carb synching/balancing mod

[Agemax]

has anyone used this mod before? i used to use it on my old cb550f honda and it did make a difference. just wondered if it would work on the GS range as well.

basiclly, you screw in 4 adapters into your manifolds as if you were going to synch your carbs but you leave the adapters in place and connect up 1+4 and 2+3 with a section of tube all the time during running.

makes sense to me plus you have the added bonus of having the adapters already in place if you feel the need to synch your carbs​

 

[1948man]

I have the permanent adapters and have been using individual rubber caps on each port. The cap on #1 cylinder was occasionally getting "Coughed" off during cold startup so I put the original allen bolt back in since that cylinder is easy to access. I like your solution and look forward to additional comments from knowledgeable members.

 

[robertbarr]

I use a similar setup on the '01 Bandit. There are no adapters; there are nipples already in place, with caps, from the factory.

The problem is, you'd need fingers 8" long and 1/4" in diameter to reach any of them once the carbs are installed, even if you could put up with the heat. I replaced the caps with lengths of vacuum tubing and routed them up to the tops of the carbs where I can get right to them.

I'm not sure what you mean by "connect up 1+4 and 2+3 with a section of tube", though. I could see individual lengths of tube, capped at the end. The carbs / intakes are going to experience vacuum at different times, so there would be continuous flow back & forth if you connected the intakes together. -- or am I not reading that correctly?

 

[Redman]

has anyone used this mod before? i used to use it on my old cb550f honda and it did make a difference. just wondered if it would work on the GS range as well.

basiclly, you screw in 4 adapters into your manifolds as if you were going to synch your carbs but you leave the adapters in place and connect up 1+4 and 2+3 with a section of tube all the time during running.

makes sense to me plus you have the added bonus of having the adapters already in place if you feel the need to synch your carbs​

I think I understand what you are saying. You are saying that iff you connect 1 &4 together and then connect 2&3 togeter then 1&4 will run at the same vacuum and 2&3 will run at same vacuum. I think that is what youy are saying.

But -and I am not engine design expert- I dont think that makes any sence. Yes, 1&4 piston do up and down together (as do 2&3) but they are 180 degrees out of phase. One is on intake while other is on compression. So you got a vaccum pump (intake stroke) sucking air out of a compressor (compression stroke) -- what does that do for anything. (<<<<see later post revising this statement>>>>.)
Seems like that would be worse than just leaving the ports open to attmosphere.

Not trying to argue with you, but it just does not make any scence to me.

Dave

<< Later note:
Okay, I reread you post and now see that you just asked if anybody has tried this, and didnt ask for opinouns or other comments. My appoligies if I seemed argumenitive.

So, to answer your queston:
No, have not tried that.
.

 

[Flyboy]

One is on intake while other is on compression. So you got a vaccum pump (intake stroke) sucking air out of a compressor (compression stroke)

Hi Dave, not quite, as the adapters sit up stream from the intake valve, so the cylinder on the intake stroke will be pulling from the other one on compression, but not from the cylinder directly, as the intake valve will be closed, it will be pulling through the other cylinder's carb, in effect.
But, I too do not see how it can be benificial, we spend all the time and effort getting our air boxes to seal properly so all air is drawn through the filter, this kind of defeats the object, methinks.

But no, I havn't tried it, I do agree on leaving the adapters in place, but with individual blank off plugs.

 

[hampshirehog]

Just like Brit twins with twin carbs (Bonnies, RGS etc). The carbs are linked with a rubber tube on the manifold side. These bikes were never designed for using vacuum gauges and loads are miles out of balance (you can jerry rig vacuum gauges) but are corrected reasonably well by the link pipe. Bear in mind the link pipe is 1/4 inch id (I think, or thereabouts) which will be much less restrictive than balance adaptors.

 

[Redman]

Hi Dave, not quite,
....
.....

Ah, yah, mental malfunction on my part. Let me think of this again, using what I would have learnt in grade school science (had I been paying attention) and what have observed since.

Lets see, 1&4 go up and down together, and 2&3 go up and down togethere.

When both pistons going up, one cyclinder is on compression stroke (so valves pretty much closed) and other cyclinder is on exhaust stroke (so intake closed and exhaust open), so if the connection between the two ports, then not much happening.

WHen going down, one cyclinder is on intake (so inlet open exhaust closed) and one is on power (so valves pretty much closed).

So, I still dont see where/what/how there would be any bennif to connection 1 port to 4, and 2 port to 3. Maybe some things happen during the valve overlapp.

So, no, I have not tried this, and no I dont see when/why this would be benificail.

Dave

PS, Again, I dont intend to be argumentive. Just trying to better understand.

.

 

[1948man]

So Hampshire Hog, let me see if I understand you correctly. The larger link on the old Bonnies was actually helpful but the more restrictive link with smaller vacuum lines would be unlikely to help much but wouldn't hurt anything and would leave a convenient setup for being ready to sync the carbs. Is that fairly close to the idea?

 

[Graham]

Yamaha made a YICS system on the XJ motor in the 80s witch link all four carbs with an in head vacuum tube. The XJ engines are strong motors for their day.

 

[Buddy]

I've seen something simular in the automotive field. Holley sold a dual plain manifold that had a built in balance tube that connected the two sides. Claimed to boost mid and high end power like a single plane while keeping good low end like a dual plane. I don't know how it would translate to a multi carb appilcation though.

Buddy

 

[Agemax]

on my 550 honda it improved tickover and low to midrange throttle was much smoother

 

[Crazy_Russian]

ive ran similar setup on my 68 bug with 1776cc and dual 34 webbers, it helps them sink up also gives a small increase on the bottom end. (will also try this with my 2110cc whenever i get around to finishing that motor)
also on Ukrainian Dneprs MT10-36 and MT11-32 (similar to Russian Urals) some people experimented with this similar setup (boxer 2 cylinder with dual carbs) noticed a little smoother running motor and more botom end power, but it all flatned out at the top. i think someone did a dino run with one of those with a small hp increase at low RPMs... but its bean years since ive played with those and don't remember all the info anymore.
so im kinda curies to what your final results would be it maybe more beneficiary to link all 4 of them up together?:-k

 

[GS750]

So who is going to give this a try then??

 

[1948man]

Sounds like Agemax is on the verge of volunteering.

 

[Crazy_Russian]

i would love to, except im all torn apart at the moment and need to order parts :-(

 

[GS750]

i would love to, except im all torn apart at the moment and need to order parts :-(

I feel your pain!!!
Sadly, My bike is down at the moment too

 

[hampshirehog]

So Hampshire Hog, let me see if I understand you correctly. The larger link on the old Bonnies was actually helpful but the more restrictive link with smaller vacuum lines would be unlikely to help much but wouldn't hurt anything and would leave a convenient setup for being ready to sync the carbs. Is that fairly close to the idea?

That's what I'm guessing. On my carb gauges the holes in the adaptors are much smaller than 1mm - quite a lot of puff needed to blow through them. It definitely wouldn't hurt but with that resistance I can't see that it'll help either.

 

[UncleMike]

Hey Agemax, any results?

 

[Agemax]

not yet, Mike. experimenting with different size adapters. definately has an improved effect on tickover and low throttle response. trying out different internal diameters to see what difference it makes

 

[UncleMike]

not yet, Mike. experimenting with different size adapters. definately has an improved effect on tickover and low throttle response. trying out different internal diameters to see what difference it makes

Very interesting. Keep us updated!