Exhausted GT750

[tz375]

After last week's trip to the dyno and seeing how much smoke came out of the exhausts until the bike was warmed up, I thought I'd take a peak inside.

Obviously it ran hard and burned off any surplus oil, so they are probably pretty clean inside

OK, I admit I know that isn't close to being true, but I was interested to see how bad they were. Construction is fairly simple. The four baffle plates through which the baffle tube passes are spot welded to the inner half of the muffler shell and it's easy to see the spot welds. In addition there are two damper plates of perforated steel welded into the front sections of the pipe with a series of small sport welds.

Splitting the pipe was fairly easy and took about 30 minutes with an angle grinder to grind both upper and lower weld flanges down far enough to get past the weld ins down to virgin metal (about half way). The front edge had to be cut through with a hacksaw and so did teh rear (outlet) end of the muffler.

The amount of oily carbon in there was nothing short of ridiculous - probably half a pound in one half shell. What that does to performance is anyone's guess, but I'm going to speculate that the effect is not positive.

If anyone is interested, I'll post some pictures of a fileted muffler.

[Craig380]

I'd like to see that please, TZ. A couple of years back someone cut open a GT550 upper pipe to see what was inside, which was revealing about the design of the pipe ....

The design seems completely at odds with performance requirements, with the flat baffle internal plates etc. According to pics on Rick Brett's UK Kawa site, the internals of early Kawa triple pipes on the H1, S2 etc are effectively an expansion chamber within the chrome outer shell ....

[Barry S.]

Yes, please post them, makes you wonder if a straight pipe wouldn't run as well as stock.

[Suzsmokeyallan]

Here we are somewhat back on a topic that you and I agreed to disagree on Richard, the "timing" of oil the pumps delivery on its initial metering slope.
It will be interesting to see just how much unburnt oil you are actually throwing into the pipes on a stock pump lever setting.

[tz375]

Not exactly Allan.

What I offered to upload were pictures of a set of old pipes that last ran 20 some years ago under who knows what conditions. There's no connection between years of old oil in these pipes and how I adjust my oil pump for modern oil for the way I run my bikes. We are looking at ancient history here. I'm not offering to dismantle new pipes that I have run on a bike to compare them to some other set of conditions.

This set are full of oil and carbon and it's obvious why Suzuki put a drain in the last (rear) section that runs cool and oil drops out of suspension.

I should let you know though, that the clean baffles I fitted before the dyno runs, basically came out as clean as they were when they went in. It would be interesting to see tow sets of pipes with pumps set to different settings run over the same conditions and to compare the carbon and oil buildup. But then we'd have to compare different oils and the effect of different riding styles and so on through all the variables.

[Suzsmokeyallan]

Yup that would be a new project to run an oily comparison on,

[advant63]

here is a repost of my 550 disection for comparison.
viewtopic.php?f=2&t=1484&start=15

[tz375]

This is the split



In this shot, you can see the way the baffle plates are spot welded into the inner half shell and rub or vibrate against the other shell.



This shows the perforated mesh at the front section of both inner and outer shells.



The baffle tube was inserted again after the wadding was removed to show its location. Note that the tube is still clean after a couple or three dyno runs


This is the back end of the pipe where it's relatively cold and oil that wasn't burned drops out of suspension and coats the whole section with carbon and oil. As Allan pointed out, too much oil on a bike that doesn't get run hard will create this sort of oil mess.


Unfortunately, no rear cone inside in the the way that Kawasaki did with the S and H series bikes. Doesn't look like it should work, but it did. And that was back in the seventies.

[tz375]

Advant,

Thanks for that link to the 550 pipes which share many design similarities.

[TLRam1]

Doesn't look like it should work, but it did. And that was back in the seventies.

My thoughts exactly Richard, thanks for the photos. .

[Craig380]

Great stuff, thanks Richard!

[Barry S.]

here is a repost of my 550 disection for comparison.
viewtopic.php?f=2&t=1484&start=15

No pics?

[ja-moo]

I doubt there was much, if any "expansion chamber" effect with the Kawi pipes and their rear internal cone. It was more of a cleaner flow to get to the baffle diameter. These old pipes weren't really anything more than mufflers. JMHO