cam chain tensioner blow out

[thewiz]

On my 3rd cam chain tensioner plug replacement in as many days now and I'm really loosing patience .....I have glued the hell out of them using 3M 8001 with no luck .... I'm ready to take some of the more drastic measures that I have found here while searching for solutions to fix this for good ..... metal soft plug ala moderator John, JB Weld ... maybe even drill and tap for a pipe fitting ... not sure yet which route I'll take .... BUT ... Do these plug blow-outs indicate a worse problem that requires attention? AND .... Why wouldn't the crank case vent to the airbox siphon off the excess engine blow-by which I think is the causing problem? This a fine running, totally stock F, 50K miles with everything hooked up .....

[John]

Just for $hits and grins, check the crankcase breather port, and the hose for obstructions. Also check the port on the top/front of the airbox for obstructions. I had an overpressurization problem with the Bag Lady. It blew the vent hose off the engine. I found the port in the airbox was plugged. Problem cured.

[thewiz]

Had the seat and tank off yesterday checking to be sure everything was connected up but didn't pull the airbox ... ugggh .. ... guess I'll wrestle it off of there tomorrow and check what you said ... thx, John.

[Ken Talbot]

Normally, there is no pressure behind the plug as the shaft of the tensioner is locked in place - it does not move. However, if the tensioner bolt is stripped, the continual revving and slowing of the motor will change tension on that side of the chain, which will work the end of the plunger in and out. This will pump up pressure behind the plug and blow it out. If the chain is not too worn, you will get away with this for a long time as the chain will be tight enough, even with a loose adjuster, to not jump a tooth on a cam. How confident are you in the condition of the locking bolt on your tensioner?

[thewiz]

hmmmm .....

I have a spare tensioner so I have been keeping one with a new plug glued in so I can swap 'em in a few minutes. All of my XSs have had issues with these rubber plugs. The assemblys feel like they work smoothly ... neither screw or lock nut appear stripped ... but I don't twist very hard on the screw when I preload it to install or on the lock nut once I release the preload either. So ... I'll check that closely on the one I'm about to use and the one I'll take off too ... and make sure that tensioner shaft is not pumpin up the cavity with air and blowing out the plug .... thx for that ..... gotta figure out somethin' ... I'm down to only two plugs left ...

[Ken Talbot]

Re: hmmmm .....

Originally posted by thewiz
but I don't twist very hard on the screw when I preload it to install or on the lock nut once I release the preload either.

Say what?

You push the plunger into the body of the tensioner and lock it in place lightly with the stopper bolt. Finger tight is enough. This is good.

You place the assembly onto the front of the motor and bolt it in place. (assuming correct alignment to the "C" mark on the timing plate, good gasket, etc, etc). This is good.

You release the stopper bolt and listen for the click of the plunger moving in against the chain. This good.

You torque the stopper bolt to 4.3 ft-lbs with a low-range torque wrench as per factory spec. This is very important.

You torque the lock nut to 6.5 ft-lbs with the same torque wrench. This is good.

Is this a more long-winder explanation of what you're doing? You had me wondering when you talk about doing the lock nut right after releasing the pre-load.

[thewiz]

Yes ... those are the steps alright .... I think I have not had the bolt tight enough so the tensioner foot may have been floating some ... ... thus causing the condition you described earlier.

[AlanB]

Hi Wiz,

If the stopper bolt is not tensioned enough, and the plunger is "floating", there should be some pretty clear marks on the flat face of the plunger. You should have no more than a couple of shiny circular marks from the foot of the stopper; if there are "sliding" marks, it needs to be tighter!

Just try to avoid stripping the thread!

You should also be able to check this by looking into the end of the tensioner with the engine running...... before you fit the new plug! If the plunger is moving in and out, you have a problem; it should be clamped tight.

AlanB

[TADracer]

Or ..... you can take a shot at making yourself a manual tensioner and do away with all this. There may even be some aftermarket tensioners that will fit.

[thewiz]

Yup ...

Tadrcr ... I saw that really cool tensioner fab on the forum some time ago ... very slick, but a bit beyond my capabilities, I fear ... love it though, thx.

Alanb ... think you're right, ... I will fire it up and look in there while watching the plunger .... but I'm pretty sure it'll be floating around ... believe I need to tighten the bolt more. Something Ken Talbot mentioned in his earlier reply got me to thinking that I have left it too loose ...probably cuz I know that overtorqueing can strip and bend these fairly delicate parts. I have a low value torque wrench and I think I'm gonna' use it and I bet ya' dollars to donuts it will cure this annoying problem. Soon as it warms up here in an hour (and the Ibuprofen kicks in), I'll give it a twist ... thx for the input.

[skids]

Re: Yup ...

If you run the engine with the tenioner plunger able to move, your valves are going to go south on ya!

[thewiz]

epilogue ..

Today after checkin' to see if I had possibly not tightened the bolt on the tensioner in the bike, I took the spare tensioner, in which I had glued a new plug a couple of days back, and began to install it on the bike in place of the one that just blew out. Before I even got it on the bike and after working the plunger back and forth a few times the rubber plug had immediately begun to squirt out. To my surprise the weather strip cement I had used was still uncured underneath the plug. Thankfully, I had not left the bolt loose as I had suspected thus allowing the foot to float around ... the glue had simply failed. I JB Welded the plug in place this time and rode much of the day and it's still in place. Hopefully this is the end of that story. Thanks everyone for all the input ...