TwinMax Use and Results Benchmarking

[jgrm1]

I synched my TBs for the first time this weekend. I used my new TwinMax to perform the synch and want to benchmark my results with other TwinMax users. At idle, I was able to get the needle movement centered around zero at the Max sensitivity setting. No problem there.

When I attempted to perform the high-speed synch, I checked the synch at both 2500 RPM and 4000 RPM. If I zeroed the needle at 2500 RPM, then the needle would be close to the left 1 (-1) on the scale at 4000 RPM. Alternatively, if I zeroed at 4000 RPM, the needle would be close to the right 1 (+1) at 2500 RPM.

What I ended up doing was splitting the difference by adjusting the right throttle cable until the TwinMax needle was just to the right of zero at 2500 RPM and just to the left of zero at 4000 RPM. The most sensitive I could set the TwinMax during high speed synching was about 85% Max without succumbing to frustration.

 Are these results similar to what others have found?
 Should there be a difference in readings at different RPMs?
 Should I have picked either 2500 or 4000 RPM and zeroed the needle there without regard to the other engine speed?
 Should I have been able to perform the high-speed synch at the Max sensitivity setting?

Any input is appreciated since this is the first time I performed this adjustment and the first time to use my TwinMax. I searched the archives on this topic and did not find anything specific to my questions.

-Jeff

[Conrad (RAD) Sudduth]

Hi Jeff

I am confused. The process should be,zero the Twin Max first with the bike not running. Then set the TB's at idle using the bypass screws so that the Twin Max is at zero. Then check the TB's at higher RPM's and adjust using the right hand cable adjuster on the TB so that once again the Twin Max is at zero.

When you are done the needle should be dead center on the Twin Max at all RPM's.

You can even do what I do and that is road test at all RPM's and adjust the cable accordingly so that the Twin Max is dead on at zero under load on the road at all RPM's.

A quick tip. Shut the bike down every other time checking the TB’s and rezero the Twin Max. I find it sometimes moves on me especially during road tests.

rad

[This message has been edited by Conrad (RAD) Sudduth (edited 08-13-2001).]

[jgrm1]

Hi Rad,

Thanks for the response. I did follow the correct procedure as you outlined. Where I have a question is, if zeroed at one steady RPM (2500), is it normal to then not be at zero at another steady RPM (4000)? I am questioning linearity at different points in the RPM band.

Have you been able to set up your bike so your needle stays zeroed across the rev range? Is not being able to maintain a needle at zero across the rev range why it is recommended to sync at one point (either 2500 or 4000) only?

Thanks,
Jeff

[jgrm1]

Rad,

Another quesiton, during high-speed sync, where was your sensitivity setting when you were able to peg "zero" at different RPMs? If the sensitivity is turned down far enough, I too could show zeros at different RPMs. I got sensitivity up to about 85% of max during my high-speed sync when I noticed this non-linear behavior at differnt RPMs.

Thanks,
Jeff

[Conrad (RAD) Sudduth]

Jeff

I suspect that when people tell you they synced their TB’s in 5 minutes they spent their time syncing the TB's with the bypass screws in the garage.

This is important but really only the beginning. First you must be sure that your cables have the specified slack in them. then If you want your S to be real smooth you must spend the time working with the cable adjuster until the Twin Max stays on zero at all RPM's with the Twin Max set for max sensitivity.

It can take me an hour on the road stopping and adjusting the cable and road testing again and again until they are right on.

When they are right on all the way through the RPM range under load on the road my S is smooth and gets great gas mileage.

rad

[rob_wijhenke]

In general I spend 15 minutes. 3 minutes setting it up, have tools ready, 5 minutes on bypass screws, 5 minutes on cable adjuster, 2 minutes wrapping up.

I get best results when it's not too warm outside, between 15 and 20 degrees C. is good. If the it's warmer the results may vary.

The procedure as Rad describes is the same I use, making the engine run smooooth, no surging.

I do find that I have to sync every 2500-3000 km's for best results.

(*_*)

[jgrm1]

Rob,

I did wonder if ambient temperature made a difference to sync'ing. Yesterday, it topped 38-deg C (100-deg F) in the garage when I was playing with the TBs. Yes, I did have a fan in front of the bike.

-Jeff

[jclark]

One special thing to watch out for, is the 'making sure you have a good seal'.

The Twinmax( TM ) hoses that come with it seem to not fit the Throttle Body( TB )access ports very well after a few uses.
Make sure you have a good seal here ( otherwise you are balancing your bikes air pumping with the TM as an active participant in the process. This is only desireable if you plan to ride with the TM as a permanent fixture of your intake equipment).
I have replaced the hoses, ( I use fuel hose as it is rather stiff and will not kink when heated as much as the clear hose and it can be sized to tighter than what it ships with ) and it makes quite the differnce!

Whew.

jeffthat's enough for now...

[jgrm1]

A follow-up to my original post. I took the 'S on a weekend trip this weekend and was not quite satisfied with the way she felt after performing the 12K mile service. Curious about what Rad said above, I pulled the TwinMax out when returning home. Rad was right, you can get the throttle bodies pretty close throughout the RPM range. What I noticed the second time around is that you have to give everything a chance to "gel" for 3-5 seconds when holding the throttle at a certain RPM. When set to Max sensitivity, the TwinMax needle will move at the slightest change in RPM. It is difficult to hold the throttle that consistently when revving the bike in the garage.

After adapting to this sensitivity and giving everything a chance to settle, I was able to get the TBs spot on. The bike now feels smoother than it ever has. This is the first time the TBs have been properly synchronized. At the 600 and 6000 mile service, the mechanic said, "they're close enough."

Thanks,
Jeff

[Conrad (RAD) Sudduth]

Jeff

You have discovered what I found out, that the static BMW shop EQ will not produce results as good as the Twin Max on the road.

One point. Pay close attention to Jclark's point. An improper seal will produce poor results. I almost canned my Twin Max due to irregular readings until I purchased two reducers and added tubing from my cannesterectomy. The fit on my TB’s is now very snug. I have no fluctuation at all under hard acceleration to red line. I have tested this under hard acceleration to over 100MPH.

Good luck

rad

[jgrm1]

I was able to achieve my results in the garage. I don't have a tank bag, so I have not ridden the bike with the TM hooked up. At first, I could not figure out why having the bike under load would make a difference to the TBs, but after understanding the sensitivity to RPM issue, it makes sense. How did that old Operation board game commercial go? "It takes a very steady hand!"?

-Jeff

[Rapt]

OR a throttle lock.

[roger albert]

Yeah, a throttle lock helps a lot.
Both in the garage and on the road.

Note that the synching with cable and screws alone only works when your throttle butterfly stops are well zeroed. If they're not, and you compensate with the bypass screws, then you introduce an offset between the sides that will keep you from balancing across the range later. It's easy on low mileage bikes like most of ours, but over time...

Anyway, just be aware that there's actually a lot more to it, and you may have to adjust your technique at some point in the future.

take care
roger

[herbg]

Speaking of TwinMax ... has anyone had any experience with the Morgan Carbtune II(http://www.carbtune.com/index.html) and, if so, how does it compare to the TwinMax. I've heard good things about this product but the TwinMax seems popular with the BMW crowd.

I use a mecury manometer to sync the Dellorto's on my bevel-drive Ducati's but before I start with the R11S, I would prefer something less lethal around the garage.

Any thoughts?

Thanks,

[MarkC]

herbg; I use the Morgan Carbtune II, and it's OK. If you insert the supplied air restrictors in the hose, the rods sometimes don't move, or will partially rise. If you don't use the restrictors, the rods will bounce too much to get an accurate reading. To cure this, I cut the restrictor at an angle, slightly enlarging the area in which air can pass. Now the rods bounce very little, but enough that an accurate reading can be done.

I haven't used the TwinMax, but have used a mercury gauge for the past few years on my prior Oilhead. I feel the mercury gauge is slightly better (the Carbtune should be held vertically level so the rods will float and not bind in their tubes) than the Carbtune, but not as ecological (reason I prefer the Carbtune).

MarkC

[Rapt]

Personally I think electronic (Twinmax) is the way to go for the cost of the "mechanical" Carbtune system.

Carbtune is essentially a manometer, but without the mercury. Its also larger than the Twinmax. (Like 11" vs 7".)