anyone linked their intakes with fuel pipe? as seen on another site

[solorider]

I saw this mod on I think the us fz1 site where you link cylinders 1-4 and 2-3 with some fuel pipe, the original mod was using some T pieces but it was mentioned that you get the same effect by just linking as I have mentioned, I know my idle sounds different, as to smoothness I haven't noticed any difference, perhaps I may have to try the mod with the T pieces.

[Falcon 269]

Some say it works, others don't notice any difference to merit having extra pipes running over the top of the carb linkages.  I'm in the latter camp.

If you can't feel any difference with the simple 1 - 4, 2 - 3 connections, don't waste time on the T-piece thing.  That's not a good idea anyway because it increases the chances of an air leak on the intake side.

[solorider]

I think the idea stems back to the late 70s and early 80s when Yamaha did link the intakes with a passage on some of their bikes called YICS, it was there to improve efficiency in the midrange, and it did work, but I suppose as emissions regs took over and bikes got more efficient and the cost of extra machining the system was removed, I know when I blanked the system off on one bike I had it was noticeable, with a slight power dip in the midrange, but then the passage was larger than the fuel pipe I was using, I believe the passage was around 8-10mm and it was in the cylinder head to aid swirl in the combustion chamber.

[ghostbiker]

I did the crossover mod with T's and later changed to just pipes.
Initially I noticed a slightly smoother tickover, this didn't change when I went to just pipes.
Since then I have had other mods like ivans and ignition advancer and ais removed. I did go back to the OE way last year and didn't notice a diff.... Maybe it helps unmodded bikes maybe it helps any or maybe its in the mind.

[sirgalahad3]

I think the idea stems back to the late 70s and early 80s when Yamaha did link the intakes with a passage on some of their bikes called YICS, it was there to improve efficiency in the midrange, and it did work, but I suppose as emissions regs took over and bikes got more efficient and the cost of extra machining the system was removed, I know when I blanked the system off on one bike I had it was noticeable, with a slight power dip in the midrange, but then the passage was larger than the fuel pipe I was using, I believe the passage was around 8-10mm and it was in the cylinder head to aid swirl in the combustion chamber.

That takes me back. I still have a genuine YICS service tool. It was used to blank off the passages you mention in the head so the carbs could be balanced.
I tried the pipe mod on my xs1100 and I noticed no difference. It is certainly an old idea.

[solorider]

I think the idea stems back to the late 70s and early 80s when Yamaha did link the intakes with a passage on some of their bikes called YICS, it was there to improve efficiency in the midrange, and it did work, but I suppose as emissions regs took over and bikes got more efficient and the cost of extra machining the system was removed, I know when I blanked the system off on one bike I had it was noticeable, with a slight power dip in the midrange, but then the passage was larger than the fuel pipe I was using, I believe the passage was around 8-10mm and it was in the cylinder head to aid swirl in the combustion chamber.

That takes me back. I still have a genuine YICS service tool. It was used to blank off the passages you mention in the head so the carbs could be balanced.
I tried the pipe mod on my xs1100 and I noticed no difference. It is certainly an old idea.

the YICS system is a good idea and it did work, but for it to work you need to have the passages inside the inlet port for it to cause a swirl and also the small amount of extra mixture that gets sucked in, as to the mod that I have done it is doubtful that it will work as good as the YICS system but it could help in a small degree, the only way to tell would be a rolling road session and the mixture checked, I know when the XJ650 first came out it was criticised because of the lack of low down power, when Yamaha fitted YICS the low down power was improved with no top end power loss.