Amen, Skull. I've given up trying to help guys who won't help themselves. There's information on identifying carb sets at Mike's XS and in the Carb Guide, and no excuse in the world for not doing a little reference work.
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Acceleration problems
- Thread starter Khosatral Khel
- Start date
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- Tags
- carburetors
Khosatral Khel
XS650 Member
Pic of the carb
Khosatral Khel
XS650 Member
Just checked the float levels and they are set to 27mm. I think the mechanic was just mistaken when he said 17mm.
Khosatral Khel
XS650 Member
The Jets used
Khosatral Khel
XS650 Member
Ok. Again I'm not a mechanic and have only done a handful of things on a car and only oil and air filters on a bike. So taking apart a bike is a little intimidating, that being said I went down the rabbit hoLe and took the carbs off checked the float bowls and adjusted the needles by one notch making it leaner.I put it back together with really no prolems. Surprising myself. Guess what? The bike runs great and I got it up to 85 on the freeway no problem. Thank you everyone for your help and patience!
Nice job!
Congrats. Can be daunting but with help and patience it gets easier each time. Not so complicated really.
RFeng
XS650 Addict
Perfect! Congrats!
great [emoji106]AWFaneuf
XS650 Enthusiast
Hey fellas hate to jump in the middle here but I'm lost when it comes to technology, I'm probably posting in the wrong place. I have a 79 special
That backfires upon deceleration, it also seems to Rev out a bit upon "vigorous" acceleration before it everything seems to catch up and begin responding accordingly. Almost like the clutch is slipping I have no clue what it could be could it be similar to what the original poster is experiencing. Again sorry for hopping on your thread.
That backfires upon deceleration, it also seems to Rev out a bit upon "vigorous" acceleration before it everything seems to catch up and begin responding accordingly. Almost like the clutch is slipping I have no clue what it could be could it be similar to what the original poster is experiencing. Again sorry for hopping on your thread.
To me, it sounds like you have an air leak--likely around the carb boot, or perhaps the air/fuel mix screw is off a bit...but just a guess at this point. I don't think you have the same condition as this original post, but some of the initial questions will apply: we need more info. You say it's a '79 Special, are you running stock carbs? Is this something that just happened, meaning you did some work to it, and now it's occurring or has this been happening for a while, etc...
AWFaneuf
XS650 Enthusiast
Thank you for getting back to me, I just got the bike it does have the stock carbs to the best of my knowledge, I haven't done anything to the bike. The guy I bought it from gave me the paperwork for the work he had done to the bike recently, he had just had the carbs rebuilt before parking it and selling it. I did a bit of research on the air mix screw and I thought it said that it should be 2 and 1/4 turns out. I put it in that position and seemed to run a bit better at first, it was no longer back firing at an idle. I looked to see if there were any noticeable leaks around the carbs and didn't see anything but that certainly doesn't mean that there isn't something amiss there.
A quick way to tell if you have an air leak is to get the bike running and then spray starter fluid around the intakes, and even around the choke area (Just stay away from the air filter side of the carb)... if there's a change to the bike's speed (faster or slower), you have a leak. With old carb boots, there may be small cracks or not sealing correctly... the rubber gets hard and it could be as simple as that.
Up above across the top of this page there is a "tech" tab, and scrolling down, you'll see a TON of carb tech support/info. I would recommend reading through them. You should have BS38 carbs, and they are great when set up correctly.
If the previous owner had the carbs rebuilt...why? Did the person doing the work change the jets? Did they use aftermarket or genuine parts? Either way, the air/fuel mix may or may not be correct... and usually it's just a guide...so a quarter to a full turn in or out may be needed. Every carb is a bit different, but the stock setting is a good starting point. Depending on how long it was "parked", the jets and/or air passages could be clogged, so my vote would be to take the carbs off and thoroughly clean them, passages, etc. verify the jets, verify the float height so you know what you have.
AWFaneuf
XS650 Enthusiast
Thank you so much for your help, to the best of knowledge the guy had the carbs rebuilt upon the mechanics advice, the bike then sat for just over a year before I bought it. I will definitely read the material you suggested and try testing it with the starting fluid, then next step would be taking of the carbs, which I was trying to avoid, I have not done much work on motorcycles but have rebuilt carbs on cars, so I'm hoping it isn't too much for me to do. I gotta start somewhere though thankfully I have another bike if I get in over my head. Thanks again.
AWFaneuf
XS650 Enthusiast
If the carbs are clogged or not set up correctly this could cause the engine to Rev high during hard acceleration?
Anything is possible if the carbs aren't set up correctly...but I'm not sure what you mean by Revving high during hard acceleration--usually when you pull the throttle, you want/expect the bike to rev high. But if you mean, you pull the throttle and then let go, and it stays revving and then slowly goes down... then yes. That is why I think it's an air leak and/or an air-fuel mix issue. You may need to turn the air/fuel mix in a bit to richen up the idle.
AWFaneuf
XS650 Enthusiast
When I'm accelerating immediately after shifting into 4th and 5th gear the engine is lagging upon acceleration the tach is climbing the engine Rev is increasing but the bike isn't responding then eventually my speed increases, this only last a second or two but have never experienced it on other bikes. Almost similar to if you had the clutch partially depressed while attempting to accelerate quickly.
AWFaneuf
XS650 Enthusiast
I am however slightly aware that the carbs have a huge amount of effect on the performance and so many things can go wrong. I really need to learn as much as I can about them not just for my own education but If you can fix carbs and know how to get bikes titled in my state you can make a fortune on Facebook marketplace. I already figured out the title angle now just need to focus on the carbs.
Classic symptoms of a clutch slipping. Very possible the springs or plates are worn out. First thing is to check and make sure your clutch is adjusted correctly. Also you need to use the correct oil.
As GLJ pointed out, it sounds like clutch slipping...and likely nothing to do with your carbs. Check the adjustment process (again in the Tech section) and if that all checks out, could be time for new plates, springs, etc. Super easy to do, but does require pulling the side cover, etc.
