New bike, new questions

So if this is not my issue, what could also be a culprit. So when I start it up and get it warm, it idles fine. Once its warm, if I rev it, it will stay at a very high idle (showing full advance with a light) for some time and then will eventually go back to normal idle. While I was riding it, I would come to a light/stop and pull in the clutch and the idle would be at what I presume around 3k (it was almost like a nice cruise control when riding..haha). Once stopped, I would shift into first and engage the clutch momentarily to bring the idle down and then it would idle fine again sitting at the light.

On another note and possibly unrelated, while messing with the bike yesterday I had it just idling for a few minutes. I noticed that randomly every 30 seconds to a minute the bike would have a small backfire, stumble for just a second, then return to a normal smooth idle. I guess I was just lucky on my last XS that I got spoiled. I just cleaned out the carbs, set the mixture and never had another issue after that.
 
As Gary said, the freshly greased rod may be a little sluggish still at first until the grease gets worked in. Give it a good ride or two before passing judgement on the "fix".
 
Quote:
" Once its warm, if I rev it, it will stay at a very high idle (showing full advance with a light) for some time and then will eventually go back to normal idle. While I was riding it, I would come to a light/stop and pull in the clutch and the idle would be at what I presume around 3k"

BS38 carbs.......................you likely have air leakage around the carb intake area. It takes very little leakage to cause hovering high idle.
Have you looked at the needle jet O-rings. If they are worn out, they will let unmetered fuel/air into the engine and cause high idle.
 
RG, I will definitely be spraying something around the carbs to check for leaks and look at the o rings a little closer
 
So I installed the advance springs from Mikes and it seems the weights snap back a little harder. I started the bike and did notice the RPMs would hang less and for less time. I then went at the carbs/boots with some spray to see if I had a leak, and had no change in idle speed. I went for a short ride and the bike went to idle nicely at stops. I don't think im out of the woods with it, but its better for now. My only issue now is while at cruising speed, if I give full throttle in any gear, I have a hesitation. Not a stumble as is the engine kicks off or jerks, it just sputters and wont do much until I back off and play with the throttle and can then get it to pull smoothly. Does this sound like a rich or lean condition, and could it possibly be remedied with the fuel mixture screws?
 
It could be rich or lean, lol. A hesitation or big flat spot is usually a lean indicator. Stumbling or "gurgling" is usually a rich indicator, but stumbling could be lean too. You had the bowls off to check/clean them but you didn't mention checking the jet sizes. With your pod filters and straight pipes, some changes from stock will be needed. Maybe some have been done already but maybe they're not quite the right ones yet. For your '78-'79 carb set, stock pilot was a 27.5 and the main was a 135. You'll need to see what's in there now. I would suggest starting with one up on the pilots (#30) and at least two up on the mains (#140). You may need even a little bigger on the mains with your straight pipes, but only testing will tell you for sure. Also, you'll need to lean the needle settings a step with the larger mains.

Both the main and pilot are mounted in the float bowls on these carbs so there's no need to remove the whole carb set. Just drop the bowls.

No, a mix screw adjustment probably won't fix your problem. It is mostly for setting the idle mixture. Do make sure it's set right for that though. Spec for your carb set is 2.25 turns out but they sometimes like as much as 2 1/2 or 2 5/8.
 
IMG_4155.JPG IMG_4156.JPG So I haven't been posting lately as I've been trying to ride this thing while the weather will let me. I pulled the carbs apart today because I cant take the drivability anymore. I saw a little bit of fuel around the idle screw so I think I've got a small leak. I also pulled the jets and saw I do have 78/79 carbs with factory jetting. I'm looking for some advice on where to get new jets (thinking 30/140 from boats.net), I'd like to go up at least one size in both. I also need to source the idle screw o-rings and the gasket on the float valves?? I'm not sure what they're called. Pics attached for what I need.

Thanks for the advise!
 
About the only part readily available from Yamaha would be the seal washer for the float needle seat .....

http://www.boats.net/parts/detail/yamaha/Y-214-14195-00-00.html

Yamaha usually only lists stock jet sizes for any given model. They may have the larger sizes you want if they were used in some other model but I couldn't tell you the part numbers. The main and pilot jets used in these are nothing special, just common Mikuni jets available most anywhere. Two types of pilots were used in the 650 carbs over the years. Your set requires the VM22/210 type with the metering orifice at the top by the screwdriver slot .....

Uoaj1xt.jpg


Your BS38s use what is called the small round main. It is Mikuni type N102/221 .....

M98LIeO.png


As I said, both of these are common jet types and can probably be purchased locally at a shop that caters to dirt bikes and ATVs. The mix screw o-ring is something you'll have to find a replacement for yourself. Yamaha never listed or sold it as a separate part, just as part of a whole new screw .....

S2lH1ef.png


I have successfully used a 1.5mm thick x 3mm I.D. size but it is a little large. You will need to keep it well lubed as you install the screw so it will go in the hole. A better option may be a slightly smaller 1.5 x 2.5 size.
 
Yes, you will need to do that as well. In some of the 650 carb sets, you can get away without it but your '78-'79 set pretty much requires it with any increase in main jet size. Stock setting is in the middle #3 slot. Move the clip up one to the #2 slot. That will lower and lean the needle setting.

uVUwOei.jpg


Also make sure you assemble the needle components correctly. The thick plastic spacer washer goes on top of the e-clip, thin metal washer and the little spring under it .....

JBHxvr2.jpg
 

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