WR250R Cam Chain help needed

[simonpig]

Whats up wrenching gods. I'm stuck. Heres the situation:

After 20,000 miles, my WRR engine starting feeling loose. Seems like the Cam chain has developed some stretching, so I decide to order a new cam chain and am in the process of replacing it.

Several mistakes were made in the order of operations:
1. I remove the tensioner before spinning the crank to TDC mark on the flywheel. After several cranks, its seems like the valves stopped at their natural TDC position—as chain starts skipping on the cam gears, not sure?



2. Second question is, How the hell do I remove the cam chain? Do I have to actually split the case? Or is there a chain breaker tool, master link setup, I'm missing? Its a continuous chain.

[clintnz]

Do you have the maintenance manual? If not get one. It's relatively easy to follow.

It probably doesn't matter much if the crank isn't at TDC now, or where the valves are, it will matter when you go to reassemble. The manual will have detailed instructions on setting up the timing.

Dunno about the WR but it would not be unusual to have to remove the head & some stuff off the end of the crank to replace a continuous cam chain.

Measure up & compare the 2 chains before you install the new one - higher miles WRR's are rare & any info about what wears out & when would be very useful to those who are racking up the miles.

Cheers
Clint

[simonpig]

I do have the manual, and it looks like I will need to remove the generator, and some other stuff off the end, which worries me because I'm not sure if I need specialty tools.

After doing some independent internet research, it looks like I've solved the first question—the answer being very simple. When going to reinstall everything, turn the Crank to TDC mark, set the timing marks on the cam gears to match with the lobes pointing at 10 and 2. Done.

[ttpete]

You'll probably need a puller to remove the alternator rotor.

[Pete-NZ]

Brake the old chain... brake the new chain..join them togeather
pull the new one though as you pull the old one out... disconect the two
re-pin the new one back togeather...
The guys at the local Honda shop showed me that years ago..
I have done 3 bikes that way...

[simonpig]

How do you rivet the pin back securely. Don't want to risk it breaking inside the motor. Save a youtube video where someone tacked it with a tig welder.

Bought a rotor puller and am waiting for that to arrive. The other tool called for was a sheave for holding the rotor, but I have a impact wrench so don't need it for removing, though reinstalling might be a problem?

Originally Posted by Pete-NZ

Brake the old chain... brake the new chain..join them togeather
pull the new one though as you pull the old one out... disconect the two
re-pin the new one back togeather...
The guys at the local Honda shop showed me that years ago..
I have done 3 bikes that way...

[ttpete]

I don't think you'll need to break the chain on that one. That's done on multi cylinder bikes that have the chain coming up between the cylinders.

[markk53]

Your bike uses a HyVo chain. It should not wear out in 20,000 miles, they should last the lifetime of the engine. If it is worn out it would be the fault of a junk cam chain tensioner. I do know about those since I've been involved in making tensioners for Kawasakis and now Hondas for the past three years. Automatic tensioners mostly suck in design, especially the ratchet style. That is how I got into this, junk tensioners in two of my bikes.

Measure your cam chain over the prescribed number of links to see if it actually IS worn out or if you are dealing with a JUNK tensioner. My bet is at the least the tensioner is junk, possibly chain too, but possibly not if you're lucky. There is no way in hell I'd ever put an automatic cam chain tensioner back in a bike if the cam drive failed. I went through two OEM tensioners in my KLX650 in less than 14,000 miles, the last one allowing the cam chains (2 on the 650) to wear beyond tolerance.

After installing the manual tensioner I have over 30,000 miles with only about .050" adjustment made as the new HyVo chains seated in. Virtually no adjustment in the past 10,000 or more miles... I forget when I last did it. You adjust the tensioner when the engine is at full operating temperature if the cam drive ticks, not clatter, but ticks. I also had to put a manual tensioner in my Zephyr 550 - that was actually one I had to make so when I did I made five of them and sold the five. It kind of blossomed.

If you want to take care of the tensioner issue, contact me and I will see what can be done for a manual unit for less than any other company will sell one, probably $30 plus shipping. I have fitted one for a YZF425, but don't know if it fits up to any others. It is identical to that of a KLX650, but uses a different thru bolt set up which is no big deal. All I need is the pattern of the tensioner body.

Here is a sample of my work in a KLX250:



If you want references for my abilities should you need them, just do a google search on Krieger Cam Chain Tensioners. Like I said earlier, it kind of blossomed. I've sold tensioners in 29 countries and I think now to all 50 states in the U.S. and all provinces of Canada, to the tune of around 700-800 units. You'll find a lot of satisfied riders, including some on this forum. You may find where I worked with a KLX250/300 rider to make the tensioner (apparently the only one available for them). I can help if needed. Email me from here if you wish.

[simonpig]

Interesting. I had a feeling it might be the hydraulic cam chain tensioner. The only thing is that upon inspection, you cant tell its working or not since it relies on oil pressure.

The cam sprockets look ok to me, and not worn at all. I was going to pull the rotor today and pull the chain to compare it to a new one to see. You mentioned measuring it while on the crank. How do you do that?

FYI, just want to note this the WR250R dual sport model and not the 250F racing yamaha's. Does this manual chain tensioner work on my bike?

Originally Posted by markk53

Your bike uses a HyVo chain. It should not wear out in 20,000 miles, they should last the lifetime of the engine. If it is worn out it would be the fault of a junk cam chain tensioner. I do know about those since I've been involved in making tensioners for Kawasakis and now Hondas for the past three years. Automatic tensioners mostly suck in design, especially the ratchet style. That is how I got into this, junk tensioners in two of my bikes.

[simonpig]

Rookie mistake, bought a rotor puller 33mm x 1.5 outside thread, as opposed to "M33" x 1.5 inside thread puller. Arghhh. Oh well, must stay zen...

Pulled the generator cover today, zipped off the rotor nut with an impact wrench, but had to leave the guts open until I can get the proper tool.

Going to see if I can borrow one from a friends shop tomorrrow.

[markk53]

Originally Posted by simonpig

Interesting. I had a feeling it might be the hydraulic cam chain tensioner. The only thing is that upon inspection, you cant tell its working or not since it relies on oil pressure.

The cam sprockets look ok to me, and not worn at all. I was going to pull the rotor today and pull the chain to compare it to a new one to see. You mentioned measuring it while on the crank. How do you do that?

FYI, just want to note this the WR250R dual sport model and not the 250F racing yamaha's. Does this manual chain tensioner work on my bike?

I've been in touch. I am getting a gasket to do the job, we'll communicate on this. I've done the CBRF/F2 and the CBRF3/F4/F4i tensioners which used oil pressure. They just block off the flow, no problem.

There should be a spec for measuring the cam chain while on the bike if it is a dual overhead cam. It is measured from one pin to another over a certain number of teeth. Unless you have several thousand miles with a junk tensioner, I'm betting it's still good.

[simonpig]

Was able to borrow KTM spec generator rotor tool which worked. Finally pulled the chain and compared the old with new. Guess what, the chain is fine.



It was a hassle tearing into the engine to find this out, but I don't mind. I'm happy to have the experience.

Now I know the chain isn't the fault, it just must be something with the tensioner.

The only other thing would be that the valves are so bad out of spec that its causing the chain to feel like it's loose inside the engine? Is that even possible? I'll leave that to more experienced mechanics to explain.

Going to put it all back together and then check the valves to see where they're at.

[simonpig]

Thanks for reaching out. Let me know if you'd like me to make any measurements for you to the existing tensioner or to take pictures of it.

Originally Posted by markk53

I've been in touch. I am getting a gasket to do the job, we'll communicate on this. I've done the CBRF/F2 and the CBRF3/F4/F4i tensioners which used oil pressure. They just block off the flow, no problem.

There should be a spec for measuring the cam chain while on the bike if it is a dual overhead cam. It is measured from one pin to another over a certain number of teeth. Unless you have several thousand miles with a junk tensioner, I'm betting it's still good.

[simonpig]

Measured Valves today to order shims for adjustment, the readings after 20K are as follow:

EXHAUST
Left: .009" (.23 mm)
Right: .010" (.25 mm)

INTAKE
Left: .005" (.13 mm)
Right: .004" (.10 mm)


The Factory Specs are
EXHAUST: .0091–.0118" (.23–.30 mm)
INTAKE: .0051-.0079" (.13–.20 mm)

Not bad for 20K, no?

[Jedaha]

Originally Posted by simonpig

Measured Valves today to order shims for adjustment, the readings after 20K are as follow:

EXHAUST
Left: .009" (.23 mm)
Right: .010" (.25 mm)

INTAKE
Left: .005" (.13 mm)
Right: .004" (.10 mm)


The Factory Specs are
EXHAUST: .0091–.0118" (.23–.30 mm)
INTAKE: .0051-.0079" (.13–.20 mm)

Not bad for 20K, no?

Clearances look good for the mileage, when comparing to my WR250F I just rebuilt the head after 6,000 kms.
I was adjusting the shims every 1000 k's, it drove me mad, thats main reason I bought a WRR.

The WRR I bought has 10,000 km on it and it too sounds like the cam chain is slapping around a bit.
Especially when you rev the bike and the revs fall back, there is a clatter at a certain rpm.
Have you resolved your would be tensioner issues.

As far as the timing chain is concerned mine on my WRF was stretched at 6000 Km as cam marks could no longer be aligned, so I replaced it. It's good that the R model is not wearing them out as quick.