Exhausts/Silencer and bits.

[lavrentyuk]

Having had my exhaust collar vibrate loose, rapidly joined by the bolt holding the silencer/Exhaust clamp to the bottom of the engine as I couldn't immediately pull over, meant that the collar self destructed its M50 thread on the tarmac.

Bugger.

I was firkling through my extensive collection of used bits this morning and discovered that I have a few different sizes of threaded exhaust collar, and at least two types of exhaust.

As I have had various engines over the years - and am currently running a 301 engine in a 250 frame and running gear - is anybody able to determine the differences in set up? Any measurements in difference for the threaded collar? Which exhaust (250 or 251/301) has the tighter bend?

This is the trouble when for years you just lob various bits into plastic boxes without labels as indicating what they came off.

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[lavrentyuk]

I spent a good hour looking at exploded parts diagrams to no avail as yet.

A few years ago I'm sure I knew the difference in the bend of the pipe - but can't remember now. Thanks for the above anyway, I'll have a perusal.

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[lavrentyuk]

I find myself wondering if the flange twixt thread and collar might stop it going the whole depth on one or the other, thus enabling it to vibrate loose if it isn't pushing all the way up against the gasket. I have both types. The length of the thread appears the same.

Exhaust wise there is a different bend and length - I believe the 251/301 needs a tighter curve to clear the mudguard, but other opinions and experiences are available.

[Blurredman]

Didn't something that might be pertinent to this thread come up already fairly recently?




viewtopic.php?f=5&t=12536

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[lavrentyuk]

Indeed, and memory says that is what happens when a 250 header pipe is used.

I'm used to tightening the giant nut every year or so, but not every trip which has been happening.

It gets rather too tight for normal loctite, and I usually use a high temperature grease (copper or aluminium) so it doesn't weld itself in as can happen on my old BMW, but I'm going to safety wire it on now as a belt and braces approach.

[Andy_C]

From someone who has had a few MZs over the years.

To keep the barrel nut from undoing itself on all my bikes I used to lockwire them in position.

If you drill a small hole through the front engine bolt you can easily get some lockwire through the hole and then one of the square shaped cutouts in the nut in a position so that when you tension the lockwire it is pulliing the nut tight.

It sometimes takes a while to get the wire in just the right position.

Never had any problems with the exhaust barrel nut becomming loose after wiring them in place.

I no longer have any MZ's but sometimes drop in here.

Cheers/

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[lavrentyuk]

I find the 2T oil turns into a cooked solid at that hot point, and whilst it *may* help it seal it can also make it difficult to get off. Decoking - a rare thing with modern oils fortunately - starts there. The HT grease is something I was taught to do in the dim and distant past after several bikes had problems with corrosion in that area. Can't really be helping the collar stay in place though. This is the first MZ that I've had this repeating problem with - and I've had a few.

I will likely wire it on regardless now, had enough of messing with it. I shall also be putting a bit of Silicone on the sealing area. Should stop the 2T oil from penetrating towards the thread and cooking there as well.

Had a bad back for a few days now but as soon as I'm up and about again I will be playing with various collars and exhausts in the workshop.

Old bikes, don't you love them.

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[lavrentyuk]

[img][img]https://www.mzriders.com/gallery/pic.php?mode=small&pic_id=1180[/img][/img]

A photograph showing some of the available exhaust collars.

Not the flange behind the thread on the top one. The differing lengths of available thread on the bottom two.

The middle one was acquired from Burwins today = and is described as suitable for Saxon 251/301 engines (which mine is from) and Kanuni (got one of those in the back of a garage too).

I shall be playing with them next week when my spine co-operates!

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[lavrentyuk]

I have more - but these are the three types. Most are the top one, which is what I've been using. Interesting that Burwins - a pretty knowledgeable crowd when it comes to MZ - sell the middle one for 251/301s. I have a clutch of gaskets so will be trying them all and report back.