carb associated problem

[ossylad]

hi all... in the continuing saga of trying to identify a strange 'metallic' noise at low revs, thinking the noise does sound rather like high pressure gas escaping.... i removed the tank earlier and began checking all likely culprits i.e. leaking joints, gaskets etc all seems ok on the exhaust side, although interstingly i have found an 'open' piece of pipe shoved onto a pipe leading off the carb to engine duct (dont know if this is the right word!) the pipe is situated after the carb and before the cylinder block. all the others on the other 3 cylinders have a rubber blanking off cap, secured with a spring clip. this pipe seems to be a bit of clear plastic tubing!  and im sure that the 'sound' may be coming from here.... a sort of 'missing'..... can anyone explain why this has been done? or should it be like the other 3 cyclinders and blanked off. the engine runs smoother and slightly higher revs when you put your finger on it. and petrol is drawn up the tube!  i'm puzzled. if anyone has any ideas on this i would be grateful. 

cheers  ian

[movenon]

To help us a little:
What year is your bike ?
It would help to post a picture then we can see whats going on. To avoid "shot gunning solutions".
If it a problem its fixable just feed us more info.
George

[ossylad]

hi

im sorry.... my bike is  a 1991 3xw its AN fj1200 ABS I managed to get a look at a parts catalogue and there should be a blanking piece on there with a clip. i think the piece of clear pipe in place may be there from when the previous owner had been balancing the carbs and forgot to put the blanking grommet and clip back on! i have temp blocked the pipe up and ordered a new grommot from my local yamaha dealer   ( only a couple of quid!). the bike seems to run a lot better now!!!! or am i imagining things!!!  all comments greatfully received. cheers   ian

[movenon]

Glad you are making headway.
But I am still puzzled. My bike is a 1990 and that's my reference point. 

I think you should have one vacuum hose going up to the ignition advancer. It is attached to the middle of the 3 vacuum ports (the ones with rubber caps and spring clips).  The hose feeds on top of the engine going up to the advancer mounted on the frame under the fairing on the right side. I am not sure what line you are talking about that you are plugging ?

The vacuum line I am referring to has an insulated covering on it to protect it from the engine heat. Should be easy it identify.    Pictures ?
Perhaps someone with 91 might stop in and add some information.
George

[ossylad]

hi george, i will take a photo of it.... im confused more now!! i could do with an overhead view of a sorted engine and carbs to compare. i will take a pic and re post cheers   ian

[andyb]

Sounds like the vacuum advance line, but translation is difficult.  It's a hose dammit, clear pipes are used in labs and by people doing drugs!

Did the 91+ use that system for timing advance?  Sounds like someone had just replaced it with what they had handy, for whatever reason.  Blanking it for the time being will be good enough.

[Biker Bandit]

How do Ossylad...

It sounds exactly as you say and the blanking cap has gone awol at some point. Blanking this back up will most certainly help the running. The metallic noise could be that without the cap that cylinder would be running too lean and causing some pre-ignition.

If it help I could always call over (presuming you are in Ossy near Burnley/Blackburn) to have a look and check it out and bring my vacuum gauges if you want to make sure things are all balanced.

I have the same model FJ as you and I also have most parts for a 3CV and I've rebuilt carbs many times... there's no vacuum advance pipe used on my 3XW.. I think this was a 1TX fitment if I'm not mistaken  

Just let me know  

[Arnie]

Just confirming the 'Biker Bandit' post.

There is NO vacuum line running from any of the manifold vacuum taps on the '91 bikes.
They should all be capped in use.

Arnie

[ossylad]

thanks for that arnie... ive blanked it off now and the engine seems to run a whole lot smoother and quieter!  revs a little higher too. this bike is a voyage of discovery, i wonder what else i will find... nest job is to replace fork oil seals and fit progressive springs.  cheers

[Arnie]

Fork seals, yep sure, go for it

Progressive springs, why bother?
They're barely any stronger than the weak OEM springs and not worth even changing. 
Go ahead and bite the bullet and buy either a set of Randy's fork valves or RaceTech emulator valves and straight rate springs to suit.
Either will improve your fork action immensely.

Note: I have RTEmulators in my forks and am happy with them, but have not tried the RPM valves Randy has had developed.  Others say they are a real improvement over the RTEmulators.
If I was making the choice today, I'd probably buy from the valves Randy.  rpmracingca.com

Arnie