bike doesn't perform like it should

[Gord]

Completely dismantled motor to put in new cam chain. installed new rings lapped and shimmed valves to spec. Motor is running good but on highway won't go over 74 mph. It has pod filters on carbs and an 80s Jarden exhaust system I am thinking it is a carb issue any suggestions

[DiverRay]

#1!! What year and model is the bike?
The early bikes have a mechanical advance system, as well as the vacuum retard that needs to be connected to the #2 carb(2nd from left when sitting on the bike).
What pod filters do you have? Some are KNOWN to cause problems because of the design!
How much fuel do you have in the tank? Specials do NOT run well when low!!!
With a little more info, we should be able to give you someplace to start looking for your problems.

[Gord]

bike is a 1979 special it has K&N pod filters. tank was full. vacuum is working. i synchronized the carbs

[MaximPhil]

bike is a 1979 special it has K&N pod filters. tank was full. vacuum is working. i synchronized the carbs

Hi Gord,
Welcome to XS11club. Fuel lines not kinked.? Breather hole in cap clear ?
Phil

[Bax]

Hi Gord, A few things to check. The wires going to the timing pickups are a known weak point and break inside the insulation on the loop back. While you have the timing cover off make sure the advance rotates freely. IFRR 75mph is like 5000 RPMs in 5th which is at the max advance. On bikes with mech advance timing I've read that folks had similar issues when an ignition box from 80 and up were swapped into the bike, need to verify part numbers. Can you achieve higher RPMs in lower gears or does it stumble consistently at the same place on the tach?

---Bax

[DiverRay]

Try a run with the petcocks set to prime. That runs off the front lines, and if you do have a kink in the line, that may help it to run. Do just one side, test, then the other. That should let you know if it's only one line. I know I STILL have some feed problems on my '79SF, Left side only, and I've played with it all summer...

[jetmechmarty]

FWIW, I have a Jardine 4 into 1 on mine. It performs very well, IMHO.

[Gord]

Thanks for the suggestions I will go through bike again.

[2WheelFun]

Mine was pinched fuel line when it acted like that. You will find the issue, keep at it!

[Gord]

Thanks for you advice went through fuel system. the carbs were rebuilt. Pulled off pod filters revved up engine only one of the sliders moved. Moved them manually and only the one comes down slow the other three just drop down. I assume I have to replace diaphragm.

[DiverRay]

Do all 4 if you do any! One "bad" is just the first to go.

[Bax]

Hi Gord, Those diaphgrams are available from JBM as a replacement part. I've used them, there on my bike.

http://www.jbmindustries.com/

---Bax

[Gord]

thanks for the help. Bax thanks for letting me know where to find the diaphragms. Will order soon but first i have some more riding to do.

[jetmechmarty]

Thanks for you advice went through fuel system. the carbs were rebuilt. Pulled off pod filters revved up engine only one of the sliders moved. Moved them manually and only the one comes down slow the other three just drop down. I assume I have to replace diaphragm.

80-81 YAMAHA XS1100 CARBURETOR SLIDE PISTON & RUBBER DIAPHRAGM

At $20 each, these are going to be tough to beat. They came up on another forum. No complaint listed. The diaphragm is as original.

[Bonz]

Simple and maybe silly thought here... Are the diaphragms sealed around the top of the carb body and in their groove correctly? If they are not in the groove and seated properly they will do what you described.