Let's make sure these carbs are good to go on a fresh top-end rebuild. Customer did a good job with them; but we must make sure! Mikuni BS34 II rack, 1978 Yamaha XS1100 project.
This was an *INCREDIBLY* thorough and informative video, THANKA YOU! Currently dealing with some fueling issues on my 78 XS1100 and I strongly suspect I under-appreciated the nuance of properly setting up and checking the float valves correctly.
There's also a video on float drop which pertains to these BS carbs you might find interesting. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-9W9EHNo8RTA.html
In another life, I had 3 XS1100s (a 79, 80 and and 81 - all specials). Back then there was no RU-vid,. I so could have used this video then. I eventually got all 3 running perfectly, but I did one ton of fiddling with the carb sets to get there. I don't have any of this bikes anymore, but this was a real pleasure to watch you work and explain.
Rewind to 1981 I did the same thing on a KZ650. Took me about a month tinkering with pods and a Kerker exhaust to dial it in. And those were VM 26’s or 28’s round slides not CV’s which are much harder to tune. Consider sticking around by liking, sharing and subscribing. Thanks.
Great vid. Love all your stuff. Had an xs750 way back. The overbent float tangs will limit seat opening and therefore float bowl refill rate. (He said "seat opening"). It could run itself out of fuel if ridden hard.
Thanks. Keep in mind, it's a theory of mine only, as I have no way to prove the case I made, but I know for sure, float level especially in some fiddly engines (not saying this one is fiddly -- yet) is quite critical. Cheers.
Brilliant explanation of fuel needle issues, A friend has recently bought an 81 GS850G that is running poorly,the carbs look very similar, he has cleaned the carbs and I gave him my carbtune balancer, but he is struggling to get them to balance on number 2 carb, I suspect it's had after market jet kits fitted and could have similar issues to the XS1100's.
Hmmm... that could caused by a number of things, bad carb holder seal (vacuum issue), valves out of adjustment, lousy compression therefore, poor intake pulse, like from a bad valve in one cylinder (though unlikely, them Suzuki's are pretty bomb proof also)... Usually float valve issues on some bikes which are more finicky than others, results in poor idle and doesn't pop off on acceleration all that well, or one cylinder cuts in and out under hard throttle, especially... or, too rich on a cylinder or cylinders as the case may be in multiple carb floats. I don't know, it should be able to be balance. But it's possible, again some engines are just very finiky about float levels in carbs. When I see service manuals with a float level at a certain height, lets say 14mm, and there is no tolerance like + or - .5mm or something like that... I suspect they mean exactly 14mm and so that's why I use a dial caliper to set them. Cheers. Thanks for watching and commenting.
@@MotoRestoFL Thanks for the quick reply, I suspect all of the above might be an issue with it in one way or another, time will tell. He has just got into buying and restoring classic Jap bikes and is in a steep learning curve due to always having new stuff. When you did the float height check on the XS11, did you take reading from the casting base were the float bowl gasket sits, or on the upper edge of the carb body? The video cut right at that point and it was impossible to see. Honda's seem to say measure from the base of the body below the gasket on a lot of 70's bikes like the GL1000.
Rubber tipped one looked very much like a Hitachi float valve like used on my XJs. Can you give me a good starting point for running an xs1100 stock engine with non filtered velocity stacks and open headers? Drag bike build starting to form.
I'm currently restoring my 1979 XS1100F and in the carbs now. Cleaning, blowing out, replacing parts as necessary, etc. Question; should the floats, float? I'm checking for leaks, and placed them in a can f fuel to test them. One floated, the other three did NOT. being made of brass I can assume they are a bit heavier than the plastic ones, But since one of mine floated, and the other three did NOT, I'm curious! response will be of great help! I'veenjoyed watching your videos on the Classic's for some time!
Absolutely the floats need to float. Especially in fuel. Brass floats very often crack and get fuel inside them, weighing them down. You may not have felt it when you put them in the fuel to test, but most certainly, they filled up enough to sink. You bet, they gotta float, hence the name. Cheers.
The air screw on the top in the yamaha work shop man uale it states do not ajust set at factory it should have a plastice cover i set mine with a kit to 2 vacum if memory serves me i had 2xs1100 1979 81 did over 250000miles all over europe 😢😢happy days now reiterd to thailand have 8 bikes xv 750 my no one 76 years young ex uk citeson😂😂
Can’t clean the slow circuit thoroughly in cases where the carbs have been abandoned and ignored for years, which is how we that restore them, always receive the pasts. That requires removal and servicing the o-ring that seals it. The Yamaha manual is assuming a new machine that is running properly. The manual also has info on removing the plug and servicing the pilot screw.
