1980 xs11 special dies with throttle

[Radioguylogs]

I have been satisfied with K&L carb float needles in my 4 XS bikes.

I set them all according the factory spec. In some cases, I had to make big float height adjustment to accommodate the K&L needles, even thought they looked the same length as OEM.

I did check the actual fuel level on one bike using clear tubing. The bike had to be running to get consistent results. All of the carbs landed just where they should be-> 3mm down from the gasket surface, which is level with the bowl screw washers.

The only problems I have experienced with the K&L carb kit parts are:
(1) Pilot jets wrong size- other jets OK
(2) The wires on the top of the float needles are sometimes bent by handling, and they should be straightened to relieve pre-load on the needle spring.

I am aware other members have drastically different opinions and results.

[darylcaribou69]

Thank you for the advice on the fuel height. I'll rig something up to find a proper height.

I know the 1980s had fixed needle positions but I tore into the slides and needles and there are grooves and clips on them. So this tells me either I have other than 1980 carbs or 1980 carbs with the wrong parts. This would explain some of these issues. I guess I thought I knew what I was looking at before but I guess not. I'll have to find a carb identification guide. There are no passages between main and pilot towers in the bowls so I think they just used the wrong parts.

[motoman]

Thank you for the advice on the fuel height. I'll rig something up to find a proper height.

I know the 1980s had fixed needle positions but I tore into the slides and needles and there are grooves and clips on them. So this tells me either I have other than 1980 carbs or 1980 carbs with the wrong parts. This would explain some of these issues. I guess I thought I knew what I was looking at before but I guess not. I'll have to find a carb identification guide. There are no passages between main and pilot towers in the bowls so I think they just used the wrong parts.

True , no grooves or clips for different float heights on 80-XJ Mikuni carbs. Since you show having an 80 Special,hopefully with original carbs, in which case the 80-81 Specials use 5GL16 metering rods. The 80-81 Standards use a different length and longer taper length float needles. Right off, Ive forgotten what numbering/lettering they use, but they ARE different. Main jet/pilot jet size is still the same as 81 Specials.....110 across all four/42.5 pilot jets, and to work correctly, they ALL need to be Genuine Mikuni not aftermarket K&L or RD jets.

[skids]

True , no grooves or clips for different float heights on 80-XJ Mikuni carbs. Since you show having an 80 Special,hopefully with original carbs, in which case the 80-81 Specials use 5GL16 metering rods. The 80-81 Standards use a different length and longer taper length float needles. Right off, Ive forgotten what numbering/lettering they use, but they ARE different. Main jet/pilot jet size is still the same as 81 Specials.....110 across all four/42.5 pilot jets, and to work correctly, they ALL need to be Genuine Mikuni not aftermarket K&L or RD jets.

I think it is proof that he has the transitional "morphodite" carbs.

[skids]

I think it is proof that he has the transitional "morphodite" carbs.

Well, I take it back. Maybe that was something (slotted needles) that didn't come from the Yami factory. I really don't know.

[motoman]

I have been satisfied with K&L carb float needles in my 4 XS bikes.

I set them all according the factory spec. In some cases, I had to make big float height adjustment to accommodate the K&L needles, even thought they looked the same length as OEM.

I did check the actual fuel level on one bike using clear tubing. The bike had to be running to get consistent results. All of the carbs landed just where they should be-> 3mm down from the gasket surface, which is level with the bowl screw washers.

The only problems I have experienced with the K&L carb kit parts are:
(1) Pilot jets wrong size- other jets OK
(2) The wires on the top of the float needles are sometimes bent by handling, and they should be straightened to relieve pre-load on the needle spring.

I am aware other members have drastically different opinions and results.

In referance to #1, K&L and RD main jets have larger orfice compared to designated same size Genuine Mikuni jets. From orfice measurements, K&L main jets are approx. 2 sizes larger than Genuine Mikuni main jets of marked same size.

[darylcaribou69]

I managed to track down some NOS 5gl16 needles they are a full half mm thicker trhan the ones that were in it. The ones that were in the carbs when I got them were some aftermarket ones, they were 2.5mm wide at the top where the genuine ones are 3mm wide at the top. I would assume these will make a difference. I'm waiting for one of them, then I'll get the carbs re assembled and set the float heights using an actual fuel height not just the float height. With the aftermarket needles and seats this may also be an issue.

[skids]

I managed to track down some NOS 5gl16 needles they are a full half mm thicker trhan the ones that were in it. The ones that were in the carbs when I got them were some aftermarket ones, they were 2.5mm wide at the top where the genuine ones are 3mm wide at the top. I would assume these will make a difference. I'm waiting for one of them, then I'll get the carbs re assembled and set the float heights using an actual fuel height not just the float height. With the aftermarket needles and seats this may also be an issue.

From post 76: Are the Main jet needles stock or do you have aftermarket needles? The needles have not been shimmed upwards have they?

Well, I am glad you checked.

[darylcaribou69]

Got busy with school and the weather got cold and have not been able to do any work on the bike until I warmed up to about 30 degrees today.

I found some NOS needles. Got lucky on eBay paid $18 for 3 of them, then $15 for the last one. Put them in the slides, they are a full half millimeter thicker than the ones that were in there. There used to be all kinds of play in them and they didn't seal well and didn't allow vacuum to build up above the slide to lift it. All of this combined seems to be what was the issue.

Put the carbs in today, bike fired right up, I let it warm up , took it off the choke and it idles as it should. Went to turn the throttle expecting a stumble and for it to die and the bile revved up smoothly without a problem. Went back to idle and did it again and again. Revs awesome now.

So, this issue was a combination of broken pickup wires, aftermarket carb parts and dirty carb circuits.

Thank you all for the advice given. I hope this thread can help someone else troubleshoot their bike.

[skids]

I found some NOS needles. (snip)

So, this issue was a combination of broken pickup wires, aftermarket carb parts and dirty carb circuits.

Good find! Glad you found the issues.

[Radioguylogs]

Yes, great to hear you sorted it all out.

Thanks for reporting the result so we all benefit from your experience.

[motoman]

Good to hear the issue has been sorted. Now, see how it acts under load. A lot different how it acts when under load as opposed to just 'fre-revving'. If it now idles fine, you first need to set idlemixtures and THEN sync those carbs. This will help eliminate a lot of issues when under load.

[darylcaribou69]

I plan on doing the tuning in the spring when it warms up and isn't stupid cold out. I just wanted to get the carbs in and the bike started to make sure those needles would allow it to run.

Thinking about it now, when I bought it the previous owner said the bike ran awesome then it was put in the back of the garage. When they went to run it a couple years later he said it wouldn't go, he took the carbs off and they were gummed up. He brought them to a shop to get them rebuilt and when he got them back the bike wouldnt run right. It makes sense now because of all of the after market stuff in them.

[skids]

The only thing that I let the shop do is change tires on the rims. I don't even let them put remove or reinstall the wheels!

[darylcaribou69]

That's about all I was going to have the shop do. Haha! Wrenching is half of the fun. And you make sure things get done right.