MORE of the CAM CHAIN ADJUSTER/ TIGHT NEW CHAIN syndrome

[timmer]

From what I've read here , this seems to be a common situation.
This is the 1st one of these motors I've done.

What I have now is :
New chain/ New top end,
The sr500 mod to the cam chain guide (that Jim turned us on to)
Head & rocker box torqued.
Valve adjusters backed off yet,

At first it seemed the 6 holed base plate of the Cam Chain adjuster wouldn't seat.. the chain is so tight.
but, after backing out the adjuster nearly out it seated and I stuck the 6 bolts in.
I rolled the crank nut round by hand a few times with no binding and yet I'm wondering if I should be investigating further or if this sounds typical to you gents.
The acorn cap on will only screw on leaving roughly .080" space before seating,
(hand tight). Will this chain loosen enough after it runs for a few minutes?
Any thoughts appreciated

 

[5twins]

There seems to be a rash of these scenarios lately and I just don't understand why. New chains have always been tight, but they can't be any tighter than they've always been. The rear run of the chain will be pulled taught with no bow from slack in it, that's as tight as it can be (and has always been). I've put in probably half a dozen new chains over the years and never encountered this issue. As I suggested before to someone else with this issue - maybe add a washer under the acorn cap nut so it will tighten down without bottoming out on the adjuster screw. I'd leave it there for the 1st few runnings of the engine until the chain loosens up some. You don't want the cap nut bottoming out on the adjuster screw because it will start turning it in tighter as you continue and finish tightening the acorn nut. That will press the tensioner into the chain really hard, probably too hard, and rapid wear could occur in the tensioner rubber shoe. The chain may stretch out quickly and prematurely too.

 

[Jim]

The sr500 mod to the cam chain guide (that Jim turned us on to)

It was pointed out in that mod thread that MikesXS chrome guide nuts stick about a MM further into the chain cavity... pushing the guide in the same amount. That would make the chain tighter. Did you use Mikes nuts or the originals?

 

[authenticnovelty]

I had a similarly concerning situation with a new endless chain installed in an engine rebuild last week (My first as well).

Mentioned beginning here:
http://www.xs650.com/threads/1978-x...whining-engine-sound.54000/page-2#post-592529

Definitely worth noting Jim’s suggestion on the guide nuts if you replaced. I kept the originals and only replaced the chain, the guide and the tensioner arm.

Cut and dry, It pretty much goes as 5twins said above...

I installed the tensioner plate without the tension rod or threads in then added after. I initially disregarded the cap nut on the first start and set the tensioner following standard procedure then valves and ignition etc. started engine with a few kicks and let it run for a while. Maybe half an hour as i checked around on things and let fresh oil circulate through the system. I dabbed the oil that had dripped from tensioner, hand tightened the cap nut back on until it stopped naturally without turning the adjuster. Nothing was adjusted further, so there was still a gap between the cap nut and the plate. I went for a 4-5 mile ride at low speed below 3000rpm to run through the gears and feel things out then let it rest overnight. The following morning the chain had stretched and the tension issue was resolved. I reset all adjustments cold and the cap nut fit as normal.

Its definitely unnerving initially. Hope this helps.

 

[timmer]

Thanks Jim/ 5 twins/ and authentic !
I suspected and was concerned that this was going to take place, given the fact that the whole "getting the link in with a new tight chain / yet cam timed has been posted quite a lot. My tensioner arm assy is original. My chrome guide nuts are OEM with annealed original copper washers. Did two of the sr500 guide mods, 1st one's usable probably, but I bought shit for two so I went to match JIms numbers to the nats ass, LOL
5twins: I do have the type E (is it?) tensioner. my threaded piece measures 60 mm , and the pusher is 14 mm. Is this wrong >? its a 447 motor I bought on it's own, it's motor number starts 2FO / 1978 ?

 

[650Skull]

78E, 79F, 79SII, 80SH all started with 2F0..........

 

[authenticnovelty]

This thread should clear up any questions you may have regarding tensioners.

http://www.xs650.com/threads/cam-chain-tensioners.1056/

Also, once you identify your exact bike via the full serial number, it is worth noting that early 1978 standard and the late 1978 special series is a transion point for many parts on the bike, including the tensioner according to this thread. My early 78 has a D tensioner, even though the bike is called an XS650E. I’m assuming the XS650SE would include the E tensioner.

 

[5twins]

The letter designation for year or model really isn't related to the tensioner letter designation. The type D tensioner was installed from the '76C model up into the '79F models, but you will find a type E tensioner on some '79 bikes. Not sure if it was a mid-year change or possibly model specific, like the Special got the type E while the Standard continued to get a type D. I guess it's really not important exactly when the change occurred. It's easy enough to tell the two types apart just by looking at them and their parts. The important thing to know is that it's a good idea to upgrade to a type E if you have a type D.