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Throttle Valves - any aftermarket substitutions or ?
I was just wondering if anyone has found an aftermarket source for the Throttle valves in the GL1200. It would be great to find a set of 4 that are a little cheaper than the $81.45 price ea. from an online store. I would like to buy a new set of the Throttle valves and Jet Needles for my 1986 GL1200.
Just thought I would ask.
Thanks, Don W., Winchester, KY
#1 10-27-2008, 12:52 PM,
I am curious to know what is wrong with your parts. Diaphrams gone? These don't nomally wear out before the rest of the machine.
Tim Johnson
1984 GL1200I
1975 GL1000
2002 GasGas trials.
1956 Norton Dominator
#2 11-07-2008, 10:18 AM,
Here is a note I sent to a gl1200 tech trying to figure out my carb problem.
"I have wrestled with my carbs and had them out of the bike 5 times and still can't get the high speed performance issue sorted out. I messed with the original carbs several times and never could get them right in 4 attempts so I bought a newer set of carbs. Unfortunately, old careful, meticulous, stupid me forgot to take the throttle valves out of the new carbs before I cleaned the outside of them with spray-on carb cleaner so I ruined the throttle valves. So consequently I had to go back to my original throttle valves from my original Interstate carbs. I have synched and synched 'til I'm blue in the face and have had decent levels of throttle operation and everything but 4500 rpm and higher when on the highway in 5th gear. I do like to run 80+ mph on my bike and you can really hear the carbs stumbling, (especially at 90+)."
What I do know about my current throttle valves is that they do have some scuffs on them where they contacted the sides of the carb body. I have carefully rebuilt the carbs and set float heights to within a few thousanths of an inch. I have installed a brand new fuel pump, new spark plugs, and new(er) coils and wires. The bike still stumbles and fights itself at high speeds.
I just really want to get my bike to perform at all throttle positions properly.
My 2004 Ninja 250 works great at all RPM ranges from 1500 rpm to 13500 and
from 0 to 110 mph. I would really like to get my 1200 to run as smoothly in all rpm ranges. I realize 4 carbs are much more difficult to tune and the bike is an '86, but I hope I can get this issue sorted out.
Thanks, DW
#3 11-07-2008, 11:23 AM,
Does it feel like it is stumbling from a lean mixture condition @ higher throttle settings, higher RPM?
If the slides lift and drop freely, and there are no holes or tears in the diaphragms I would be inclined to look at main jet/needle combinations. It might be worth your while to run it hard/fast for a bit and then pull in the clutch and flick the kill switch simultaneously, coasting to a stop with a dead engine. Then pull and read the plugs right there on the side of the road. They will tell you a lot about the condition of the mixture. If you are stumbling from a lean condition you may be able to correct it some by shimming the needles up in the slides. Try .040" ( 40 thou.) for starts. If you hunt you might be able to find a set of needles with a different taper. Honda lists 4 different needles. There are two different main jets available, the #108 and the #125. It is possible that you have the smaller jet which is intended for higher altitude use. Other than that, make sure you are getting adequate fuel, and since you have replaced the fuel pump I am assuming you have checked delivery of the new pump to spec. New fuel filter? Also, you might try raising the float level a smidgen above spec. just to be sure. Air filter could be an issue. The K & N filters pass more air than the stock paper unit, and filter better and I haven't heard anyone blame them for any adverse mixture conditions when they are not over oiled.
I have been assuming you are dealing with a mixture issue, but be sure it is not an ignition miss. If you haven't already done it the "wiredgeorge" modification is worth while <!-- m --><a class="postlink" href=""> ... &Itemid=26</a><!-- m --> it will assure you get full voltage to your coils, sometimes a problem on these bikes.
Tim Johnson
1984 GL1200I
1975 GL1000
2002 GasGas trials.
1956 Norton Dominator
#4 11-07-2008, 02:27 PM,

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