the starter was it going to sound like a coffee can full of marbles? Maybe nothing would happen at all. Maybe I'd be right back where I started and just crank and crank with no fire. I twisted the throttle three times, pulled in the clutch, hit the starter and almost instantly it fired right up!

I warmed it up and checked for leaks then rode it around for about an hour. I'm going to put a few more hours on it and then check the intake valve clearance and see how much, if any, deviation there is and decide where to go from there.

 

[Bearcat]

Update on my 250X:

The intake valves had 0.000" clearance with 1.600mm shims and wouldn't start. I ordered the two closest sizes that RMATV had in stock (1.450 & 1.400).

I popped the 1.45s in there released the tensioner, rotated the engine by hand a few times and remeasured... still 0.000" on the intakes. Pulled it apart got the 1.40s in there, same deal, measured and got 0.102mm (spec is 0.120mm (+/- 0.030mm) so the target is between 0.150mm and 0.090mm). That's on the tighter side but I don't have any thinner shims so it'll have to do for now.

I put it all back together and sat back just staring at it wondering if I'd forgotten anything important. After a few minutes I was satisfied that I'd done my best and figured it was time to put some gas in the tank and give it a try. I've never dug into a bike this far and was full of doubt and question. When I hit the starter was it going to sound like a coffee can full of marbles? Maybe nothing would happen at all. Maybe I'd be right back where I started and just crank and crank with no fire. I twisted the throttle three times, pulled in the clutch, hit the starter and almost instantly it fired right up!

I warmed it up and checked for leaks then rode it around for about an hour. I'm going to put a few more hours on it and then check the intake valve clearance and see how much, if any, deviation there is and decide where to go from there.

Nice work DJ, you're going to be the resident 250X guru! It's a great confidence builder, especially when you hit the happy button and she lights off without sounding like a can full of marbles. That is a nice clean looking bike you got there.

 

[DJ_MI]

Nice work DJ, you're going to be the resident 250X guru! It's a great confidence builder, especially when you hit the happy button and she lights off without sounding like a can full of marbles. That is a nice clean looking bike you got there.

Thanks! I’m happy to have a running bike to get my fix with because my KLX desperately needs some work.

 

[DJ_MI]

I've been getting some miles on the X lately and doing a little fuel economy testing while doing it.


I got up to 69 MPH. It might have a few more left in there but not much. 40-45 MPH seems to be the sweet spot where it's not winding out too much.

It went 50.7 miles on 0.945 gallons for an average of 53.6 MPG. I'm impressed!

 

[DJ_MI]

It’s been a while…

I sent the head to Millenium Technologies for a valve job. I got it back but haven’t had time to get it back together yet. The end of winter is near so I’m going to have to make the time!