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GSXR Carbs fixed my problem! (long)
My stock Mikuni carbs have always been a problem, one has a crack and leaks fuel and the needle valve seat O-rings leak every year and have to be replaced. Besides performance has always been poor. When the needle valves themselves began to leak and I replaced them the fuel wouldn't flow into the carbs fast enough to keep the engine running at speed and it would run out of fuel on the freeway. I thought about getting replacements but realized that any I found would also be as old as mine and still pieces of crap even if they were in good shape. Yamaha seems to put the cheapest carbs they can find anywhere in their bikes, like Hitachi's on some models, yuck! The carb companies make better ones like RS flat slides but the cost is too high, at $250 each.
After a lot of searching I settled on Suzuki GSXR 1100 stock carbs which have flat slides but are also CV type. They are 36mm but still 40mm on the outside and will fit the XS1100 rubber boots. The only major problem is the spacing between the center two carbs is a bit wider and had to be reduced to fit the Yamaha. I got a set on ebay for $70 that looked perfect and were just like new. I had to cut a piece out of the middle of the bars that hold the carbs together with a bandsaw and moved them together so the butterfly shafts just touched and cut the bar that operates the chokes and overlap the end to secure them with a screw. The carbs are designed for dual push-pull throttle cables but the single pull cable will work with an extension. They are also made to use a cable operated choke. I tried a push-pull choke for a car but it was hard to pull and wouldn't stay out. I decided on the speed shift lever from an 18 speed bike and that works great. It mounts on the bars, is easy to work and stays in any position. They can be found at swap meets or bike shops if there isn't an old bike laying in the back yard. Get the kind with a plain lever with no click stops or racheting mechanism and get the cable to go with it. You will also need a 6mm cable stop to clamp on the end of the cable that goes into the carb. I found a 1/4" stop at Auto Zone and turned it down to 6mm in a lathe. The stock airbox has to go unless you can find a way to get the rubber boots to fit the bigger 60mm inlets on the new carbs. I already had pod filters but they won't fit so I cut out the opening with an X-acto knife to use them for now. K&N makes a set of dual filters that are oval and have two openings so each one fits on two carbs but they are expensive. It was a bit tricky to get the carbs on at first, I had to loosen the screws in the two outer mounting boots so they could swing out a bit and sprayed the spigots with WD-40 to get them to go in easier, then tightened up the bolts after I got the carbs in. The GSXR 1100 has #122.5 mainjets and #30 pilot jets so the jetting was just about perfect. All I've done so far was change the pilot jets to #35 to make starting easier and stop some of the popping when cold. The old XS carbs had #45 pilot jets but they don't need to be that large. I left the needle clip in the 2nd position form the top. The mixture looks good and will pass emissions with no problem. I think just about any 36mm GSXR 1100 or Bandit 1200 carbs will work as long as they are from an oil cooled model. The ones from a GSXR750 or 600 sport bike won't work because they are downdraft. Also the Bandit has #102 main jets so they may need to be changed. There are no fuel leaks now, the bike runs much smoother and the accelleration is a lot better, especially during roll on from 40-80 or while passing. Now it feels like and 1100 again, not a 750 in a 600 lb. chassis. There is currently a set of GSXR 1100 carbs on ebay for $99.00, not bad for new carbs. The only problem I haven't completely solved yet is adjusting the idle mixture screws which are on the bottom of the carbs at the front. I can't get to the middle two carbs to adjust the screws unless I remove the whole rack but 2 to 2 1/2 turns out seems to be about right. I'm going to take pictures of the installation and put up on a website
when I take the whole assembly off again for some more work.
After a lot of searching I settled on Suzuki GSXR 1100 stock carbs which have flat slides but are also CV type. They are 36mm but still 40mm on the outside and will fit the XS1100 rubber boots. The only major problem is the spacing between the center two carbs is a bit wider and had to be reduced to fit the Yamaha. I got a set on ebay for $70 that looked perfect and were just like new. I had to cut a piece out of the middle of the bars that hold the carbs together with a bandsaw and moved them together so the butterfly shafts just touched and cut the bar that operates the chokes and overlap the end to secure them with a screw. The carbs are designed for dual push-pull throttle cables but the single pull cable will work with an extension. They are also made to use a cable operated choke. I tried a push-pull choke for a car but it was hard to pull and wouldn't stay out. I decided on the speed shift lever from an 18 speed bike and that works great. It mounts on the bars, is easy to work and stays in any position. They can be found at swap meets or bike shops if there isn't an old bike laying in the back yard. Get the kind with a plain lever with no click stops or racheting mechanism and get the cable to go with it. You will also need a 6mm cable stop to clamp on the end of the cable that goes into the carb. I found a 1/4" stop at Auto Zone and turned it down to 6mm in a lathe. The stock airbox has to go unless you can find a way to get the rubber boots to fit the bigger 60mm inlets on the new carbs. I already had pod filters but they won't fit so I cut out the opening with an X-acto knife to use them for now. K&N makes a set of dual filters that are oval and have two openings so each one fits on two carbs but they are expensive. It was a bit tricky to get the carbs on at first, I had to loosen the screws in the two outer mounting boots so they could swing out a bit and sprayed the spigots with WD-40 to get them to go in easier, then tightened up the bolts after I got the carbs in. The GSXR 1100 has #122.5 mainjets and #30 pilot jets so the jetting was just about perfect. All I've done so far was change the pilot jets to #35 to make starting easier and stop some of the popping when cold. The old XS carbs had #45 pilot jets but they don't need to be that large. I left the needle clip in the 2nd position form the top. The mixture looks good and will pass emissions with no problem. I think just about any 36mm GSXR 1100 or Bandit 1200 carbs will work as long as they are from an oil cooled model. The ones from a GSXR750 or 600 sport bike won't work because they are downdraft. Also the Bandit has #102 main jets so they may need to be changed. There are no fuel leaks now, the bike runs much smoother and the accelleration is a lot better, especially during roll on from 40-80 or while passing. Now it feels like and 1100 again, not a 750 in a 600 lb. chassis. There is currently a set of GSXR 1100 carbs on ebay for $99.00, not bad for new carbs. The only problem I haven't completely solved yet is adjusting the idle mixture screws which are on the bottom of the carbs at the front. I can't get to the middle two carbs to adjust the screws unless I remove the whole rack but 2 to 2 1/2 turns out seems to be about right. I'm going to take pictures of the installation and put up on a website
when I take the whole assembly off again for some more work.
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