[Redline]

Just a heads up in case people have a similar issue.

Took the bike in for it's 24,000km service (on it's 1st birthday).

Recently it has suffered from some engine knocking under load, and the morning of the service it suddenly lost power after 6000-7000rpm.

Fine up to that approx rpm then it would free rev above it without power.

Good timing as it was service time.

Anyway, they just called to say it looks like the camshaft tensioner was the issue with the free reving, and might be the cause of the knocking as well. Although I'm also having them check the shims.

Will report back when returned next week.

cost 700thb, just over US$20.

 

[arn]

A failed tensioner can take a lot of things along with it, including the timing chain guides, and if the ground up rubber from the guides stays in the oil too long, then.....

Was there any unusual clicking sound from the cold engine?

 

[Redline]

Was there any unusual clicking sound from the cold engine?

Yes.

A clicking/ticking sound, for the first maybe, 1km or 5 minutes.

 

[arn]

That's diagnostic.

Doesn't seem to be much to get bothered about especially as the noise disappears abruptly once the engine warms up, but 1000km of running (esp fast running as in touring) once that ticking starts is enough to destroy anything the abrasive laden oil comes into contact with. A proper tensioner should last at least 40 -50K km.

 

[Redline]

Cheers for the info.

1000km of running (esp fast running as in touring) once that ticking starts is enough to destroy anything the abrasive laden oil comes into contact with.

Such as?

A proper tensioner should last at least 40 -50K km.

Cheap bike made with cheap parts.

Actually had the spark plug and headline bulb need replacing within the first year, the spark plug at the 12k service, which I found a bit odd. Rear bulb blew within two weeks and was replaced FoC.

The Camshaft Tensioner isn't covered by warranty and is down as 'wear and tear'. Do we really need to replace the headlight bulb, sparkplug and c/s tensioner every year.

 

[arn]

I had more than my share of cam tensioner problems on a CRF 230 derived bike (HH Karizma). The first failed at 30K km. After that there was a load of completely defective spares which arrived at the authorized dealer. Some of those tensioners lasted less than 1 K km, mainly on account of the ribbon "spring" inside being made of some form of dead soft steel, which could be deformed repeatedly in any direction without breaking.

To cut a long story short, one trip with one of these brand new tensioners saw the bike grind to a halt, about 800 km away, fortunately, in a city, and a major railhead at that - it had to be transported back by train.

Damages - block, piston, camshaft, crank bearings, and sundry other items like the timing chain, chain guides.

It took them 6 months to sort out the cam tensioner before they came up with a improved version. One of those has been sitting in that bike for almost 60000 km now, no problems.

 

[sendler]

Yeah, if the cams jumped timing due to no timing chain tension, you could have bent valves or worse.

 

[somebody5788]

If it still runs right now it's not likely he bent valves, it's not very common for cars with chains to jump and bend valves but then again a car doesn't rev to 10k usually.

A tensioner is a very precise piece with very little tolerance for imperfections. If it even had the smallest imperfection it wouldn't take long for it to fail and it's possible you just had a lemon in that respect. I wouldn't expect it to become a common failure but only time will tell.

 

[sendler]

If it still runs right now it's not likely he bent valves, it's not very common for cars with chains to jump and bend valves

Cars with timing belts used to be "non interference" as the belts were known to break if neglected. Most cars that used a chain did so because the valves would hit if the timing jumped. I think nowadays just about any modern engine will hit as there are just too many trade offs involved in leaving that much empty space for the valve cutouts. But, the CBR250R is relatively low compression so who knows. It is probably discussed in the service manual if anybody feels like looking it up.

 

[furious_blue]

It's hard to imagine why they can't design a cam chain tensioner that can 'go the distance'. The Honda Blackbird was known for breaking cam chain tensioners. The one on my Blackbird broke at somewhere around 30,000 miles. The loose chain makes a bit of a racket when it scrapes the case. The replacement broke at somewhere around 50,000 miles.. I decided to just leave it broken and live with the intermittent noise (the bike now has about 70,000 miles)..

 

[arn]

It's hard to imagine why they can't design a cam chain tensioner that can 'go the distance'. The replacement broke at somewhere around 50,000 miles.. I decided to just leave it broken and live with the intermittent noise (the bike now has about 70,000 miles)..

Well, I guess you have got lucky OR the the engine on the Blackbird does not go west even after putting on significant miles on it with a damaged tensioner, unlike the smaller Hondas.

 

[furious_blue]

Well, I guess you have got lucky OR the the engine on the Blackbird does not go west even after putting on significant miles on it with a damaged tensioner, unlike the smaller Hondas.

I went back and re-read your post about the havoc caused by the tensioner on a CRF 230.

The CRF is in the class of engines that would be considered a very high performance race engine ?

The Blackbird while it makes good power and torque is not a really highly stressed engine for sane streetwork.. In normal tune it's not running 'on the edge'.. The part that breaks is just the actual tensioner plunger/pusher assembly, not the tensioner shoe. I guess that makes the tensioner failure on this bike not such a big deal..

 

[arn]

I went back and re-read your post about the havoc caused by the tensioner on a CRF 230.

The CRF is in the class of engines that would be considered a very high performance race engine ?

The Blackbird while it makes good power and torque is not a really highly stressed engine for sane streetwork.. In normal tune it's not running 'on the edge'.. The part that breaks is just the actual tensioner plunger/pusher assembly, not the tensioner shoe. I guess that makes the tensioner failure on this bike not such a big deal..

What we get is a detuned, low compression version of the CRF230, which makes only 17bhp. The mode of failure of the tensioner was similar (spring no longer tensioning the chain) to what you have described.

The similarity end there. Unless you were flogging the Blackbird, the engine would probably be working at 25% capacity even while on the highway, whereas the 17bhp engine is at almost 75% throttle while cruising on the highway at 100 kph, more if there is a headwind or an incline. Those 800 km were all highway, with only one food halt, not long enough for the engine to cool down enough to produce the characteristic noise. Not that I'd have been unduly worried, though, as I had no idea as to the consequences. After that episode, a spare tensioner was always in the box containing the spares.

 

[somebody5788]

Cars with timing belts used to be "non interference" as the belts were known to break if neglected. Most cars that used a chain did so because the valves would hit if the timing jumped. I think nowadays just about any modern engine will hit as there are just too many trade offs involved in leaving that much empty space for the valve cutouts. But, the CBR250R is relatively low compression so who knows. It is probably discussed in the service manual if anybody feels like looking it up.

My old Audi was notorious for snapping belts if you didn't replace them on time, I'm well experienced in that respect. It also had a 10.3:1 compression ratio where the bike has like 10.9 so it wasn't that different. But in cars that come into our shop with rattling chains like is typical on the VW VR6 2.8l engines they VERY rarely damage the valves. It is still an interference engine too.

The best comparison would be to a Honda in this case though. Some of the cars upgrade to the pistons to the 1000RR pistons and yet the stock compression ratio is closer to that of what our 250's have. So they obviously share design characteristics and we've had a lot of high mile Civics in the shop that have skipped timing due to negligence, usually they are savable though.

Like I said, if it still ran he'll probably be ok. If it stopped and wouldn't start then I would be worried.

 

[Redline]

Word back from the dealer and it was the 'lifter assembly' that needed to be replaced.

 

[sendler]

Word back from the dealer and it was the 'lifter assembly' that needed to be replaced.

I wonder what that is. There is nothing in this bike that I would call a lifter. That usually refers to a hydraulic valve compensating element that this bike doesn't have. All we have is the valve shim. I would ask them to see the old part and snap a photo of it before they even have the chance to tell you no. I wonder if he meant to say rocker. Maybe that is your engine rattle. I hope you don't have to wait forever for your part, whatever it needs.

 

[kflaig]

Here's the parts diagram for that area:

FWIW it doesn't look like Honda has replaced any "old" part numbers with new ones in this area suggesting that so far they don't think that there is a bad-part issue.

 

[arn]

Here's the parts diagram for that area:

FWIW it doesn't look like Honda has replaced any "old" part numbers with new ones in this area suggesting that so far they don't think that there is a bad-part issue.

Are you sure that's the right diagram?

I think the cam tensioner is located on the rear of the block near the crankcase, secured by two fasteners

Edit: realized on further reading that the valvetrain was being discussed

 

[250 Tom]

To have a cam chain tensioner go out that quick is just not right. Its either a poor design or poor quality of the part. Way to many problems with a bike thats only in its first year. What the hell is next? Maybe honda should recall all the damm things and start over.

 

[Redline]

I wonder what that is. There is nothing in this bike that I would call a lifter. That usually refers to a hydraulic valve compensating element that this bike doesn't have. All we have is the valve shim. I would ask them to see the old part and snap a photo of it before they even have the chance to tell you no. I wonder if he meant to say rocker. Maybe that is your engine rattle. I hope you don't have to wait forever for your part, whatever it needs.

I'm friends with the American manager who's dealing with it in the dealership and will get all the info I can. The part was due to arrive today but the distribution center is just moving to a new base so it should be just after new year. Usually all parts arrive the next day as the dealership is only an hour away from the dist. center here in BKK.

Will try to get all the info on it.

btw,

The clicking sound that was heard when cold and mentioned by Arn, what exactly is that? What part was hitting off what other part?