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-   -   1980 xs11 special dies with throttle (http://www.xs11.com/forum/showthread.php?t=46983)

darylcaribou69 10-23-2017 05:53 PM

1980 xs11 special dies with throttle
Hello all! I've been reading away on this site for a while but this is my first post.

I recently purchased the bike from a guy who had it in the back of his shed for a "few years". The bike is stock except for the exhaust it's a 4 into 2. When I got it I cleaned the carbs, the PO had them "professionally" rebuilt with a K&L kit with 120 main jets. I read that K&L jets are garbage so I bought the genuine mikuni 42.5 pilots. After the clean the bike wouldn't idle so I went ahead and did the second cleaning for the carbs. I broke them off the rack and boiled them. They seemed to work better for a while but when the bike is warm it wouldn't idle and when it did idle it would die when I touched the throttle. Figured it was running lean, I richened the idle mixture, same thing happened. It would take a while to start then would idle nice and smooth, like butter. touch the throttle and it dies. Carb clean #3 followed. Put them back in, bike wouldn't fire at all, replaced the plugs and she came to life. Struggles to start then idles smooth as melted butter soaked silk. Touch the throttle and it dies.

Any suggestions?

Right now i'm just trying to get the bike so I can ride it up the road to see if it's actually worth my time and money. The carbs have a good bench sync, I'm not sure if a bad sync would cause it to die when the throttle is opened.

The only thing I can imagine it being would be something in the ignition. The vacuum advance works, I can see it move when the cover is off. Not really sure what else could be wrong in the ignition department. I'm more proficient with mechanical stuff.

The battery is new. Stock airbox with new filter. No vacuum leaks around the manifolds.

Maybe the diaphragms aren't sealing properly and not allowing the slides to go up? The diaphragms are good, no holes.

Not sure what's going on with it. Any advice will be greatly appreciated.


darylcaribou69 10-23-2017 06:04 PM


video of the bike

MaximPhil 10-23-2017 06:18 PM

Hi Daryl,
Welcome to XS11.
I like your : I'm more proficient with mechanical stuff.
That covers many of us here on the site. Even some of the electrical gurus hate the electrics :D
Hang on someone will be along soon with suggestions.
Excellent first post with plenty of detail of what you have done. :)
Electrickery and ignition is a mystery to me :eek:


dansmith65 10-23-2017 07:15 PM

Have you looked at the plugs right after stalling it with the throttle? I'm wondering if the mid-range carb tuning is providing the correct air/fuel mixture. Also wondering if you could tell that by looking at the plugs.

Have you checked the fuel level in the bowls? http://www.xs11.com/xs11-info/tech-t...balancing.html

disclaimer: Take what I say with a grain of salt, I have no experience working on these. I have been doing lots of reading and am trying to apply what I've learned.

jetmechmarty 10-23-2017 07:29 PM

Spark? Advance wires under cover.

Eastcoaster 10-23-2017 08:03 PM

Did you pull out the emulsion tubes when you cleaned the carbs and really go over every opening?

darylcaribou69 10-23-2017 08:12 PM

Yes the emulsion tubes were removed. Every passage I could find and some I couldn't find were cleaned then blown out with compressed air.

Thanks for the replies.

motoman 10-23-2017 08:17 PM

+1 0n Eastcoaster's statement. Also, assuming bike still also has the later model carbs as it should, those main jets need to be changed back to their original STOCK sizes....110's across all four carbs, and also NEED to be Genuine Mikuni with the Genuine Mikuni curly-q logo stamped into them on top opposite of sizing numbers. Also, to make sure those are the original later model carbs, when pulling the emulsion tubes out, check the stamping on top, sides of metering rods. The teeny stamped sizing SHOULD be 5GL16 for the Specials. Can't remember sizing designation of them if bike is a Standard, but both models also had different sized metering rods. The Special metering rods were a tad shorter and have a quicker taper compared to the Standard metering rods.

skids 10-23-2017 08:35 PM

Go with middle of the range on the float setting. You can use the manometer method, but if you go with the 1980 carb setting, you will be close.
Synch the carbs yet?

TopCatGr58 10-23-2017 09:23 PM

Hey Daryl,

A couple of things about what you said bother me. You first mention the K&L 120 MAINS, then you say you got and put in Mikuni 42.5 Pilots, but you didn't say whether you changed the MAINs and what size IF you did. Like Motoman said, the OEM sizes were 110 across all 4. You did say you have aftermarket 4-2 pipes which probably breath/flow a little easier than the stock exhausts, but hopefully not so much to require a jetting change YET.

The other thing is that it's an 80. There were some bastardized carbs during the production years transition from 79-80. The 78-79 carbs have a sharing tunnel between the MAIN jet tower and the pilot Jet tower, the pilot jet feeds from this tunnel, and the pilot jet towers were capped off with screws. This is why the Mains were so big=ie 135. In 80, Yamaha still had a lot of the main jet needles/emusion tubes with the sharing tunnel opening and sharing tunnel between the two jet towers, and so they capped off the pilot towers with rubber plugs. Later in production they closed off the sharing tunnel, and let the pilot jet feed directly from the float bowl. But even with the sharing tunnel, the newer carb body style still used the smaller MAIN jets of 110 size.

So....now, if the Pro did the carb rebuild with the K&L kits, they usually come with the rubber pilot jet tower caps, but they are not needed with the 80 carb bodies that do NOT have the sharing tunnel, they are only used when there is the sharing tunnel AND the corresponding tunnel in the end of the emulsion tube. MY question is do you know if you have the sharing tunnel or not in your carbs, and are you using the rubber block off plugs, and are they really needed?


skids 10-23-2017 10:00 PM


Originally Posted by skids (Post 503861)
Go with middle of the range on the float setting. You can use the manometer method, but if you go with the 1980 carb setting, you will be close.
Synch the carbs yet?

Uhhh, for some unknown reason, I thought you had 81 carbs. Forget about the manometer method... 1980's had either later carbs or transitional ("morphodite") carbs, like TC was describing. Or of course, someone could have put older carbs on your bike. Be aware that if your carbs have two hoses per pair, the airbox will need to have nipples that are not filled with resin (like the later airbox) to accommodate the breather hoses.

DiverRay 10-24-2017 12:02 AM

Clip a timing light on #1, and watch what happens when you apply throttle. Light keeps flashing=good, light quits=bad. Do it again with #2, and tell us the results. My guess is a bad pickup coil wire or two and loss of spark when you twist the throttle.

darylcaribou69 10-24-2017 06:46 AM

Thanks for the replies. I'm going to pick up the 110 mains today and while I'm in the carbs I'll look to see what ones I have. I didn't see a passage from the main to pilot so I don't think I need the caps.

And I always love am excuse to buy another tool so I think the timing light is in the cards today as well.

Will update as the train gets rolling.

skids 10-24-2017 12:42 PM

You can hook up a spark plug indicator light in-line with a lead and twist the throttle. However, if you don't have any of the screw-on spark plug tips, it may be a bit futzy holding the connections while throttling.

darylcaribou69 10-24-2017 01:20 PM

Update!!! Got a timing light. Spark stays strong through the stall. Bike ran awesome for a couple seconds when first started. Started without choke very easy.(I had the idle screw wicked rich) so that explains that. I was able to rev it right after it started. I actually thought it was working right. Then it warmed up and died when I opened the throttle. The wires under the ignition cover look good. Carbs are on the way out now.

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