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PostPosted: Tue Sep 11, 2018 4:55 pm 
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On the main road
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Joined: Mon Oct 24, 2016 12:35 pm
Posts: 131
Location: Macon, GA
Country: USA
Bikes owned: 76 GT750, 72 H2 750, 84 RZ350, 67 YR1, 82 MB5
^ thanks for the reply! May have to inquire on the pipe to hold for future use if purchased.

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1976 Suzuki GT750 (Maui Blue), 1972 Kawasaki H2 750 Mach IV (Candytone Blue), 1984 Yamaha RZ350 (KRR- Yellow/ Black).


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PostPosted: Tue Sep 11, 2018 6:46 pm 
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Moto GP
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Joined: Mon Dec 13, 2010 4:32 pm
Posts: 3256
Location: southwestern Pennsylvania
Country: USA
Bikes owned: 69 T350 thru 75 GT750
Yes, Jemco is still in business making pipes. I talked to them this morning about the 3-into-1 they are making for my GT550.

They have a Facebook page, but it doesn’t have much info: https://www.facebook.com/Jemco-Exhaust-Systems-159783504044199/
They have a new email address: jemcoexhaust@gmail.com

_________________
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 73 project
T350 69, 71 & 72 project
T250 72
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE


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PostPosted: Tue Sep 18, 2018 8:36 pm 
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Expert racer

Joined: Tue May 18, 2010 5:38 pm
Posts: 1410
Location: New Hampshire
Country: USA
Bikes owned: Suz, Yam, Honda, Kaw.
Jabcb,

Can you post videos of what your GT750 and future GT550 with Jemco 3 into 1 sound like please.

I ran Bassanis on my 73GT550 3 into 3. They seem to boost right where the stock engine has peak torque... as if it needed more. This causes ping problem I could not solve properly with those stock cyl heads and occur only when you backed off throttle in that RPM range. Avoidable (close throttle fully) but annoying if you did not. They did not increase redline before ran out of breadth. Getting redline was well past peak hp with pipes. But a huge midrange hit when accelerating which was nice and no problems.

I found a set of Ocelot 3 into 3s couple seasons now maybe. The tune length is 8 inches shorter than Bassanis. SO much better IMO. The bike still runs good low and midrange maybe a loss but don't feel it and this is where I ride mostly. The GT550 as you know is tuned like and enduro, nice for street and still there. However. they pull well into redline and above, To me the GT550 ran out of breadth too soon (endura thing again) and the added +1000 RPM or more increase in power band is nice so nice. They sound better too IMO. Not race pipes, perform like street pipes IMO. When I took measurements the bassanis seam similar in design to jemcos 3 into 3 design so did not try, High speed seem longer tuned length, but not sure (eye pictures). I just looked at jim lomas, now his gt550 look more in line with OCelots with more section/steps. Those interest me.

Now a 3 into 1 simply can sound awesome. I had /know polaris 1980s triple snowmobile with 3 into 1 and sound great same with the mild yamaha triples (no exhaust power valve models) of the late 90s early 00s. 3 into 1 it can be done right but those design look nothing like what is offered for our bikes. To me the the key is to reduce length of each down pipe, short manifold, so when each cylinder has its turn to use the tuned pipe it share it less with the others. There isn't much time when 3 cyls share 360 degrees and if one of other pipe(s) signal is still bouncing around that can't be good. Just my opinion and years of experience running 80s and 90s sleds and the non race type as well performance type with EX power valves with sweet fat 3 into 3s for higher RPM power bands.

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Current Bikes
74 GT250 (T350 upgrade),
76 GT250 (T350 upgrade),
71 T350,
70 T350,
74 GT380,
75 T500,
73 GT550,
75 GT750,
72 Yamaha DS7 (R5 upgrade),
77 Yamaha RD400 (Daytona Cyls),


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PostPosted: Wed Sep 19, 2018 4:34 am 
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Moto GP
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Joined: Mon Dec 13, 2010 4:32 pm
Posts: 3256
Location: southwestern Pennsylvania
Country: USA
Bikes owned: 69 T350 thru 75 GT750
I don’t have a video of the GT750. Its currently laid up with a gas tank liner that is screwing with the vacuum petcock. Not sure how long it will be till I fix the gas tank.

The GT750 PO had rebuilt the engine. His documentation included mod advice from smokeriders. Have no idea what porting changes he may have done. The bike had vintage 3-into-3 chambers when I got it. Pretty much no power below 4k rpm, and then zoom-zoom above 4k. I live in a very hilly area — that 4k rpm light switch was really annoying.

Got the Jemco 3-into-1 for low end power. Now the bike pulls strong from about 2k rpm. Its definitely strong up past 5k rpm. I can’t comment on the 5 to 7k rpm performance — haven’t spent much time in that rev range & just don’t remember.

_________________
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 73 project
T350 69, 71 & 72 project
T250 72
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE


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PostPosted: Wed Sep 19, 2018 8:30 am 
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Moto GP
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Joined: Mon Nov 03, 2008 10:47 am
Posts: 6004
Location: Illinois
https://www.youtube.com/watch?v=6L6N_MYfuNY

That's a Strader 3 into 1 and it was burning too much oil at the time so it's a bit flat. The Jemco design is way more quiet and throttle response is better.

I don't have a decent video of the Jemco system, but it sounds much like any of the other 3 into 1 systems on youtube.

Biggest advantage is weight - or lack of it. It saves about 20-30 pounds of exhaust weight and that makes a huge difference to handling and performance.

I have a Jemco 3 into 1 on one of my GT750s and Jemco 3 into 3 on another and the 3 into 1 is much quieter and sounds much better. Sounds almost like a turbo 6 cylinder letting rip.


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PostPosted: Wed Sep 19, 2018 2:59 pm 
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Around the block

Joined: Tue Jul 03, 2018 4:32 pm
Posts: 78
Country: Usa
Bikes owned: '74 GT250
I have always loved Jemco because Jon runs a small company that builds real cone expansion chambers not some huge production company with stamped pipes. His pipes are always made with care and each set is unique. There are a couple posts on his facebook of some really bad work a customer says he did with missing welds and so on I can't see how it could be his work though hes always had such a good reputation.


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PostPosted: Wed Sep 19, 2018 4:26 pm 
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Moto GP
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Joined: Mon Dec 13, 2010 4:32 pm
Posts: 3256
Location: southwestern Pennsylvania
Country: USA
Bikes owned: 69 T350 thru 75 GT750
Indy650 wrote:
I have always loved Jemco because Jon runs a small company that builds real cone expansion chambers not some huge production company with stamped pipes. His pipes are always made with care and each set is unique. There are a couple posts on his facebook of some really bad work a customer says he did with missing welds and so on I can't see how it could be his work though hes always had such a good reputation.

I saw that post about the missing welds. There was a reply that Jon had been sick for a while. They told the guy to send the pipe back and they would fix it.

_________________
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 73 project
T350 69, 71 & 72 project
T250 72
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE


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PostPosted: Wed Sep 19, 2018 4:45 pm 
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Joined: Tue May 18, 2010 5:38 pm
Posts: 1410
Location: New Hampshire
Country: USA
Bikes owned: Suz, Yam, Honda, Kaw.
This is the only 3 into 1 jemco for GT750 I can find. Yes sounds like most 3 into 1s but video too brief and one rpm

https://www.youtube.com/watch?v=qyJFRhVROlU


Was wondering what gt550 would sound like with 3 into 1.

I agree Jemco 3 into 3 are loud. Both for GT750 and even T500. I think if the silencer pipe diameter was smaller would help some. Think Bell's book gives guideline... never checked if the area matches what he thinks or greater. Stuck smaller pipe inside silencer on Gt750 and noise level dropped, but didn't run it to see what a mess I may have made

Does sound like the Jemco 3 into 1 is nice. Looks nice in the PICs jabcb added

Has anyone tried Jim Lomas pipes 3 into 3 for GT550. Funny how different they look from his long skinny pipes for GT750. As mentioned, I like the shorter length of the r GT550. I'll try to take a pic of my GT550 Ocelots. Ever since Photobucket changed not sure where to post it....try something else.

I was looking at another gt550, but that bike sold yesterday :( . wanted that to have different exhaust.

_________________
Current Bikes
74 GT250 (T350 upgrade),
76 GT250 (T350 upgrade),
71 T350,
70 T350,
74 GT380,
75 T500,
73 GT550,
75 GT750,
72 Yamaha DS7 (R5 upgrade),
77 Yamaha RD400 (Daytona Cyls),


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