610 cam chain rattle

[Flynn]

Hi, is this the sound of a cam chain rattle:



I have done about 360 miles since the cam chain and rocker arm bearing job. I plan to take a look inside the engine at the 1000km mark (620 miles) after which I will update my findings with pics.

Nerb1 (a motorbike vlogger on youtube) had a Husqvarna 610 and said that his engine blew because he didn't replace the cam chain tensioner with the cam chain.

I questioned this on advrider.com and the boys generally thought that it wouldn't have made a difference as the cam chain tensioner only exerts a little force on the plastic guide blades.

Here is the thread:

http://advrider.com/index.php?threads/cam-chain-tensioner-help.1117439/

Here is the Nerb1 video were he mentions in detail in the comments section the reason for failure:

Here is the cam chain tensioner disassembled:

Now, I may not be very clever, but other than vibrations causing it to advance (which would seem a bit hap hazard) I can't see how it is meant to work.

Based on the advice I have received on the venerable advrider.com I just put it back in and adjusted it so that it is touching but not exerting pressure on the guide blade, but I am paranoid about it not working.

Also it would appear that I have an oil leak from the base cylinder gasket:

 

[Spice Weasel]

My bike leaked like that before i sealed the rocker cover with gasket sealant. Check yours is sealed properly. I put some sealant under the heads of the inspection cover bolts aswell.

 

[Flynn]

Thanks for the tip, I only used a thin smear of anaerobic sealant (which doesn't seem to seal that well) for the rocker cover gasket as it is not under any pressure. I am more worried about the engine sounding like it is going to shake itself apart!

I am sure it wasn't sounding like this a few weeks ago, it sounded quieter I think. Maybe it is my idle speed which has gone up and causing a resonance, who knows.

 

[Spice Weasel]

Thanks for the tip, I only used a thin smear of anaerobic sealant (which doesn't seem to seal that well) for the rocker cover gasket as it is not under any pressure. I am more worried about the engine sounding like it is going to shake itself apart!

I am sure it wasn't sounding like this a few weeks ago, it sounded quieter I think. Maybe it is my idle speed which has gone up and causing a resonance, who knows.

I just went to TMS in town and got a big tube of black gasket sealant, i use it for everything, havent had any probs yet. I do think your bike is noisy, but would wait on other opinions
This is the only vid i have of my bike running, for you to compare
> Click for link to video <

 

[Flynn]

You're bike sounds hella smooth Weasel. I am tempted to go and tighten the cam chain tensioner up manually but since the mechanism is supposed to be auto tensioning I struggle to justify doing that rather than let it do it's thing, assuming I reassembled it correctly and it's working. I do plan to check everything over at 1000kms, there is a chance I may have access to a garage for a period of time in which I will be able to do that as I really don't fancy doing it out on the pavement.

 

[EricV]

I am tempted to go and tighten the cam chain tensioner up manually but since the mechanism is supposed to be auto tensioning I struggle to justify doing that rather than let it do it's thing, assuming I reassembled it correctly

My opinion is that if you have any doubt about the CCT being re-assembled correctly, or working properly, then you'd do well not to go with a "ride and see how it goes" approach. I'd suggest playing w/ the Search function here and on AdvRider- I recall there being a thread that had a good dis-assembly/re-assembly pictorial. If I'm recalling correctly there's even a how to on how to make the stock auto-tensioning CCT into a manual CCT, but I could be wrong.

 

[mg94]

That sounds more like valves needing adjusting.
The cam chain is pretty easy to check: just unscrew the two screws holding the CCT assembly, use a screwdriver to charge the spring, insert the CCT assembly and then release the spring while hodling the assembly against the cylinder. Then, lock the spring again and see how much stroke you got left. If it's nearing the end of it, replace the chain. Keep in mind that your CCT doesn't have tick marks on it, so it's a bit trickier to check how much you've got.

 

[Flynn]

Just an update on the search. So far I have found two threads and in both of them videos with the bikes making the same rhythmic clicking noise. I'll keep you posted.

 

[Flynn]

Well, here are the fruits of a forum search spanning two days.

These videos all have the same top end sound:

No answers yet though. Suggestions are mainly valves and cam chain tension. The auto decomp activating makes a less regular and deeper sound.

That sounds more like valves needing adjusting.
The cam chain is pretty easy to check: just unscrew the two screws holding the CCT assembly, use a screwdriver to charge the spring, insert the CCT assembly and then release the spring while hodling the assembly against the cylinder. Then, lock the spring again and see how much stroke you got left. If it's nearing the end of it, replace the chain. Keep in mind that your CCT doesn't have tick marks on it, so it's a bit trickier to check how much you've got.

I have just replaced the cam chain (since done 600km) and I have also stripped and cleaned the tensioner but I don't trust it:



I put the tensioner back together but I don't know where the spring goes, so I just left it at the bottom. Is it supposed to slot into any of the internal components? This is how I put the tensioner back together:



I know the spring is in there but how does it engage the rest of the mechanism?



It would be a shame to do the hard work and then find that the cam chain is wearing too much because the tensioner wasn't working properly.

I find it hard to visualise you're description of checking the tensioner, I understand how to check the one with the clicks but not how to check this type.

I just don't understand how this tensioner is meant to work. Every thread on this website assumes that you have the new type of tensioner with the ratcheting mechanism.

I want to adjust the tensioner but I don't want to adjust it the wrong way. I don't want to reset it by accident because I tensioned it with the engine open last time I did it so I don't want to have to open the engine again to tension it.

Is it okay to try adjusting the tensioner with the engine running to see in real time if it has an effect on the ticking noise or is that a sure fire way to blow the engine?

I am going to do some listening around the engine with a screwdriver and then the next step will be to try tightening the cam chain tensioner slightly, but it will be most beneficial if I can do it with the engine running but first I need to know if that is safe.

 

[Flynn]

I forgot that I made this thread. As an update, I adjusted the valves to .006mm but I tested it with a .005mm feeler gauge and it felt the same as it did with the .006mm so they are at spec allowing for a margin for error.

I can only suspect as someone suggested on advrider that a loose cam chain is causing the valves to be loose at idle. I have tried to rev the bike up and listen for the valve lash but it is hard because I can't tell whether the noise is being drowned out or going.

I am going to adjust my auto tensioner manually and see if that helps.

 

[Flynn]

Today I tackled this issue. I have been wary of doing anything regarding the cam chain tensioner in case it made the chain loose and skip.

I was very careful and took the tensioner out. Immediately I noticed that it was still at the minimum adjustment.

There are two sounds, both of which are caused by the tensioner and cam chain mechanism.

I noticed that the plunger was very loose and could be shaken in and out even though it was at the minimum adjustment. When the plunger shakes it shakes against the adjustment screw which shakes against the housing and that is responsible for a "loose marbles" sound in the engine.

But the main loose valves sound is coming from the cam chain vibrating against the guide blade and then the guide blade vibrating against the tensioner.

I confirmed this by adjusting the tensioner with the engine running. The trouble is the tensioner won't stay put.

If I could find out what pitch the screw is I could try jamming it with a nut or replacing it with a threaded stud and use a jam nut with that.

Rather than pay £50 for a simple mechanism.

Here is how the tensioner was:

Yes my cam chain was new but regardless the tensioner wasn't even against the guide blade.

Anyone got ideas for modifying this type of tensioner so that the plunger stays put?

 

[BiG DoM]

IMO - Do not monkey around - spend the money and buy the APE manual tensioner and peace of mind.

 

[Flynn]

Okay, point taken I am very pleased that I finally got to the bottom of this issue and can make my bike sound normal. Edit: Gonna try some threadlock on the adjuster screw as a temporary measure.

 

[Flynn]

Well I know this might be considered "monkeying around" but I can't see how it would hurt. I used a nut on the adjustment screw to jam it and keep the tensioner plunger about 1.5mm (about 1/3rd of it's travel) out at all times. No more cam chain rattle and a manual tensioner for free! It just means I have to use nuts like shims to adjust it rather than turning a screw.

I also noticed some threads missing from the adjustment screw which is why it is not holding it's adjustment. It's not getting off the bottom rung so to speak.

 

[BiG DoM]

Indeed a manual tensioner is not rocket science and I guess if it works for you, and as you say for free, well go for it!

 

[Flynn]

Also just Googling for cam chain tensioner info it turns out Husky copied the Honda design for this type of tensioner.

This video shows an XR400 tensioner and it is exactly the same right down to the internal gubbins:

That is the best way to convert it to manual.

Although the threaded rod he uses looks like it has threads which are way finer than what the threads are in the tensioner housing, but go figure.


Edit:

Okay, I had a go at this today after my threadlock temp fix didn't hold.

You use the cap screw hole (the screw that covers the adjustment screw) to screw a rod or long bolt through.

The only problem with this method is that it still lets the plunger go in and out (but not past the minimum you have set) which causes an annoying rattling.

After I had done what was suggested in the video I had the idea of putting all the internal gubbins back in and then screwing a bolt in place of the access cap screw to prevent the adjustment screw from being able to back out.

Then the adjustment screw would hold the plunger and not let it rattle around so much. I might try that tomorrow.

Anyway, the below pictures show the steps and they create a functional manual tensioner although unless you have the plunger adjusted all the way out there is scope for a quite annoying rattling sound, but it is perfectly safe.

Adapting the tensioner:


The finished article:



What you should have taken out:


I hope this saves someone the hassle of thinking they have to find a manual tensioner. I think the best option might be to simply replace the cap screw with a longer screw to hold the adjuster screw in place though otherwise the rattling will be annoying.