TWINMAX problems

[Big Lad]

I adjusted the valve clearances on my '94 1100GS today ( My first time !) and all went well. They were a little tight though.
Anyway, I then went onto using my new Twinmax and thought it'd be the easy bit !. I'd printed out the 'for dummies' part 2 guide and also Migsel's guide, but couldn't make any sense out of them. To make matters worse, I forgot the original settings.

I managed to get idle on zero ay max sensitivity, but reving to 4k sent the needle to the left and no matter what I do to the screws or the r/side throttle adjuster, I can't seem to change it. My idle speed was too low before I started today, it was running at about 950/1000 rpm and I couldn't raise the idle speed at all with the left and right screws.

Has anyone got an EVEN simpler guide to the process from scratch ?.

I could always go to the dealer, but I really want to learn to do all this myself.

 

[The Mechanic]

Stop stop stop...stop!

Go back to the valve clearances again first, you must must must do this, ensure that you have set them correctly...it'll be good practice and you'll get to know yer bike intimately (so to speak).

Leave the Twinmax on the bench and forget about that for the moment.

Right have you done the valve clearances properly (no disrespect intended)?

Now carefully with a snug fit screw driver very gently turn in both brass screws (idle air by pass screws) until they just bottom out.
DO NOT FORCE THEM INTO THEIR SEATINGS YOU WILL DAMAGE THE THROTTLE BODIES.

Next screw (one at a time) out each by two and a half complete turns (put a mark Tippex or magic marker on the screw and housing) the mark on the screw must pass the other mark on the throttle body two and a half times. This gives you a base setting to start from.

Next ensure that the throttle cables are not caught up or misplaced in any way. Check their routing is not fouled. Twist the throttle a few times and ask youself does it feel ok. Good now place your finger against the right hand throttle actuator (the bit the throttle cable goes round on the throttle body) operate the twist grip with your free hand, do the same with the opposite side and ask your self do both 'feel as though they are moving at the same time. This may sound strange but your pinkies are very good at detecting out of synch movement.

Now re-read the instructions for the Twinmax, is the battery ok and have you set up the Twinmax properly? The idea is that vacuum from both cylinders reacts upon the meter needle and indicates which is the stronger of the two cylinders, adjustment being a balancing act of deft screw manipulation and meter needle observation....personally I prefer vac guages as these tend to be more accurate FOR ME THAT IS ANYWAY!

Good luck you are on your own now, but if you still can't get it right it could be because there is something fundamentally wrong with the engine, valve burnt, gasket fault etc etc.

Hope you are successfull

 

[The Mechanic]

Me again....

Sorry, the throttle plates will need to set up too. These are the discs that allow more or less air into the inlet tract after the throttle bodies, if these are out then you will need to follow closely the set-up guide which is quite straught forward. You were part way there doing the finger test on the throttle operation.

One sure fire way to ensure synchronous operation BEFORE Twinmax setting is to take off the inlet tubes (hoses from the air filter to throttle bodies) peer inside the throttle body and twist the twist grip ...see the plate moving ...take a drill with at least 15mm diameter gently place this under the plate between the body and lower edge. Now with another identical sized drill and whilst maintaining the same throttle position try and slide the drill between the throttle plate and lower body on the other side. Adjust the right side cable to achieve unity.

Put everything back and fire her up warm her up to 5 bars on the RID and get on with Twinmaxing her. DON@T FORGET TO SUPPLY SOME EXTRA COOLING a fan or two would be good.

 

[Big Lad]

Cheers Tony.
I did the valve adjustments using the 'for dummies' guide (appropriate). I checked and double checked the gaps and by the time the valve covers were back on, they were all within spec. The r/s valve cover bolt at the top left seems a bit knackered. I VERY carefully did them up bit by bit, diagonally, but the said bolt screws in and won't tighten. It just keeps on screwing, if that makes sense. After a quick ride, there was no oil leaking. Do you think this is going to be a problem ?.

 

[Big Lad]

Just tried again with the twinmax. The thing is, the Haynes manual says that the freeplay on the throttle cable and choke are by the l/s throttle body and should be adjusted there. Migsel says that the adjuster is on the handlebar and the dummies part two seems to make no mention of adjusting the cables during the idle test at all.

DO I NEED TO SLACKEN THE THROTTLE CABLE ?. IF SO, HOW MUCH BY AND FROM WHERE..HANDLEBAR, LEFT OR RIGHT SIDE THROTTLE BODY ?

AT IDLE, I CAN GET THE NEEDLE ON THE TWINMAX IN THE CENTRE ON MAX, BUT NO MATTER HOW FAR I TURN THE SCREWS OUT, THE IDLE STAYS AT 950 RPM AND FEELS LIKE IT'LL CUT OUT.

Any tips would help, otherwise it's a trip to Sawbridgeworth!

 

[Big Lad]

 

[ferguscawley]

Simon

The whole idea here is to get the throttle bodies opening together in synch. Forget the adjuster at the twistgrip. This can be done later. The way the GS works is that there is just one cable going from the twistgrip to the LH throttle body. When this cable is actuated, the LH throttle body then turns a little pully which actuates the RH throttle body. Take a good long look at the LH throttle body, twist the grip a few times and get a good understanding of how the system works.
What happens over time is that the cable going from the LH throttle body to the RH throttle body can stretch and this causes an imbalance between the two throttle bodies. A stretch of 1mm can cause enough imbalance to make bike run shit.

You say you have the throttle balanced at idle. This is good. This means that your two big brass adjuster screws are set right. Ignore these from now on. Once you start to open the throttle by 5 to 10 % these screws don't matter anymore. What matters now are the throttle butterlfys (the plates that are turned by the cables). This is why the guidebook tells you to use 4000 rpm as a target for balancing the throttles.

In order to get them balanced, use the adjuster on the RH throttle body only. This may take some time but it is worth it. I don't use a twinmax myself - I prefer the vacuum gauges suggested by Tony. Anyway, if using the twinmax, set it for minimum sensitivity first, get it balanced there and then increase sensitivity, balance again etc etc. You can get as anal about these settings as you want, but once the bike is smooth and pulling cleaning wihtout too much vibration, you've got it.

Best of luck.

Here is the RH adjuster I mentioned above ..

 

[Big Lad]

Cheers Ferg.
I took Tony's advice and re-checked the valves. I'm glad I did. They seemed tighter than when I adjusted them the other day. I spent about two hours in the garage this afternoon and really took my time. By the time I'd finished, the gauges were sliding through just barely touching the sides. ( Somehow the r/side valve cover nut 'located' this time and screwed in ok ( I did them all hand tight only ).
I started the engine and all seems fine so far. I'm now waiting for the rain to stop before I go for a run with the twinmax in my tankbag.
I'll let you know how I get on this time. Thanks again.