'78 XS1100E, '80 carbs low rpm funk

[DEEBS11]

Thank you for telling us how the problem was resolved. Glad to hear that you are back on the road.

[Dan Hodges]

Everybody with an XS needs the factory shop manual and you can buy one on E-Bay.. You also need a good set of preferably late carburetors because your carbs as you described them are junk and you will never get them to work properly. Getting a nice set of carbs for one of these bikes is difficult but getting one to run properly with junk carbs is impossible. Again, you need a shop manual.

[DiverRay]

A few of us have pdf versions of the shop manual. send me a pm of the year/model of your bike and I'll see if I can send you the manual. They are too big to post, usually, and may be too big for gmail.

[Rasputin]

A few of us have pdf versions of the shop manual. send me a pm of the year/model of your bike and I'll see if I can send you the manual. They are too big to post, usually, and may be too big for gmail.

I never have any issue sending them in Gmail. Most do require Google drive though as the files are large but my gmail automatically converts.

[gtem]

Everybody with an XS needs the factory shop manual and you can buy one on E-Bay.. You also need a good set of preferably late carburetors because your carbs as you described them are junk and you will never get them to work properly. Getting a nice set of carbs for one of these bikes is difficult but getting one to run properly with junk carbs is impossible. Again, you need a shop manual.

A few points: 1) I do in fact have a factory service manual for '78-'79 E/F models.

2) In case you missed my latest update, the bike is running great with the '80 carbs now that the needle clip/washer issue has been addressed!

[gtem]

To avoid confusion with the Midnight Special carb tinkering thread I thought I'd update this separately:

I rode the bike with it's current configuration of '80 Special carbs with 110 mains and 42.5 pilots the rest of the season, it was running the best it had, though in warmer weather the response from 3000 and below was still not the cleanest/smoothest, maybe "good enough" for many people but I could tell it was still too rich, even with just .75 turns out on the idle mixture screw. Starting to mess with the '80 Midnight Special, as well as having my '00 Voyager on the road, prompted me to dig back into the '80 Special carbs on this '78 E.

One thing I realized was that I've been riding around with spark plugs two ranges colder than stock (BP8ES, not BP6ES). The bike came to me with dyna "green" coils and non-resistor wires, and as a reminder, has a RC Engineering 4-1 with some fiberglass matting in the baffle, stock airbox with filter. I'm going to try NGK 7131 BP6R6ES plugs, and I also got my hands on a set of the smoother, longer, less tapered standard/venturer style needles, which I just installed along with #120 mains. Will report back how this setup runs.

[cajun31]

To avoid confusion with the Midnight Special carb tinkering thread I thought I'd update this separately:

I rode the bike with it's current configuration of '80 Special carbs with 110 mains and 42.5 pilots the rest of the season, it was running the best it had, though in warmer weather the response from 3000 and below was still not the cleanest/smoothest, maybe "good enough" for many people but I could tell it was still too rich, even with just .75 turns out on the idle mixture screw. Starting to mess with the '80 Midnight Special, as well as having my '00 Voyager on the road, prompted me to dig back into the '80 Special carbs on this '78 E.

One thing I realized was that I've been riding around with spark plugs two ranges colder than stock (BP8ES, not BP6ES). The bike came to me with dyna "green" coils and non-resistor wires, and as a reminder, has a RC Engineering 4-1 with some fiberglass matting in the baffle, stock airbox with filter. I'm going to try NGK 7131 BP6R6ES plugs, and I also got my hands on a set of the smoother, longer, less tapered standard/venturer style needles, which I just installed along with #120 mains. Will report back how this setup runs.

Those 80 special carbs never had and adjustable needle. Only the earlier 78 and 79 carbs did. You need to remember you are dealing with completely different carbs from the earlier to the later carbs. If they as you stated ae running it's best, it was because you had them tuned pretty close. From 3000 and lower had more to do with the idle circuit possibly still not tuned in rather then the main jet and circuit you are now changing. You don't have any modifications on your setup that would require going to larger mains or for that matter larger pilots. One other thing to keep in mind is that when tuning in the idle circuit these old machines run better on the richer side then lean and you will have less worry with less heat. Messing with the main circuit is just going to cost you fuel mileage.

[gtem]

I appreciate the continued feedback Jim. I'm not talking about adjustable needles, I'm referring to swapping the shorter/more tapered 5GL16 "Special" needles for the longer more gentle tapered 5IZ7, which from what I've gathered, were paired with the larger 120 mains from the factory on 1980 Venturers/Standards. And I agree 100% that given my list of modifications, I *should* be able to use stock jetted '80 Special carbs. I also agree that I may very well be barking up the wrong tree messing with any other circuits when the most likely culprit is the idle circuit. But at this point, I feel like I've to the best of my ability eliminated the other variables on the idle circuit, and am now looking at that 1/4 throttle area where I *think* the needle taper could come into play. I'm curious to see what putting the right spark plugs in there will do for me, looking at them last night they're actually D8EAs, so not only a colder plug, but missing the more projected insulator. I'm picking up correct plugs today, we'll see maybe this wasn't a carb thing all along but a wrong plug issue. Thanks again for the help!

[cajun31]

I appreciate the continued feedback Jim. I'm not talking about adjustable needles, I'm referring to swapping the shorter/more tapered 5GL16 "Special" needles for the longer more gentle tapered 5IZ7, which from what I've gathered, were paired with the larger 120 mains from the factory on 1980 Venturers/Standards. And I agree 100% that given my list of modifications, I *should* be able to use stock jetted '80 Special carbs. I also agree that I may very well be barking up the wrong tree messing with any other circuits when the most likely culprit is the idle circuit. But at this point, I feel like I've to the best of my ability eliminated the other variables on the idle circuit, and am now looking at that 1/4 throttle area where I *think* the needle taper could come into play. I'm curious to see what putting the right spark plugs in there will do for me, looking at them last night they're actually D8EAs, so not only a colder plug, but missing the more projected insulator. I'm picking up correct plugs today, we'll see maybe this wasn't a carb thing all along but a wrong plug issue. Thanks again for the help!

If you don't have the earlier 80 carbs with the shared main/pilot jet with the black rubber plugs then those two circuits are completely separate and those needles are only affecting the main circuit. Unless your original main jet needles were warped or damaged some other way I would leave those alone. Again, just until you get it figured out and then you can play around with things. I believe you are on the right track with the spark plugs. I had read discussions on forums that many use cooler plugs when they are riding in extremely hot conditions, i.e. in the desert etc....

[gtem]

The latest with the '78E is that I took a look at the plugs, and I have no idea how I didn't notice this before, but the outer two were B8ES and the inner two were BPR6ES, no idea what the previous owner was trying to accomplish, and it's possible he had them installed with the colder B8ES on the inner cylinders and I inadvertently swapped things while tuning and tinkering last year. Also of note, this was after some suburban low speed commuting, plugs 1-3 were a dark tan, and plug four was sooty. I installed four brand new 6PR6ES (bike has dyna green coil with non-resistor plug caps), and did a bench leakdown test. Cyl #4 was showing a bit of wetness at the pilot air jet after sitting with a column of fuel in about 3 feet of fuel line above it. I'm going to take a look at this float valve again. On this set of '80 carbs, I had previously replaced o-rings, polished float needle seats, and replaced just one of the valves that was problematic. Looks like I'll replace atleast one more now. The sooty plug on #4 makes sense if I have a leaky float valve on that cylinder.

So I've got the non-Special needle and 120 mains setup installed and ready to test out and see if that helps with the rich transition-throttle situation, I also caved and ordered up #40 mains. I can't wrap my head around why my basically stock bike would be too rich on the idle circuit with stock #42.5 jets, but the two known variables are that it's 1980 carbs that were designed for a 1980 motor with 1mm larger intake valves and different cam/ignition timing, and it's possible that my RC Engineering exhaust with its added packing to the baffle is actually flowing worse than a stock 4-2. Whatever it is, I will try the #40s and see if that helps.

[Schming]

JAT you may want to try the exhaust with no or a bit less packing on the baffle as flow is choked into a 4 into 1 already.

[gtem]

JAT you may want to try the exhaust with no or a bit less packing on the baffle as flow is choked into a 4 into 1 already.

That's what I'm thinking. I tried swapping the pretty dense fiber glass packing for some steel wool before, didn't really keep it in long enough to notice anything aside from more noise. Without any packing this RC pipe is seriously loud. For a serious drag racer or someone looking to make some noise it's just the ticket maybe, but this is my all-rounder and something I like to be able to tour on.

[LAB3]

Having hotter plugs in cylinders 1&4 could be an attempt to make them run hotter since 2&3 have less surface area to radiate heat. I'm not well enough versed on the XS11 carbs to say for sure but there's other inline fours that use different jets on 1&4 than are in 2&3, this happens at the factory. If you remain eagle eyed when going over a parts fische you'll often find these differences.

[cajun31]

Having hotter plugs in cylinders 1&4 could be an attempt to make them run hotter since 2&3 have less surface area to radiate heat. I'm not well enough versed on the XS11 carbs to say for sure but there's other inline fours that use different jets on 1&4 than are in 2&3, this happens at the factory. If you remain eagle eyed when going over a parts fische you'll often find these differences.

On the Midnight Specials they did just that from the factory. Oem they came with 110s in 1&4 and 112s in 2&3.

[motoman]

I appreciate the continued feedback Jim. I'm not talking about adjustable needles, I'm referring to swapping the shorter/more tapered 5GL16 "Special" needles for the longer more gentle tapered 5IZ7, which from what I've gathered, were paired with the larger 120 mains from the factory on 1980 Venturers/Standards. And I agree 100% that given my list of modifications, I *should* be able to use stock jetted '80 Special carbs. I also agree that I may very well be barking up the wrong tree messing with any other circuits when the most likely culprit is the idle circuit. But at this point, I feel like I've to the best of my ability eliminated the other variables on the idle circuit, and am now looking at that 1/4 throttle area where I *think* the needle taper could come into play. I'm curious to see what putting the right spark plugs in there will do for me, looking at them last night they're actually D8EAs, so not only a colder plug, but missing the more projected insulator. I'm picking up correct plugs today, we'll see maybe this wasn't a carb thing all along but a wrong plug issue. Thanks again for the help!

gtem, for helpful info., the 5GL16 metering rods used in the 81' Specials ARE factory matched up with 110Mikuni main jets. 81' Special carbs are what I have on my bought new 81' Venturer 1100 and work perfect. Bike is still all original cept for the corbin seat and Heli fully adjustable bars.