11 replies to this topic

[fenghuang]

Simplex off. Duplex set going on.
Fitting it with the engine in the car.
The set came with a split chain, and a joining link with two tiny circlips.

The crank sprocket goes on easily.
The cam sprocket is very smug. So snug it's difficult to know when the key way and woodruff key are miso ex, or whether it's just tight.

I've greased the end of the cam, but that hasn't helped so far.
I wondered about beating the sprocket up to make the fit easier, but didn't know whether that could make enough difference whilst not being too hot to hold.

Any tips for aligning the cam sprocket with the key and then knowing it's on far enough?

AND
Having read cam chain tensioners aren't necessary with duplex chains, I've removed mine (including the bracket).
Although I've not managed to get the sprockets on properly yet, it does look as though there will be a little bit of slack in the chain. Is this as it should be?

[gazza82]

The cam will go on once you start to tighten it. Clean up the inner surface that goes over the cam with emery but I wouldn't heat it at all or you make take the temper out. It should have .002-.004" end float when on with a new "triangle" plate. Mine is tight on the cam but I've put in on and taken it off a couple of times although it will only "seat" if I tighten the nut on the cam. And it does need a little leverage to get off again.

 

I remember on the Midget I fitted a duplex to there was a small amount of play in the chain, but I've not fitted my new IWIS chain yet to this engine to check .. still getting the crank woodruff key to fit! (My IWIS chain also has two small circlips so you may have the same). So leave the tensioner on even with a duplex ...

Edited by gazza82, 12 October 2015 - 03:29 PM.

[KernowCooper]

I run the tensioner with a duplex chain, and so does AC Dodd the engine Guru here on TMF

[fenghuang]

Any tips on getting the keyway aligned when you can't see the key?

I was only thinking of heating up the sprocket with boiling water, or a hot air gun. If the thermostat opens at 82c that should be a long way from hot enough to effect the temper.

I assume there isn't a duplex tensioner?

[Spider]

I like to get them 'snug', just firm enough that they need light leverage to get them off. On many builds that I do, they used fixed sprockets, so I tend to have them on and off a few times during the build so reaching for the puller every time would be an unnecessary PITA.

 

Sometimes the bores of the sprockets need a little work, some 240 - 400 emery is fine for this.

 

Sometimes the Keyways need touching up. I trial fit the keys, before trying to fit the sprockets. You could use a diamond file on them (I've got some broaches that I use). A small lead on taper on the keys can also help get them started when fitting them altogether.

 

I often use a torch pointed under the cam sprocket to be able to see and line up the keyway to the key.

 

I like the factory tensioners and always use them, they are really good. Not sure why someone would suggest not fitting them? Maybe in an all out racer where you're chasing every 1/10th of a HP you'd leave it off, but for a street engine that you'd like to get some decent milage from, the tensioners are great.

[fenghuang]

Post deleted.

(2hr 30m of tring to fit the ******* can speocket and finally there.)

Edited by fenghuang, 13 October 2015 - 12:38 PM.

[Spider]

So, just to clarify a little, with the chain on the sprockets, and if you turn the crank or cam a little, you can get the keys lined up and they'll go on?

 

Yeah?

 

OK, so fit them!  It won't matter if the dots aren't aligned at all, as long as when the chain is first fitted, they are aligned, after that, you can rotate them around as much as you like. You can (and should) check before putting them right home that the dots align, just in case something got out of kilter. 

[fenghuang]

Apologies.
2min after I posted the now deleted re-plea for help I got the buggers on. I thought I'd hit Send on the post edit but had obviously lost the signal on my phone.

Pure luck that I got them on. Just a lot of jiggling and swearing.
I did consider putting the sprockets on and then worrying about the chain, but I wasn't at all incident that I could a) align the pro mets correctly once they were fitted, or b) get the tiny circlis on the chain joining link whilst reaching down the side of the engine bay. If I'd been doing it with the engine out, that would have been different. But I'll know next time to take the engine out!

Thanks for the help anyway.

[Spider]

Just a lot of jiggling and swearing.

 

Oh, I think that's our collective bad.

 

We all assumed - incorrectly - that you already knew that you had to swear, it doesn't work otherwise.

 

Glad you got there in the end.

[fenghuang]

Perhaps if I'd start swearing earlier, I could have used a lower profanity setting throughout, rather than using a ****** big ****** later.

[Spider]

Perhaps if I'd start swearing earlier, I could have used a lower profanity setting throughout, rather than using a ****** big ****** later.

 

I guess, though I've never tried that approach.

 

I start BIG and end BIG, though some days, I'm sure it still isn't BIG enough,,,,,,

[fenghuang]

Gives an entirely new meaning to cross head screwdriver.