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CBR250R Spark Plug Failure and Subsequent Valve Train Damage

26K views 88 replies 9 participants last post by  shisoshin 
#1 · (Edited)
CBR250R Tight Valves, Spark Plug Failure, and Top End Damage

So about a week I hopped on my bike headed to work. I stopped at the local fuel station that has non-ethanol fuel, and topped off the tank. After filling up, I started losing power, and limped the rest of the way to work. It died at a stop sign, I pushed it to the top of the overpass just before work, and coasted down eased the clutch out, and got it going. When I stopped to show my identification, it died again.

I made arrangements and trailered it home. I pumped all of the fuel out, and removed the tank. I went to my local Honda dealer and ordered 06160-KYJ-920 Fuel Filter Kit for $55 (yikes). Today I received a call from the parts manager letting me know that the filters were back ordered.

With the filter being on the suction side of the fuel pump, is there any reason I cannot replace the filter with a standard Honda 16900-MG8-003 fuel filter?

UPDATE 1


I'll try to cover everyone's questions.

First, the bike ran fine the last time I took it out, which admittedly was a couple of months ago due to all of the rain we have been getting lately. The bike started and ran fine for the five miles or so that it took to get to the gas station, and gave the first signs of distress were very shortly after.

Second, there is a faint "tide line" inside the tank at around half a tank of what looks like varnish. I almost always park the bike with a full tank, so I don't know how long that has been there. Otherwise, the tank looks typical.

Here is a coincidence, when I pulled the rider's seat, my peg puck had fallen down near the intake snorkel...

I took several measurements, and verified that the filter is indeed on the suction side of the pump. I will replace the filter with the proper one when it comes in, but this one should make do to verify whether or not I have other issues, low voltage, weak fuel pump, etc.

The filter is close enough in length, but I added a layer of foam tape to get the diameter right. This filter fits scores of other Honda motorcycles including Goldwings and SuperSports, so I do not believe that volume or capacity will be an issue.













UPDATE 2

So, here's a little update. The problem does not look to have been fuel related at all.

Since I wanted to cover all of my bases, I picked up a fuel and air filter, and a spark plug.

While I already had the tank off, it would be an opportune time to change the spark plug, remove the PAIR valve and install the block-off plate.

When I pulled the spark plug, my heart sank. It suddenly occurred to me what was causing the problem...




Since I figured that any damage that had been done was done, I swapped the plug, reinstalled the fuel tank, and poured in a gallon of fresh fuel.

I cycled the key several times to ensure that the fuel system was primed, and hit the start button.

The engine turned over fine, I got one pop, but the engine did not start...

I've got to head over to my dad's place and pick up my compression gauge and spark tester. Hopefully I have a 10mm adapter for the compression gauge.

Now my big concern is how much damage that little piece of ground electrode did bouncing around in there.

UPDATE 3

Looks like I've put 77 miles on the bike since I got it out of storage and to the new house. Which is about right, a quick ride after unloading it to a friend's house that's 15 or so miles away, a couple of trips around the block, and a trip to work.



Now for the bad news...

Less than 15PSI compression.



UPDATE 4:

I verified top dead center.


I verified that the cams were in the correct cycle. The lines don' exactly line up with the top of the head, hmmm.




I removed the cap that retains the rocker arm shaft, and used one of the cam cover bolts to extract it while pushing down on the valves with my thumb to relieve the tension.


I then removed the shims from the top of the valve stems.



To test to see if the intake valves seated now that the rocker arm wasn't in contact, I filled the intake port with some two-stroke fuel. The right valve leaks more than the left, but both leak.

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#2 · (Edited)
I wouldn't; just due to line sizes, sealing issues, and stagnant fuel volume differences. Also, if I recall correctly, the fuel filter is actually on the pressure side of the pump, and remains pressurized. I'd wait on the original part to come in personally.

But, bigger question is, how do you know it was the fuel filter? I've never heard of anyone having issues with them, and they are not part of the maintenance schedule. Did you take the original one off and try to blow through it? It just sounds like there could be something else at fault here instead.

If that really is the problem, Partzilla has it for $35. http://www.partzilla.com/parts/detail/honda/HP-06160-KYJ-920.html
 
#4 ·
As cbrlocal said, make sure it is in fact a problem with the fuel filter before you throw money down for a new one. It's possible you could have gotten some really crappy gas at that last fill-up. Or there could be something else going on with bike, and it just happened to coincide with the last refueling.

If it is a fuel filter issue (I have my doubts that it is), I think you'd need to get the one specifically designed for the CBR250R. And even though a local dealer doesn't stock it and Honda currently has it on backorder, that doesn't mean that one of the big online dealers won't have it in stock and ready to ship.

You could give Partzilla a call and ask them if they have it in stock in their own warehouse: 06160-KYJ-920 FILTER KIT, FUEL $35.76
 
#5 ·
I'm curious....cbrlocal and MotoMike seem skeptical that the problem could be the gas filter.
cbrlocal even says "I've never heard of anyone having issues with them, and they are not part of the maintenance schedule."
I'm just wondering why something so vital to the performance of the bike has become so reliable since I began riding in the 1980s.
When I started riding gas filters being clogged were a lot more common (of course we had petcocks back then too).
Is it simply because gasoline is refined better these days and much better quality than we used to deal with decades ago?
Or perhaps because the cutting-edge additives that have come along in the modern era keep the fuel system that much cleaner?
It used to be that if your bike died while operating a clogged gas filter was one of the FIRST things you'd suspect.
 
#6 · (Edited)
In my experience with maintaining gravity feed carbureted fuel systems, it was pretty rare to see an inline fuel filter or fuel petcock bowl/screen so clogged up with gunk or dirt that the flow of fuel would be completely obstructed. That said, it was routine to replace those $2 inline filters and clean out petcock bowls on a fairly regular basis. That was especially true for dirt bikes, which are just prone to collecting crap in the fuel tank due to the operating environment. On older street bikes, rust forming inside the steel fuel tank and then flaking off was a big culprit.

Aside from the problem of dirt in the tank, when it comes to operating/ride-ability problems with old school carburetor systems, it was typically a case of either bad gas (stale 'low volatility' gas, or water contaminated fuel), or simply very old gas left in the carb bowl turning to varnish during storage, and gumming up the jets and internal passageways to the point that even if the bike starts, it won't take throttle input.

As for the OP's issue with his EFI equipped CBR250R I'm thinking it could be bad gas, perhaps water contaminated, as a possible cause. It could also be a case of low voltage at the fuel injector causing the engine to die. But those are just "internet guesses"... even for those of us who are old motorcycle wrenches with years of experience, it's often difficult or impossible to accurately diagnose a problem on a bike that is not right in front of you in the shop.
 
#7 ·
I'll try to cover everyone's questions.

First, the bike ran fine the last time I took it out, which admittedly was a couple of months ago due to all of the rain we have been getting lately. The bike started and ran fine for the five miles or so that it took to get to the gas station, and gave the first signs of distress were very shortly after.

Second, there is a faint "tide line" inside the tank at around half a tank of what looks like varnish. I almost always park the bike with a full tank, so I don't know how long that has been there. Otherwise, the tank looks typical.

Here is a coincidence, when I pulled the rider's seat, my peg puck had fallen down near the intake snorkel...

I took several measurements, and verified that the filter is indeed on the suction side of the pump. I will replace the filter with the proper one when it comes in, but this one should make do to verify whether or not I have other issues, low voltage, weak fuel pump, etc.

The filter is close enough in length, but I added a layer of foam tape to get the diameter right. This filter fits scores of other Honda motorcycles including Goldwings and SuperSports, so I do not believe that volume or capacity will be an issue.












 
#8 ·
... Here is a coincidence, when I pulled the rider's seat, my peg puck had fallen down near the intake snorkel...
So did you remove the side stand puck from the area of the air box snorkel and try running the bike again, before taking apart the fuel tank, pump and filter? That puck blocking the intake snorkel would certainly explain why the bike wasn't running right.
 
#9 ·
If the tank isn't bad inside, I would doubt you would need a new filter.

I'm thinking you have (had) water/condensation in the tank and it got stirred-up when you filled the tank.

I'd try new gas, and keep an eye on the level (you said you do). I might also look at the seal and drain around the gas cap to see if there's a possibility that rain water could enter the tank instead of draining.
 
#10 ·
Puck has been removed.:wink2:
 
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#14 ·
You very well may be correct Mike, and checking voltage at the battery will be on my list of troubleshooting once I get the bike back together.

The battery has been on a Battery Tender since I got it home since I ran it dead trying to start it.

At this point I regret giving the info about the bike's symptoms, since all I really wanted to know was if there was any documented reason why I had to use the filter specific to this bike.

While I do appreciate the help that was offered, I do have quite a bit of troubleshooting experience with EFI systems.
 
#16 ·
mine clutch started after leaving key in overnight
[live on a handy long sloping downhill run]
and needed revs kept high if slowing/stopping,,
reminding me that symptom of yours..

leaving it sit for a month doesnt help the case
for battery being in good nick [unless tended]..
but together with then filling with new petrol
[of whatever quality] keeps petrol in the picture..

semi/blocked intake might contribute..

i also never had any problem with filtering
on petcock fed road hondas over many years..

with your attitude and experience the problem
whatever it might actually be seems to have
little chance of survival..

members responding to a problem here
without doubt do so with good will
and no negative expectations
[ :) ]
 
#17 ·
So, here's a little update. The problem does not look to have been fuel related at all.

Since I wanted to cover all of my bases, I picked up a fuel and air filter, and a spark plug.

While I already had the tank off, it would be an opportune time to change the spark plug, remove the PAIR valve and install the block-off plate.

When I pulled the spark plug, my heart sank. It suddenly occurred to me what was causing the problem...




I've got to head over to my dad's place and pick up my compression gauge and spark tester. Hopefully I have a 10mm adapter for the compression gauge.

Now my big concern is how much damage that little piece of ground electrode did bouncing around in there.
 
#18 ·
Or not...

I don't think the electrode and the ground strap broke off, I think they were hammered to bits by detonation.

The CBR, from what I've seen, has a habit of building up deposits in the combustion chamber that causes detonation. Sometimes that also leads to a burned valve.

I recall one of the owners that had that problems said they usually run the engine at low RPMs all the time. That makes me think the engine needs revs and a strong fuel system cleaner (like Techron Concentrate) once per season to keep the chamber and valves clean.

But I'd like to hear other opinions.
 
#19 ·
I run relatively low RPM's, nothing extreme, but I do ride below 4k on flat, level ground. Sendler does the same; don't think he's had any issues related.

Regardless, that plug is toast. Not sure why the higher RPM's would have helped the bike to run; spark is spark, and if it didn't make it at idle, it shouldn't have made it at higher RPM's.
 
#20 ·
Low compression, the missing piece of that ground electrode is probably embedded into a valve seat right about now...
 
#22 ·
Not many, I'll have to check the odometer, but less than 1,500.

I put 1,100 of those on it in the first year, but with my work schedule and moving into a new house, I haven't rode it much in the last year and a half. Mostly just crank it up, let it get to operating temperature, and give it a few revs with a few short trips here and there. I took about a 35 mile round trip a few months ago, and then the 35 mile trip to work last week.
 
#25 ·
Looks like I've put 77 miles on the bike since I got it out of storage and to the new house. Which is about right, a quick ride after unloading it to a friend's house that's 15 or so miles away, a couple of trips around the block, and a trip to work.



Now for the bad news...

Less than 15PSI compression.

 
#26 ·
I'd check the valve clearances prior to taking the top end completely apart... you may find that one of the valves has significantly more clearance than it should. Needless to say, it will be interesting to see what you find once you have the cylinder head off.
 
#27 ·
Why? I know that I had FOD in the cylinder, what does identifying which valve/valve seat is damaged before removing the head do for me?

I'm not making a science project out of this. The plug was dry, so I don't think I poked a hole in the piston, but I don't know how much damage is there. I may have 87,000 little dents in top of the piston. The piece of FOD may have damaged the piston and compression rings, or more than likely, it lodged in an exhaust valve causing damage to the seat or possibly bending the valve. Either way, I will need to pull the head to fully assess the damage caused, and determine which parts will need to be repaired/replaced.
 
#31 ·
Okay, so the engine is out sitting in the little stand that I threw together to hold it while I pulled it apart. I know that I did not need to pull the engine, but there is three years of Louisiana humidity funk and 1,177 miles of road gunk that I can now clean.



Since Mike's follow up post mentioned tight valves, and since it'd only take a minute to check, I figured why not.

The crank and timing plug required a hammer and punch to loosen after I potato chipped a coin and washer. They will be replaced with a pair of CRF socket head caps.

This leads me to believe that either they were tightened that way when the valves were inspected, or the inspection did not involve removing them...

The exhaust valves are in tolerance, but on the loose side of the range. The intake valves on the other hand, have less than 0 gap and are definitely leaking, as evidenced by the piece of plastic I used to cover the intake port.

I do not see any evidence of damage to the piston looking through the open intake port, nor through the spark plug hole.

If I can get my hands on a borescope, sure wish I was an Android user right now, I'll inspect the cylinder without removing the head, if not, the gasket is only $12.

I want to adjust the intake valves, but I'm kind of leery of trying to pull the rocker arm shaft while it is under tension.
 
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#40 ·
... The crank and timing plug required a hammer and punch to loosen after I potato chipped a coin and washer. They will be replaced with a pair of CRF socket head caps.

This leads me to believe that either they were tightened that way when the valves were inspected, or the inspection did not involve removing them...

The exhaust valves are in tolerance, but on the loose side of the range. The intake valves on the other hand, have less than 0 gap and are definitely leaking, as evidenced by the piece of plastic I used to cover the intake port...

If you have zero clearance on the intakes valves you cannot have a piece of plug electrode jammed in the valve face as it would hold the valve open and the clearance would get bigger.

If the inspection plugs were very tight (factory over tighten them or didn't grease the threads) i suspect the 600 mile service was never performed and you needed shims replacing after initial bedding in...
Not everyone removes the timing caps when doing a VCI... with the valve cover off, it's easy enough to find TDC by noting the position of the cam sprocket dimples as well as rocker arm to shim clearance, while rotating the rear wheel with the transmission in gear. So it's possible that those timing caps were not removed (given that the Thai factory is known to tighten the crap out of them) for the 600 mile VCI.
 
#33 ·
The mail lady delivered that very spark plug from Amazon last week. It's sitting on the table waiting for me to decide where to go next.

If I had a box of assorted shims, I'd just adjust the valves, and do a compression check, but fear that there may be damage to the intake valve seats, and not from my mysterious missing bit of electrode...
 
#35 ·
The crank has been rotated to to TDC, and the cams are in the proper position, valves closed, there is no valve lash, the cam is contacting the rocker arm through 100% of its rotation.
 
#36 ·
If you have zero clearance on the intakes valves you cannot have a piece of plug electrode jammed in the valve face as it would hold the valve open and the clearance would get bigger.

If the inspection plugs were very tight (factory over tighten them or didn't grease the threads) i suspect the 600 mile service was never performed and you needed shims replacing after initial bedding in.

You have two courses, re-shim and reassemble the bike, or remove the head to check the inlet valve seats first.

From your previous posts i would think you are going to remove the head (whatever we say its not going to stop you) as you have come this far and want to make sure rather than risk not checking stuff.
 
#38 ·
I'm expecting damage of some kind to the piston, chamber, or valves - but I hope I'm wrong.

That's not completely unusual for CBRs, even low mileage ones. Odd things happen without warning for some reason, yet they don't have a reputation for blowing-up when ridden hard at the track. With the low mileage you have (<1200), I wouldn't expect any serious carbon build-up that would cause detonation. Strange for sure.

We have seen stock plugs go bad and plugs with unexplained damage as well. I don't recall seeing a lot of answers though.
 
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