MCS Exhaust questions.

[tammyanddaveky]

Hi all!

Please bear with me, I am learning all this stuff...Poor Hubby and Dad, I have taxed their brains too often...LOL.

I am wondering...on the Greeves MCS she runs like a pro with the Blooie Pipe or Megaphone exhaust (though it does cause the large Newfounland to go bonkers and chase and bite at the tires, I am sure her eardrums vibrate as do us humans within 5 miles of the ole gal ).

We do have an aftermarket up pipe with an early form of "baffling" or oiled mesh like fiber...point...the Greeves doesn't run properly at all with the aftermarket mystery make exhaust IF the baffling is in...she will run very rich in the mid range and just sounds off...I believe the sound is referred to as 4 or 8 stroking??

Now, if we remove the baffling..she runs as good as she does with the megaphone...from reading the above posts I am assuming that the removal of the baffling undoes the "expasion chamber" effect. Am I correct in that?
Now, without the baffling, might as well run the megaphone exhaust as the noise is very close to the same level.

Another note...from running the "high" pipe or aftermarket, you leg tends to lean/rub on it, there is a metal mesh for heat protection of the leg....HOWEVER, just a few weeks ago the pressure from our leg on the high pipe caused one of the studs from the (remember, please be patient and bear with me..I am sure I am not going to use the right part name here) exhaust port on the barrel to break! Fortunately for us...Frank had a bolt that fit, we just ground the head off the bolt, then heated up the barrel very slowly and the old stud screwed right out.

I would love any and all feedback on another form of aftermarket exhaust that would be suitable...would love to see a wassel on her, but haven't seen one that would work, even with modifications. Really...I am all for the megaphone, BUT Hubby thinks it rude even during the day.

Please, jump in and correct my erroneous terms...I need all the help I can get!

Thanks guys!
Tammy

[Brian Thompson]

Hi Tammy,

Hope the leg's feeling better!

Don't worry about being new to all this, there's a lot to learn and it never stops, believe me...!!!

The first thing I'll do is move this post to the Scrambles machines subforum. That's where all the 'mechanical' type posts for the scrambles bikes go (not for the engines though, there are seperate places on the forum for Greeves or Villiers engine stuff!) Really, this area of the forum is more for posts about 'Historical and Archive' information, rather than 'mechanical'/'how to' type queries.

I'm sure some of the guys will have some good advice to offer you and help out and don't forget even more help is available to GRA Members through the club-have you joined up yet?! To be honest it sounds as though you could do with trying to find a good book/website that can help you understand some of the 'basics' of how two stroke engines and exhaust pipes work together. This will help you interpret any responses the lads give to your questions, and assist you in undersatnding how to set the bike up. It might even be worth entrusting the 'final set-up' to a GOOD bike shop local to you, someone that understands classic two strokes. Could be a good investment having come this far with the resto? The racing guys over in the UK have to abide by pretty strict noise regulations and the old megaphones are rarely used thease days. They were nicknamed 'vacume cleaners' due to them sucking up all the dirt into the engine due to their location underneath.....a point worth bearing in mind as well as the loudness issue!

With these bikes the exhaust system is a very important part of how well the engine runs, as is the condition and settings of both the ignition system and the carburettor, not to mention other things like the condition of the cranckshaft seals inside the engine. This gets even harder if the pipe is non-standard...!

Every engine tends to vary a bit on settings too, so it's not always easy to give precise settings that will work for one bike to the next. Start by making sure that the ignition timing is SPOT ON, and the carb settings (including jet sizes, slide, etc) are also as near to specs as possible, then go from there.

Brian.