Aftermarket muffler size question

[Guest]

Hello all. Right now my '80 GS850G has a 4 into 1 exhaust with a really beat up Yoshimura short exhaust. I would like to replace it with another muffler. The ID of the header where it meets the midpipe is a good 2 3/4". Would it be too restrictive to purchase a muffler that has a 2" or even 2 1/4" inlet diameter? My carbs are VM29's.

Thank you,

Raz

[Steve]

Something doesn't jive here, if you have an '80 850, it should have BS32 carbs, not VM29s.

Regardless, unless you are looking for the ultimate in free-flowing exhaust hardware and that last tenth of a horsepower, there should be no problem with a smaller inlet.

My son's bike has what I have been told is a Jardine system on it. Although the inlet to the muffler is about 2 inches or so, it all ends up going out a 1-inch hole at the back.

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[razooki]

Steve, it came with those carbs when I bought it last year. At the time I tried to get them identified and they are indeed VM29s.

[Steve]

OK, let's try going the other direction:

Are you SURE it's an '80?

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[razooki]

Well, that's what the papers say. I know this question came up last year when I was trying to identify the carbs and apparently (at least in Canada) there might have been some '79 parts that were used on the '80 models.

[Steve]

Forget the papers, what does the BIKE say?

Look at the serial number plate on the steering neck.

A few other parts to notice:
Brake disks, solid or slotted?
Charging system, separate rectifier and regulator or combined?
Ignition, points or electronic triggers?
Turn signal cancelling system is different from '79 to '80, easy to tell by control on left handgrip.

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[koolaid_kid]

Does it have a kickstarter?

[Steve]

Hah! Forgot about that one.

That would be a REAL QUICK indicator, wouldn't it?

Or would that be a real KICK indicator?

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[razooki]

Going by the VIN it's a 1980. It has slotted rotors and no points, the R/R was all in one but I replaced it with a Yamaha one I think. No kick starter.

[Steve]

Well, all that says it's an '80, I just wonder why it has the VMs on it.

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[razooki]

That question I will leave to those more knowledgeable than me to answer. They are VM29s because they have the 2 cable set up and the large bolts for the bowls. I know the PO had ordered the carb boots for CV carbs because they were way too large for the VMs. From that aspect I got the bike for a bargain because I did not even pay for it what these carbs are supposedly worth. Maybe the PO changed the head with one with the smaller ports for the VM series carbs? At any rate, back to my original question, I guess I'll be OK if I get a muffler that has an opening smaller than the one on the headers?

[Steve]

Yep................

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